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Practically all solar phenomena are more or less relative to the solar magnetic field. It produces relatively stable structures like sunspots or prominences and is responsible for spectacular dynamic phenomena like flares or coronal mass ejections. However, the generation, amplification and destruction of magnetic fields remain poorly understood. The knowledge of its magnitude and direction is crucial for interpreting measurements of other parameters, and it can be measured usually by a polarimetry at some special spectral lines, which should be sensitive to the Zeeman effect. To answer what physical mechanisms are responsible for heating the corona, what causes variations of radiative output in the Sun, and what mechanisms trigger flares and coronal mass ejections and so on, many large aperture solar telescope have been developed (such as VTT, GREGOR, NST) or have being developed (such as DKIST, EST), and the Stokes polarimetry is their most important observational device for determining the magnetic field. The Chinese large solar telescope (CLST) with a 1.8-m aperture is a classic Gregorian configuration telescope with an alt-azimuth mount. It will be the second largest solar telescope in the world for a long time. And it is the main task for the Chinese large solar telescope (CLST) to measure the solar polarization with a high accuracy and sensitivity. However, as a classic Gregorian configuration telescope with an alt-azimuth mount, the telescope system itself will introduce instrumental polarization. And it also will change constantly with the rotating of the telescope. Therefore a calibration unit which produces light of known polarization states is necessary to measure the Muller matrix of the system and apply the correction numerically on the measured Stokes vector.
Supported by National Natural Science Foundation of China (11178004, 11727805) | 0.803601 | 3.611883 |
The near future will be extremely interesting. I think it is important to accept that Nature pays no heed to what we humans think about it. Will the greenhouse theory survive a significant cooling of the Earth? Not in its current dominant form. Unfortunately, tomorrow’s climate challenges will be quite different from the greenhouse theory’s predictions. Perhaps it will become fashionable again to investigate the Sun’s impact on our climate. __ Henrik Svensmark
Does The Sun Influence Earth’s Climate? If So, How?
According to spokespersons for the Climate Apocalypse movement, variable energy from the sun has no appreciable influence on the global climate. But as we shall see below, a number of intelligent and well-trained scientists hold different views on that topic. First, we will look at the “cosmic ray hypothesis,” which states that a less active sun (fewer sunspots) allows more galactic cosmic rays to reach Earth’s atmosphere, where they help form “cooling clouds” which partially deflect a greater amount solar heating from the Earth.
A few years ago Henrik Svensmark described a mechanism how solar activity could change cloud cover. Was this the long-sought solar amplifier? The proposed process involves a series of steps where the sun’s magnetic field shields the earth’s atmosphere, at times more and at times less, from cosmic rays – thus acting as a modulator. The tiny galactic particles then act as seeds for condensation and cloud formation, which in turn regulate the Earth’s temperature. This mechanism allowed Svensmark to establish a correlation between solar activity and clouds… ___
When the Sun is active, its magnetic field is better at shielding us against the cosmic rays coming from outer space, before they reach our planet. By regulating the Earth’s cloud cover, the Sun can turn the temperature up and down. High solar activity means fewer clouds and and a warmer world. Low solar activity and poorer shielding against cosmic rays result in increased cloud cover and hence a cooling. As the Sun’s magnetism doubled in strength during the 20th century, this natural mechanism may be responsible for a large part of global warming seen then.
… The outcome may be that the Sun itself will demonstrate its importance for climate and so challenge the theories of global warming. No climate model has predicted a cooling of the Earth – quite the contrary. And this means that the projections of future climate are unreliable. A forecast saying it may be either warmer or colder for 50 years is not very useful, and science is not yet able to predict solar activity.
The Solar Effect on Ozone Hypothesis
Another hypothesis for how the sun might affect global climate is put forward by Stephen Wilde:
In essence: The Sun affects the ozone layer through changes in UV or charged particles. When the Sun is more active there is more ozone above the equator and less over the poles, and vice versa. An increase in ozone warms the stratosphere or mesosphere, which pushes the tropopause lower. There is thus a solar induced see-saw effect on the height of the tropopause, which causes the climate zones to shift towards then away from the equator, moving the jet streams and changing them from “zonal” jet streams to “meridonal” ones. When meridonal, the jet streams wander in loops further north and south, resulting in longer lines of air mass mixing at climate zone boundaries, which creates more clouds. Clouds reflect sunlight back out to space, determining how much the climate system is heated by the near-constant incoming solar radiation. Thus the Sun’s UV and charged particles modulate the solar heating of the Earth.
… The jet streams are high-level rivers of fast moving air threading between the climate zones, and are driven by temperature, humidity and density differentials between the different types of air mass:
An equatorward shift of the climate zones gives the jets more room to loop north and south, and that gives more meridonal jets (the north-south components of the jets).
A poleward shift of the zones pushes the jets poleward, forcing them to more closely following the lines of latitude, that is, more zonal jets (the east-west components).
Such shifts are also associated with the Arctic Oscillation, wherein a positive phase results in the climate zones being pulled poleward and the jets adopting a more zonal (straighter) pattern. A negative phase results in the opposite. A more frequent positive phase is associated with a more active Sun due to cooling of the polar stratosphere (less mesospheric ozone descending through the polar vortex) and consequent lifting of the polar tropopause. A more frequent or more pronounced negative phase (as observed to a record extent during the very low solar minimum between cycles 23 and 24) is associated with a less active Sun due to warming of the polar stratosphere (more mesospheric ozone descending through the polar vortex).
Matching Solar Variability w/ Northern Hemisphere Temperature Trends
It is clear from all satellite data that the Sun’s output varies with sunspot activity. The sunspot cycle averages 11 years, but varies from 8 to 14 years. As the number of sunspots goes up, total solar output goes up and the reverse is also true. Satellite measurements agree that peak to trough the variation is about 2 Watts/m2. The satellites disagree on the amount of total solar irradiance at 1 AU (the average distance from the Earth to the Sun) by 14 Watts/m2, and the reason for this disagreement is unclear, but each satellite shows the same trend over a sunspot cycle (see SCC15 Figure 2 below).
… This is Figure 31 from SCC15. The top plot (a) shows the northern hemisphere temperature reconstruction (in blue) from SCC15 compared to the atmospheric CO2 concentration (in red). This fit is very poor. The second (b) fits the CO2concentration to the temperature record and then the residuals to TSI, the fit here is also poor. The third plot (c) fits the temperatures to TSI only and the fit is much better. Finally the fourth plot (d) fits the TSI to the temperature record and the residuals to CO2 and the fit is the best.
… While the correlation between SCC15’s new temperature reconstruction and the Hoyt and Schatten TSI reconstruction is very good, the exact mechanism of how TSI variations affect the Earth’s climate is not known. SCC15 discusses two options, one is ocean circulation of heat and the other is the transport of heat between the Troposphere and the Stratosphere. Probably both of these mechanisms play some role in our changing climate.
The article above with its corresponding graphics reveal a remarkable fit between solar variability and actual temperatures. The authors do not suggest a mechanism for the solar effect on climate, but their data strongly suggests that the effect is real.
The Maunder Minimum was a time of very low sunspot numbers and very cold global climate. Coincidence? I think not.
An update of David Archibald’s observations of Solar Cycle 24. Archibald and others keep watch on the sun, so you won’t have to.
There is a lot more happening that affects the global climate than a mere trace gas (0.04% of the atmosphere) which also happens to be necessary for plants to grow.
Start with the sun and potential variability. Then go to the oceans, and the massive amounts of heat that are stored and released from that reservoir in oscillatory cycles — and how many atmospheric chemicals, including CO2, that the ocean absorbs and transforms. Then look comprehensively at atmospheric phenomenon of a chemical, physical, and biological nature — including massive storms and other energy transfers. Look at aerosols, volcanic activity, and black soot. Then look at temperatures, if you must, but on a much larger scale (and over a much longer time scale) than is currently being done over land, ocean, and ice masses. If you still have a significant unexplained temperature residual at this point, look at human activity — such as land use changes, the urban heat island effect, and industrial pollution. If significant residuals still remain, look at CO2 if you must — but the total CO2 cycle including the meniscule part of the CO2 cycle that human activities contribute to.
Even then, continue looking for further significant factors potentially affecting climate, in an open-minded way.
The climate apocalypse movement is a feeble-minded pseudo-scientific attempt by politicians and political cronies to cash in on the public’s gullibility and unwise trust in politicised science.
We are going to need a lot more guillotines!
Update: Another near-term ice age scare | 0.800373 | 3.324389 |
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In the 18th century, the great scientific challenge of the age was to find a way for mariners to determine their position at sea. One of the most successful solutions was to measure the position of the moon in the sky relative to the fixed background of stars.
Because of parallax effects, this measurement depends on the observer’s position. And by comparing the measured position to a table of positions calculated for an observer in Greenwich in England, mariners could determine their longitude.
There was one problem, however. Calculating the moon’s position in advance is harder than it seems. The sun exerts a small but significant gravitational tug on the moon. And that makes the motion of the Earth, moon, and sun a three-body problem, one that many mathematicians have foundered on before and since.
The difficulty is that this kind of three-body motion is chaotic in all but a few special cases. So there is no easy way of calculating their exact positions in the future. This caused errors in the lunar navigation tables that sometimes led to inaccurate and potentially fatal results.
Nevertheless, mariners made the best of this flawed technique until the middle of the 19th century, when chronometers became cheap and accurate enough to be widely used onboard ships. Eventually, the chronometer method, famously pioneered by John Harrison, became the preferred way to calculate longitude.
However, the three-body problem continues to haunt mathematicians. The problem these days is to determine the structure of globular star clusters and galactic nuclei, which depend on the way black hole binaries interact with single black holes.
The advent of powerful computers allows mathematicians to iteratively calculate the positions of these black holes. But it requires enormous computational resources, and even then, some solutions remain beyond their ken. So a new, more powerful way to solve the three-body problem is desperately needed.
Enter Philip Breen at the University of Edinburgh and a few colleagues, who have trained a neural network to calculate such solutions. Their big news is that their network provides accurate solutions at a fixed computational cost and up to 100 million times faster than a state-of-the-art conventional solver.
They start with a typical training method for neural networks. This requires a database of three-body problems with the solutions calculated by a state-of-the-art solver.
Breen and co first simplify the problem by limiting it to those involving three equal-mass particles in a plane, each with zero velocity to start with. They choose the starting positions at random and solve the three-body motion using a state-of-the-art approach called Brutus. They then repeat this process 10,000 times.
The team use 9,900 examples to train their neural network and 100 to validate it. Finally, they test the network with 5,000 entirely new situations and by comparing the predictions to those calculated by Brutus.
The results make for interesting reading. The neural network accurately predicts the future motion of three bodies and, in particular, correctly emulates the divergence between nearby trajectories, closely matching the Brutus simulations. “We have shown that deep artificial neural networks produce fast and accurate solutions to the computationally challenging three-body problem over a fixed time interval,” say Breen and co.
What’s more, they test the neural network’s predictions by checking how well they conserve energy. With a few tweaks, the network’s predictions meet the energy conservation conditions with an error of just 10-5.
That’s an impressive outcome that has significant potential. In particular, Breen and co say the neural network could help solve three-body problems in situations that become computationally unfeasible for Brutus.
So their vision is to create a hybrid system. In this case, Brutus will do all the heavy lifting, but when the computational burden becomes too great, the neural network will step in until it becomes acceptable again.
In this, way neural networks should make it possible to simulate the motion of black bodies inside galactic nuclei and globular star clusters much more accurately than ever before.
And that’s just the beginning. “Eventually, we envision, that network may be trained on richer chaotic problems, such as the 4 and 5-body problem, reducing the computational burden even more,” say Breen and co.
Ref: arxiv.org/abs/1910.07291 : Newton vs The Machine: Solving The Chaotic Three-Body Problem Using Deep Neural Networks | 0.866948 | 3.353463 |
The galaxy NGC 4380 looks like a special effect straight out of a science fiction or fantasy film in this Hubble Picture of the Week, swirling like a gaping portal to another dimension.
In the grand scheme of things, though, the galaxy is actually quite ordinary. Spiral galaxies like NGC 4380 are one of the most common types of galaxy in the Universe. These colossal collections of stars, often numbering in the hundreds of billions, are shaped like a flat disc, sometimes with a rounded bulge in the center. Graceful spiral arms outlined by dark lanes of dust wind around the bulging core, which glows brightly and has the highest concentration of stars in the galaxy.
Imaging was gathered using the Wide Field Camera 3 (WFC3) aboard the Hubble Space Telescope (HST). This camera, which replaced Wide Field Planetary Camera 2 (WFPC2) in May 2009, provides Hubble with powerful imaging capabilities including broad wavelength coverage, wide field of view, and high sensitivity. For this image of NGC 4380, filters of the following wavelengths were used: 475 nm, 814 nm, and 1.6 μm.
Note: NGC 4380 is the designation of this galaxy in the New General Catalogue of Nebulae and Clusters of Stars, which is often called more simply New General Catalogue or NGC. It is one of the largest comprehensive catalogs, currently containing 7,840 objects including galaxies, star clusters, emission nebulae, and absorption nebulae. | 0.83687 | 3.217942 |
(Inside Science) -- Roughly 1.3 billion years ago, around the time multicellular life was starting to spread on Earth, a pair of black holes collided and released a torrent of gravitational energy into the cosmos. Today, physicists announced they had spotted that energy here on Earth.
“We have detected gravitational waves,” said David Reitze, a physicist at Caltech and executive director of the Laser Interferometer Gravitational-Wave Observatory, or LIGO, at a press conference Thursday morning in Washington, D.C. “We did it!”
The announcement, coinciding with the publication of a peer-reviewed paper in Physical Review Letters with 1,004 co-authors making up the LIGO Scientific Collaboration, marks the first confirmed detection of gravitational waves, a phenomenon predicted by Albert Einstein a century ago.
Einstein’s general relativity equations revealed that accelerating masses should send waves rippling through spacetime at the speed of light. Few if any physicists doubted the waves’ existence, and the 1993 Nobel Prize in Physics was awarded for work that provided strong though indirect evidence for them.
But actually detecting them was a monumental challenge. Even a strong gravitational wave passing through Earth disturbs objects only by around one-thousandth the diameter of a proton.
Nevertheless, physicists calculated that certain extremely violent events -- massive black holes or neutron stars spiraling into each other, for example -- could release enough gravitational energy to be detected on Earth. In 1992 the National Science Foundation green-lighted LIGO to build two facilities, in Livingston, Louisiana and Hanford, Washington.
The detector works by bouncing laser beams between exquisitely polished mirrors positioned at the ends of perpendicular 4-kilometer-long tunnels that form an enormous ‘L’. When the returning beams intersect at the L’s vertex, they interfere with each other and create patterns on a detector screen. If a disturbance were to cause one tunnel to become slightly longer or shorter than the other, the laser interference pattern would change in a way that would reveal information about the source of the disturbance.
In the process of building the two detectors, scientists designed some of the most precise mirrors and lenses ever made. Multiple detectors are necessary because local disturbances like a falling tree can jiggle the mirrors, causing false positives.
“You can only believe [signals are] real if you see them both at the same time from places that are far apart,” said Gabriela Gonzalez, also at the press conference. She is a physicist at Louisiana State University in Baton Rouge, and spokesperson for the LIGO collaboration.
VIRGO, a third detector based in Cascina, Italy, will help scientists better pinpoint gravitational wave sources when it comes online again later this year. Other detectors are being built in Japan and India.
The LIGO detectors operated from 2002 to 2007 and again, along with VIRGO, from 2009 to 2010, but they did not catch a wave during these runs. Project leaders then took them all offline to upgrade them so they could increase their search volume by more than 1,000 times.
Rebranded as Advanced LIGO, the experiment came back online last year and, according to today’s announcement, almost immediately both the Livingston and Hanford observatories spotted a signal resembling a gravitational wave from merging black holes.
“It was amazing,” Gonzalez said. “This was a gift of nature.”
Rumors of a detection began swirling shortly after the September 14, 2015 finding, but project officials remained coy while they analyzed their data to make sure they sure they weren’t fooled by a spurious event or system test. It wasn’t until mid-January that LIGO scientists ruled out other causes and decided by majority vote that they had seen a real event.
The black holes LIGO detected were both around 30 times the sun’s mass, and when they merged into one larger black hole, the collision sent out the gravitational energy equivalent to what is contained in three suns. Black holes of that size had been theorized but not observed before.
“Now we know they exist,” Gonzalez said, adding, “This is the first of many [detections] to come.”
Scientists not involved in LIGO applauded the announcement. “It’s absolutely real, it’s spectacular, the data are freaking amazing. It’s beyond what anyone really believed we would see,” said Scott Ransom, an astronomer at the National Radio Astronomy Observatory in Charlottesville, Virginia. “They got the dream detection on day one.”
LIGO data will also help theorists further test and refine the theory of general relativity, already one of the best-tested theories ever, said Nicolas Yunes, a physicist who studies general relativity at Montana State University in Bozeman. “Now we can get to work.”
“I’m so thrilled to see the work has paid off,” said John Mather, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland and senior project scientist on the James Webb Space Telescope, which will launch in 2018 to study the universe’s most distant objects. The Webb telescope could be aided by future LIGO finds, Mather said. “We’re very eager to follow up on what [LIGO] can tell us,” he said. “Everyone with a telescope will be trying to follow up every announcement that’s made.”
LIGO scientists have long said that the experiment’s main purpose is not to detect gravitational waves, but to do astronomy. Gravitational waves could provide a way to study the universe’s most extreme objects -- extremely dense neutron stars and black holes that are difficult or impossible to study with light.
“LIGO has opened a new window on the universe, a gravitational wave window,” said Kip Thorne, a physicist at Caltech and LIGO co-founder. “Each time a window has been opened up, there have been big surprises.”
“It’s the first time universe has spoken to us through gravitational waves,” Reitze added. “[W]e’ve been deaf to gravitational waves, and now we can hear them. That’s just amazing to me.” | 0.80605 | 3.528973 |
- Artistic representation of the exoplanet Kepler-1625B with its planned moon, which is believed to be the size of Neptune.
- A new study suggests that the first serious exomoon candidate is probably the occupying nucleus of a giant baby planet.
- In October 2018, astronomers Alex Tecchi and David Kipping of Columbia University announced that they would testify about the world in the form of Neptune, the Kepler-1625b, a massive alien planet about 8,000 light years from Earth.
- This was great news: if confirmed, the new world, known as Kepler-1625B-I, would be the first moon discovered beyond our solar system. But confirmation has proved difficult.
Techey and Kipping insisted at the time that the detection, using observations from NASA’s Kepler and the Hubble Space Telescope, was temporary.
Another research team has argued against the existence of Kepler-1625B-I, and another has insisted that the data is inconclusive at this time. Therefore, a year later, Kepler-1625B-I remains a candidate instead of a world candidate.
However, this situation did not prevent other scientists from trying to understand how the potential exomoon arose. In fact, a new study addressed that question and got an intriguing answer.
Astronomers find that the Kepler-1625B-I is approximately 10 times more massive than Earth. The object appears to be orbiting its parent planet as Jupiter at an average distance of 1.9 million miles (3 million kilometers).
Mani L. of UCLA At the Bhowmick Institute of Theoretical Physics, Bradley Henson. The Kepler-1625B-I seen on the planetary satellites of the solar system is probably “the planetary satellites of the solar system have a much greater mass and angular momentum.
It is not clear why Kepler-1625B-I is formed in the same way as the moons of the Solar System. The great moons of Jupiter, for example, are probably covered with a disk of material that orbits the newborn planet a long time ago.
- Modeling work suggests that the Kepler-1625B-I is much larger in this way, Hansen said.
- It is possible that the Exomoon candidate is an ancient planet that was gravitationally occupied by Kepler-1625b.
- Which is twice as massive as Jupiter.
- But it doesn’t work either; “All the landscapes that assemble.
- Capture Kepler-1625B-I after the host planet is formed suffer the problem that they produce a moon that is too small or too close,” Hanson Es wrote.
- Instead, his new modeling job suggests that both bodies were captured shortly after birth.
- It is likely that two ascending objects occupy the same orbital neighborhood: a portion of space around an astronomical unit (AU) of the host star.
- (An AU is the average Earth-Sun distance, approximately 93 million miles or 150 million km).
- In this scenario, the planetary nucleus that becomes Kepler-1625B produces more gas than its neighbor, strengthening its dominance in the eternal relationship.
The way gas accumulation works is a very strong function of the mass, Hansen told Space.com. If you move a little, you start moving very fast, so it is essentially a winning situation,” he said.
One of them captured all the gases in the surrounding area and became a gas giant. The one that crawled a little got stuck in this main phase and due to the increased gravity [of its neighbor’s satellite].
Even in this stable state, the Kepler-1625B-I is likely to have so much gas that it is not a good terrestrial-planetary analog, Hansen said. Therefore, even if the potential Exomoon resides in the habitable zone of its host star.
The range of distances where liquid water may exist on the surface of the world, the Kepler-1625B-I is probably not a great candidate for life as the earth.
A common occurrence?
- Elements of this landscape may have played in our own neck of the cosmic forest, Hansen said.
- For example, it is possible that Neptune and Uranus are giant gaseous protocores that originated in the kingdom of Jupiter and Saturn.
- In these two later worlds the head of engulfing gas begins, the idea continues.
- Iinstead of gravity, occupies Neptune and Uranus, tilting them both to their current location.
- In fact, this process can help explain the abundance of the mass world of Neptune in the Milky Way galaxy.
- Which appears to be higher than expected by traditional planetary formation models.
- “If we begin to take into account the fact that multiple nuclei can interact in the same places, it is possible that not everyone becomes a giant planet,” he said.
- This may be this race against time.
The search for a possible Exmoon raises the hopes of a real-life Pandora or Andor In search of mini moons: Exmoon could have its own satellite.
More ways to search for alien planets
Mike Wall’s book, “Out There” (Grand Central Publishing, 2018; illustrated by Carl Tait) on the discovery of foreign life, is now available.
All about space banners More space? You can get 5 issues from our companion magazine “All About Space” for the latest amazing news from Last Frontier for $ 5!.
Join our space forum to chat about the latest missions, the night sky and more! And if you have a news suggestion, correction or comment.
A new study analyzed why large and Neptune-sized exoplanets are rare
A new study analyzed why large and Neptune-sized exoplanets are rare: Sub-Neptunes- extrasolar planets with Ready between 2.7 and 3 times Earth – are much larger than planets the size of Neptune and larger.
- A new study proposes that this fall is so sudden because the Sub-Neptune atmosphere merges easily with the magma oceans on its surface.
- When the planets reach approximately 3 times the size of the Earth.
- This is a clear advantage in the data, and it is quite dramatic.
- We are surprised that the planets want to stop growing almost 3 times the size of the Earth, “said Dr. John, a planet scientist at the University of Chicago. Edwin Kight said.
- It is believed that Sub-Neptune has oceans of magma on its surfaces, which remain warm thanks to a thick layer of hydrogen-rich atmosphere.
- Dr. “So far, almost all models have ignored this magma, but it is considered chemically inert, but liquid rock flows almost like water and is very reactive,” Kight said.
- Dr. Kight and his colleagues considered the question of whether the ocean could begin to dissolve the atmosphere, because the planets receive more hydrogen.
- In this scenario, when a sub-Neptune occupies more gas, it accumulates in the atmosphere.
- And the downward pressure begins to form where magma meets the atmosphere.
- First, magma raises excess gas at a constant rate, but as pressure increases, hydrogen begins to dissolve in magma much more easily.
- Not only that, but a little of the additional gas remaining in the atmosphere increases the atmospheric pressure and, therefore.
- A large fraction of the gas that arrives later will dissolve in magma,” said Dr. Cometa explained.
- Thus, the growth of the planet stops before it reaches the size of Neptune.
- The authors of the study call it the “fugitive crisis”, after the word that measures the ease with which a gas dissolves in a mixture as a function of pressure.
- “The theory fits well with existing observations,” Dr. Comet mentioned.
- “There are also many markers that astronomers can see in the future.”
- “For example, if the theory is correct, then planets with oceans of magma that are cold enough to crystallize on the surface must show different profiles, because it will prevent the ocean from absorbing so much hydrogen.”
Awaiting confirmation from another 4900. Studies of these many planets have revealed things about the range of possible planets in our universe and have taught us that there are many for which there are no analogues in our solar system.
- For example, thanks to the new data obtained by the Hubble Space Telescope.
- Astronomers have learned more about a new class of exoplanets known as “overpopulated” planets.
- The planets of this class are basically young gas giants that are comparable in size to Jupiter but have masses that are only slightly taller than those on Earth.
- This causes the density of cotton candy in its atmosphere, hence its cheerful nickname.
- The only known examples of this planet live in the Kepler 51 system, a young Sun-like star located about 2,615 light years away in the Cygnus planetarium.
- Within this system, three exoplanets have been confirmed (Kepler-51B, C and D) that were first detected by the Kepler space telescope in 2012. However.
- It was not until 2014 that the density of these planets was confirmed, and This was a big surprise.
- Three giant planets that orbit the star Kepler 51 similar to the Sun compared to some planets in our solar system.
- While these gas giants have atmospheres that are formed by hydrogen and helium and are the same size as Jupiter, they are also a hundred times lighter in terms of mass.
- How and why their atmospheres would skyrocket remains a mystery, but the fact that the nature of their atmosphere makes the Super Puff planets a leading candidate for atmospheric analysis.
- This is exactly what an international team of astronomers, led by Jessica Libby-Roberts of the Center for Astrophysics.
- And Space Astronomy (CASA) of the University of Colorado, Boulder, tried to do. Using data from Hubble, Libby-Roberts.
- And his team analyzed the spectra obtained from the Kepler-51B atmosphere and to see if the components (including water) were there.
- When the planets passed in front of their stars, the light absorbed by their atmosphere was tested in infrared wavelengths.
- To the team’s surprise, they discovered that the spectra of both planets had no revealing chemical signatures.
- This was attributed to the presence of salt crystals or photochemical clouds in its atmosphere.
Therefore, the team relied on computer simulations and other devices to say that the Kepler-51 planets are mostly hydrogen and helium, covered with a thick mist made of methane.
This is similar to Titan’s movement to the atmosphere of Saturn (Saturn’s largest moon), where there are clouds of methane gas primarily in the nitrogen atmosphere that obscure the surface.
“It was completely unexpected,” Libby-Roberts said. “We had planned to visit large water absorption facilities, but they weren’t there. They forced us out!
However, these clouds provided the team with valuable information on how Kepler-51B and D compare with other low-mass gas-rich exoplanets observed by astronomers.” As Libby-Roberts stated in a CU Boulder press release.
- We knew they were low density. But when you break a cotton ball in the form of Jupiter, it is really low density.
- It definitely prevents us from coming to visit us. We expected to find water, but we could not observe the signature of any molecule.
- The team was able to improve the size and mass of these planets by measuring their effects of time.
- In all systems, there are slight changes in the planet’s orbit period due to its gravitational attraction, which can be used to obtain the mass of a planet.
- The team’s results coincided with previous estimates for the Kepler-51B, while estimates for the Kepler-51D indicated that it is a little less massive (also known as more bloated) than before.
- The team also compared the spectra of the two superpoletas with other planets and obtained results that indicated that cloud / fog formation is associated with the planet’s temperature.
- This supports the hypothesis that the planet is colder, it will be the cloud that some astronomers have discovered thanks to recent discoveries of exoplanets.
Sincerely: Geoff Mercy
Last but not least, the team noted that both Kepler-51B and D are losing gas quickly. In fact, the team estimates that the ancient planet (which is closer to its original star) is throwing tens of billions of tons of matter into space every second.
If this trend continues, the planets will be significantly reduced in the next billion years and can become mini-Neptune. In this sense, this would suggest that exoplanets are not so uncommon after all, which makes mini-catches seem very common.
- While the solar system is about 4.6 billion years old, Kepler-51 dates back to about 500 million years.
- The planetary model used by the team suggests the possibility of planets forming beyond the Kepler-51 frost line, the limit beyond which unstable elements freeze.
- This is an extreme example of what is great about the exoplanet in general.
- They give us the opportunity to study worlds that are very different from ours.
- But place the planets in a broader context in our solar system.
In the future, the deployment of next-generation instruments, such as the James Webb Space Telescope (JWST), will allow astronomers to investigate the atmosphere of the Kepler-51 planets and other superpoletas. | 0.874138 | 3.809074 |
Supermassive black holes (SMBHs) found in the centres of many galaxies are understood to play a fundamental, active role in the cosmological structure formation process. In hierarchical formation scenarios, SMBHs are expected to form binaries following the merger of their host galaxies. If these binaries do not coalesce before the merger with a third galaxy, the formation of a black hole triple system is possible. Numerical simulations of the dynamics of triples within galaxy cores exhibit phases of very high eccentricity (as high as e∼ 0.99). During these phases, intense bursts of gravitational radiation can be emitted at orbital periapsis, which produces a gravitational wave signal at frequencies substantially higher than the orbital frequency. The likelihood of detection of these bursts with pulsar timing and the Laser Interferometer Space Antenna (LISA) is estimated using several population models of SMBHs with masses >rsim 107 M⊙. Assuming that 10 per cent or more of binaries are in triple systems, we find that up to a few dozen of these bursts will produce residuals >1 ns, within the sensitivity range of forthcoming pulsar timing arrays. However, most of such bursts will be washed out in the underlying confusion noise produced by all the other 'standard' SMBH binaries emitting in the same frequency window. A detailed data analysis study would be required to assess resolvability of such sources. Implementing a basic resolvability criterion, we find that the chance of catching a resolvable burst at a 1 ns precision level is 2-50 per cent, depending on the adopted SMBH evolution model. On the other hand, the probability of detecting bursts produced by massive binaries (masses ≳107 M⊙) with LISA is negligible. © 2010 The Authors. Journal compilation © 2010 RAS.
Pau Amaro-Seoane, et. al., (2010) Triplets of supermassive black holes: Astrophysics gravitational waves and detection.Monthly Notices of the Royal Astronomical Society402:42308. DOI: http://doi.org/10.1111/j.1365-2966.2009.16104.x
Monthly Notices of the Royal Astronomical Society | 0.846135 | 3.955985 |
Astronomers have discovered, for the first time, moons forming in the disk of debris around a large exoplanet. Astronomers have suspected for a long time that this is how larger planets—like Jupiter in our own Solar System—get their moons. It’s all happening around a very young star named PDS 70, about 370 light years away in the constellation Centaurus.
The accepted theory of how planets form is called the nebular hypothesis. It all starts with the formation of a star in an enormous cloud of gas called a giant molecular cloud (GMC). As the star forms, the cloud is shaped into a rotating flattened disk of gas and dust called a protoplanetary disk, or circumstellar disk. Matter starts to coalesce into clumps in this disk, and these clumps turn into planets.
If the mass of a planet forming in the disk grows greater than approximately 10 Earth masses, something else happens. Due to its mass, that planet opens up a gap in the protoplanetary disk. As material passes through that gap, it can get close enough to the planet that the planet’s gravity dominates the host star’s gravity. That material is then trapped in a circumplanetary disk (CPD) rotating around the planet, like a disk within a disk.
Much of the material within a circumplanetary disk is accreted into the forming planet. But not all of it. The same forces that created planets out of the circumstellar disk go to work. They can create moons out of the material rotating in the disk around the planet.
Now a team of astronomers have spotted this circumplanetary disk, and moons forming in it, for the first time.
The lead author of the study outlining these findings is Andrea Isella, an astronomer at Rice University in Houston, Texas. The findings were published in The Astrophysical Journal letters, and is titled “Detection of Continuum Submillimeter Emission Associated with Candidate Protoplanets.”
“Planets form from disks of gas and dust around newly forming stars, and if a planet is large enough, it can form its own disk as it gathers material in its orbit around the star,” Isella said. “Jupiter and its moons are a little planetary system within our solar system, for example, and it’s believed Jupiter’s moons formed from a circumplanetary disk when Jupiter was very young.”
It’s all happening around the star PDS 70. That star was in the news about a year ago when astronomers captured the first-ever image of a newly-forming planet in a circumstellar disk. That planet is called PDS 70b. That discovery was big news at the time, for good reason.
PDS 70b isn’t the only planet orbiting the star. There is another planet, PDS 70c, also in orbit, and they’re both gas giants. Both those planets were detected by the European Southern Observatory’s (ESO) Very Large Telescope (VLT) in optical and infrared. The warm glow of hydrogen accreting into the pair of planets is what gave them away.
The team combined the VLT observations with new radio observations from the Atacama Large Millimeter/sub-Millimeter Array (ALMA.) The result is convincing evidence of a protoplanetary disk around the outermost star, PDS 70c.
“For the first time, we can conclusively see the telltale signs of a circumplanetary disk, which helps to support many of the current theories of planet formation,” said Andrea Isella, lead author.
“By comparing our observations to the high-resolution infrared and optical images, we can clearly see that an otherwise enigmatic concentration of tiny dust particles is actually a planet-girding disk of dust, the first such feature ever conclusively observed,” he said. According to the researchers, this also is the first time that a planet has been clearly seen in these three distinct bands of light.
One Question Answered, Another One Asked
PDS 70b and c display different characteristics, and the team behind this study isn’t exactly sure what it all means.
PDS 70c, the outermost star of the pair, is as far from its star as Neptune is from the Sun. It’s in the exact same location as an obvious knot of dust seen in the ALMA data. Since this planet is shining so brightly in the infrared and hydrogen bands of light, the astronomers can convincingly say that a fully-formed planet is already in orbit there. The bright infrared and hydrogen bands show that nearby gas is still being accreeted onto the planet’s surface, finishing its adolescent growth spurt.
Astronomers estimate that PDS 70c is approximately 1 to 10 times the mass of Jupiter. “If the planet is on the larger end of that estimate, it’s quite possible there might be planet-size moons in formation around it,” noted Isella.
But PDS 70b has something else going on. That planets, which is about the same distance from its star as Uranus is from the Sun, has a mass of dust trailing behind it like a tail. And the astronomers aren’t sure how it fits in.
“What this is and what it means for this planetary system is not yet known,” said Isella. “The only conclusive thing we can say is that it is far enough from the planet to be an independent feature.”
Astronomers are pretty sure that the process they can see playing out around PDS 70c is the same process that worked to create Jupiter’s moons. It’s worth noting, however, that our Solar System’s other gas giant is distinct from Jupiter. Saturn’s moons were probably created as a result of a circumplanetary disk, but its icy rings were likely created by comets and other rocky bodies crashing into each other.
These exoplanetary systems are notoriously difficult to observe in optical and infrared light. The energy from the star in those parts of the spectrum drowns out the light from planets. But not for ALMA.
ALMA focuses on radio waves, and stars only emit radio waves weakly. The team says that they can continue to observe the PDS 70 system with ALMA to watch as it changes and develops.
“This means we’ll be able to come back to this system at different time periods and more easily map the orbit of the planets and the concentration of dust in the system,” concluded Isella. “This will give us unique insights into the orbital properties of solar systems in their very earliest stages of development.”
The discovery of this circumplanetary disk and the probable moons forming in it are interesting in their own right, but the way the team found the disk is also promising for the future. While others have been found, this study is the most convincing.
“There are a handful of candidate planets that have been detected in disks, but this is a very new field, and they are all still debated,” Isella said. “(PDS 70 b and PDS 70 c) are among the most robust because there have been independent observations with different instruments and techniques.”
In the conclusion of their paper, the authors say, “We argue that optical, NIR, and (sub)millimeter observations are highly complementary because they probe diverse aspects of planet accretion processes and are affected by different systematic errors.” They also note that ALMA alone can’t do the work. By combining the different observations they have opened these exoplanets and their disks up to more detailed study.
From the study: “As ALMA and existing optical telescopes are reaching their full imaging capabilities, forthcoming observations of nearby circumstellar disks characterized by cavities and gaps like those observed in PDS 70 might reveal more newborn planets interacting with their natal disk. Such observations are fundamental to investigating the processes responsible for the formation of planetary systems.” | 0.910773 | 4.074055 |
The Voyager Planetary Mission
Original Article published by Jet Propulsion Laboratory California Institute of Technology here
JUPITER Voyager 1 made its closest approach to Jupiter on March 5, 1979, and Voyager 2 followed with its closest approach occurring on July 9, 1979. The first spacecraft flew within 206,700 kilometers (128,400 miles) of the planet’s cloud tops, and Voyager 2 came within 570,000 kilometers (350,000 miles).
Jupiter is the largest planet in the solar system, composed mainly of hydrogen and helium, with small amounts of methane, ammonia, water vapor, traces of other compounds and a core of melted rock and ice. Colorful latitudinal bands and atmospheric clouds and storms illustrate Jupiter’s dynamic weather system. The giant planet is now known to possess 16 moons. The planet completes one orbit of the Sun each 11.8 years and its day is 9 hours, 55 minutes.
Although astronomers had studied Jupiter through telescopes on Earth for centuries, scientists were surprised by many of the Voyager findings. The Great Red Spot was revealed as a complex storm moving in a counterclockwise direction. An array of other smaller storms and eddies were found throughout the banded clouds.
Discovery of active volcanism on the satellite Io was easily the greatest unexpected discovery at Jupiter. It was the first time active volcanoes had been seen on another body in the solar system. Together, the Voyagers observed the eruption of nine volcanoes on Io, and there is evidence that other eruptions occurred between the Voyager encounters.
Plumes from the volcanoes extend to more than 300 kilometers (190 miles) above the surface. The Voyagers observed material ejected at velocities up to a kilometer per second.
Io’s volcanoes are apparently due to heating of the satellite by tidal pumping. Io is perturbed in its orbit by Europa and Ganymede, two other large satellites nearby, then pulled back again into its regular orbit by Jupiter. This tug-of-war results in tidal bulging as great as 100 meters (330 feet) on Io’s surface, compared with typical tidal bulges on Earth of one meter (three feet).
It appears that volcanism on Io affects the entire jovian system, in that it is the primary source of matter that pervades Jupiter’s magnetosphere — the region of space surrounding the planet influenced by the jovian magnetic field. Sulfur, oxygen and sodium, apparently erupted by Io’s many volcanoes and sputtered off the surface by impact of high-energy particles, were detected as far away as the outer edge of the magnetosphere millions of miles from the planet itself.
Europa displayed a large number of intersecting linear features in the low-resolution photos from Voyager 1. At first, scientists believed the features might be deep cracks, caused by crustal rifting or tectonic processes. The closer high-resolution photos from Voyager 2, however, left scientists puzzled: The features were so lacking in topographic relief that as one scientist described them, they “might have been painted on with a felt marker.” There is a possibility that Europa may be internally active due to tidal heating at a level one-tenth or less than that of Io. Europa is thought to have a thin crust (less than 30 kilometers or 18 miles thick) of water ice, possibly floating on a 50-kilometer-deep (30-mile) ocean.
Ganymede turned out to be the largest moon in the solar system, with a diameter measuring 5,276 kilometers (3,280 miles). It showed two distinct types of terrain — cratered and grooved — suggesting to scientists that Ganymede’s entire icy crust has been under tension from global tectonic processes.
Callisto has a very old, heavily cratered crust showing remnant rings of enormous impact craters. The largest craters have apparently been erased by the flow of the icy crust over geologic time. Almost no topographic relief is apparent in the ghost remnants of the immense impact basins, identifiable only by their light color and the surrounding subdued rings of concentric ridges.
A faint, dusty ring of material was found around Jupiter. Its outer edge is 129,000 kilometers (80,000 miles) from the center of the planet, and it extends inward about 30,000 kilometers (18,000 miles).
Two new, small satellites, Adrastea and Metis, were found orbiting just outside the ring. A third new satellite, Thebe, was discovered between the orbits of Amalthea and Io.
Jupiter’s rings and moons exist within an intense radiation belt of electrons and ions trapped in the planet’s magnetic field. These particles and fields comprise the jovian magnetosphere, or magnetic environment, which extends three to seven million kilometers toward the Sun, and stretches in a windsock shape at least as far as Saturn’s orbit — a distance of 750 million kilometers (460 million miles).
As the magnetosphere rotates with Jupiter, it sweeps past Io and strips away about 1,000 kilograms (one ton) of material per second. The material forms a torus, a doughnut-shaped cloud of ions that glow in the ultraviolet. Some of the torus’s heavy ions migrate outward, and their pressure inflates the Jovian magnetosphere, while the more energetic sulfur and oxygen ions fall along the magnetic field into the planet’s atmosphere, resulting in auroras.
Io acts as an electrical generator as it moves through Jupiter’s magnetic field, developing 400,000 volts across its diameter and generating an electric current of 3 million amperes that flows along the magnetic field to the planet’s ionosphere.
SATURN The Voyager 1 and 2 Saturn flybys occurred nine months apart, with the closest approaches falling on November 12 and August 25, 1981. Voyager 1 flew within 64,200 kilometers (40,000 miles) of the cloud tops, while Voyager 2 came within 41,000 kilometers (26,000 miles).
Saturn is the second largest planet in the solar system. It takes 29.5 Earth years to complete one orbit of the Sun, and its day was clocked at 10 hours, 39 minutes. Saturn is known to have at least 17 moons and a complex ring system. Like Jupiter, Saturn is mostly hydrogen and helium. Its hazy yellow hue was found to be marked by broad atmospheric banding similar to but much fainter than that found on Jupiter. Close scrutiny by Voyager’s imaging systems revealed long-lived ovals and other atmospheric features generally smaller than those on Jupiter.
Perhaps the greatest surprises and the most puzzles were found by the Voyagers in Saturn’s rings. It is thought that the rings formed from larger moons that were shattered by impacts of comets and meteoroids. The resulting dust and boulder- to house-size particles have accumulated in a broad plane around the planet varying in density.
The irregular shapes of Saturn’s eight smallest moons indicates that they too are fragments of larger bodies. Unexpected structure such as kinks and spokes were found in addition to thin rings and broad, diffuse rings not observed from Earth. Much of the elaborate structure of some of the rings is due to the gravitational effects of nearby satellites. This phenomenon is most obviously demonstrated by the relationship between the F-ring and two small moons that “shepherd” the ring material. The variation in the separation of the moons from the ring may the ring’s kinked appearance. Shepherding moons were also found by Voyager 2 at Uranus.
Radial, spoke-like features in the broad B-ring were found by the Voyagers. The features are believed to be composed of fine, dust-size particles. The spokes were observed to form and dissipate in time-lapse images taken by the Voyagers. While electrostatic charging may create spokes by levitating dust particles above the ring, the exact cause of the formation of the spokes is not well understood.
Winds blow at extremely high speeds on Saturn — up to 1,800 kilometers per hour (1,100 miles per hour). Their primarily easterly direction indicates that the winds are not confined to the top cloud layer but must extend at least 2,000 kilometers (1,200 miles) downward into the atmosphere. The characteristic temperature of the atmosphere is 95 kelvins.
Saturn holds a wide assortment of satellites in its orbit, ranging from Phoebe, a small moon that travels in a retrograde orbit and is probably a captured asteroid, to Titan, the planet-sized moon with a thick nitrogen-methane atmosphere. Titan’s surface temperature and pressure are 94 kelvins (-292 Fahrenheit) and 1.5 atmospheres. Photochemistry converts some atmospheric methane to other organic molecules, such as ethane, that is thought to accumulate in lakes or oceans. Other more complex hydrocarbons form the haze particles that eventually fall to the surface, coating it with a thick layer of organic matter. The chemistry in Titan’s atmosphere may strongly resemble that which occurred on Earth before life evolved.
The most active surface of any moon seen in the Saturn system was that of Enceladus. The bright surface of this moon, marked by faults and valleys, showed evidence of tectonically induced change. Voyager 1 found the moon Mimas scarred with a crater so huge that the impact that caused it nearly broke the satellite apart.
Saturn’s magnetic field is smaller than Jupiter’s, extending only one or two million kilometers. The axis of the field is almost perfectly aligned with the rotation axis of the planet.
URANUS In its first solo planetary flyby, Voyager 2 made its closest approach to Uranus on January 24, 1986, coming within 81,500 kilometers (50,600 miles) of the planet’s cloud tops.
Uranus is the third largest planet in the solar system. It orbits the Sun at a distance of about 2.8 billion kilometers (1.7 billion miles) and completes one orbit every 84 years. The length of a day on Uranus as measured by Voyager 2 is 17 hours, 14 minutes.
Uranus is distinguished by the fact that it is tipped on its side. Its unusual position is thought to be the result of a collision with a planet-sized body early in the solar system’s history. Given its odd orientation, with its polar regions exposed to sunlight or darkness for long periods, scientists were not sure what to expect at Uranus.
Voyager 2 found that one of the most striking influences of this sideways position is its effect on the tail of the magnetic field, which is itself tilted 60 degrees from the planet’s axis of rotation. The magnetotail was shown to be twisted by the planet’s rotation into a long corkscrew shape behind the planet.
The presence of a magnetic field at Uranus was not known until Voyager’s arrival. The intensity of the field is roughly comparable to that of Earth’s, though it varies much more from point to point because of its large offset from the center of Uranus. The peculiar orientation of the magnetic field suggests that the field is generated at an intermediate depth in the interior where the pressure is high enough for water to become electrically conducting.
Radiation belts at Uranus were found to be of an intensity similar to those at Saturn. The intensity of radiation within the belts is such that irradiation would quickly darken (within 100,000 years) any methane trapped in the icy surfaces of the inner moons and ring particles. This may have contributed to the darkened surfaces of the moons and ring particles, which are almost uniformly gray in color.
A high layer of haze was detected around the sunlit pole, which also was found to radiate large amounts of ultraviolet light, a phenomenon dubbed “dayglow.” The average temperature is about 60 kelvins (-350 degrees Fahrenheit). Surprisingly, the illuminated and dark poles, and most of the planet, show nearly the same temperature at the cloud tops.
Voyager found 10 new moons, bringing the total number to 15. Most of the new moons are small, with the largest measuring about 150 kilometers (about 90 miles) in diameter.
The moon Miranda, innermost of the five large moons, was revealed to be one of the strangest bodies yet seen in the solar system. Detailed images from Voyager’s flyby of the moon showed huge fault canyons as deep as 20 kilometers (12 miles), terraced layers, and a mixture of old and young surfaces. One theory holds that Miranda may be a reaggregration of material from an earlier time when the moon was fractured by an violent impact.
The five large moons appear to be ice-rock conglomerates like the satellites of Saturn. Titania is marked by huge fault systems and canyons indicating some degree of geologic, probably tectonic, activity in its history. Ariel has the brightest and possibly youngest surface of all the Uranian moons and also appears to have undergone geologic activity that led to many fault valleys and what seem to be extensive flows of icy material. Little geologic activity has occurred on Umbriel or Oberon, judging by their old and dark surfaces.
All nine previously known rings were studied by the spacecraft and showed the Uranian rings to be distinctly different from those at Jupiter and Saturn. The ring system may be relatively young and did not form at the same time as Uranus. Particles that make up the rings may be remnants of a moon that was broken by a high-velocity impact or torn up by gravitational effects.
NEPTUNE When Voyager flew within 5,000 kilometers (3,000 miles) of Neptune on August 25, 1989, the planet was the most distant member of the solar system from the Sun. (Pluto once again will become most distant in 1999.)
Neptune orbits the Sun every 165 years. It is the smallest of our solar system’s gas giants. Neptune is now known to have eight moons, six of which were found by Voyager. The length of a Neptunian day has been determined to be 16 hours, 6.7 minutes.
Even though Neptune receives only three percent as much sunlight as Jupiter does, it is a dynamic planet and surprisingly showed several large, dark spots reminiscent of Jupiter’s hurricane-like storms. The largest spot, dubbed the Great Dark Spot, is about the size of Earth and is similar to the Great Red Spot on Jupiter. A small, irregularly shaped, eastward-moving cloud was observed “scooting” around Neptune every 16 hours or so; this “scooter,” as Voyager scientists called it, could be a cloud plume rising above a deeper cloud deck.
Long, bright clouds, similar to cirrus clouds on Earth, were seen high in Neptune’s atmosphere. At low northern latitudes, Voyager captured images of cloud streaks casting their shadows on cloud decks below.
The strongest winds on any planet were measured on Neptune. Most of the winds there blow westward, or opposite to the rotation of the planet. Near the Great Dark Spot, winds blow up to 2,000 kilometers (1,200 miles) an hour.
The magnetic field of Neptune, like that of Uranus, turned out to be highly tilted — 47 degrees from the rotation axis and offset at least 0.55 radii (about 13,500 kilometers or 8,500 miles) from the physical center. Comparing the magnetic fields of the two planets, scientists think the extreme orientation may be characteristic of flows in the interiors of both Uranus and Neptune — and not the result in Uranus’s case of that planet’s sideways orientation, or of any possible field reversals at either planet. Voyager’s studies of radio waves caused by the magnetic field revealed the length of a Neptunian day. The spacecraft also detected auroras, but much weaker than those on Earth and other planets.
Triton, the largest of the moons of Neptune, was shown to be not only the most intriguing satellite of the Neptunian system, but one of the most interesting in all the solar system. It shows evidence of a remarkable geologic history, and Voyager 2 images showed active geyser-like eruptions spewing invisible nitrogen gas and dark dust particles several kilometers into the tenuous atmosphere. Triton’s relatively high density and retrograde orbit offer strong evidence that Triton is not an original member of Neptune’s family but is a captured object. If that is the case, tidal heating could have melted Triton in its originally eccentric orbit, and the moon might even have been liquid for as long as one billion years after its capture by Neptune.
An extremely thin atmosphere extends about 800 kilometer (500 miles) above Triton’s surface. Nitrogen ice particles may form thin clouds a few kilometers above the surface. The atmospheric pressure at the surface is about 14 microbars, 1/70,000th the surface pressure on Earth. The surface temperature is about 38 kelvins (-391 degrees Fahrenheit) the coldest temperature of any body known in the solar system.
The new moons found at Neptune by Voyager are all small and remain close to Neptune’s equatorial plane. Names for the new moons were selected from mythology’s water deities by the International Astronomical Union, they are: Naiad, Thalassa, Despina, Galatea, Larissa, Proteus.
Voyager 2 solved many of the questions scientists had about Neptune’s rings. Searches for “ring arcs,” or partial rings, showed that Neptune’s rings actually are complete, but are so diffuse and the material in them so fine that they could not be fully resolved from Earth. From the outermost in, the rings have been designated Adams, Plateau, Le Verrier and Galle.
Jupiter’s giant red storm
Triton Neptune’s main moon
Neptune is the third most massive planet. Like the rest of the gas giants, Neptune has no definite surface layer. Instead, the gas transits into a slushy ice and water layer. The water-ammonia ocean serves as the planet’s mantle, and contains more than ten times the mass of Earth.
Earth and its moon pictured from space | 0.877209 | 3.993272 |
Last week, the New Horizons spacecraft went by Pluto, consummating a decade-long reconnaissance of our local cosmic backyard, yielding never-before-seen faces and features, and projecting an image of Pluto in our minds that is based in reality — an image that is of a geologically active world, rather than just a ball of frozen rock and ice.
One of the latest close-up images of Pluto reveals 3,500-metre-high icy mountains near the equator. Located in the darkened whale region and neighboring the lighter heart region, scientists believe that these mountain ranges are only a 100-million years old (quite young relative to a 4.56 billion year old planetary system), pointing to increasing speculation that geologic activity is still ongoing. The image reveals a lot of structures that are roughly 2 kilometres across. But remarkably enough and notwithstanding the fact that Pluto has been hit by objects in the Kuiper belt, a relatively large region of Pluto is crater-less, including the plains above which these mountain ranges lie. This is contrary to earlier predictions. According to scientists, Pluto has a mysterious heat source that is driving such geologic activity and mountain building and that is leading to crater-less plains by cobbling the surface with fresh material. The source of this energy is not decisively known yet. In fact, Pluto is not gravitationally captured by another giant planet that can provide tidal heating. Furthermore, Pluto and Charon are in tidal equilibrium and are both tidally locked so there are no mutual tidal forces to cause heating and power Pluto’s geologic activity. The geologic activity is essentially Pluto’s own. As such, it is being speculated that Pluto has radioactive elements in its underlying rock core ( which is about 60 percent of Pluto’s mass) that lead to the activity. Or, it could just be left-over reserve energy from Pluto’s formation (giant impact that lead to Charon). Another possible explanation is thawing and freezing subterranean oceans that store heat.
Another latest image reveals significant details of a vast, frozen crater-less plain in the center left of Pluto’s very remarkable heart-shaped region and located north of the icy mountain ranges. According to scientists, this is also a relatively young region, no more than a 100 million years old. The crater-less appearance is also indicative of recent and ongoing geologic activity that repaves the surface with fresh material. But, the surface appears to be broken into frozen cracks and irregularly-shaped polygon regions that are ringed by narrow, meandering troughs, some of which are interlaced with dark material. Clusters of small mounds and smooth hills are also visible, tracing the troughs. Pits are also visible, but probably made by erosion resulting from sublimation, rather than winds as on Earth. The irregularly shaped polygon-like structures could be indicative of convection between the carbon monoxide and the methane and nitrogen atmosphere on the surface and Pluto’s heat on the interior. It is possible that this is a Rayleigh-Benard convection — a type of convection which develops in a layer being heated from below and cooled from above. The upper boundary would be denser than the lower boundary, leading to an eventual convection pattern. Another possible explanation is thermal contraction (a process where cooling materials change dimensions as they cool) cracking those polygon structures onto the plains.
Analysis of the western half of the Pluto’s heart region by the New Horizon’s Ralph instrument reveals a large deposit of frozen Carbon Monoxide ice around the area, specifically in the region outlined in the figure below. The source of such a specific heightened concentration is so far unknown.
The New Horizons team was able to construct an atmospheric model of Pluto. It seems to be a predominately pure nitrogen atmosphere. But also methane further down in altitude. In addition, there’s hydrocarbon forming in the atmosphere that then falls off to cover the surface, giving Pluto its red colour. Findings by the New Horizons Solar Wind Around Pluto (SWAP) instrument also reveal that Pluto’s atmosphere is escaping away, leaving a nitorgen-packed tail of plasma, flowing away from the sun. The gas is being lost at a rate of 500 tonnes per hour. The plasma tail is indicative of solar winds ionizing the nitrogen and carrying it away. That is because Pluto’s gravity is quite weak — about one-fifth of Earth’s gravity. So, the atmospheric molecules are ionized by the solar ultraviolet light and have enough energy to billow away and escape Pluto’s weak gravity. The solar wind, which is a continuous supersonic outflow of gas from the sun’s corona, then picks up the ionized molecules past Pluto to form a plasma tail, indicated by blue in the diagram below.
Pluto’s Moon Charon
Pluto’s moon Charon appears to be surprisingly young and oddly enough, possesses a series of craters, a 6 km deep canyon at the upper right, cliffs, and troughs across it. The ranges of cliffs extend about 970 kilometres across Charon. This is all indicative of internal geologic activity. The largest crater lies at the south pole, at about about 97 kilometres across. Charon also harbors a dark region located near the north pole, at 320 kilometres across. Scientists have dubbed this dark spot “Mordor”. This region might have possibly arisen from material drifting off from Pluto’s atmosphere and onto Charon. But, it’s quite a mystery why Pluto and Charon are quite different indeed. Pluto is predominantly made up of icy water, while Charon harbors immense cliffs and canyons. It’s hypothesized that internal stresses inside Charon could be responsible for these remarkable fractures across Charon’s surface.
Pluto’s Smallest Moon Hydra
Small but still remarkable, the New Horizons team also obtained images of Pluto’s moon Hydra. Although a little grainy, the photo is still quite informative. It indicates that Hydra is a stompy, potato-looking thing and about 43 by 33 kilometres in size.
The New Horizons spacecraft has a size that’s comparable to a piano stuck to a satellite dish. It includes propulsion, navigation, communications systems, and payload. It has 16 thrusters for trajectory corrections and altitude control. It has star-tracking navigation cameras to determine the directions in which the spacecraft is pointed at and also the orientation of the instruments. They essentially capture images of stars in the field of view and compare them with an onboard map of 10,000 stars. Onboard are also sensors that detect the angle to the sun and the spin rate. New Horizons operates on a single radioisotope thermoelectric generator that uses pills of plutonium, and this is a very limited power source. In fact, New Horizons uses the same CPU as the PlayStation 1. It uses fairly high frequency radio waves (via the X band but not the KU-band) to reduce transmission times to Earth.
New Horizons Payload
a) The Long Range Reconnaissance Imager (LORRI): a high resolution imaging system, with an input aperture 21 cm wide. Exposure times are form 0 milliseconds to about 30,000 milliseconds in 1 millisecond intervals. The images can then be compounded together at a rate of 1 image per second.
b) The Pluto Exploration Remote Sensing Investigation (PERSI): consists of of two instruments: the Ralph and Alice. The Ralph camera combines anchromatic, color imaging, and Infra-red imaging spectroscopy techniques. It is the camera that gave us the currently famous red Pluto photo. There are 16 pixels in LORRI for every pixel in Ralph, but Ralph fills in the colour. The Alice instrument measures the composition and temperature of Pluto’s upper atmosphere, while also performing some atmospheric escape measurements.
c) The plasma and high energy particle spectrometer suite (PAM): PAM consists of two instruments: the SWAP (Solar Wind At Pluto) to measure solar wind velocity and density and The PEPSSI (Pluto Energetic Particle Spectrometer Science Investigation) to measure atmosphere escape rate by determining energy and composition of plasma around the spacecraft and the density of Pluto’s pick-up charged particles.
d) The Radio Science Experiment (REX): Instrument to measure Pluto’s radius, surface pressure, and temperature of lower atmosphere.
And the entire cost for this Pluto mission, 15 years in the making, is just 700 million dollars, far less than what people paid for the last Harry Potter movie, which grossed over 1.3 billion dollars.
Horizons of Discovery Ahead
I have no doubt that there will be a huge wave of discovery sweeping ahead in the times to follow! This fascinating little (or maybe large) world will open up new horizons and deliver a string of cosmic surprises over the next few years! After all, we have just received less than 2 % of the total 50 gigabytes that New Horizons has collected during its flyby. The transfer rate is only 2 kilobytes per second so there’s still a plethora of data to be sent down for the next 16 months. There are also plans by NASA to fly by two potential Kuiper belt targets, 4.8 billion kilometres away from Earth, in early 2019. But, it’s a tantalizing thought that this is the last new planet that we will be able to see in our lifetime. It’s indeed a once-in-a-lifetime opportunity. So let’s relish this moment for as much as we can!
Featured image courtesy of NASA: Most detailed image sent back to Earth before the flyby. Taken at 768,000 kilometres away. | 0.874838 | 3.883992 |
A cataclysmic collision not only created Earth’s moon, but may have also knocked Earth over on its side, scientists proposed.
In a paper published last week by the journal Nature, the scientists say their numerical simulations indicate that the collision of a Mars-size object with the early Earth left our planet tilted at an angle of 60 to 80 degrees and spinning rapidly, once every two and a half hours, or almost 10 times as fast as today.
But the simulations also show how the dynamics of the moon and Earth slowed down and straightened up over the next four billion years of the solar system, leaving them where they are today.
“For the first time, this paper has a model that says we can start in one place and explain all of that without invoking any other follow-on event,” said Sarah T. Stewart, a professor of earth and planetary sciences at the University of California, Davis. “And that’s new, and that’s exciting.”
“Where did the moon come from?” has been a persistent question over the eons. Among the rocky planets of the inner solar system, Earth is an anomaly. Mercury and Venus have no moons at all, and Mars has only a couple of potato-shape tiny moons (both less than 15 miles across) that may be captured asteroids.
Earth’s moon, by comparison, is a giant, more than 2,000 miles in diameter.
In recent years, the preferred explanation for the origin of the moon has been “the big whack”: very soon after the formation of Earth and the rest of the solar system, the Mars-size interloper that astronomers have named Theia bumped into Earth. The resulting slosh of debris coalesced into a slightly larger Earth and the moon in orbit around Earth.
The hypothesis explains a lot, in particular how to create a big moon. (Others have suggested that the moon formed elsewhere and was then captured by Earth’s gravity or that the two formed at the same time, in orbit around each other, but no one could calculate how these could plausibly occur.)
But there remained nagging discrepancies between the moon as it exists and the predictions of the big whack model. For one, the composition of the moon is very similar to that of Earth. Planetary scientists would have thought the moon would more closely resemble Theia.
In 2012, Dr. Stewart and Matija Cuk, then a postdoctoral researcher, proposed a variation, that Theia slammed into Earth at high speed, scrambling up the materials of the two bodies. The resulting Earth would also have been spinning fast, and they explained how the gravitational interactions with the sun would have then slowed everything.
“We changed the impactor,” Dr. Stewart said. “We changed the energy. We’re changing momentum. We’re changing the way the moon forms. We’re now changing the whole dynamical sequence. Everything is different except the words, ‘giant impact.’”
Dr. Stewart and Dr. Cuk said the revised calculations explained most everything about the moon.
But there was still a nagging discrepancy — a five-degree tilt of the moon’s orbit compared with the orbits of the planets and most everything else in the solar system. It’s what astronomers call the plane of the ecliptic.
The motion of moons and planets follow an orderly set of rules, Dr. Stewart said. “It makes very clean predictions, and when something goes against the orderly set of rules, it requires something special happening,” she said. “The clean prediction is the moon is in the ecliptic. Period. That’s where it should be.”
At its birth, the moon was quite close to Earth, probably within 20,000 miles. Because of the tidal pulls between Earth and moon, the moon’s orbit has been spiraling outward ever since, and as it does, Earth’s pull diminishes and the pull of the sun becomes more dominant.
By now, with the moon a quarter of a million miles from Earth, the sun’s gravity should have tipped the moon’s orbit to lie in the same plane as the ecliptic. Last year, two astronomers proposed that planetesimals perhaps as big as the moon itself buzzing through the inner solar system tipped the moon’s orbit through repeated close passes.
Dr. Cuk, now a scientist at the SETI Institute in Mountain View, Calif., came up with an alternate idea: Maybe the moon’s orbit is still tilted, because the Earth started off very tilted. The flexing of the Earth and the moon by the gravitational tidal forces dissipates energy, causing the moon to spiral outward. The dynamics can become complicated.
“The lunar spin axis does interesting things,” said Dr. Cuk, the lead author of the new Nature paper.
For example, tidal locking — where one side of the moon always faces Earth — is lost for a while before locking in again. It is possible that the far side of the moon was originally the near side.
Dr. Stewart said some of the transitions in orbits could have heated up the interior of the moon, and signs of that melting might be observable in rocks on the moon.
Alessandro Morbidelli, one of the astronomers who proposed the planetesimals hypothesis, said nothing was proved yet, and both models relied on assumptions. “Certainly it is an interesting model and it will trigger a lot of future work,” he said of the new paper. “I think that our model cannot be ruled out.” | 0.880696 | 3.930944 |
NASA probe nears unexplored dwarf planet Ceres
CAPE CANAVERAL, USA – A NASA science satellite on Friday, March 6, will wrap up a 7-1/2-year journey to Ceres, an unexplored dwarf planet in the main asteroid belt between Mars and Jupiter, scientists said on Monday, March 2.
The Dawn spacecraft visited the asteroid Vesta before firing its electric ion engine to continue on to Ceres, a round, 600-mile-wide (970 km-wide) mini-planet that is the largest body in the asteroid belt.
Earth's moon, by comparison, is about 2,160 miles (3,480 km) in diameter.
The solar-powered probe is expected to put itself into orbit around Ceres at 7:20 am EST (1220 GMT) on Friday. However, radio telescopes on Earth will not be in position to pick up Dawn's signal until later in the day, National Aeronautics and Space Administration officials said at a news conference.
"The approach has gone flawlessly so far," said Dawn Project Manager Robert Mase of NASA's Jet Propulsion Laboratory in Pasadena, California.
Scientists are eager for their first close-up look at a dwarf planet, believed to be a building block left over from the formation of the planets 4.6 billion years ago.
"They're literally fossils that we can investigate to understand the processes that were going on at that time," said Dawn scientist Carol Raymond, also with Jet Propulsion Laboratory.
Another NASA spacecraft, New Horizons, will fly by the distant dwarf planet Pluto in July. Pluto, once considered one of the planets of the solar system, was later downgraded to a dwarf planet.
Ceres, namesake of the Roman goddess of agriculture, is already providing intrigue. Pictures relayed from Dawn last month show bright streaks on its surface, including two very bright spots inside a crater.
"These spots were extremely surprising," Raymond said.
Scientists suspect Ceres may have had an underground ocean early in its history that later froze. Impacting asteroids or comets could then have exposed patches of highly reflective ice.
Europe's Herschel space-based telescope previously detected water vapor on Ceres, a clue that impacting bodies may periodically send plumes of watery material shooting into space.
"In the initial views of Ceres, we see many strange features: smooth areas, areas that chaotically fractured and craters of all shapes and sizes," Raymond said. "Of particular interest are the bright spots ... which stand out against Ceres' dark surface."
It will take Dawn about a month to position itself for 14 months of observations of Ceres. In all, the mission is costing NASA $473 million. – Rappler.com | 0.881382 | 3.172743 |
Gaia, ESA’s billion-star surveyor, is detecting stars and measuring their properties in order to build up the most precise 3D map of the Milky Way. By accurately measuring the motion of each star, astronomers will be able to peer back in time to understand the Milky Way’s history, its evolution and its destiny.
In general, as Gaia registers stars, only data covering the object of interest are transmitted to the ground. However, in the densest regions on the sky there are more stars close to each other than the detection and processing system of Gaia can cope with, which could result in a less complete census in these crowded areas.
To help mitigate this, a scientific selection of high-density regions is made to cover them in a special imaging mode, as illustrated here. These types of observations are carried out routinely every time Gaia scans over these regions.
The image, taken on 7 February 2017, covers part of the Sagittarius I Window (Sgr-I) located only two degrees below the Galactic Centre. Sgr-I has a relatively low amount of interstellar dust along the line of sight from Earth, giving a ‘window’ to stars close to the Galactic Centre.
The stellar density here is an incredible 4.6 million stars per square degree. The image covers about 0.6 square degrees, making it conceivable that there are some 2.8 million stars captured in this image sequence alone.
The image appears in strips, each representing a sky mapper CCD (see this animation of how Gaia’s camera works). The image has been lightly processed to bring out the contrast of the bright stars and darker traces of gas and dust. Zooming in reveals some imaging artifacts relating to the CCDs, including some vertical striping, as well as short bright streaks indicating cosmic rays. Analysis of these images will only start once the effort required by the routine data processing allows.
Gaia’s first catalogue of more than a billion stars, based on the first 14 months of data collection, was released in September 2016. The next release is targeting April 2018, with subsequent releases foreseen for 2020 and 2022. | 0.828696 | 3.623443 |
With the historic fly-by of Pluto last month, NASA’s New Horizons spacecraft gave us an up-close look at the former 9th planet, showing that it is a dynamic world with icy plains, tall mountains, and an atmosphere. But now that New Horizons has passed by Pluto, it has the infinite cosmic horizon in its stead. So what’s next for the $700 Million spacecraft? Its battery will keep it going for a few more decades, and it will likely pass beyond the edge of the solar system, in the stead of the Voyager crafts. What else is ahead?
The good news is that, as vast and empty as space is, there are a lot of small islands of rock. Most are icy bodies several kilometres across, most akin to comets than planets. But understanding the large population of what we call Kuiper Belt Objects (KBOs), gives us insights into the abundance of raw materials that were present 4.5 Billion years ago during the formation of the solar system. Understanding what was there can help us understand what life needs to develop, and what life on Earth used during its 3 Billion years of evolution.
The most promising of the icy rocks that happen to pass close to the trajectory of New Horizons is called 2014 MU69, an icy rock suspected to be about 50 kilometres wide. There were actually three candidate objects for New Horizons to target, but 2014 MU69 was chosen because there is a 100% chance of reaching it with the fuel that the spacecraft has left after the Pluto flyby.
The flyby won’t take place for another four years, in 2019, but it also depends on a mission extension that the New Horizons team will have to apply for next year. Presuming all goes well we should get an up close view of a KBO that we have never seen before. In the meantime, New Horizons continues to send back data from the Pluto flyby, and once analysed, we should see some new and interesting science yet to come from Pluto. | 0.867558 | 3.473487 |
mBot Solar System
Contributed By: Kayoe Stewart
Click here for a forum post that is associated with this classroom project. We would be happy to help you out with any questions you or your students may have.
mBot Solar System
Simulating the Planets using mBots
As a robotics and astronomy geek, I wanted to see if I could blend the two and use mBots to simulate how the planets in our solar system orbit around the sun. Astronomy is an amazing topic that typically intrigues students because of the wonder and mystery of space. The enthusiasm of the students sometimes makes it easier for teachers to introduce some of the concepts covered in this unit.
However, a big challenge in learning about space is that we cannot observe outer space firsthand. This aspect makes it difficult as a teacher to demonstrate aspects of our solar system, and beyond, in ways that the students can grasp and visualize.
One of the fundamentals in understanding our solar system is being able to visualize the relative positions and orbits of the planets. The sheer scale of the solar system makes it challenging to fully comprehend where these objects exist relative to each other. We typically rely on models to help our students understand this relationship. A quick example of one of these models is the standard set up in the gym or outside with some balls of different sizes to represent the planets and string to measure distances. This model is relatively easy to set up but it can be hard to demonstrate how these solar system bodies then move in relation to each other. I thought 'why not use robots to help take this to the next level? The mBot allows me to calculate exactly how the planets move around the Sun. More importantly though, I can simulate how each planet moves compared to the other planets. Plus, I can automate it all so that everything happens with the push of a button.
We fell in love with this little robot a long time ago because of its low cost and high versatility. Because it uses scratch language (something that many students are already familiar with) it is relatively easy to just jump into the world of robotics with these little guys.
Whenever I start to work with a new device or platform I first try to figure out two things, what I call the "floor" and the "ceiling". To do this, I ask the following questions:
How much time do you need to spend playing in order to familiarize yourself with the device and get started?
This is the floor. Something that is intuitive and easy to figure out has a low floor. As the amount of time needed initially and the challenge in getting started goes up so does the floor.
How versatile is the equipment and how far can you take it?
This is the ceiling. Something that is very versatile has a high ceiling meaning that there is a lot of room to grow.
The mBot is very easy to just jump into so it has a very low floor. At the same time its versatility gives it a high ceiling meaning it isn't just a one trick pony and can be used to explore much more complicated aspects of coding and engineering.
We have already professed our affection for these robots in an earlier post titled Mastering the mBot by Makeblock. If you are new to the game please click the link to learn about how to start using the mBot. In this post we will be starting to test the limits to how much you can do with these robots and attempt to address other aspects of the science curriculum.
As we have said in previous posts, the mBots have many curriculum connections. So many that it would take forever to mention them all. The versatility of these innovative robots results in many different applications with tie-ins to many subjects. We have already talked about how these robots can be used to explore music, language arts, science, mathematics and much more. In using mBots for something as specific as modelling the solar system we can start to refine our focus on specific units and outcomes in the science and math curriculum.
Grade 6 Space
205-2 select and use tools in manipulating materials and in building models
104-8 demonstrate the importance of using the languages of science and technology to compare and communicate ideas, processes, and results
300-23 describe the physical characteristics of components of the solar system—specifically, the sun, planets, moons, comets, asteroids, and meteors
105-1 identify examples of scientific questions and technological problems that are currently being studied
205-8 identify and use a variety of sources and technologies to gather pertinent information
Grade 9 Space
312-4 describe and explain the apparent motion of celestial bodies
209-4 organize data, using a format that is appropriate to the task or experiment
Grade 10 Motion
116-7 analyse natural and technological systems to interpret and explain their structure and dynamics
213-3 use instruments for collecting data effectively and accurately
214-8 evaluate the relevance, reliability, and adequacy of data and data collection methods
325-1 Describe quantitatively the relationship among displacement, time, and velocity
Grade 7 Mathematics
GCO: Shape & Space (SS): Use direct and indirect measurement to solve problems
SCO: SS1: Demonstrate an understanding of circles by: • describing the relationships among radius, diameter and circumference of circles • relating circumference to pi • determining the sum of the central angles • constructing circles with a given radius or diameter • solving problems involving the radii, diameters and circumferences of circles
Eight planets is a lot to begin with. So to make things more achievable I started with the four innermost planets (Mercury, Venus, Earth and Mars). The first step in this process was to do some research to determine the following for EACH of the four rock planets:
– Distance from the Sun
– The total distance travelled in one orbit around the Sun
– The amount of time in days it takes to orbit the Sun
These numbers are used to calculate two very important variables, the speed that each planet travels through space (their velocity) and the path that they each travel through space (their trajectory). In my research, I found a handy table from Northwestern University that breaks down these numbers for all eight planets in our solar system (http://www.qrg.northwestern.edu/projects/vss/docs/space-environment/3-orbital-lengths-distances.html). In building the code I made sure that it was easy to input these three variables so that most of the code could be left untouched (ie. each time I wanted to adjust the code for the different planets I only had to change these numbers).
Here are links to the programs for the four innermost planets, a blank program if you want to input the values yourself as well as a screenshot of the code for planet Earth.
You can see that this program is divided into two sections. The bottom section is where we input our variables that will help us calculate the numbers we need. Using the table linked above, we see that the Earth orbits at 93 million miles from the Sun, the total distance it travels in a year is 534 million miles and it takes 12 months (or 365 days) to do this. The mBots can't handle large numbers in the millions so I moved the decimal place for these distances to the left four places. If you look closely you can see that I defined DistanceFromSun as 9300, DistanceTraveled as 58400 and AmountOfTime as 365 days. By moving the decimal to the right we are working with smaller distances but this is fine because we are only comparing how these planets move relative to each other and these numbers are still proportionally appropriate. In other words, as long as we adjust all of the distances in the same way our results will still work.
Orbit (calculating the differential)
To begin to direct an mBot we first have to understand how it moves across a surface. An mBot is what we call a differential robot. This means that the two motors can move independently and at different speeds. This differential allows the robot to turn with precision and even pivot. The first step with this is to measure the distance between the two wheels. This will help us compensate for the width of the robot. I measured this to be 130cm. To help calculate how the two wheels operate relative to each other I had to determine what my differential is.
The formula for this is: 1 minus the width between wheels divided by Distance from the Sun, or in the case of planet Earth 1 - 130 / 9300 (0.01) = 0.99. This number is very close to 1.0 which would mean that the robot is not going to turn very much, if at all. To help improve the orbits of all the planets, I added a correction factor of two to my calculations which brought the differential down to 0.97. This number will be used later on when we want to tell our two motors how fast to turn in order to drive in a circle.
Time (calculating the velocity of the planets)
For anyone who is familiar with how to calculate the velocity of an object you know that you really only need two factors, distance and time (V=d/t). We have both of these numbers from our research which makes it easy to run this calculation (Velocity of Earth in millions of miles per day = 58400 / 365 = 160).
Making the Robot Move
Now that all of the numbers are calculated we can start determining how fast the mBot's motors should be moving to both maintain the appropriate distance from the centre (the sun) and move at the proper speed. To help with this I created a variable called TurnRight. This variable is defined in the upper section of the code.
If we go back to the concept of differential motors we know that we can easily program our robot to drive in a circle by making one motor go faster than the other. In this case we are setting the velocity of our M1 motor to the full value of the variable we have defined as Speed (VM1 = 160). To make the Earth robot turn I have set the M2 motor velocity to be dependent on the differential or orbit (VM2 = Speed / Differential or 160 / 0.97 = 155).
Turning it on and off
Finally, I wanted to be able to turn this program on and off so that it wasn't running when I didn't want it to. I used the light sensor on the top of the robot as an on switch and programmed the robot to wait until I covered the light sensor with my finger to start. I also used the ultrasonic sensors in the front of the robot as the off switch. This way if I placed my hand in front of the robot it would stop the program.
The Activity (suggestions for delivery and assessment)
The benefits of such an activity are that it applies to a number of different subjects at a number of different grade levels. Where and how far you take this is completely up to you and how you feel it fits in your classroom. Whatever grade level you are teaching or whatever unit you are on it is important to start by going over the code so that the students understand (at least at a certain level) the inner workings of the program.
In grade six students are encouraged to use solar system models to help simulate the movement of the planets. Again, this is sometimes challenging because it is hard to visualize the orbits without a more complex model. The advantage of using the mBot model is that we can focus more on the relative motion of the planets compared to each other and not just on their relative distances from the sun. This leads to a more realistic and complete simulation of the planetary orbits and better comprehension.
As a starting point to this unit, grade six classes are also encouraged to create wall charts and tables listing the various bodies and their key characteristics. This model can be an excellent application of such information as the students can take the data they have researched such as orbit lengths and use it in the simulation.
In grade nine the students are required to better understand the apparent motion of celestial bodies. Again, they are to demonstrate this though models but in this upper grade they are now not only exploring the rotation of these objects but their revolution (orbit around the sun).
If you are using this activity in either grade six or nine I would recommend that the students first run the program for Mercury to see just how the robot and the code works. This initial introduction gives you and your class an opportunity to dissect the code in order to better understand it's bits and pieces. I have included programs for all four planets but, if time allows, I would suggest using the blank program also provided and challenge the students to input the necessary values that they researched on their own. Based on these values, students can predict the path of each "planet". This can be done either relative to the other orbits or numerically based on their observations of Mercury's orbit. After formulating predictions they can then experiment by running the code. Keep in mind that Mercury will need roughly 11 feet of space which means that when it's time to move on to the other planets you will need to move to a larger area like the gymnasium.
Because it's kind of hard to imagine tiny robots as massive, round bodies orbiting in space, I used balloons to represent the planets. Balloons were a fun and easy choice because I was able to match the true colour of the planets and inflate them to the proper relative size. Because balloons are nice and light, it was easy to stick them to the robots with a bit of tape and not have to worry about them interfering with the simulation. Challenge your students to get creative and use many types of recyclables (as long as they're not too heavy) to build models of the four rock planets that can be attached to their robots. As an educator, assess content knowledge because, in order to accurately represent the planets, you have to know a thing or two about what they look like (size, colours, composition, atmosphere etc.).
If your school is lucky enough to have four mBots, each robot can be programmed as a different planet to run at the same time. This is ideal and makes it easy for your students to observe the timing of all four orbits. Using tools such as stopwatches, they can be challenged to record the time it takes for each of the "planets" to revolve a certain number of times. If you only have one mBot at your school the students can still tackle the same challenge but by running one robot (and one program) at a time. In both of these cases the students will be able to compare each robot’s orbit to the actual orbits of the planets. For example, Mercury only takes three months to make one trip around the Sun which is one quarter of the time it takes the Earth. If we have done our calculations and research correctly we should our robots mirror this. Following this you can challenge them to represent their results pictorially or graphically to help summarize the information.
If you are incorporating this activity in your grade 10 motion unit you can focus more on the formulas used to calculate the speed or velocity of each planet. Even though the numbers used in this simulation are not necessarily the actual measurements for distances (due to us adjusting the decimal place), the relationship between the four robots is bang on compared to the relative velocities of the four planets. As an added experiment, students can calculate the actual velocities of the planets using the real numbers for each. They can then compare these velocities to the velocities they are generating in their program. Again, if we are using the correct values, the numbers generated by our program should mirror the actual velocities of the planets.
This activity also has a number of connections to the math curriculum in middle school. The obvious tie-in is to the grade seven classroom where the students have to demonstrate an understanding of circle geometry. This includes knowing the relationship between a circle's radius, diameter and circumference. This activity is an excellent application of these concepts and makes for a perfect opportunity to assess comprehension of these relationships.
Extensions and Modifications
We have only simulated the orbits of the four innermost planets. If time allows, and you want to take this activity a bit further, your students can work together in figuring out the key measurements for the four gas giants. In our original design of this model Mars' orbit has a diameter of just under 60 feet. Therefore, in order to expand this to the outermost planets you will have to make some adjustments to the code so that the orbits for the rock planets are proportionally smaller. When I expanded to include the gas giants I had to do the following:
- move the decimal for my distances one more place to the left (e.g. 9300 to 930 for Earth's distance from the Sun)
- changed Time from days to months (365 to 12 for Earth)
The grades six and nine curriculums also require an understanding of the relative motion of the Moon around the Earth. As an added challenge, students can extend this activity and attempt to simulate the movement of the Moon with their mBots. To do this, students would simply have to research these key values for the Moon and have the program calculate the rest for them. This can even be carried over to the lunar systems of other planets such as Jupiter and Saturn that have multiple major moons.
As awesome as the mBot is, not everyone has one. Because of this, I also created a LEGO Mindstorms EV3 project that does the same thing. If you only have access to LEGO kits here is a link to the Mindstorms project which includes programs for all four rock planets.
One important piece of this activity is making sure that you are allowing for enough space for the robots. In running the program for Mercury you only need to allow for a diameter of roughly 11 feet (small enough for a classroom). However, when you run the program for Mars you are looking at about 55 to 60 feet of floor space. With this in mind, you will need a large space like the gymnasium to do the entire simulation. With Mercury only needing 11 feet of space though, you can start in the classroom before moving to the gym. Spending the first bit of this activity in the classroom will give you some focused time to dissect the code and better understand how everything works. Running the simulation for Mercury in the classroom also can lead to discussions on what differences you may see with the other three programs. Students can measure the diameter and radius for Mercury and make predictions for the other planets (based on their research). At the same time, they can predict the timing for the remaining three planetary orbits based on the time it takes Mercury to complete one circle. This time in the classroom can also be used to prepare the other robots and get ready for the larger simulation.
One of the most noticeable drawbacks of the mBot is that the wheels sometimes do not have consistent traction. A combination of a lightweight robot, motors that can sometimes be temperamental and low batteries all can lead to issues with the accuracy of your program. In this case, I always made sure I was using fully charged batteries and that none of my motors were loose. This helped me make sure that the robots weren't going off course too much. Even with doing this though, I still noticed some deviation with the robots at times. It is important to mention this to your students to prepare them for any minor differences. It would also be worth your while to have some back up batteries and tools on hand so that you can make corrections on the fly.
Our hope is that as teachers incorporate this activity in their classroom they consider how to really make it their own. I have presented it in such a way that anyone can incorporate it easily into their classroom but we have also left it open for improvements and adjustments. We would love to hear from you and your progress on implementing this activity in your classroom. In addition to this, if you have gone so far as to make modifications, add on extensions, or even connect it to another part of the curriculum we would love for you to share.
Kayoe is a lover of all things STEM. He has been working in science education for 16 years with the past 10 of those years being at Science East heading their robotics and coding programs. Recently, through a partnership with Brilliant Labs, he has been working on building content and capacity for both organizations. | 0.872074 | 3.082935 |
A few evenings ago, a small group of friends came to my house to watch the Geminidsmeteor shower. We put a lot of effort into preparing our for the experience by chopping down trees which obscured the view, stocking up on charcoal and meat for the braai, setting out comfortable garden chairs and inviting the right people. By all accounts, the shower exceeded the most optimistic predictions and would have been a marvellous show had we not been clouded out. What was to be an edifying evening of astronomy turned into a pleasant social gathering.
Had the weather cooperated, though, what would we have seen? First of all, the Geminids are pretty average meteors. If you’ve ever seen a shooting star flit across the sky like a faint spark of light, then you have an idea of what the average Geminid looks like (Other showers are predominantly very slow bright meteors, others are dense swarms. Each is unique). The best reports showed in excess of 140 meteors per hour, which means that in a single minute of viewing you could expect to see at least two meteors.
If you watched the shower for long enough, you would begin top notice a pattern: They all seem to come from the same point in the sky – near one of the fainter stars of the constellation Gemini, in this case, which is why this shower is called the Geminids. Now this is only an illusion – they are all travelling in straight lines parallel to each other. In reality, the earth is ploughing through a region of space where these meteoroids (debris left behind from an extinct comet) are present, and it’s only an effect of perspective that makes them appear to radiate out from that point. | 0.888188 | 3.229677 |
A graveyard orbit, also called a junk orbit or disposal orbit, is an orbit that lies away from common operational orbits. One significant graveyard orbit is a supersynchronous orbit well above geosynchronous orbit. Satellites are typically moved into such orbits at the end of their operational life to reduce the probability of colliding with operational spacecraft and generating space debris.
A graveyard orbit is used when the change in velocity required to perform a de-orbit maneuver is too large. De-orbiting a geostationary satellite requires a delta-v of about 1,500 metres per second (4,900 ft/s), whereas re-orbiting it to a graveyard orbit only requires about 11 metres per second (36 ft/s).
For satellites in geostationary orbit and geosynchronous orbits, the graveyard orbit is a few hundred kilometers above the operational orbit. The transfer to a graveyard orbit above geostationary orbit requires the same amount of fuel as a satellite needs for about three months of stationkeeping. It also requires a reliable attitude control during the transfer maneuver. While most satellite operators try to perform such a maneuver at the end of their satellites' operational lives, through 2005 only about one-third succeeded. However, as of 2011, most recently decommissioned geosynchronous spacecraft were said to have been moved to a graveyard orbit.
where is the solar radiation pressure coefficient and is the aspect area [m²] to mass [kg] ratio of the satellite. This formula includes about 200 km for the GEO-protected zone to also permit orbit maneuvers in GEO without interference with the graveyard orbit. Another 35 kilometres (22 mi) of tolerance must be allowed for the effects of gravitational perturbations (primarily solar and lunar). The remaining part of the equation considers the effects of the solar radiation pressure, which depends on the physical parameters of the satellite.
In order to obtain a license to provide telecommunications services in the United States, the Federal Communications Commission (FCC) requires all geostationary satellites launched after March 18, 2002, to commit to moving to a graveyard orbit at the end of their operational life. U.S. government regulations require a boost, , of about 300 km.
A spacecraft moved to a graveyard orbit will typically be passivated.
Uncontrolled objects in a near geostationary [Earth] orbit (GEO) exhibit a 53-year cycle of orbital inclination due to the interaction of the Earth's tilt with the lunar orbit. The orbital inclination varies ± 7.4°, at up to 0.8°pa.:3
While the standard geosynchronous satellite graveyard orbit results in an expected orbital lifetime of millions of years, the increasing number of satellites, the launch of microsatellites, and the FCC approval of large megaconstellations of thousands of satellites for launch by 2022 necessitates new approaches for deorbiting to assure earlier removal of the objects once they have reached end-of-life. Contrary to GEO graveyard orbits requiring three months' worth of fuel, large satellite networks require orbits that passively decay into the Earth's atmosphere. For example, both OneWeb and SpaceX have committed to the FCC regulatory authorities that decommissioned satellites will decay to a lower orbit — a disposal orbit—where the satellite orbital altitude would decay due to atmospheric drag and then naturally reenter the atmosphere and burn up within one year of end-of-life.
- List of orbits
- SNAP-10A – nuclear reactor satellite, remaining in a 700-nautical-mile (1,300 km; 810 mi) sub-synchronous Earth orbit for an expected 4,000 years
- Spacecraft cemetery, in the Pacific Ocean
- Orbital periods and speeds are calculated using the relations 4π2R3 = T2GM and V2R = GM, where R = radius of orbit in metres, T = orbital period in seconds, V = orbital speed in m/s, G = gravitational constant ≈ 6.673×10−11 Nm2/kg2, M = mass of Earth ≈ 5.98×1024 kg.
- Approximately 8.6 times (in radius and length) when the moon is nearest (363 104 km ÷ 42 164 km) to 9.6 times when the moon is farthest (405 696 km ÷ 42 164 km).
- "Method for re-orbiting a dual-mode propulsion geostationary spacecraft – Patent # 5651515 – PatentGenius". Archived from the original on 2013-11-10. Retrieved 2012-10-28.
- "ESA - Space debris mitigation: the case for a code of conduct". www.esa.int.
- Johnson, Nicholas (2011-12-05). Livingston, David (ed.). "Broadcast 1666 (Special Edition) – Topic: Space debris issues" (podcast). The Space Show. 1:03:05-1:06:20. Retrieved 2015-01-05.
- "Archived copy" (PDF). Archived from the original (PDF) on 2015-04-02. Retrieved 2015-03-07.CS1 maint: archived copy as title (link)
- "FCC Enters Orbital Debris Debate". Archived from the original on March 8, 2005.
- "US Government Orbital Debris Standard Practices" (PDF).
- Anderson, Paul; et al. (2015). Operational Considerations of GEO Debris Synchronization Dynamics (PDF). 66th International Astronautical Congress. Jerusalem, Israel. IAC-15,A6,7,3,x27478.
- Brodkin, Jon (4 October 2017). "SpaceX and OneWeb broadband satellites raise fears about space debris". Ars Technica. Retrieved 28 April 2019. | 0.813187 | 3.623696 |
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At last, on July 1, 2004, the Cassini spacecraft fired off its breaking rocket, glided into orbit around Saturn, and started taking pictures that left scientists in awe. It wasn't as if they hadn't been prepared for such wonders. The weeks leading up to Cassini's arrival at Saturn had served to intensify their already heated anticipation. It seemed as if each approach-picture taken was more enticing than the one preceding it.
The discovery of a moon for Makemake may have solved one perplexing puzzle concerning this distant, icy object. Earlier infrared studies of the dwarf planet showed that while Makemake's surface is almost entirely frozen and bright, some areas seem to be warmer than other areas. Astronomers had suggested that this discrepancy may be the result of our Sun warming certain dark patches on Makemake's surface. However, unless Makemake is in a special orientation, these mysterious dark patches should cause the ice dwarf's brightness to vary substantially as it rotates. But this amount of variability has not been observed.
For those craters smaller than 30 kilometers in diameter, he discovered impacts both increased and decreased porosity in the upper layer of the lunar crust.
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Why hide these accomplishments? It has been difficult to argue for a conspiracy because no theory has offered a sufficiently convincing motive. An idea called "the frontier theory of history" provides two.
This does not mean that soul mates must always have strong lunar contact in their birth charts. The compatibility between Moon signs is another important factor. Each of the 24 possible combinations (for example, his Leo Moon combined with your Aquarius Moon, or your Virgo Moon combined with his Sagittarius Moon) presents its own emotional chemistry. It's certainly true that compatibility can take many forms. Nevertheless, in determining whether two people are a perfect match, the Moon is one of the first places any good astrologer will look. Beyond just a physical or intellectual attraction, lunar energy signifies a deep and psychic bond between lovers.
Most of the moons of our Solar System are intriguing, frigid, and dimly lit ice-worlds in orbit around the quartet of outer, majestic, gaseous giant planets that circle our Star, the Sun, from a great distance. In our quest for the Holy Grail of discovering life beyond our Earth, some of these icy moons are considered to be the most likely worlds, within our own Solar System, to host life. This is because they are thought to hide oceans of life-sustaining liquid water beneath their alien shells of ice--and life as we know it requires liquid water to emerge, evolve, and flourish. In April 2017, a team of planetary scientists announced that they have discovered the presence of hydrogen gas in a plume of material erupting from Enceladus, a mid-sized moon of the ringed, gas-giant planet Saturn, indicating that microbes may exist within the global ocean swirling beneath the cracked icy shell of this distant small world. Currently, two veteran NASA missions are providing new and intriguing details about the icy, ocean-bearing moons of the gas-giant planets, Jupiter and Saturn, further heightening scientific fascination with these and other "ocean worlds" in our Solar System--and beyond. | 0.873323 | 3.268486 |
June 30, 2015 – The infrared spectrometer on NASA’s Pluto-bound New Horizons spacecraft has detected frozen methane on Pluto’s surface, which is not surprising because Earth-based astronomers first observed the chemical compound on Pluto in 1976.
“We already knew there was methane on Pluto, but these are our first detections,” said Will Grundy, the New Horizons Surface Composition team leader with the Lowell Observatory in Flagstaff, Arizona. “Soon we will know if there are differences in the presence of methane ice from one part of Pluto to another.”
Methane (chemical formula CH4) is an odorless, colorless gas that is present underground and in the atmosphere on Earth. On Pluto, methane may be primordial, inherited from the solar nebula from which the solar system formed 4.5 billion years ago. Methane was originally detected on Pluto’s surface by a team of ground-based astronomers led by New Horizons team member Dale Cruikshank, of NASA’s Ames Research Center, Mountain View, California.
The instrument known as Ralph, a “Honeymooners” reference that classic TV fans can appreciate, was built by Ball Aerospace in Boulder, Colorado.
Come Fly with New Horizons on its Approach to Pluto
Images from New Horizons show the view from aboard the spacecraft closes in on the Pluto system for a July 14 flyby.
This time-lapse approach movie was made from images from the Long Range Reconnaissance Imager (LORRI) camera aboard New Horizons spacecraft taken between May 28 and June 25, 2015. During that time the spacecraft distance to Pluto decreased almost threefold, from about 35 million miles to 14 million miles (56 million kilometers to 22 million kilometers). The images show Pluto and its largest moon, Charon, growing in apparent size as New Horizons closes in. As it rotates, Pluto displays a strongly contrasting surface dominated by a bright northern hemisphere, with a discontinuous band of darker material running along the equator. Charon has a dark polar region, and there are indications of brightness variations at lower latitudes.
This movie, from New Horizons’ highest-resolution imager, shows Pluto and Charon as the spacecraft closes in. In the annotated version, Pluto’s prime meridian (the region of the planet that faces Charon) is shown in yellow and the equator is shown in pink. Credits: NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute
“Alice” Instrument Practices for Sunset and Sunrise Observations of Pluto’s Atmosphere
The New Horizons spacecraft has made a critical observation in preparation for its upcoming observations of Pluto’s tenuous atmosphere. Just hours after its flyby of Pluto on July 14, the spacecraft will observe sunlight passing through the planet’s atmosphere, to help scientists determine the atmosphere’s composition.
“It will be as if Pluto were illuminated from behind by a trillion-watt light bulb,” said Randy Gladstone, a New Horizons scientist from Southwest Research Institute, San Antonio.
On June 16, New Horizons’ Alice ultraviolet imaging spectrograph successfully performed a test observation of the sun from 3.1 billion miles away (5 billion kilometers), which will be used to interpret the July 14 observations.
New Horizons is now less than 11 million miles (18 million kilometers) from the Pluto system. The spacecraft is healthy and all systems are operating normally.
The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, designed, built, and operates the New Horizons spacecraft, and manages the mission for NASA’s Science Mission Directorate. The Southwest Research Institute leads the science team, payload operations and encounter science planning. New Horizons is part of the New Frontiers Program managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. | 0.826836 | 3.755015 |
Dubai: While much has been reported of recent explorations to Mars and the Moon, a joint European-Japanese mission has just completed a crucial manoeuvre on its journey to Mercury – swinging past Earth.
The spacecraft, BepiColombo, on a mission launched in October 2018, is trying to achieve an orbit around the innermost planet, a task which will require a seven-year trajectory, Space.com reported. The spacecraft came 12,963km away from Earth on Friday, approaching at an angle designed to slightly reduce its speed with respect to the sun. That adjustment will allow BepiColombo to head deeper into the solar system, the website said.
The mission needs to make sure it isn't travelling too fast when it arrives at Mercury in 2025 or it won't be able to go into orbit around the diminutive world, BBC reported.
"It would be so nice if we could take an express transfer and then we'd be there in a few months, but that doesn't work for this mission," Elsa Montagnon, the flight controller in charge of BepiColombo at the European Space Agency (Esa), told BBC News.
Apart from this flyby of Earth, the spacecraft needs to execute eight other manoeuvres – two at Venus and six at Mercury between 2021 and 2025 before the planet’s gravity traps the probe in December 2025.
What will BepiColombo do on Mercury?
Once BepiColombo arrives on Mercury, it will split into two constituent spacecraft. The first probe will orbit relatively high above Mercury's surface and focus on studying the magnetosphere, the region of space governed by the planet’s magnetic field
The second BepiColombo probe will approach closer to Mercury's surface and will focus on analysing the planet's composition. Scientists hope this work will help them understand how Mercury - and, in turn, the entire solar system - formed.
It is hoped the parallel observations can finally resolve the many puzzles about the hot little world. One of the key ones concerns the object's oversized iron core, which represents 60 per cent of Mercury's mass. Science cannot yet explain why the planet only has a thin layer of rocks, BBC reported.
Have there been other attempts to study Mercury?
This is only the third mission to study Mercury up close, a difficult task given its proximity to the sun. Nasa’s Mariner10 spacecraft flew past the tiny world three times in the 1970s, while Nasa’s Messenger spacecraft orbited Mercury from 2011 to 2015.
How much will it cost?
The mission which was launched in October 2018 costs around 3 billion euros (Dh11.9 billion). | 0.81494 | 3.168128 |
A black hole is a region of space-time that experiences such strong gravitational effects that nothing can escape it, not even light… hence it is a black hole! So, what is space-time? Space-time was a conceptual tool that emerged from Einstein’s General Theory of Relativity (in 1905) to describe the strong gravity regime. It links the three dimensions of space with time to make a four-dimensional space-time continuum. Space-time is often portrayed as a warped coordinate system that is distorted by the presence of mass (think of a snooker ball (mass) being placed on a bedsheet (curvature of space-time), see this great demo).
When the mass is large enough (e.g. stars merging or galaxies colliding) relativity predicts that space-time is warped so much, black holes can be formed. The edge of a black hole, beyond which nothing can return, is called the event horizon. This "point of no return" in a black hole is defined by the Schwarzschild radius (Rs) and is equal to 2GM/c^2 (G = gravitational constant, M = mass of black hole). And whats at the centre of a black hole? Current theory points towards it being a singularity (a point of infinite density), but no one can be sure (for now?); nothing can be sent inside to check and (more importantly!) retrieved to shed light on the issue.
So is the famous picture showing us the edge of the event horizon, or something else?! Well, it’s not the event horizon. So what is it...
The area surrounding a black hole is a rather apocalyptic zone. It is occupied by dust and gas, millions of degrees hot, that is orbiting at a fraction of the speed of light. This is known as the accretion disc and is a flat disc of matter surrounding the black hole. Images of the black hole over time has led scientists to state that the matter in the accretion disc is orbiting clockwise, and completes an orbit every two days.
The innermost stable circular orbit of matter is actually at 3Rs, within that all matter plummets towards the black hole never to be seen again. Light, however, has no mass and can orbit closer. Nonetheless, even light can have momentum and is affected by the warping of the space-time continuum. You may have heard of gravitational lensing? This is when light is ‘bent’ around a large mass, such that even if a galaxy is exactly behind a closer galaxy we would still be able to see the further galaxy (albeit possibly distorted) since light from the distant galaxy can be bent around the closer galaxy, like a lens. Lensing is a great example of the bending of light due to the warping of spacetime by a heavy mass. Here is a great example of gravitational lensing in a recent APOD picture:
Another thing to think about: what plane or tilt is the accretion disc relative to how we are looking at it? If we see the accretion disc flat-on, then we wont see much distortion of the light from the accretion disc itself. However, if the accretion disc is at any other tilt angle (i.e. such that part of the accretion disc is behind the black hole) then it’s light will be warped above and below the black hole. In this case, we will see the type of black hole shown in the Interstellar movie (below) where the accretion disc is side-on, and the light you see above and below the black hole is actually the light from the accretion disc going over-round-and-under the black hole as well as under-round-and-over the black hole. Confusing, I know! It really changes the way we think about light and space; and all dreamt in the inner recesses of the brains of very clever people over 100 years ago. Brilliant.
So, what does the iconic first black hole image actually show us?!? The black circle you see in the centre is not the event horizon; it is the blurry radius beyond which we begin to see light. Surrounding that we see light from the accretion disc which (at this resolution), seems to be relatively flat-on (i.e. not like the Interstellar black hole image).
Well there you have it. A black-hole, imaged, in our lifetime. An awesome achievement of ingenuity. A milestone reached. Next stop (and hopefully very soon): An image of the black hole at the centre of our very own Milky Way… stay tuned. | 0.867448 | 4.04988 |
NASA’s Chandra X-Ray Observatory snapped this image of the aftermath of a thermonuclear explosion of a white dwarf star. It’s beautiful, right? According to NASA, it’s the result of a type Ia supernova, involving more than one star in close proximity to amplify the scale of the blast.
G299 was left over by a particular class of supernovas called Type Ia. Astronomers think that a Type Ia supernova is a thermonuclear explosion — involving the fusion of elements and release of vast amounts of energy − of a white dwarf star in a tight orbit with a companion star. If the white dwarf’s partner is a typical, Sun-like star, the white dwarf can become unstable and explode as it draws material from its companion. Alternatively, the white dwarf is in orbit with another white dwarf, the two may merge and can trigger an explosion.
Regardless of their triggering mechanism, Type Ia supernovas have long been known to be uniform in their extreme brightness, usually outshining the entire galaxy where they are found. This is important because scientists use these objects as cosmic mileposts, allowing them to accurately measure the distances of galaxies billions of light years away, and to determine the rate of expansion of the Universe.
Sometimes space is just “woah.” [NASA] | 0.914847 | 3.350122 |
For the generations of Americans who grew up watching "Star Trek" and "Star Wars," it's almost impossible to react to the loss of the space shuttle Columbia as some of our parents and grandparents might have, shaking their heads in sorrowful exasperation: those brave young men and women had no business up there in the first place. Homer Hickam's sweet memoir, Rocket Boys, captures the transition vividly. If you grew up watching satellites in the night sky and humans rocketing into space, doubts don't register. Space is the final frontier.
For the Columbia astronauts, that turned out to be grimly true. But in their lives, and less impressively in our own, Captain Kirk's mantra expresses a heartfelt assumption. Of course space is the final frontier, which mankind, perhaps alongside Vulcans, Wookies, and other rational species, will explore and occupy. A future, however distant, without the Galactic Republic or the United Federation of Planets would be not only a disappointment but a surprise.
But why, exactly? The urge to explore space ("conquer" has fallen out of favor) is usually justified as a scientific imperative. In its cruder version, the argument is that the space program creates "spinoffs." There are many of these—not including, by the way, the products most associated with astronauts, Tang, Velcro, and Teflon, which the Los Angeles Times notes were all developed independently of the space effort. Although NASA's list of spinoffs is long, it's a little deflating to find on it, alongside CAT scans, such breakthroughs as smoke detectors and cordless drills.
So its advocates typically offer a second scientific argument for America's space program. This might be called the "pure theory of space exploration": forget utility, it's all for the sake of knowledge. We have to explore the universe in order to satisfy our desire, as a species, to know. There is a certain nobility to this argument, but it shoots too high and begs too many questions. As a species, after all, we're ignorant of many things. Why is it more important to probe the vastness of space rather than the ocean depths? For that matter, why astrophysics and not metaphysics? Thus the idealism of this appeal often collapses back into the materialist logic of spinoffs: the knowledge that comes from exploring space will relieve man's estate more reliably than oceanography, let alone fruitless metaphysics.
Modern science's idealism is elusive; in its own way, utopian. It can't help trying to turn the earth into a paradise…unless instead it tries to lift man off the earth and into paradise. The latter is a revealing variation on the pure theory of space exploration. If human imperfections (e.g., greed, wars, budget cuts) frustrate science in its desire to transform the earth, then the alternative is to transform man by taking him away from the earth.
Here one encounters the romanticism of manned space-flight at its most extravagant: we as a species must soar into the heavens because we expect to discover heaven, a pure, beautiful, undefiled realm in which man himself can be regenerated. Space represents a second chance for mankind, a new world where we may start over and avoid our earthly mistakes. Though itself a product of mundane political bargaining, the international space station is a symbol of this aspiration, that through scientific cooperation men may overcome all their political and cultural divisions.
The same impulse sparks the resistance to the "militarization" of space. This pristine realm should not be forced to give up its innocence, to spoil its promise by taking sides, as it were, in the human fray. Yet man can't avoid taking the earth with him into space, because he takes his nature with him, with all the moral virtues and vices that entails.
In the happy faces of the Columbia crew before liftoff and while in orbit, we saw something that had nothing to do with spinoffs or the accumulation of knowledge: the sheer fun of the adventure. Their joy was connected, of course, to the mission's riskiness, for both as participants and observers we recognize that great and noble deeds, including deeds of exploration, make a kind of claim on the human soul. It was not the crew's racial, ethnic, and international diversity that made the ship's loss so poignant. It was the fact that this multifarious equality culminated in so many expressions of human excellence. Theirs was, in that sense, a very American story.
We need to remind ourselves that most exploring has been tied, one way or another, to empire; to the military, diplomatic, and commercial dictates of politics. This consideration, so clear in the space program's formative anxieties about Sputnik and Yuri Gagarin, has faded from mind, leaving the space program adrift. We honor the Columbia Seven best by thinking boldly about space exploration and exploitation, commercial and governmental. When he stepped off the ladder and onto the surface of the moon, Neil Armstrong declared that he had taken a giant step "for mankind," and he had. But he planted on the lunar surface an American flag. | 0.911137 | 3.026908 |
When the European Space Agency’s Huygens probe visited Saturn’s moon Titan last month, the probe parachuted through humid clouds. It photographed river channels and beaches and things that look like islands. Finally, descending through swirling fog, Huygens landed in mud.
To make a long story short, Titan is wet.
Christian Huygens wouldn’t have been a bit surprised. In 1698, three hundred years before the Huygens probe left Earth, the Dutch astronomer wrote these words:
“Since ’tis certain that Earth and Jupiter have their Water and Clouds, there is no reason why the other Planets should be without them. I can’t say that they are exactly of the same nature with our Water; but that they should be liquid their use requires, as their beauty does that they be clear. This Water of ours, in Jupiter or Saturn, would be frozen up instantly by reason of the vast distance of the Sun. Every Planet therefore must have its own Waters of such a temper not liable to Frost.”
Huygens discovered Titan in 1655, which is why the probe is named after him. In those days, Titan was just a pinprick of light in a telescope. Huygens could not see Titan’s clouds, pregnant with rain, or Titan’s hillsides, sculpted by rushing liquids, but he had a fine imagination.
Titan’s “water” is liquid methane, CH4, better known on Earth as natural gas. Regular Earth-water, H2O, would be frozen solid on Titan where the surface temperature is 290o F below zero. Methane, on the other hand, is a flowing liquid, of “a temper not liable to Frost.”
Jonathan Lunine, a professor at the University of Arizona, is a member of the Huygens mission science team. He and his colleagues believe that Huygens landed in the Titan-equivalent of Arizona, a mostly-dry area with brief but intense wet seasons.
“The river channels near the Huygens probe look empty now,” says Lunine, but liquids have been there recently, he believes. Little rocks strewn around the landing site are compelling: they’re smooth and round like river rocks on Earth, and “they sit in little depressions dug, apparently, by rushing fluids.”
The source of all this wetness might be rain. Titan’s atmosphere is “humid,” meaning rich in methane. No one knows how often it rains, “but when it does,” says Lunine, “the amount of vapor in the atmosphere is many times that in Earth’s atmosphere, so you could get very intense showers.”
And maybe rainbows, too. “The ingredients you need for a rainbow are sunlight and raindrops. Titan has both,” says atmospheric optics expert Les Cowley.
On Earth, rainbows form when sunlight bounces in and out of transparent water droplets. Each droplet acts like a prism, spreading light into the familiar spectrum of colors. On Titan, rainbows would form when sunlight bounces in and out of methane droplets, which, like water droplets, are transparent.
“Their beauty [requires] that they be clear….”
“A methane rainbow would be larger than a water rainbow,” notes Cowley, “with a primary radius of at least 49o for methane vs 42.5o for water. This is because the index of refraction of liquid methane (1.29) differs from that of water (1.33).” The order of colors, however, would be the same: blue on the inside and red on the outside, with an overall hint of orange caused by Titan’s orange sky.
One problem: Rainbows need direct sunlight, but Titan’s skies are very hazy. “Visible rainbows on Titan might be rare,” says Cowley. On the other hand, infrared rainbows might be common.
Atmospheric scientist Bob West of NASA’s Jet Propulsion Laboratory explains: “Titan’s atmosphere is mostly clear at infrared wavelengths. That’s why the Cassini spacecraft uses an infrared camera to photograph Titan.” Infrared sunbeams would have little trouble penetrating the murky air and making rainbows. The best way to see them: infrared “night vision” goggles.
All this talk of rain and rainbows and mud makes liquid methane sound a lot like ordinary water. It’s not. Consider the following:
The density of liquid methane is only about half the density of water. This is something, say, a boat builder on Titan would need to take into account. Boats float when they’re less dense than the liquid beneath them. A Titan-boat would need to be extra lightweight to float in a liquid methane sea. (It’s not as crazy as it sounds. Future explorers will want to visit Titan and boats could be a good way to get around.)
Liquid methane also has low viscosity (or “gooiness”) and low surface tension. See the table below. Surface tension is what gives water its rubbery skin and, on Earth, lets water bugs skitter across ponds. A water bug on Titan would promptly sink into a pond of flimsy methane. On the bright side, Titan’s low gravity, only one-seventh Earth gravity, might allow the creature climb back out again.
Back to boats: Propellers turning in methane would need to be extra-wide to “grab” enough of the thin fluid for propulsion. They’d also have to be made of special materials resistant to cracking at cryogenic temperatures.
And watch out for those waves! European scientists John Zarnecki and Nadeem Ghafoor have calculated what methane waves on Titan might be like: seven times taller than typical Earth-waves (mainly because of Titan’s low gravity) and three times slower, “giving surfers a wild ride,” says Ghafoor.
Last but not least, liquid methane is flammable. Titan doesn’t catch fire because the atmosphere contains so little oxygen–a key ingredient for combustion. If explorers visit Titan one day they’ll have to be careful with their oxygen tanks and resist the urge to douse fires with “water.”
Infrared rainbows, towering waves, seas beckoning to sailors. Huygens saw none of these things before it plopped down in the mud. Do they really exist?
“…there is no reason why the other Planets should be without them.”
Original Source: [email protected] | 0.82674 | 3.924651 |
Europe's Cheops telescope begins study of far-off worlds
Europe's newest space telescope has begun ramping up its science operations.
Cheops was launched in December to study and characterise planets outside our Solar System.
And after a period of commissioning and testing, the orbiting observatory is now ready to fulfil its mission.
Early targets for investigation include the so-called "Styrofoam world" Kelt-11b; the "lava planet" 55 Cancri-e; and the "evaporating planet" GJ-436b.
Discovered in previous surveys of the sky, Cheops hopes to add to the knowledge of what these and hundreds of other far-flung objects are really like.
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The Swiss-led telescope will do this by watching for the tiny changes in light when a world passes in front of its host star.
This event, referred to as a transit, will betray a precise diameter for the "exoplanet". When this information is combined with data about the mass of the object - obtained through other means - it will be possible for scientists to deduce a density.
And this should say a lot about the composition and internal structure of the target.
Kelt-11b has provided a good early demonstration. This is a giant exoplanet some 30% larger than our own Jupiter that orbits very close to a star called HD 93396. Kelt-11b is a seemingly "puffed up" world with a very low density - hence the comparison with expanded foam.
From the way the light from the star dips when Kelt-11b moves in front to make its transit, Cheops' exquisite photometer instrument is able to determine the planet's diameter to be 181,600km (plus or minus 4,290km). This measurement is over five times more precise than was possible using a ground-based telescope.
The European Space Agency (Esa) is part of the collaboration behind Cheops. Its project scientist Dr Kate Isaak lauded the performance of the new observatory.
"We have a very stable satellite; the pointing is excellent - better than requirements. And this is going to be a real benefit to the mission," she told BBC News.
"From the spacecraft side, from the instrument side, from the analysis of the data that we're getting - we can see that this mission has huge promise."
Prof David Ehrenreich from the University of Geneva said quite a few early observations made with Cheops would be of "super-Earths".
"These are planets that are assumed to be rocky like Earth - but much bigger, more massive. And much hotter, too. Lava worlds," he explained.
55 Cancri-e fits into this category. More than eight times as massive as Earth, it takes just 18 hours to circle its parent star. Scientists believe it to have a global ocean of molten rock on its surface.
About 80% of observing time on Cheops is reserved for the project consortium. Led from the universities of Bern and Geneva, this team has members in eleven European nations (with Esa as a partner also). The other 20% of time is being offered to the community at large. And the first of these external proposals will be studied in coming days. Cheops will look at a burnt-out, or white dwarf, star to see if there is any planetary material moving around it.
Nobel Laureate Prof Didier Queloz, from the universities of Cambridge and Geneva, said the goal of Cheops was to improve our ideas for how planets were created.
He told the BBC: "We have built a whole theory of planet formation by observing only the eight planets of our Solar System, but by extending our observations to other kinds of planets that have no counterpart in our Solar System - we should be able to add the missing parts of this theory and get, let's say, a bigger perspective on how we actually fit in."
Science planning for Cheops is run out of the Geneva; the telescope itself is controlled from Spain, at the National Institute for Aerospace Technology in Torrejon on the outskirts of Madrid.
While the coronavirus crisis has meant considerable disruption for many space projects, Cheops has been largely unaffected.
"The completion of the test phase was only possible with the full commitment of all the participants, and because the mission has an operational control system that is largely automated, allowing commands to be sent and data to be received from home," said Prof Willy Benz from the University of Bern and principal investigator on the mission.
Cheops is a short form that stands for CHaracterising ExOPlanet Satellite.
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On a comet’s first visit to the inner solar system, astronomers’ first task is to determine its orbit to see where it’s going, and where it’s come from.
Our solar system’s comet reservoir, the Oort Cloud, is a vast, spherical volume of space with a hollow middle in which the sun and planets reside, stretching almost halfway to the nearest star. At such distances, an orbital snail’s pace is sufficient to balance the Sun’s feeble gravity.
Oort Cloud comets reach the inner solar system after free-falling for millennia. Unless they pass a planet (or impact the sun), their outbound loss of speed mirrors their inbound gain, until they arrive at their apex at the same slow pace they began.
At any distance from the sun, there is an escape velocity below which bodies remain captive. Until recently, no solar system object had ever been known to possess a significant excess of solar escape velocity.
Asteroid ’Oumuamua, discovered in 2017 only when outbound, possessed speed in excess of escape velocity, which it must have had inbound — the first interstellar object. The second, Comet Borisov, appeared five weeks ago.
At its closest approach to the sun in early December, Borisov will peak at over 25 miles per second. At twice the earth’s distance, no body orbiting the sun has come anywhere close to having this much speed — 40% more than escape velocity.
These peripatetic projectiles mesh perfectly with the solar system’s origin story: comets formed among the giant planets, then crashed into the sun or planets or got flung to the Oort Cloud — or beyond. So, somewhere in our galaxy, aliens may currently be studying one of our escapee comets as it whizzes past their world for the first and last time.
Next column: Mercury in solar silhouette.
Chris Anderson manages the College of Southern Idaho’s Centennial Observatory in Twin Falls. He can be reached at 732-6663 or [email protected].
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OGLE-2016-BLG-1266: A Probable Brown-Dwarf/Planet Binary at the Deuterium Fusion Limit
We report the discovery, via the microlensing method, of a new very-low-mass binary system. By combining measurements from Earth and from the Spitzer telescope in Earth-trailing orbit, we are able to measure the microlensing parallax of the event, and find that the lens likely consists of an + super-Jupiter / brown-dwarf pair. The binary is located at a distance of kpc in the Galactic Plane, and the components have a projected separation of AU.
Two alternative solutions with much lower likelihoods are also discussed, an 8- and 6- model and a 90- and 70- model. Although disfavored at the 3- and 5- levels, these alternatives cannot be rejected entirely. We show how the more-massive of these models could be tested with future direct imaging.
M. D. Albrow
The growing number of detections of super-Jupiter-mass objects, both isolated and in orbit around objects of higher mass, raises challenges of interpretation and classification.
Formal definitions of what constitutes a “planet” tend to be based on the mass or interior physics of the object. The IAU Working Group on Extrasolar Planets (which existed until 2006) considered the deuterium fusion limit ( for solar metallicity) to be the dividing line between planets and brown dwarfs for objects that orbit stars. They also considered substellar objects with masses above the deuterium fusion limit to always be brown dwarfs. The NASA Exoplanet Archive adopts a looser definition for inclusion in their planet tables, namely that the inclusion of an object as a planet is made provided that its mass is less that 30 and it is associated with a host star111Confusingly, the Archive violates its own policy by including objects with brown-dwarf hosts. https://exoplanetarchive.ipac.caltech.edu/docs/exoplanet_criteria.html.
On the other hand, the logical definition for what constitutes a “planet” would be based on formation mechanism, i.e., whether the object formed in a disk or through direct collapse of the gas cloud. This might suggest a distinction between super-Jupiter-mass objects that orbit stars and those that orbit hosts of comparable mass (i.e., very low mass, brown dwarf-brown dwarf binaries), and raises questions about how to classify those without hosts. In fact, the observational community tends to make a distinction between super-Jupiters orbiting stars and those orbiting brown dwarfs. Best et al. (2017) refer to 2MASS J11193254-1137466 (a member of the TW Hydrae Association) as a pair of 3.7 brown dwarfs, and suggest that the system is a product of normal star formation processes. In contrast, Lovis & Mayor (2007) refer to the 10.6 object orbiting the 2.4 star TYC 5409-2156-1 as a planet, and argue that an abrupt transition between planets and brown dwarfs has little meaning if both categories of objects are formed by the same physical process. Likewise Carson et al. (2013) argue that a planetary classification rather than brown dwarf is appropriate for a 12.8 body orbiting the 2.5 host star, And.
Formal definitions do not capture these nuances. The IAU makes a specific distinction for isolated objects located in young star clusters: below the deuterium-burning limit, they are classified as “sub-brown dwarfs” (Boss et al., 2007). However, the classification of an object at or below the deuterium fusion limit that is gravitationally bound to another sub-stellar object is not currently defined by the IAU. Neither is the case of an isolated object of that mass located outside a young cluster.
Precise definitions are complicated by the fact that without observing the actual formation of the objects, it is impossible to say what mechanism led to their formation and where the boundary should be. For example, Mordasini et al. (2009) show that it is theoretically feasible to grow super-Jupiters by core accretion in a proto-planetary disk up to at least . At the same time, Schlaufman (2018) has recently suggested that any companions to solar-type stars with mass should not be considered planets, i.e., could not have formed by core accretion. However, since the Schlaufman study was based solely on transiting (i.e., short period) objects, it is unclear whether or not this result truly reflects something about formation rather than the subsequent migration of the objects. Defining the boundary between “planets” and “brown dwarf companions” is further complicated by the question of whether or not gravitational instability of a disk should be considered to form planets or brown dwarfs. Certainly, though, the choice of the deuterium fusion limit as the planet / brown-dwarf boundary is arbitrary and confusing (Baraffe et al., 2008).
It is unclear at this time whether brown-dwarf/super-Jupiter binaries belong to the population of objects that formed like binary stars from the collapse of molecular clouds, or if some other mechanism, such as ejection from a higher-multiplicity system is responsible. Hydrodynamic simulations of the collapse of a large star-forming molecular cloud by Bate (2012) resulted in 450 stars and 800 brown dwarfs. Of these, some brown dwarfs with masses below were formed but no binaries with primary masses below .
Understanding the differences in super-Jupiter-mass objects as a function of their host mass requires the discovery of more such objects, especially those with very-low-mass (brown dwarf) hosts. In addition to the Best et al. (2017) binary, a handful of very-low-mass binaries have been detected by photometric methods in young open clusters and star forming regions (Luhman, 2013). However, mass estimates for these objects rely on theoretical models of their evolution. The uncertainties are large, and the results are strongly dependent on the assumed age of the systems.
Microlensing offers an entirely different avenue for probing the population of very-low-mass binaries. In recent years three very-low mass binaries have been detected through the channel of gravitational microlensing (Choi et al., 2013; Han et al., 2017a). In contrast to the photometric detections, microlensing binaries can have direct and reliable mass estimates, independent of brown-dwarf evolutionary theory. Furthermore, these objects are located at large distances in the Galactic Disk and are outside of young, star-forming clusters.
In this paper we report the detection of a fourth very-low mass binary system by microlensing. This new system is composed of a 15.7- brown dwarf plus a companion just below the deuterium fusion limit.
2 Gravitational Microlensing
Gravitational microlensing is an effect for which the brightness of a distant star (the source) is magnified due to the bending of light by the gravity of a nearer object (the lens). Typically, microlensing events are detected each year in the direction of the Galactic Bulge by the OGLE222http://ogle.astrouw.edu.pl/ogle4/ews/ews.html, MOA333https://www.massey.ac.nz/iabond/moa/alerts/ and KMTNet444http://kmtnet.kasi.re.kr/kmtnet-eng/ surveys.
The characteristic angular scale for microlensing is the Einstein radius,
where is the total mass of the lens system, , are the distances from Earth to the lens and source, is the lens-source relative parallax, and .
The magnification, , of a standard binary microlensing event can be described by seven parameters in the lens frame. These represent the angular separation of the lens components (), their mass ratio (), the angular source radius in units of (), the angle of the source trajectory from the lens axis (), the angular distance of closest approach of the source to the lens center of mass in units of (), the time of closest approach () and the Einstein radius crossing time (). Two additional linear parameters, the source and blend flux and , are required for each data set to map the magnification onto the observed flux , i.e.,
If the source angular radius, , can be measured independently (usually from its color and an assumption that it lies behind the same column of dust as the Galactic Bulge), then the angular Einstein radius can be determined.
Additionally, if the microlensing event can be viewed by two observers with a significant spatial separation (say from Earth and a distant Solar-orbiting satellite; Refsdal 1966) or if the event timescale is long enough that Earth moves appreciably in its orbit, then the microlensing parallax vector (Gould, 2004; Calchi Novati & Scarpetta, 2016) may be measured. Then , and hence can be determined.
The event OGLE-2016-BLG-1266 (17:51:24.86, -29:44:32.1) J2000.0, galactic coordinates , was alerted by the Optical Gravitational Lensing Experiment (OGLE Udalski et al., 2015) on 2016 July 4 UT 11:24, based on observations from the 1.3-m Warsaw Telescope at the Las Campanas Observatory, Chile. The OGLE observations were taken at a cadence of 55 minutes. Photometry of the OGLE images was extracted using the standard OGLE difference-imaging pipeline.
OGLE-2016-BLG-1266 was also observed by the Korea Microlensing Telescope Network (KMTNet Kim et al., 2016) using identical telescopes at the Cerro Tololo Inter-American Observatory in Chile; the South African Astronomical Observatory at Sutherland, South Africa; and the Siding Spring Observatory, Australia. It was identified as SAO42T0504.003968 (Kim et al., 2017; Kim, 2018 in preparation). Both the OGLE and KMTNet observations were taken as part of regular surveys, with cadence uninformed by the detection of the event. For KMTNet, the event is located in two overlapping survey fields, BLG02 and BLG42, giving an effective cadence of 15 minutes. The primary KMTNet observations were taken in the band, supplemented by an occasional -band observation.
Photometry was extracted from the KMTNet observations using the software package PYDIA (Albrow, 2017), which employs a difference-imaging algorithm based on the modified-delta-basis-function approach of Bramich et al. (2013). The data from field BLG02 observed from SAAO were discarded as they were affected by a cosmetic feature of the detector. The remaining KMTNet lightcurves were filtered using various image quality criteria and without reference to the lightcurve.
The event was also observed by the Spitzer space telescope at a wavelength of 3.6 m using the IRAC instrument (Fazio et al., 2004). These observations were acquired as part of a multi-year project to measure the distances of microlensing planets in the Galaxy (Calchi Novati et al., 2015a; Yee et al., 2015). OGLE-2016-BLG-1266 was announced as a Spitzer target at 2016 July 10 UT 21:15, based on the possibility that it would rise to high magnification, and uploaded to Spitzer the next day. The first observation was at UT 18:18 on 16 July. In total, 6 observations were taken during the following 7 days. The sequence of observations was terminated at that point due to Spitzer’s Sun-angle restriction. The event was observed for a further 9 epochs by Spitzer in 2017 after the magnification had fallen to baseline levels. Spitzer photometry was extracted using the methods described in Calchi Novati et al. (2015b).
4 Microlensing model from Earth-based observations
The combined ground-based lightcurve of OGLE-2016-BLG-1266 is shown in Figure 1. It displays a smooth double peak, suggestive of a resolved source crossing a pair of caustics, generated by a binary lens.
Our analysis of the lightcurve was undertaken using a modified version of the GPU-accelerated code of McDougall & Albrow (2016). Initially we performed a search over a fixed grid of , where is the distance from the centers of caustics (a reparameterisation of ). This established a number of possible approximate solutions that were used as starting points for Markov Chain Monte Carlo minimization using the EMCEE ensemble sampler (Foreman-Mackey et al., 2013). The magnification calculations used the image-centered inverse ray shooting method (Bennett & Rhie, 1996; Bennett, 2010) for locations within three source radii of a caustic, the hexadecapole approximation (Pejcha & Heyrovský, 2009; Gould, 2008) for distances between 3 and 30 source radii, and the point-source binary-lens approximation otherwise. For the ray shooting calculations, we used a fixed source limb-darkening coefficient, , appropriate for the source star color that we derive in the following section. From these Markov Chains, a single viable solution was identified at , corresponding to the source passing over one of the two triangular caustics produced by a close binary. The corresponding lightcurve and caustic geometry are shown in Figure 1. In this paper we plot lightcurves on a scale of , where , and and are model-dependent. We note that the model implies a small negative blending for the OGLE data (), equivalent to the flux of an star. As discussed by Park et al. (2004), such low-level negative blending is a normal feature of microlensing photometry in very crowded bulge fields.
5 Source star radius
Using KMTNet CTIO BLG42 images in the and bands, we have constructed a DoPHOT (Schechter et al., 1993) instrumental color-magnitude diagram (CMD) for stars in a 3 arcmin 3 arcmin box centered on the event (left panel of Figure 2). From this diagram we measure the red clump centroid to be at . From regression of -band flux against -band flux during the event, checked by a two-parameter fit of the -band-determined magnification profile to the -band data, we determine a deblended instrumental source color and thus an offset from the clump .
We have also constructed an instrumental CMD from -band images acquired with the ANDICAM instrument at the 1.3-m CTIO telescope, and -band catalog measurements of the field from the VVV survey (Saito et al., 2012) (right panel of Figure 2). Although -band images were acquired at CTIO simultaneously with the -band images, we opt to use VVV measurements for the CMD as they are deeper. We measure the red clump in this CMD at . From regression of ANDICAM and measurements of the microlensing event, we determine , which when adjusted for an offset (determined by regression of field stars) implies an instrumental source color and an offset from the red clump .
In principle, color offsets from the Red Clump are filter dependent. However, since our measurement of is essentially zero, it implies an offset from the clump of zero in any filters. Thus we count this measurement as implying , and average it with our previous measurement, , to obtain a final offset of .
OGLE-2016-BLG-1266 has a galactic longitude close to , so from Nataf et al. (2013) and Bensby et al. (2013) we adopt an intrinsic clump centroid . From the offset of the deblended source color from the red clump center on the instrumental CMDs, we calculate the intrinsic source color . Additionally, from the parameter determined from the lightcurve model, we find on the KMT BLG42 instrumental system, and .
From the source angular radius and the lightcurve model we can compute . The geocentric lens-source relative proper motion is then .
Comparing and with samples from the Han & Gould (2003) model of the Galactic Bulge and Disk, Figure 7 in Penny et al. (2016), (and at this stage ignoring any difference between and ) we note that is at the extreme of what is possible for a Bulge lens, so the lens is likely in the Galactic Disk. (See also Figure 1 in Han & Chang (2003)). Our measurement of implies a total lens mass of 10 if the lens distance is 1.3 kpc and 100 if the distance is 5.1 kpc.
6 Parallax Constraints
The orbit of Earth around the Sun introduces a parallax effect on ground-based observations of microlensing events (Gould, 1992, 2000). Although present for all such observations, it is usually only detectable for events with a timescale d. The effect manifests as a sinusoidal perturbation on an otherwise-linear projected source trajectory in the lens plane (see for example Han et al. (2017b, a); Park et al. (2015); Furusawa et al. (2013)).
In addition to this annual parallax effect, we fit for the satellite parallax effect. The Spitzer telescope is in an Earth-trailing solar orbit, behind Earth in 2016. At the time of peak magnification, Spitzer was located at coordinates (RA,DEC) = (10:25,09:08) and a distance of 1.484 AU from Earth. Perpendicular to the direction of OGLE-2016-BLG-1266, the projected distance of Spitzer from Earth was AU. When viewed from Spitzer, the source trajectory across the lens plane is offset by a vector , in directions (perpendicular, parallel) to the trajectory observed from Earth. The parallel offset is simply,
but the perpendicular offset suffers from a four-fold satellite parallax degeneracy due to the symmetry of the magnification field about the lens axis,
as illustrated in Gould (1994). The sign convention we adopt here is that a positive value of indicates that, during its projected trajectory, the source approaches the lens on its right hand side.
We make an initial fit to the Spitzer lightcurve by adopting the ground-based model parameters and exploring a grid in to offset from . These constant offset values are used as the reference indices for the grid, but the calculations of the actual model Spitzer lightcurve use the true offset of each data point at its epoch of observation.
At each point in the grid we map the magnification to the observed Spitzer flux using Equation (2).
To include the Spitzer source flux constraint derived in the previous section, we penalise with an additional term,
where is the -band to -band flux ratio and is the uncertainty in (Shin et al., 2017). Mathematically, this is entirely equivalent to a prior on the probability of the model parameters that generate . We elected not to use the Shin et al. (2017) method of adding an additional penalty for deviations greater than 2-.
The grids in for the unconstrained and source-flux-constrained cases are shown in Figure 3. Comparing the constrained with the unconstrained solutions, it is clear that there is a broad region in space that is consistent with both the source-flux-constrained and unconstrained models for the Spitzer data.
In the unconstrained case, the lowest- solution corresponds to a small region at , which is not visible in the corresponding flux-constrained map. It is instructive to consider the penalty that the source flux constraint imposes for this particular . The -band to -band source-flux ratio constraint is from our CMD analysis. The unconstrained model at that point has . It is very unlikely that our -band flux measurement is in error by a factor of 8 (i.e., more than 2 magnitudes). Thus we consider that this “best” of the unconstrained models is ruled out by the -band measurement, and we only consider the constrained models from here on.
To explore the identified solution space, we have run full EMCEE Markov Chains incorporating the standard binary microlensing model with two parallax parameters for the combined ground-based and Spitzer data, incorporating the Spitzer source flux constraint. Chains seeded from various points in space all converged to one of the two points indicated with plus signs in Figure 3.
Solution A (“green plus”) corresponds to trajectories for which the six 2016 Spitzer data points are located to the left of the central caustic in Figure 1, interior to (i.e., closer to the lens axis than) the Earth-viewed trajectory. In this region, the magnification is declining smoothly with a steeper slope than the ground-based model. The minimum is located in this solution region at .
Solution B (“yellow plus”) is located slightly exterior to the Earth-viewed trajectory. The lightcurve corresponding to this Spitzer-viewed trajectory incorporates a small peak close to the first data point due to a high magnification region in an extension of a cusp from the planetary caustic. The minimum for this solution is located at , and is disfavored relative to Solution A by .
The microlensing parallax, , depends on as
where is the distance of Spitzer from Earth, perpendicular to the line of sight to the lens. At the peak of the event, , so that Solution A (“green plus”) has , while Solution B (“yellow plus”) has .
7 Satellite degeneracy
As discussed at the beginning of the previous section, there exists a four-fold degeneracy in (Equation ( 4)). To further investigate the satellite degeneracy, we adopted the A (green) and B (yellow) source-flux-constrained solutions from Figure 3 and ran EMCEE chains to explore the complete set of solution regions.
For Solution A at (green plus symbol in the right panel of Figure 3), the and trajectories lie along the lens axis and are almost identical for . We refer to these as the A (“green”) solutions.
In contrast, for Solution B (yellow plus symbol in the right panel of figure Figure 3) at , there is a separate trajectory that lies above the upper triangular caustic (and was outside the range of the grid search). We refer to these solutions as the B (“yellow”) solutions.
Microlensing parameters derived from the eight models are shown in the left columns for each geometry in Tables 1 and 2. Given the apparent degeneracies, the eight solutions correspond to three different microlensing parallaxes; small-parallax B (), large-parallax B (), and A (). Representative lightcurves for the A (green) and B (yellow) geometries are shown in Figure 4.
For the solution-A trajectories, there is a small difference in the solutions due to the small annual-parallax-induced curvature in each trajectory, with the solution being marginally favored. The solutions for each are fully degenerate.
In contrast, the second set of models (solution B) separate in for the two cases that has the same or opposite sign as (with the opposite sign models favored by ), but are otherwise degenerate in .
8 Lens orbital motion
Ignoring projection effects, a Keplerian orbit for the masses and separation derived in the previous section would have a period of about 1.6 years. This suggests that lens orbital motion may be a detectable and significant effect. We have thus extended our models with first order lens motion parameters and .
We require that the complete set of model parameters are consistent with a bound orbit, in particular that the projected kinetic energy be less than the potential energy. From Dong et al. (2009)
In convenient units, this leads to a constraint,
From Section 5, we assume that the source is at the red-clump distance, 8.18 kpc, and that . We implement the constraint as a prior, with the hard upper boundary softened by the uncertainty in .
We have run models seeded from the eight satellite-parallax degenerate solution regions discussed above. The resulting parameters are listed in the right hand columns for each geometry in Tables 1 and 2, and the geometries are displayed in Figure 5.
Chains for solution A (green) converge to almost the same solution, again with a small difference of 4 between the solutions. The overall is lowered by 12 relative to the models without lens orbital motion.
Again, as expected, the solution-B models (yellow) converge to different solutions for . The and solutions have smaller than the and solutions. Relative to the solution-A model, the best of these is disfavored by .
In Figure 6 we show the posterior parameter distribution for the solution A model (which ultimately becomes out favored model in Section 8 below). Corresponding plots for the other 7 models are similar. The effect of the kinetic energy prior is apparent in and . If it were not for this physical constraint, the data would force to . The kinetic energy prior has an effect in all cases, but each energy-constrained solution is always part of the same minimum as a corresponding unrestricted (non-physical) model.
Overall, the inclusion of lens orbital motion in the models changes slightly the other parameters, and improves slightly for all models.
Both of the A solutions imply that the lens is a binary with component masses of 16 and 12 Jupiter masses. The higher mass component is a brown dwarf, and the lower mass component is on the dividing line between a brown dwarf and a super-Jupiter planet (sub-brown dwarf). The lens is located at a distance of 3.0 kpc from Earth, and the components have a projected separation of 0.4 AU.
The “same-sign” B solutions (with relative to the A solutions) are for a 90 and 68 Jupiter-mass binary at 6.2 kpc with a projected separation of 0.9 AU, while the “opposite-sign” B solutions (with relative to the A solutions) are for an 8 and 6 Jupiter-mass binary at 2.1 kpc with a projected separation of 0.3 AU.
9 Which solution is correct?
In this section we use several lines of evidence to assess the solutions obtained above. Our approach is similar to that of Calchi Novati (2018).
9.1 The best lightcurve fit
In Tables 1 and 2 we list for each fit. In all cases, we have found that the six Spitzer data points from 2016 comprise the major source of . Irrespective of whether lens orbital motion is included in the models, the A (green) series of solutions have the best formal fit, with the models being slightly better than the models. The B (yellow) series of solutions are less favored, but not by a large amount. Formally, the probability of each solution relative to the best one is lowered by , so that the best of the large-parallax B solutions has a probability of only 0.040 relative to the A solution (i.e., a 2.5- difference), and the best small-parallax B solution has a relative probability of (4.4-). However, these formal probabilities rest on the assumption that all data are independent and Gaussian-distributed, and that data uncertainties are accurate. Such conditions are never satisfied for microlensing photometry. On this basis, we are unable to reject entirely the yellow solutions.
9.2 The Rich argument
The “Rich argument” is elucidated in Calchi Novati et al. (2015a). Briefly, for a point-lens microlensing event, when considering two alternate satellite-degenerate solutions from the same model, the one with the smallest parallax is usually correct. This is because if the true parallax solution is small, it will always generate a large-parallax counterpart. However, if the true parallax is large, then there is a much smaller probability, , that the parallax of the counterpart solution is small. This probability factor is based on the rotational symmetry of the magnification field about the lens. For incomplete satellite lightcurves, the true probability factor can be larger because a two-parameter fit can map different magnification patterns to the same flux lightcurve.
For binary lenses, the geometric degeneracy on which the Rich argument is based, exists only for cases in which the source trajectory is almost parallel to the lens axis, as is the situation we are considering here. The two B (yellow) solutions represent an analogous situation to the large- and small-parallax solutions for a point lens. However, we cannot naively apply the point-lens relative probability factor because the magnification pattern for a binary lens does not have the rotational symmetry of the single-lens pattern, and our Spitzer lightcurve does not have full coverage.
The A-solution degeneracy with either of the B solutions is not a true geometric degeneracy. It exists because of our limited epochs of Spitzer observations and would not be present if we had full temporal coverage.
We have assessed the relative probabilities of the various solutions by simulating Spitzer lightcurves for the three different parallax amplitudes () and for different angles () with respect to the source trajectory. For each simulation, we held the ground-determined microlensing parameters constant, and computed a flux lightcurve by combining the previously-determined Spitzer source and blend flux with the the magnification, at the Spitzer epochs. We then added the residuals of the Spitzer data relative to the A model fit.
To determine the probability factor for the large-parallax B solution relative to the small-parallax B solution, we have simulated lightcurves for 360 values of for the B parallax amplitude. For each of these we have made a two-parameter, source-flux constrained fit using the magnification at the constant B parallax amplitude, found from the transformation , and allowing the angle to vary. For each , we accumulate the between the large-parallax and small-parallax fits. We then compute the probability that a true small parallax would have a large parallax degeneracy as being the fraction of angles for which is less than some threshold value. We then repeat this exercise in reverse, generating a set of large-parallax simulations, and finding the small-parallax fits. The ratio of these two probabilities then gives the a-priori probability of a large parallax solution relative to a small one for the given geometry, satellite observation epochs, source-flux constraints, and observation residuals, independent of the actual measured satellite flux values. To simplify the interpretation, we have made these synthetic lightcurves and fits without including the effects of lens orbital motion.
We adopt a threshold similar to the range of actual measured for our different degenerate solutions discussed in the previous sections. We find that there is a 0.43 probability that a true small B parallax would generate a large B parallax degenerate solution. If the source trajectory were exactly parallel to the lens axis, we would expect this factor to be exactly 1.0. (In the current geometry, the factor rises to unity were we to increase our threshold to 80.) We find that there is a 0.40 probability that a true large B parallax can generate a small B parallax degenerate solution. This probability is much larger than what would be the case for continuous Spitzer lightcurve coverage. Combined, we find an overall probability of 0.935 of a large B parallax relative to a small B parallax.
To determine the probability factor for the A model relative to the small-parallax B model we carry out a similar calculation, but use the A model parallax amplitude rather than the parallax of the alt solution. From these calculations we find that there is a 0.33 probability that a true small B parallax would generate a degenerate solution with the parallax amplitude of the A model, a 0.37 probability that a true solution with the parallax amplitude of the A model would generate a degenerate small-parallax B solution, and an overall probability of 1.11 of an A-model parallax relative to a small-parallax B model.
In summary, we have found that the overall a-priori relative probability factors stemming from this specific geometry and set of Spitzer observation epochs are close to unity, so have little effect on our relative assessment of the different solutions.
9.3 Galactic rotation
For a flat rotation curve, and from the Local Standard of Rest (LSR) perspective, the rotational component of the proper motion of a disk star interior to the Sun’s orbit and relative to the Bulge, , is independent of the star’s distance. Projected onto the lens plane, the disk of the Milky Way rotates in a direction North of East. In the absence of random velocity dispersions for the disk and Bulge, we would expect disk lenses to have a relative proper motion in this direction if we were observing from the LSR. Adopting , and a Bulge distance of 8.18 kpc, gives . Added to this overall disk rotation, individual disk stars have a velocity dispersion, . Given its low galactic latitude, the lens in OGLE-2016-BLG-1266 is almost certainly part of the old thin disk, for which .
From its location on the CMD, we assume our source star is part of the Bulge population. We have adopted , as an average of the Y and Z direction Bulge velocity dispersions from Bland-Hawthorn & Gerhard (2016). To compare the relative lens-source proper motion for our various models with that expected for disk lenses, we transform to the LSR by adding the projection of Sun’s peculiar velocity, , to the relative lens-source proper motion. The resultant LSR relative lens-source proper motions, for each model, are shown in Figure 7 along with the galactic expectation, with a dispersion .
We can see that the A (green) solutions for are well aligned with Galactic Disk rotation. The B (yellow) solutions for are also plausible, but the remaining models are rather improbable.
For each model solution, we can form a probability that the lens has the expected proper motion of the Galactic Disk,
9.4 Combined probability
We have discussed three factors that we consider important for assessing the relative merits of the A and B series of models for OGLE-2016-BLG-1266. For each of these, we can assign a relative probability; from the lightcurve fits, from the Rich argument, and from the proper motion correspondence to galactic rotation. We have multiplied the three probabilities for each model and normalised to the maximum to compute a net relative probability, , also listed in Tables 1 and 2.
Considering all factors, the most-favored solutions are the degenerate A-series models. These models imply a 16- + 12- mass lens at a distance of 3.1 kpc. We note that these solutions have a significantly larger parallax ( than any of the previous events measured by Spitzer. (The next largest parallax is OGLE-2016-BLG-1195 with ; Shvartzvald et al. 2017.)
Relative to the A solutions, the best of the B solutions is the large-parallax model with a relative probability of . The small-parallax model has a relative probability of . Respectively, these models imply an 8- + 6- mass lens at a distance of 2.0 kpc and a 90- + 70- pair at 6.2 kpc. The relative probabilities correspond to 2.91- and 4.86- differences from the favored model.
9.5 Is the favored lens mass plausible?
The initial mass function (IMF) for brown dwarfs below = 0.1 M () is not well established, and may depend on environment. The Kroupa (2002) and Chabrier (2003) IMFs for single objects increases toward lower mass in this range, but there is evidence that the MF “turns over” at increasingly higher masses with age in stellar clusters (Chabrier, 2003). There is little evidence of a large decline between 0.1 M and 0.01 M in the studies of Alves de Oliveira et al. (2013); Jeffries (2012); Gagné et al. (2017). Overall, there is little reason from the lens-mass results to reject the high-parallax low-mass model in favor of the lower-parallax higher-mass one.
9.6 Falsification of the favored model
Our adopted model for OGLE-2016-BLG-1266 is for a 16- + 12- mass lens at a distance of 3.1 kpc. Given its low mass, we do not expect the lens to be directly observable with any presently conceived instruments. This is also the case for the B model, which corresponds to a binary composed of two planetary-mass objects.
However, the more massive of the plausible challenger models (B ) consists of a 90- + 70- mass lens at a distance of 6.2 kpc. From Dupuy & Liu (2017),we expect that this pair would have absolute and magnitudes of 11 and 10, and so apparent magnitudes , . This solution has a heliocentric lens-source relative proper motion of mas yr. In ten years there would be a separation of 92 mas between the lens and the source in the indicated direction. Resolving the lens and source for the high-mass model should be within the first-light capability of diffraction-limited near-infrared imagers on the coming generation of extremely large telescopes, for example ELT-CAM on E-ELT.
Objects like OGLE-2016-BLG-1266 challenge our understanding of what is meant by a planet. If the low-mass component of our favored model were associated with a star, or a brown dwarf with significantly higher mass, then it would be be described as a planet. However, with masses so close, both components of the binary may instead belong to the very low-mass end of the stellar initial mass function. We note that the survey of Mróz et al. (2017) has identified several short-time-scale binary events that may be part of such a population.
For several reasons, detecting single planetary mass objects (often referred to as “free-floating planets”) by the microlensing method is a more difficult task than detecting binary lenses. Firstly, the peak magnification is generally lower and thus will have a lower probability of detection as a microlensing event. Second, the mass of single lenses can only be inferred from a measurement of , and that parameter is extremely degenerate with blending, and subject to incorrect inference if derived from lightcurve data with any systematic correlation between neighboring points. Third, it is difficult to establish a microlensing parallax measurement for short- events, because for Earth-orbital parallax measurements the trajectory of Earth does not deviate much from linear during the event duration, and for satellite parallaxes it is difficult to target satellite observations while the event is still significantly magnified.
There are currently four published single-lens events with secure lens-mass measurements from Spitzer (Zhu et al., 2016; Chung et al., 2017; Shin et al., 2018), and two from ground-only measurements (Gould et al., 2009; Yee et al., 2009), all with masses in the brown-dwarf regime.
There are currently no secure detections of single planetary mass objects by the microlensing method (Mróz et al., 2017). The object very recently detected by Mroz et al. (2018) may be the first isolated “planet”, but even for that event, the presence of a stellar host at a separation AU cannot be ruled out.
Single planetary-mass lenses may be found more readily in the future with the advent of the WFIRST mission, which will observe Galactic Bulge microlensing events with high photometric precision and less blending than from the ground. Gould (2016) shows how the presence of stellar companions to such single-lens candidates can be detected or ruled out by WFIRST and ground-based adaptive-optics observations. We should always bear in mind that, in the absence of an evolutionary history, the designation of low-mass single lenses as free-floating “planets” may be incorrect.
Using data from the KMTNet and OGLE telescopes, and the Spitzer satellite, we have analysed the microlensing event OGLE-2016-BLG-1266. Our models show that the lens is very likely composed of a 16- + 12- binary at a distance of 3.1 kpc.
Two alternative models are unlikely, but cannot be entirely rejected. One of these models corresponds to a 6- + 8- “planet-planet” binary at a distance of 2.0 kpc. The second of these alternatives, a 70- + 90- binary at 6.2 kpc, would be directly observable with the next generation of telescopes and instrumentation.
MDA is supported by the Marsden Fund under contract UOC1602, and is grateful for the award of an ESO Visiting Fellowship in December 2017 / January 2018 during which time this paper was completed. Work by WZ, YKJ, and AG were supported by AST-1516842 from the US NSF. WZ, IGS, and AG were supported by JPL grant 1500811. Work by C.H. was supported by the grant (2017R1A4A1015178) of National Research Foundation of Korea. This research has made use of the KMTNet system operated by the Korea Astronomy and Space Science Institute (KASI) and the data were obtained at three host sites of CTIO in Chile, SAAO in South Africa, and SSO in Australia. The OGLE project has received funding from the National Science Centre, Poland, grant MAESTRO 2014/14/A/ST9/00121 to AU. Work by YS was supported by an appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory, California Institute of Technology, administered by Universities Space Research Association through a contract with NASA. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA.
- Albrow (2017) Albrow, M. 2017, MichaelDAlbrow/pyDIA: Initial release on github., , , doi:10.5281/zenodo.268049. https://doi.org/10.5281/zenodo.268049
- Alves de Oliveira et al. (2013) Alves de Oliveira, C., Moraux, E., Bouvier, J., et al. 2013, A&A, 549, A123
- Baraffe et al. (2008) Baraffe, I., Chabrier, G., & Barman, T. 2008, A&A, 482, 315
- Bate (2012) Bate, M. R. 2012, MNRAS, 419, 3115
- Bennett (2010) Bennett, D. P. 2010, ApJ, 716, 1408
- Bennett & Rhie (1996) Bennett, D. P., & Rhie, S. H. 1996, ApJ, 472, 660
- Bensby et al. (2013) Bensby, T., Yee, J. C., Feltzing, S., et al. 2013, A&A, 549, A147
- Bessell & Brett (1988) Bessell, M. S., & Brett, J. M. 1988, PASP, 100, 1134
- Best et al. (2017) Best, W. M. J., Liu, M. C., Dupuy, T. J., & Magnier, E. A. 2017, The Astrophysical Journal Letters, 843, L4. http://stacks.iop.org/2041-8205/843/i=1/a=L4
- Bland-Hawthorn & Gerhard (2016) Bland-Hawthorn, J., & Gerhard, O. 2016, ARA&A, 54, 529
- Boss et al. (2007) Boss, A. P., Butler, R. P., Hubbard, W. B., et al. 2007, Transactions of the International Astronomical Union, Series A, 26, 183
- Bramich et al. (2013) Bramich, D. M., Horne, K., Albrow, M. D., et al. 2013, MNRAS, 428, 2275
- Calchi Novati & Scarpetta (2016) Calchi Novati, S., & Scarpetta, G. 2016, ApJ, 824, 109
- Calchi Novati et al. (2015a) Calchi Novati, S., Gould, A., Udalski, A., et al. 2015a, ApJ, 804, 20
- Calchi Novati et al. (2015b) Calchi Novati, S., Gould, A., Yee, J. C., et al. 2015b, ApJ, 814, 92
- Calchi Novati (2018) Calchi Novati, S. e. a. 2018, AAS, submitted
- Carson et al. (2013) Carson, J., Thalmann, C., Janson, M., et al. 2013, ApJ, 763, L32
- Chabrier (2003) Chabrier, G. 2003, PASP, 115, 763
- Choi et al. (2013) Choi, J.-Y., Han, C., Udalski, A., et al. 2013, ApJ, 768, 129
- Chung et al. (2017) Chung, S.-J., Zhu, W., Udalski, A., et al. 2017, ApJ, 838, 154
- Dong et al. (2009) Dong, S., Gould, A., Udalski, A., et al. 2009, ApJ, 695, 970
- Dupuy & Liu (2017) Dupuy, T. J., & Liu, M. C. 2017, ApJS, 231, 15
- Fazio et al. (2004) Fazio, G. G., Hora, J. L., Allen, L. E., et al. 2004, ApJS, 154, 10
- Foreman-Mackey et al. (2013) Foreman-Mackey, D., Hogg, D. W., Lang, D., & Goodman, J. 2013, PASP, 125, 306
- Furusawa et al. (2013) Furusawa, K., Udalski, A., Sumi, T., et al. 2013, ApJ, 779, 91
- Gagné et al. (2017) Gagné, J., Faherty, J. K., Mamajek, E. E., et al. 2017, ApJS, 228, 18
- Gould (1992) Gould, A. 1992, ApJ, 392, 442
- Gould (1994) —. 1994, ApJ, 421, L75
- Gould (2000) —. 2000, ApJ, 542, 785
- Gould (2004) —. 2004, ApJ, 606, 319
- Gould (2008) —. 2008, ApJ, 681, 1593
- Gould (2016) —. 2016, Journal of Korean Astronomical Society, 49, 123
- Gould et al. (2009) Gould, A., Udalski, A., Monard, B., et al. 2009, ApJ, 698, L147
- Han & Chang (2003) Han, C., & Chang, H.-Y. 2003, MNRAS, 338, 637
- Han & Gould (2003) Han, C., & Gould, A. 2003, ApJ, 592, 172
- Han et al. (2017a) Han, C., Udalski, A., Sumi, T., et al. 2017a, ApJ, 843, 59
- Han et al. (2017b) Han, C., Udalski, A., Bozza, V., et al. 2017b, ApJ, 843, 87
- Jeffries (2012) Jeffries, R. D. 2012, in EAS Publications Series, Vol. 57, EAS Publications Series, ed. C. Reylé, C. Charbonnel, & M. Schultheis, 45–89
- Kervella et al. (2004) Kervella, P., Thévenin, F., Di Folco, E., & Ségransan, D. 2004, A&A, 426, 297
- Kim et al. (2017) Kim, D.-J., Kim, H.-W., Hwang, K.-H., et al. 2017, ArXiv e-prints, arXiv:1703.06883
- Kim (2018 in preparation) Kim, H.-W. e. a. 2018 in preparation
- Kim et al. (2016) Kim, S.-L., Lee, C.-U., Park, B.-G., et al. 2016, Journal of Korean Astronomical Society, 49, 37
- Kroupa (2002) Kroupa, P. 2002, Science, 295, 82
- Lovis & Mayor (2007) Lovis, C., & Mayor, M. 2007, A&A, 472, 657
- Luhman (2013) Luhman, K. L. 2013, ApJ, 767, L1
- McDougall & Albrow (2016) McDougall, A., & Albrow, M. D. 2016, MNRAS, 456, 565
- Mordasini et al. (2009) Mordasini, C., Alibert, Y., & Benz, W. 2009, A&A, 501, 1139
- Mróz et al. (2017) Mróz, P., Udalski, A., Skowron, J., et al. 2017, Nature, 548, 183
- Mroz et al. (2018) Mroz, P., Ryu, Y.-H., Skowron, J., et al. 2018, AJ, in press, arXiv:1712.01042
- Nataf et al. (2013) Nataf, D. M., Gould, A., Fouqué, P., et al. 2013, ApJ, 769, 88
- Park et al. (2004) Park, B.-G., DePoy, D. L., Gaudi, B. S., et al. 2004, ApJ, 609, 166
- Park et al. (2015) Park, H., Udalski, A., Han, C., et al. 2015, ApJ, 805, 117
- Pejcha & Heyrovský (2009) Pejcha, O., & Heyrovský, D. 2009, ApJ, 690, 1772
- Penny et al. (2016) Penny, M. T., Henderson, C. B., & Clanton, C. 2016, ApJ, 830, 150
- Refsdal (1966) Refsdal, S. 1966, MNRAS, 134, 315
- Saito et al. (2012) Saito, R. K., Hempel, M., Minniti, D., et al. 2012, A&A, 537, A107
- Schechter et al. (1993) Schechter, P. L., Mateo, M., & Saha, A. 1993, PASP, 105, 1342
- Schlaufman (2018) Schlaufman, K. C. 2018, ApJ, 853, 37
- Shin et al. (2017) Shin, I.-G., Udalski, A., Yee, J. C., et al. 2017, AJ, 154, 176
- Shin et al. (2018) —. 2018, ArXiv e-prints, arXiv:1801.00169
- Shvartzvald et al. (2017) Shvartzvald, Y., Yee, J. C., Calchi Novati, S., et al. 2017, ApJ, 840, L3
- Udalski et al. (2015) Udalski, A., Szymański, M. K., & Szymański, G. 2015, Acta Astron., 65, 1
- Yee et al. (2009) Yee, J. C., Udalski, A., Sumi, T., et al. 2009, ApJ, 703, 2082
- Yee et al. (2015) Yee, J. C., Gould, A., Beichman, C., et al. 2015, ApJ, 810, 155
- Zhu et al. (2016) Zhu, W., Calchi Novati, S., Gould, A., et al. 2016, ApJ, 825, 60
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January 21, 2013 report
Physicists looking to test theory of 'cosmic domain walls'
(Phys.org)—An international team of physics researchers is looking to add credence to a theory that might help explain the nature of dark matter and dark energy – using magnetometers placed strategically around the globe. As they describe in their paper published in Physical Review Letters, the aim is to measure the energy in the walls of theoretic domains that control both dark matter and dark energy.
For several years, physicists have searched in vain for an explanation of dark matter – the invisible "stuff" that makes up what is believed to be approximately 86 percent of all matter, and dark energy – the mysterious force believed to be responsible for the accelerating expansion of the universe. Because thus far no evidence has been found to support any theory that explains either, new theories continue to develop. One is the theory of cosmic domain walls. It's based on the idea that shortly after the Big Band, the universe had random energy fields, but as things cooled, different energy regions began to form dominated by an energy factor, with walls between the different regions – and that's how things stand today. A model might look like a bunch of soap bubbles that have been pushed together. The flat walls that exist at the juncture points would represent the cosmic domain walls.
In this new research effort, the aim is to measure the energy in these walls, to hopefully learn more about them and by extension, more about the nature of dark matter and dark energy. The team members believe that it should be possible to test for the energy they are looking for using simple magnetometers. But it would have to be more than one of course, because there are so many things that can be recorded by such devices – it would be difficult to attribute any readings found from just one or even two, to cosmic domain walls. To get around that problem, they propose setting up five of the devices at various locations around the globe, and then correlating them together to rule out interference and other noise.
The team isn't suggesting that if they find what they believe to be the existence of cosmic domain walls, that answers regarding dark matter and dark energy will follow soon thereafter – instead, they are simply hoping to add credence to a theory that many currently consider far outside of the domain of mainstream science.
Stable topological defects of light (pseudo)scalar fields can contribute to the Universe's dark energy and dark matter. Currently, the combination of gravitational and cosmological constraints provides the best limits on such a possibility. We take an example of domain walls generated by an axionlike field with a coupling to the spins of standard-model particles and show that, if the galactic environment contains a network of such walls, terrestrial experiments aimed at the detection of wall-crossing events are realistic. In particular, a geographically separated but time-synchronized network of sensitive atomic magnetometers can detect a wall crossing and probe a range of model parameters currently unconstrained by astrophysical observations and gravitational experiments.
© 2013 Phys.org | 0.809124 | 3.799983 |
From Dr. Tony Phillips Science at NASA
When Venus transits the sun on June 5th and 6th, an armada of spacecraft and ground-based telescopes will be on the lookout for something elusive and, until recently, unexpected: The Arc of Venus.
“I was flabbergasted when I first saw it during the 2004 transit,” recalls astronomy professor Jay Pasachoff of Williams College. “A bright, glowing rim appeared around the edge of Venus soon after it began to move into the sun.”
For a brief instant, the planet had turned into a “ring of fire.”
Researchers now understand what happened. Backlit by the sun, Venus’s atmosphere refracted sunlight passing through layers of air above the planet’s cloudtops, creating an arc of light that was visible in backyard telescopes and spacecraft alike.
It turns out, researchers can learn a lot about Venus by observing the arc. Indeed, it touches on some of the deepest mysteries of the second planet.
› View larger The arc of Venus photographed in 2004 by Riccardo Robitschek and Giovanni Maria
Caglieris of Milan, Italy. “We do not understand why our sister planet’s atmosphere evolved to be so different than Earth’s,” explains planetary scientist Thomas Widemann of the Observatoire de Paris.
Earth and Venus are similar distances from the sun, are made of the same basic materials, and are almost perfect twins in terms of size. Yet the two planets are wrapped in stunningly dissimilar blankets of air. Venus’s atmosphere is almost 100 times more massive than Earth’s and consists mainly of CO2, a greenhouse gas that raises the surface temperature to almost 900°F. Clouds of sulfuric acid tower 14 miles high and whip around the planet as fast as 220 mph. A human being transported to this hellish environment would be crushed, suffocate, desiccate, and possibly ignite.
For the most part, planetary scientists have no idea how Venus turned out this way.
“Our models and tools cannot fully explain Venus, which means we lack the tools for understanding our own planet,” points out Widemann. “Caring about Venus is caring about ourselves.”
One of the biggest mysteries of Venus is super-rotation. The whole atmosphere circles the planet in just four Earth days, much faster than the planet’s spin period of 243 days. “The dynamics of super-rotation are still a puzzle despite a wealth of data from landmark missions such as NASA’s Pioneer Venus, Russia’s Venera and VEGA missions, NASA’s Magellan and more recently ESA’s Venus Express.”
› View larger The arc of Venus as seen by NASA’s TRACE spacecraft in 2004. Credit: NASA/Trace/LMSAL
This is where the Arc of Venus comes in. The brightness of the arc reveals the temperature and density structure of Venus’s middle atmosphere, or “mesosphere,” where the sunlight is refracted. According to some models, the mesosphere is key to the physics of super-rotation. By analyzing the lightcurve of the arc, researchers can figure out the temperature and density of this critical layer from pole to pole.
When the arc appeared in 2004, the apparition took astronomers by surprise; as a result, their observations were not optimized to capture and analyze the fast-changing ring of light.
This time, however, they are ready. Together, Pasachoff and Widemann have organized a worldwide effort to monitor the phenomenon on June 5th, 2012. “We’re going to observe the arc using 9 coronagraphs spaced around the world,” says Pasachoff. “Observing sites include Haleakala, Big Bear, and Sacramento Peak. Japan’s Hinode spacecraft and NASA’s Solar Dynamics Observatory will also be gathering data.”
Pasachoff has some advice for amateur astronomers who wish to observe the arc. “The best times to look are ingress and egress–that is, when the disk of Venus is entering and exiting the sun. Ingress is between 22:09 and 22:27 UT on June 5th; egress occurs between 04:32 and 04:50 UT. Be sure your telescope is safely filtered. Both white light and H-alpha filters might possibly show the arc.” | 0.891675 | 3.915545 |
Looking at the Solar System, there seem to be two basic types of planets.
The smaller planets, including Earth, are dense, lower mass, and composed of rock. The larger worlds—Jupiter and the other giants—are massive, made of compressed gas, and possess no surface to speak of. As we learn about exoplanets orbiting distant stars, those two basic categories seem to hold. However, as astronomers map the landscape of planets, they are discovering worlds that don’t fit what we once thought, and which suggest a richer galaxy of possibilities.
The most dramatic of these so far is a mega-Earth: a world about 17 times more massive than Earth. That’s approximately the same mass as the giant Neptune, yet this planet is denser than any other yet discovered, meaning it must be made of rock. That’s puzzling: based on the theory of planet formation, no rocky world should get that huge.
The same group of astronomers has also inferred a type of exoplanet that fits in between the rocky planets and the gas giants. These “gas dwarf” worlds seem to have rocky interiors, but thick atmospheres like Neptune’s. While this proposition is less head scratching than the mega-Earth, it fills in the gap between the largest rocky planets and the smallest gas giants. This type of planet may be fairly common, even though we have nothing in the Solar System like it.
Both the mega-Earth and the mini-Neptunes are examples of how exoplanets are helping us understand planets in general. As we are learning, complex processes in a star system as it begins determine what types of planets are born, where they form, and where they end up once things calm down.
Location in a star system matters. Kepler-10c, which is the proper name for the mega-Earth, orbits its star much closer than our planet does. Its year is about 45 days long, and its surface is certainly too hot for any liquid water, especially if it has an atmosphere containing any greenhouse gases. In no way is the mega-Earth much like home.
But that’s not what makes it puzzling.
Most of the atoms in a newborn star system are hydrogen, which is the lightest chemical element. Earth effectively has no hydrogen in its atmosphere: our planet’s low mass isn’t enough to keep any around over time. Jupiter and its cousins, by contrast, are mostly made of hydrogen and hydrogen compounds. The seeds for those planets were more massive, and the larger amount of raw materials let them grow huge. Since it’s as massive as Neptune, Kepler-10c could technically have kept a thick atmosphere of hydrogen compounds, but it doesn’t seem to have one. Whether that’s because it’s too close to its star or not is another question.
However, the “gas dwarf” planets would have the same rocky structure but keep their thick atmospheres. (It’s still an open question whether Jupiter and the like have rocky centers, but those cores aren’t large if they are present.) Based on this study, the authors of the suggest that rocky planets could grow much bigger than previously thought, as long as they form far out from their host stars. That’s a claim we can’t test yet, because our methods are best suited for detecting exoplanets with small orbits.
I’m using weasel words deliberately: unlike Kepler-10c, we don’t have a lot of direct data about mini-Neptunes yet. That’s because the two main methods we have to hunt exoplanets measure different properties. The technique used by the Kepler observatory can find the size of the planet by the amount of light it blocks from the host star, but not the planet’s mass. Measuring masses requires determining how much the planet’s gravity swings the star around on each orbit, which is biased toward very heavy planets.
For that reason, we know more about the sizes of exoplanets than their masses. Kepler-10c was found to be roughly 2.4 times the diameter of Earth by the amount of light it blocked, which is smaller than Neptune. Astronomers used careful follow-up observations nearly ten years later to measure its mass using the way it affects its host star, but that won’t be possible for most exoplanets: they are either too low-mass or orbit too far to have much of an effect. (In the Solar System, only Jupiter is massive enough to produce a noticeable effect on the Sun, so it’s likely the only planet any bug-eyed alien astronomers would detect.)
For that reason, it will be difficult to confirm the presence of mini-Neptunes in most cases. But that’s the way exoplanet research has gone so far. Twenty-five years ago, we only knew about the Solar System (though I doubt many seriously thought those were the only planets in the Universe). Based on that limited data, it made sense to think that rocky planets were small and orbited close to their host stars, while giant planets were gaseous and orbited farther out. Now after thousands of exoplanet discoveries, we know there are more possible planet types than we expected, from super-Earths to giant planets orbiting their stars at roastingly close distances.
In science, imagination isn’t the limiting factor to discovery. Instead, we’re limited by the evidence: what kinds of things we can learn from experiment and observation. In the case of the mega-Earth and the mini-Neptunes, the evidence shows that galaxy of exoplanets is more wondrous than we expected. Every discovery brings us closer to understanding how planets form in all their marvelous variety. | 0.915244 | 3.960216 |
Saturn’s moon Enceladus has captivating scientists ever since the Voyager 2 mission passed through the system in 1981. The mystery has only deepened since the arrival of the Cassiniprobe in 2004, which included the discovery of four parallel, linear fissures around the southern polar region. These features were nicknamed “Tiger Stripes” because of their appearance and the way they stand out from the rest of the surface.
Since their discovery, scientists have attempted to answer what these are and what created them in the first place. Thankfully, new research led by the Carnegie Institute of Science has revealed the physics governing these fissures. This includes how they are related to the moon’s plume activity, why they appear around Enceladus’ south pole, and why other bodies don’t have similar features.
Saturn’s largest moon, Titan, is a mysterious place; and the more we learn about it, the more surprises it seems to have in store. Aside from being the only body beyond Earth that has a dense, nitrogen-rich atmosphere, it also has methane lakes on its surface and methane clouds in its atmosphere. This hydrological-cycle, where methane is converted from a liquid to a gas and back again, is very similar to the water cycle here on Earth.
Thanks to the NASA/ESA Cassini-Huygens mission, which concluded on September 15th when the craft crashed into Saturn’s atmosphere, we have learned a great deal about this moon in recent years. The latest find, which was made by a team of UCLA planetary scientists and geologists, has to do with Titan’s methane rain storms. Despite being a rare occurrence, these rainstorms can apparently become rather extreme.
What they found was that the extreme methane rainstorms may imprint the moon’s icy surface in much the same way that extreme rainstorms shape Earth’s rocky surface. On Earth, intense rainstorms play an important role in geological evolution. When rainfall is heavy enough, storms can trigger large flows of water that transport sediment into low lands, where it forms cone-shaped features known as alluvial fans.
During it’s mission, the Cassini orbiter found evidence of similar features on Titan using its radar instrument, which suggested that Titan’s surface could be affected by intense rainfall. While these fans are a new discovery, scientists have been studying the surface of Titan ever since Cassini first reached the Saturn system in 2006. In that time, they have noted several interesting features.
These included the vast sand dunes that dominate Titan’s lower latitudes and the methane lakes and seas that dominate it’s higher latitudes – particularly around the northern polar region. The seas – Kraken Mare, Ligeia Mare, and Punga Mare – measure hundreds of km across and up to several hundred meters deep, and are fed by branching, river-like channels. There are also many smaller, shallower lakes that have rounded edges and steep walls, and are generally found in flat areas.
In this case, the UCLA scientists found that the alluvial fans are predominantly located between 50 and 80 degrees latitude. This puts them close to the center of the northern and southern hemispheres, though slightly closer to the poles than the equator. To test how Titan’s own rainstorms could cause these features, the UCLA team relied on computer simulations of Titan’s hydrological cycle.
What they found was that while rain mostly accumulates near the poles – where Titan’s major lakes and seas are located – the most intense rainstorms occur near 60 degrees latitude. This corresponds to the region where alluvial fans are most heavily concentrated, and indicates that when Titan does experience rainfall, it is quite extreme – like a seasonal monsoon-like downpour.
As Jonathan Mitchell – a UCLA associate professor of planetary science and a senior author of the study – indicated, this is not dissimilar to some extreme weather events that were recently experienced here on Earth. “The most intense methane storms in our climate model dump at least a foot of rain a day, which comes close to what we saw in Houston from Hurricane Harvey this summer,” he said.
The team also found that on Titan, methane rainstorms are rather rare, occurring less than once per Titan year – which works out to 29 and a half Earth years. But according to Mitchell, who is also the principal investigator of UCLA’s Titan climate modeling research group, this is more often than they were expecting. “I would have thought these would be once-a-millennium events, if even that,” he said. “So this is quite a surprise.”
In the past, climate models of Titan have suggested that liquid methane generally concentrates closer to the poles. But no previous study has investigated how precipitation might cause sediment transport and erosion, or shown how this would account for various features observed on the surface. As a result, this study also suggests that regional variations in surface features could be caused by regional variations in precipitation.
On top of that, this study is an indication that Earth and Titan have even more in common than previously thought. On Earth, contrasts in temperature are what lead to intense seasonal weather events. In North America, tornadoes occur during the early to late Spring, while blizzards occur during the winter. Meanwhile, temperature variations in the Atlantic ocean are what lead to hurricanes forming between the summer and fall.
Similarly, it appears that on Titan, serious variations in temperature and moisture are what triggers extreme weather. When cooler, wetter air from the higher latitudes interacts with warmer, drier air from the lower latitudes, intense rainstorms result. These findings are also significant when it comes to other bodies in our Solar System that have alluvial fans on them – such as Mars.
In the end, understanding the relationship between precipitation and planetary surfaces could lead to new insights about the impact climate change has on Earth and the other planets. Such knowledge would also go a long way towards helping us mitigate the effects it is having here on Earth, where the changes are only unnatural, but also sudden and very hazardous.
And who knows? Someday, it could even help us to alter the environments on other planets and bodies, thus making them more suitable for long-term human settlement (aka. terraforming)!
Titan, Saturn’s largest moon, has been a source of mystery ever since scientists began studying it over a century ago. These mysteries have only deepened with the arrival of the Cassini-Huygens mission in the system back in 2004. In addition to finding evidence of a methane cycle, prebiotic conditions and organic chemistry, the Cassini-Huygens mission has also discovered that Titan may have the ingredient that help give rise to life.
Such is the argument made in a recent study by an international team of scientists. After examining data obtained by the Cassini space probe, they identified a negatively charged species of molecule in Titan’s atmosphere. Known as “carbon chain anions”, these molecules are thought to be building blocks for more complex molecules, which could played a key role in the emergence of life of Earth.
As they indicate in their study, these molecules were detected by the Cassini Plasma Spectrometer (CAPS) as the probe flew through Titan’s upper atmosphere at an distance of 950 – 1300 km (590 – 808 mi) from the surface. They also show how the presence of these molecules was rather unexpected, and represent a considerable challenge to current theories about how Titan’s atmosphere works.
For some time, scientists have understood that within Titan’s ionosphere, nitrogen, carbon and hydrogen are subjected to sunlight and energetic particles from Saturn’s magnetosphere. This exposure drives a process where these elements are transformed into more complex prebiotic compounds, which then drift down towards the lower atmosphere and form a thick haze of organic aerosols that are thought to eventually reach the surface.
This has been the subject of much interest, since the process through which simple molecules form complex organic ones has remained something of a mystery to scientists. This could be coming to an end thanks to the detection of carbon chain anions, though their discovery was altogether unexpected. Since these molecules are highly reactive, they are not expected to last long in Titan’s atmosphere before combining with other materials.
However, the data showed that the carbon chains became depleted closer to the moon, while precursors to larger aerosol molecules underwent rapid growth. This suggests that there is a close relationship between the two, with the chains ‘seeding’ the larger molecules. Already, scientists have held that these molecules were an important part of the process that allowed for life to form on Earth, billions of years ago.
However, their discovery on Titan could be an indication of how life begins to emerge throughout the Universe. As Dr. Ravi Desai, University College London and the lead author of the study, explained in an ESA press release:
“We have made the first unambiguous identification of carbon chain anions in a planet-like atmosphere, which we believe are a vital stepping-stone in the production line of growing bigger, and more complex organic molecules, such as the moon’s large haze particles. This is a known process in the interstellar medium, but now we’ve seen it in a completely different environment, meaning it could represent a universal process for producing complex organic molecules.”
Because of its dense nitrogen and methane atmosphere and the presence of some of the most complex chemistry in the Solar System, Titan is thought by many to be similar to Earth’s early atmosphere. Billions of years ago, before the emergence of microorganisms that allowed for subsequent build-up of oxygen, it is likely that Earth had a thick atmosphere composed of nitrogen, carbon dioxide and inert gases.
Therefore, Titan is often viewed as a sort planetary laboratory, where the chemical reactions that may have led to life on Earth could be studied. However, the prospect of finding a universal pathway towards the ingredients for life has implications that go far beyond Earth. In fact, astronomers could start looking for these same molecules on exoplanets, in an attempt to determine which could give rise to life.
Closer to home, the findings could also be significant in the search for life in our own Solar System. “The question is, could it also be happening within other nitrogen-methane atmospheres like at Pluto or Triton, or at exoplanets with similar properties?” asked Desia. And Nicolas Altobelli, the Project Scientist for the Cassini-Huygens mission, added:
“These inspiring results from Cassini show the importance of tracing the journey from small to large chemical species in order to understand how complex organic molecules are produced in an early Earth-like atmosphere. While we haven’t detected life itself, finding complex organics not just at Titan, but also in comets and throughout the interstellar medium, we are certainly coming close to finding its precursors.“
Cassini’s “Grande Finale“, the culmination of its 13-year mission around Saturn and its system of moons, is set to end on September 15th, 2017. In fact, as of the penning of this article, the mission will end in about 1 month, 18 days, 16 hours, and 10 minutes. After making its final pass between Saturn’s rings, the probe will be de-orbited into Saturn’s atmosphere to prevent contamination of the system’s moons.
However, future missions like the James Webb Space Telescope, the ESA’s PLATO mission and ground-based telescopes like ALMA are expected to make some significant exoplanet finds in the coming years. Knowing specifically what kinds of molecules are intrinsic in converting common elements into organic molecules will certainly help narrow down the search for habitable (or even inhabited) planets! | 0.877537 | 3.877636 |
Rapid destruction of Earth-like atmospheres by young stars
The discoveries of thousands of planets orbiting stars outside our solar system has made questions about the potential for life to form on these planets fundamentally important in modern science. Fundamentally important for the habitability of a planet is whether or not it can hold onto an atmosphere, which requires that the atmosphere is not completely lost early in the lifetime of the planet. A new study by researchers based at the University of Vienna and at the Institut für Weltraumforschung in Graz has shown that young stars can rapidly destroy the atmospheres of potentially-habitable Earth-like planets, which is a significant additional difficulty for the formation of life outside our solar system. The results will appear soon in the journal Astronomy & Astrophysics.
One of the most active and exciting questions in modern science is how abundant planets with Earth-like atmospheres and surface conditions and therefore the potential for harbouring life are in the universe. Much recent research on this topic has focused on planets orbiting stars called M-dwarfs, which are smaller than our Sun and are the most numerous type of star in our solar system.
The primary driver of atmospheric losses to space is the central star that the planet is orbiting. Stars have strong magnetic fields, and these lead to the emission of high energy X-ray and ultraviolet radiation. These phenomena are known collectively as the star's 'activity'. At young ages, stars have high levels of activity, and therefore emit extremely large amounts of X-rays and ultraviolet radiation. As stars age, their activities decrease rapidly. Importantly for planets orbiting M-dwarfs, while the activities of stars like the Sun decrease rapidly after a few hundred million years, M-dwarfs often remain highly active for billions of years.
The high energy radiation is important because it is absorbed high in the atmosphere of a planet, causing the gas to be heated. For the Earth, the gas is heated to temperatures of more than 1000 degrees Celsius in the upper region known as the thermosphere. This is the region in which spacecraft such as satellites and the International Space Station fly. When orbiting young stars with high activity levels, the thermospheres of planets are heated to much higher temperatures which in extreme cases can cause the gas to flow away from the planet. How rapidly atmospheres in these cases are lost has so far not been explored in detail for Earth-like planets with Earth-like atmospheres.
Researchers based at the University of Vienna and the Space Science Institute in Graz have calculated for the first time how rapidly an Earth-like atmosphere would be lost from a planet orbiting a very active young star. Their calculations have shown that extreme hydrodynamic losses of the atmosphere would take place, leading to an Earth-like atmosphere being entirely lost in less that one million years, which for the evolution of a planet is almost instantaneous.
These results have significant implications for the early evolution of the Earth and for the possibility of Earth-like atmospheres forming around M-dwarfs. For the Earth, the most likely explanation for why the atmosphere was not lost is that the early atmosphere was dominated by carbon dioxide, which cools the upper atmosphere by emitting infrared radiation to space, thereby protecting it from the heating by the early Sun's high activity. The Earth's atmosphere could not have become Nitrogen dominated, as it is today, until after several hundred million years when the Sun's activity decrease to much lower levels.
More dramatically, the results of this study imply that for planets orbiting M-dwarf, the planets can only form Earth-like atmospheres and surfaces after the activity levels of the stars decrease, which can take up to several billion years. More likely is that many of the planets orbiting M-dwarf stars to have very thin or possible no atmospheres. In both cases, life forming in such systems appears less likely than previously believed.
Publication in Astronomy&Astrophysics Letters:
C. P. Johnstone, M. L. Khodachenko, T. Lüftinger, K. G. Kislyakova1, H. Lammer and M. Güdel: Extreme hydrodynamic losses of Earth-like atmospheres in the habitable zones of very active stars
Scientific contact: Colin Johnstone, MPhys PhD Department of Astrophysics University of Vienna 1180 - Vienna, Türkenschanzstraße 17 T +43-1-4277-538 39 [email protected]
Press contact: Stephan Brodicky Press Office Corporate Communications University of Vienna 1010 - Vienna, Universitätsring 1 T +43-1-4277-175 41 M +43-664-60277-175 41 [email protected]
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University of Arizona News Release
2015 June 26
TUCSON, Arizona — A journey that will stretch millions of miles and take years to complete begins with a short trip to a loading dock.
The first of five instruments for a spacecraft that will collect a sample from an asteroid and bring it back to Earth has arrived at the Lockheed Martin Space Systems facility in Littleton, Colorado, for its installation onto NASA's Origins Spectral Interpretation Resource Identification Security-Regolith Explorer, or OSIRIS-REx, spacecraft.
Led by the University of Arizona, OSIRIS-REx is the first U.S. mission to fly to, study and retrieve a pristine sample from an asteroid and return it to Earth for study. Scheduled to launch in September 2016, the spacecraft will reach its asteroid target in 2018 and return a sample to Earth in 2023. The mission will allow scientists to investigate the composition of material from the very earliest epochs of solar system history, providing information about the source of organic materials and water on Earth.
The OSIRIS-REx Thermal Emission Spectrometer, or OTES, will conduct surveys to map mineral and chemical abundances and to take the asteroid Bennu's temperature. OTES is the first such instrument built entirely on the Arizona State University campus.
"It is a significant milestone to have OSIRIS-REx's first instrument completed and delivered for integration onto the spacecraft," said Dante Lauretta, principal investigator for OSIRIS-REx at the UA's Lunar and Planetary Laboratory. "The OTES team has done an excellent job on the instrument and I deeply appreciate their scientific contribution to the mission. OTES plays an essential role in characterizing the asteroid in support of sample-site selection."
OTES is one of five instruments from national and international partners. These instruments will be key to mapping and analyzing Bennu's surface and will be critical in identifying a site from which a sample can be safely retrieved and ultimately returned to Earth.
"OTES, the size of a microwave oven, has spent the last several years being designed, built, tested and calibrated," says Philip Christensen, OTES instrument scientist at ASU. "Now OTES is shipping out for the solar system."
The instrument will be powered on shortly after the OSIRIS-REx spacecraft begins its two-year trip to the asteroid Bennu. On arrival at Bennu, OTES will provide spectral data for global maps used to assess potential sample sites. It will take thermal infrared spectral data every two seconds and will be able to detect temperatures with an accuracy of 0.2 degrees Fahrenheit. It also will detect the presence of minerals on the asteroid's surface.
The OSIRIS-REx Camera Suite, or OCAMS, consists of three cameras that will image Bennu during approach and proximity operations. Scientists and engineers at the UA's Lunar and Planetary Lab designed and built OCAMS to image Bennu over nine orders of magnitude in distance, from one million kilometers (more than 620,000 miles) down to two meters (6.5 feet). PolyCam, the largest camera of the OCAMS suite, is both a telescope — acquiring the asteroid from far away while it is still a point of light — and a microscope capable of scrutinizing the pebbles on Bennu's surface. MapCam will map the entire surface of Bennu from a distance of three miles, and the Sampling Camera, or SamCam, is designed to document the sample acquisition. The OCAMS instrument suite is scheduled to be installed on the spacecraft in September.
The OSIRIS-REx Laser Altimeter, or OLA, will scan Bennu to map the entire asteroid surface, producing local and global topographic maps. OLA is a contributed instrument from the Canadian Space Agency.
The OSIRIS-REx Visible and Infrared Spectrometer, or OVIRS, measures visible and infrared light from Bennu, which can be used to identify water and organic materials. The instrument is provided by NASA's Goddard Space Flight Center.
A student experiment called the Regolith X-ray Imaging Spectrometer, or REXIS, will map elemental abundances on the asteroid. REXIS is a collaboration between the students and faculty of the Massachusetts Institute of Technology and Harvard College Observatory.
"The next few months will be very busy as we begin integrating the instruments and prepare for the system-level environmental testing program to begin," said Mike Donnelly, OSIRIS-REx project manager at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
NASA's Goddard Space Flight Center provides overall mission management, systems engineering and safety and mission assurance for OSIRIS-REx. The UA's Lauretta is the mission's principal investigator. Lockheed Martin Space Systems in Denver is building the spacecraft. OSIRIS-REx is the third mission in NASA's New Frontiers Program. NASA's Marshall Space Flight Center in Huntsville, Alabama, manages New Frontiers for the agency's Science Mission Directorate in Washington, D.C.
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Every rocky planet has a lithosphere, but what is lithosphere? It is the rigid outermost shell of a rocky planet. Here on Earth the lithosphere contains the crust and upper mantle. The Earth has two types of lithosphere: oceanic and continental. The lithosphere is broken up into tectonic plates.
Oceanic lithosphere consists mainly of mafic(rich in magnesium and iron) crust and ultramafic(over 90% mafic) mantle and is denser than continental lithosphere. It thickens as it ages and moves away from the mid-ocean ridge. This thickening occurs by conductive cooling, which converts hot asthenosphere into lithospheric mantle. It was less dense than the asthenosphere for tens of millions of years, but after this becomes increasingly denser. The gravitational instability of mature oceanic lithosphere has the effect that when tectonic plates come together, oceanic lithosphere invariably sinks underneath the overriding lithosphere. New oceanic lithosphere is constantly being produced at mid-ocean ridges and is recycled back to the mantle at subduction zones, so oceanic lithosphere is much younger than its continental counterpart. The oldest oceanic lithosphere is about 170 million years old compared to parts of the continental lithosphere which are billions of years old.
The continental lithosphere is also called the continental crust. It is the layer of igneous, sedimentary rock that forms the continents and the continental shelves. This layer consists mostly of granitic rock. Continental crust is also less dense than oceanic crust although it is considerably thicker(25 to 70 km versus 7-10 km). About 40% of the Earth’s surface is now covered by continental crust, but continental crust makes up about 70% of the volume of Earth’s crust. Most scientists believe that there was no continental crust originally on the Earth, but the continental crust ultimately derived from the fractional differentiation of oceanic crust over the eons. This process was primarily a result of volcanism and subduction.
We may not walk directly the lithosphere, but it shapes every topographical feature the we see. The movement of the tectonic plates has presented many different shapes for our planet over the eons and will continue to change our geography until our planet ceases to exist.
We have written many articles about the lithosphere for Universe Today. Here’s an article about the lithosphere, and here’s an article about the tectonic plates.
We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth. | 0.817247 | 3.504797 |
Please use this identifier to cite or link to this item:
|Title:||Red Misfits in the Sloan Digital Sky Survey: Properties of Star-Forming Red Galaxies|
|Department:||Physics and Astronomy|
|Abstract:||Galaxies in the Universe are primarily blue and star-forming or red and passively evolving. Here we study an outlier population of red, star-forming galaxies in the local Universe which we call Red Misfits. These galaxies are classified based on inclination-corrected optical colours and specific star formation rates derived from the Sloan Digital Sky Survey Data Release 7. We find that $\sim$11 per cent of galaxies at all stellar masses are classified as red in colour yet actively star-forming. Using the wealth of information provided by the SDSS and related products we explore a number of properties of these galaxies and demonstrate that Red Misfits are a distinct population of galaxies in the Universe and not simply blue star-forming galaxies whose colours are reddened by intrinsic dust extinction. Red Misfit galaxies exhibit intermediate, bulge-dominated disk morphologies, intermediate stellar ages, slightly enhanced dust extinction and gas-phase metallicities, and an enhanced likelihood of hosting an active galactic nucleus. The proportion of Red Misfits in galaxy groups remains constant irrespective of group halo mass or projected distance to the group centre. We conclude that Red Misfits are a transition population being gradually quenched on their way to the red sequence and that this quenching is dominated by internal mechanisms rather than environmentally-driven processes.|
|Appears in Collections:||Open Access Dissertations and Theses|
Files in This Item:
|Evans_Fraser_A_201709_MSc.pdf||9.1 MB||Adobe PDF||View/Open|
Items in MacSphere are protected by copyright, with all rights reserved, unless otherwise indicated. | 0.814157 | 3.356428 |
Located about 5.8 billion light years from Earth in the Phoenix Constellation, astronomers have confirmed the first example of a galaxy cluster where large numbers of stars are being born at its core.
Galaxy clusters are the largest structures in the cosmos that are held together by gravity, consisting of hundreds or thousands of galaxies embedded in hot gas, as well as invisible dark matter. The largest supermassive black holes known are in galaxies at the centers of these clusters.
For decades, astronomers have looked for galaxy clusters containing rich nurseries of stars in their central galaxies. Instead, they found powerful, giant black holes pumping out energy through jets of high-energy particles and keeping the gas too warm to form many stars.
Now, scientists have compelling evidence for a galaxy cluster where stars are forming at a furious rate, apparently linked to a less effective black hole in its center. In this unique cluster, the jets from the central black hole instead appear to be aiding in the formation of stars. Researchers used new data from NASA’s Chandra X-ray Observatory and Hubble Space Telescope, and the NSF’s Karl Jansky Very Large Array (VLA) to build on previous observations of this cluster.
Image Credit: X-ray: NASA/CXC/SAO/G.Schellenberger et al.; Optical:SDSS | 0.809855 | 3.52162 |
Planets Orbiting Red Dwarfs May Stay Wet Enough for Life
Small, cold stars known as red dwarfs are the most common type of star in the Universe, and the sheer number of planets that may exist around them potentially make them valuable places to hunt for signs of extraterrestrial life.
However, previous research into planets around red dwarfs suggested that while they may be warm enough to host life, they might also completely dry out, with any water they possess locked away permanently as ice. New research published on the topic finds that these planets may stay wet enough for life after all. The scientists detailed their findings online on November 12 in The Astrophysical Journal Letters.
Red dwarfs, also known as M stars, are roughly one-fifth as massive as the Sun and up to 50 times fainter. These stars comprise up to 70 percent of the stars in the cosmos, and NASA’s Kepler space observatory has discovered that at least half of these stars host rocky planets that are one-half to four times the mass of Earth.
Red dwarf planets are potentially key places to search for life as we know it, not just because there are so many of them, but also because of their incredible longevity. Unlike our Sun, which will die in a few billion years, red dwarfs will take trillions of years to burn through their fuel, significantly longer than the age of the Universe, which is less than 14 billion years old. This longevity potentially gives red dwarfs a great deal more time for life to evolve around them.
Research into whether a distant world might host life as we know it usually focuses on whether or not it has liquid water, since there is life virtually everywhere there is liquid water on Earth, even miles underground. Scientists typically concentrate on habitable zones, the area around a star where it is neither too hot for all its surface water to boil away, nor too cold enough for all its surface water to freeze.
Recent findings suggest that planets in the habitable zones of red dwarf stars could accumulate significant amounts of water. In fact, each planet could possess about 25 times more water than Earth.
The habitable zones of red dwarfs are close to these stars because of how dim they are, often closer than the distance Mercury orbits the Sun. This closeness makes them appealing to astrobiologists, since planets near their stars cross in front of them more often, making them easier to detect than planets that orbit farther away.
However, when a planet orbits very near a star, the star’s gravitational pull can force the world to become “tidally locked” to it. When a planet is tidally locked to its star, it will always show the same side to its star, just as the Moon always shows the same side to Earth. This causes the planet to have one permanent day side and one permanent night side.
The extremes of heat and cold that tidally locked planets experience could make them profoundly different from Earth. For example, prior research speculated the dark sides of tidally locked planets would become so cold that any water there would freeze. Sunlight would make water on the sunlit side evaporate, and this water vapor could get carried by air currents to the night sides, eventually leading to sheets of ice miles thick on the night sides and removing all water from the sunlit sides. Life as we know it probably could not develop on the day sides of such planets. Although they would have sunlight for photosynthesis, they would have no water to serve as the primordial soup for life to swim in.
To see how habitable tidally-locked planets really are, scientists devised a 3D global climate model of planets that simulated interactions between the atmosphere, ocean, sea ice, and land, as well as a 3-D model of ice sheets large enough to cover entire continents. They also simulated a red dwarf with a temperature of about 5,660 degrees Fahrenheit (3,125 degrees Celsius), and investigated whether all the water on these planets would indeed get trapped on their night sides.
“I’ve been interested in trying to make calculations relevant for M-star planet habitability since being convinced by astronomers that these types of planets will likely be closest (in proximity) to Earth,” said study co-author Dorian Abbot, a geoscientist at the University of Chicago.
For instance, the nearest known star to the Sun, Proxima Centauri, is a red dwarf, and it remains uncertain whether or not it has a planet. The possibility that red dwarf planets might be relatively near to Earth “means that anything geoscientists can tell astronomers about habitability of these planets will be essential for planning future missions.”
The researchers simulated planets of Earth’s size and gravity that experienced between 63 percent and 77 percent as much sunlight as Earth. They also modeled a super-Earth planet 50 percent wider than Earth with 38 percent stronger gravity, because astronomers have discovered super-Earth worlds around red dwarfs. For instance, Gliese 667Cb, a super-Earth at least 4.5 times the mass of Earth, orbits Gliese 667C, a red dwarf about 22 light years from Earth. They set this super-Earth on an orbit where it received about two-thirds as much as sunlight as Earth.
The researchers modeled three different arrangements of continents for all these planets. One was a water world with no continents and global oceans of varying depths. Another involved a supercontinent covering the night side and an ocean covering the day side. The last mimicked Earth’s configuration of continents. The planets also had atmospheres similar to Earth’s, but the researchers also tested lower levels of the greenhouse gas, carbon dioxide, which traps heat and helps keep planets warm.
When it came to super-Earths covered entirely in water, and super-Earths with continental arrangements like Earth’s, the researchers found it was unlikely that all their water would get trapped on their night sides.
“This is because surface winds transport sea ice to the day side where it is melted easily,” said lead study author Jun Yang at the University of Chicago.
Moreover, ocean currents transport heat from the day side to the night side on these planets.
“Ocean heat transport strongly influences the climate and sea ice thickness on our Earth,” Yang said. “We found this may also work on exoplanets.”
If a super-Earth has very large continents covering most of its night side, the scientists discovered ice sheets of at least 3,300 feet (1,000 meters) thick could grow on its night side. However, the day sides of these super-Earths would dry out completely only if they received less geothermal heat from volcanic activity than Earth, and had 10 percent of the amount of water on Earth’s surface or less. Similar results were seen with Earth-sized planets.
“The important implication is that it may be easier than previously thought to keep liquid water on the dayside of a tidally locked planet, where photosynthesis is possible,” Abbot said. “There are many issues that will affect the habitability of M-star planets, but our results suggest at least that water-trapping on the night side will only be a problem for relatively dry planets with large continents on their nightside and relatively low geothermal heat flux.”
Based on present and near-future technology, Yang said it would be very difficult for astronomers to gauge how thick the sea ice or the ice sheets are on the night sides of red dwarf planets and test whether their models are correct. Still, using current and upcoming technology “it may be possible to know whether the day sides are dry or not,” Yang said. | 0.88447 | 3.779215 |
Scientists Find Evidence of ‘Orphan’ Gamma-Ray Bursts
The orphan burst flared and died out over a period of 25 years. Now very faint, its peak brightness in 1993 was more than 50 times what it is today. NRAO image.
Astronomers typically study objects that are visible night after night or explode suddenly, like supernovas, but Casey Law is scouring vast amounts of data in search of bright objects that disappear, never to be seen again.
That search turned up the first of what may be many “ghost” objects in the sky: in this case, an extremely bright source of radio emissions that blazed into existence in the 1990s and then faded out over next 25 years.
Based on the extreme brightness of the radio source and the type of galaxy in which the flare-up occurred, Law argues that it was the afterglow of the explosion of a massive star, which would have emitted an undetected long-duration gamma-ray burst. Gamma-ray bursts, whose origins are still contentious, are among the most intense flashes in the universe because much of their explosive energy is collimated into a tight beam, like that from a lighthouse.
“We believe we are the first to find evidence for gamma-ray bursts that could not be detected with a gamma-ray telescope,” said Law, an assistant research astronomer in the Department of Astronomy at the University of California, Berkeley. “These are known as ‘orphan’ gamma-ray bursts, and many more such orphan GRBs are expected in new radio surveys that are now underway.”
Gamma-ray bursts, such as that detected last year accompanying gravitational waves from the merger of two neutron stars, are rarely seen because the source of the gamma rays – a relativistic jet of material emerging from the explosive merger – must be pointing directly at Earth. Perhaps only one in 100 explosions can be seen from Earth by NASA’s Fermi Gamma-ray Space Telescope, for example.
The fact that these explosions are followed by a decades-long radio afterglow provides a way for astronomers to find the rest of these explosive events, not just those heralded by a gamma-ray burst.
Finding many more gamma-ray bursts will help resolve a major question in astronomy today: What are these massive stellar explosions that generate gamma-ray bursts, and what’s left behind afterward?
Law favors the theory that the explosion – whether preceded by the merger of two very large stars or neutron stars, or marking the death of a single, massive star – produces a rapidly spinning and highly magnetized neutron star, known as a magnetar. The surrounding matter emits intense radio waves that slowly fade away, during which time the magnetar spins down and occasionally emits fast radio bursts, another mysterious “transient” event in the universe.
He and his colleagues detail their observations and conclusions in an article recently accepted by the journal Astrophysical Journal Letters and accessible now on the arXiv server.
The value of archived data
The radio source (FIRST J141918.9+394036), now too faint to show up in sky surveys but still detectable by large radio telescopes, was a bright spot in a radio survey of the sky conducted in the early 1990s by the Very Large Array in New Mexico. It was on a par with the brightest radio sources in the universe: quasars and active galactic nuclei fueled by stars and gas falling into the massive black holes in the cores of galaxies.
An artist’s depiction of a gamma ray burst, emitted in oppositely directed beams after a massive stellar explosion. While the beams often miss Earth, these explosions create a telltale transient radio glow that can be detected. NRAO image.
“We thought, ‘That was weird,’” Law said. “Its peak brightness in the ‘90s was quite high, so it was a big, big change: about a factor of 50 decrease in brightness. We basically went through every radio survey, every radio dataset we could find, every archive in the world to piece together the story of what happened to this thing.”
He and his colleagues discovered 10 other sets of radio observations of that area of the sky, in the constellation Boötes, that allowed them to document the object’s appearance and disappearance.
They concluded that the radio emissions first reached Earth in 1992 or 1993, though their first detection was around the source’s peak brightness in 1994. It then faded away over a period of 23 years. It was fainter in a 2010 survey and barely visible in 2015. It was invisible in a 2017 Very Large Array Sky Survey.
The mystery object is located inside a dwarf galaxy 284 million light years from Earth that is still forming stars: a special environment that has previously been associated with fast radio bursts and, independently, gamma-ray bursts and the formation of magnetars. This led Law to conclude that the radio emissions from the dwarf galaxy were the 25-year-long afterglow from the explosion of a massive star, perhaps more than 40 times the mass of the sun, which would have produced a long gamma-ray burst that went undetected. Most GRBs last less than a minute.
One theory is that the resulting magnetar, because of its high rotation rate and huge magnetic fields, emits periodic fast radio bursts – each just a millisecond long – as it winds down to a run-of-the-mill pulsar.
While Law is enthused by the possibility of uncovering many more orphan gamma-ray bursts, he emphasizes the value of mining archived observational data in search of astronomical events that pop up and fade out over years to decades — what his team jokingly refers to as “anti-transients.”
“Part of the story is about how much of the sky is changing, even on this long time scale, and how hard it is to test that,” he said. “It is also partly about the value of new data science techniques. Pulling out information from these rich and diverse data sets is helping us do good science.”
Law’s co-authors are Bryan Gaensler of the University of Toronto’s Dunlap Institute, Brian Metzger and Lorenzo Sironi of Columbia University and Eran Ofek of the Weizmann Institute in Israel. Law’s research is supported by the National Science Foundation (1611606).
Paper: Discovery of the Luminous, Decades-Long, Extragalactic Radio Transient FIRST J141918.9+394036
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This article is mirrored from the main ESA web portal.
Rosetta’s investigations of its comet are continuing as the mission teams count down the last month to perihelion – the closest point to the Sun along the comet’s orbit – when the comet’s activity is expected to be at its highest.
Rosetta has been studying Comet 67P/Churyumov–Gerasimenko for over a year now, with observations beginning during the approach to the comet in March 2014. This included witnessing an outburst in late April 2014 and the revelation of the comet’s curious shape in early July.
After arriving at a distance of 100 km from the double-lobed comet on 6 August, Rosetta has spent an intense year analysing the properties of this intriguing body – the interior, surface and surrounding dust, gas and plasma.
Comets are known to be made of dust and frozen ices. As these ices are warmed by the Sun, they turn directly to vapour, with the gases dragging the comet’s dust along with it. Together, the gas and dust create a fuzzy atmosphere, or coma, and often-spectacular tails extend tens or hundreds of thousands of kilometres into space.
While ground-based observations can monitor the development of the coma and tail from afar, Rosetta has a ringside seat for studying the source of this activity directly from the nucleus. One important aspect of Rosetta’s long-term study is watching how the activity waxes and wanes along the comet’s orbit.
The comet has a 6.5 year commute around the Sun from just beyond the orbit of Jupiter at its furthest, to between the orbits of Earth and Mars at it closest.
Rosetta rendezvoused with the comet around 540 million km from the Sun. Today, 13 July, a month from perihelion, this distance is much smaller: 195 million km. Currently travelling at around 120 000 km/h around their orbit, Rosetta and the comet will be 186 million km from the Sun by 13 August.
“Perihelion is an important milestone in any comet’s calendar, and even more so for the Rosetta mission because this will be the first time a spacecraft has been following a comet from close quarters as it moves through this phase of its journey around the Solar System,” notes Matt Taylor, ESA’s Rosetta project scientist.
“We’re looking forward to reaching perihelion, after which we’ll be continuing to monitor how the comet’s nucleus, activity and plasma environment changes in the year after, as part of our long-term studies.”
See our FAQ below for more on what can you expect from perihelion and the activities planned around it.
What is perihelion exactly?
Perihelion is the closest point a Solar System object gets to the Sun along its orbit (aphelion is the term given to the most distant point). The term derives from ancient Greek, where ‘peri’ means near and ‘helios’ means Sun.
How close to the Sun will the comet be at perihelion?
Comet 67P/Churyumov–Gerasimenko is on a 6.5 year elliptical orbit around the Sun which takes it between 850 million km (5.68 AU) from the Sun at its most distant, just beyond the orbit of Jupiter, and 186 million km (1.24 AU) at its nearest, between the orbits of Earth and Mars. As a comparison, Earth orbits the Sun at an average distance of 149 million km (1 Astronomical Unit, or AU).
At what moment does perihelion occur?
For this comet, the upcoming perihelion occurs at 02:03 GMT on 13 August 2015. The previous perihelion took place on 28 February 2009.
The comet during perihelion
What happens to the comet during perihelion? Will there be a big difference in activity in the coming weeks?
The comet’s activity has been growing over the last year that Rosetta has been at the comet. This is an incremental process brought about by the increase in solar energy incident on the comet, warming up its frozen ices that subsequently sublimate. Rosetta has been witnessing this gradual rise, and scientists expect that this activity will reach a peak during August and September. Outbursts are possible, but unpredictable.
Other comets plunge into the Sun at perihelion, what about this one?
Comet 67P/Churyumov–Gerasimenko does not get close enough to the Sun to be destroyed by it; its closest point is actually further than Earth ever gets to the Sun and, furthermore, the comet has survived many previous orbits. It is not, for example, classed as a ‘sungrazer’ like Comet C/2012 S1 ISON, which broke apart during its perihelion passage in November 2013.
Will the comet break apart during perihelion?
The comet has not broken apart during its many previous orbits, so it is not expected to do so this time, but it cannot be ruled out. Scientists are keen to watch the possible evolution of a 500 m-long fracture that runs along the surface of the neck on the comet during the peak activity.
What happens to the comet after perihelion?
As with the last observed perihelia, we expect the comet to continue on its orbit as normal, away from the Sun and back towards the outer Solar System again. Thanks to the heat absorbed during perihelion, the activity is expected to remain high for a couple of months before gently decreasing towards the moderate activity levels seen earlier in the mission, allowing Rosetta to get closer to the nucleus again.
Rosetta and Philae during perihelion
Does Rosetta have to do any special manoeuvres for perihelion?
Perihelion is a very different milestone to the other events such as waking up from hibernation, arriving at or landing on the comet where critical operations had to be carried out. Perihelion is simply a moment in time, and in terms of operations, it is business as usual – no special manoeuvres are required. The mission team hopes to have Rosetta as close as possible to the comet during perihelion to perform science observations without jeopardising the safety of the spacecraft, but this distance is currently decided on a twice-weekly basis for the week ahead, so the exact distance for perihelion is not currently known. During the last few months, it has not been possible to operate closer than 150 km without running into difficulties caused by the vast amounts of dust around the comet at the present time.
Are there any special science observations that will be done at the time of perihelion?
As with operations, it is also business as usual for science observations – monitoring of the comet and its dust, gas and plasma environment will continue during perihelion. Scientists are particularly keen to study the southern hemisphere of the comet, which has been in full sunlight only since May.
How long will it take Rosetta to communicate with Earth on 13 August?
The one-way signal travel time on 13 August is 14 min 44 sec.
When will we see an image from the moment of perihelion?
Rosetta’s Navigation Camera takes images several times during each 24 hour Earth day for navigation purposes, while the science camera OSIRIS has dedicated imaging slots. While the imaging schedule is not currently known for perihelion, we are hoping to be able to share both NavCam and OSIRIS image(s) with you from around the time of perihelion, during the afternoon of 13 August. Note that for OSIRIS this will depend on the data prioritisation on that day and the time it takes to downlink so this cannot be guaranteed. Time is also needed to check and process the images for release (for both NavCam and OSIRIS). We will update this section if/when more information about the timing of the image release(s) is known.
Will Rosetta and Philae be safe during perihelion?
Owing to the large amounts of dust, Rosetta will continue to operate at a safe distance from the comet throughout perihelion. We cannot predict any sudden increases in activity of the comet in advance, but the spacecraft safety remains – as always – a priority.
Philae is on the surface of the comet, although its exact location remains unknown. Having regained communications with Rosetta on 13 June the link has been unpredictable and intermittent. The mission teams are carefully analysing the situation and hope that Philae will be operational during perihelion (separate updates on Philae’s condition will be made via the Rosetta Blog).
What will happen to the mission after perihelion?
Rosetta will continue to follow the comet as it moves back towards the outer Solar System, watching how the activity decreases over time and monitoring any post-perihelion changes that may occur. The Rosetta mission is scheduled to continue until September 2016, when the nominal planning would see Rosetta spiral down to the surface of the comet, where operations would likely end.
Observing the comet from Earth during perihelion
Why is perihelion interesting for astronomers?
Near perihelion, comets reach their highest level of brightness, releasing large amounts of gas and dust. Possible outbursts and other unpredictable events might also take place around perihelion, so it is extremely important to obtain as many observations as possible during this period. While ground-based observations provide large-scale context for Rosetta’s measurements, Rosetta’s close-up data provide in turn the possibility to calibrate many of the observations made from the ground. This unique opportunity will also improve the study and interpretation of ground-based observations of other comets.
How close to Earth will the comet be at perihelion? Is this the closest it gets to Earth?
While the distance between the comet and the Sun decreases steadily until perihelion, before increasing again afterwards up to aphelion, the distance between Earth and the comet depends on their relative positions in the Solar System. At perihelion, the comet is 265 million km from Earth, but it will be closer (222 million km) during January–February 2016. Follow the positions of Rosetta and the comet through the Solar System using our Where is Rosetta? tool.
Will astronomers be observing the comet at perihelion?
Yes, a large network of professional and amateur astronomers has been observing the comet from across the globe in the past months. Observations with professional telescopes are planned every night around perihelion, relying on several robotic telescopes in many locations, and spectroscopic observations will be performed once a week. More details of the professional campaign are available here.
How can I observe the comet at perihelion?
Unfortunately, even at perihelion, the comet is too faint to be seen with the naked eye. To observe the comet, you will need a good telescope: a minimum of a 20 cm-aperture telescope is recommended. Guidance on how amateur astronomers can observe the comet is available here.
Until when is it possible to observe the comet from Earth?
The comet is currently passing from the southern sky to the northern sky, so its visibility depends on where you live. Around the time of perihelion, it can be observed from Earth in the early morning hours, just before sunrise. It will remain relatively close to the Sun in the sky, and thus observable in the early morning, for several months. Then, the comet will be in the night sky between December 2015 and March 2016, which will be the prime time for ground-based observations. By the middle of 2016 it will likely be too faint to see except by large telescopes owing to its distance from the Sun and Earth, and it will also start moving behind the Sun as seen from Earth.
Will there be any special events to mark the occasion of perihelion?
Members of the public and media are invited to join an online Google+ Hangout on 13 August, during which we hope have one or more images on the ground from around the time of perihelion. Time and guests to be announced nearer the time.
How can I follow online?
You can follow the mission in a number of ways (see esa.int/rosetta for an overview). On the day you can follow on Twitter, with official updates from @ESA_Rosetta using the hashtag #perihelion2015. Information will also be provided by the Rosetta blog and on the Rosetta Mission Facebook page. The image(s) from perihelion will be published on our main ESA web portal, esa.int, in an official press release. The Google+ Hangout will also be advertised on esa.int and will be available to watch live via ESA’s G+ page and later as a replay on G+ and ESA’s YouTube channel.
Rosetta is an ESA mission with contributions from its Member States and NASA. Rosetta’s Philae lander is contributed by a consortium led by DLR, MPS, CNES and ASI. | 0.817029 | 3.840872 |
Beacons in the sky help monitor Earth's orientation in space
Measurements of remote celestial objects detail Earth’s orientation in space.
By Laura Naranjo
Illustrations of Earth depict a circular planet, steadily rotating on its axis orbiting the sun. Reality is not so tidy. Earth is not perfectly round; it wobbles, spinning at a slightly irregular rate. Geodesists, researchers who study Earth’s shape, movement, and orientation in space, help us get where we want. Accurately accounting for an imperfect Earth means the next time you use GPS, you will locate the correct restaurant or find your way out of a remote canyon.
Maintaining such precision requires continuous effort. To keep up with Earth’s constant change, from its rotation to its tectonic movement, researchers have created terrestrial and celestial frameworks of carefully observed reference points to triangulate positions accurately. These points help form reference frames that go beyond locating Earth in space, they reveal Earth’s tiny shifts caused by earthquakes and land rebounds after ice sheets melt. Such minute changes can only be observed if Earth’s motion is precisely measured.
From radio waves to reference frames
These reference frames are based on two sources near and far: radio telescopes on Earth, and the extremely distant celestial objects they detect.
In the 1930s, engineer Karl Jansky discovered that celestial objects emit radio waves when he tried to locate radio interference. Using a large antenna, he determined Earthly sources of radio waves, yet remained puzzled by unidentified sources. After comparing the signal to astronomical charts, Jansky realized the radio waves were “star noise,” coming from the constellation of Sagittarius - 25,640 light years away from Earth.Following Jansky’s discovery, researchers raced to build dish-shaped radio telescopes. Unlike tubular optical telescopes, radio telescopes cradle an antenna in a large parabolic dish, designed to channel radio waves from very specific directions—a distant galaxy, for instance. The first dish measured only 9 meters (30 feet) across. To detect more distant celestial objects, however, dishes needed to be much larger. Many radio telescope dishes are now 25 to 100 meters (82 to 328 feet) across. “The larger dishes are more sensitive, and used more for the faint sources,” said NASA geodesist Dirk Behrend. Now hundreds of radio telescopes across Earth’s surface tilt skyward, capturing a continuous stream of radio waves.
Size was not enough, however. More powerful radio telescopes were required to study extremely remote celestial objects in greater detail. So in the 1960s, researchers developed a technique called Very Long Baseline Interferometry (VLBI) to increase resolution. “VLBI is a technique where you combine the signals from multiple radio telescopes to synthesize a much larger radio telescope,” said David Gordon a radio astronomer at NASA's Goddard Space Flight Center. As radio waves from distant objects arrive, there is a time delay in a particular part of the signal arriving at one antenna versus another antenna. In that tiny delay, researchers extract a world of data. “We can measure the separation between the antennas, the rotation of the Earth, the polar motion of the Earth, the nutation, and the source coordinates,” Gordon said.This technique permitted astronomers to study more compact celestial objects and phenomena. Through painstaking observations, researchers precisely locate cosmic sources to develop what is called the International Celestial Reference Frame (ICRF). Behrend said, “The celestial frame is based on extremely distant extra-galactic radio sources called quasars; these are remote objects, typically brighter than a billion suns, which are embedded in the center of galaxies.” Quasars are so remote that they appear fixed, making them good reference sources. “The stars around us show motion over a few years,” Gordon said. “But quasars should essentially be fixed for much longer periods of time, perhaps thousands of years.”
Researchers also use the VLBI time delays from distant fixed objects to measure ground motion underneath radio telescope sites. Continental drift causes extremely slow changes, only a few centimeters per year, or about the rate that fingernails grow. Earthquakes, however, can cause sudden changes. Precisely measuring the position of each VLBI telescope site helped develop a set of Earth-based coordinates and velocities, contributing to a terrestrial reference frame representing measurements taken at a particular point in time. In addition to VLBI telescopes, this terrestrial framework includes three other space-geodetic techniques and their instruments: Satellite Laser Ranging (SLR) telescopes, Global Navigation Satellite Systems (GNSS) antennas, and Doppler Orbitography by Radiopositioning Integrated on Satellite (DORIS) beacons.
VLBI bridges the terrestrial and celestial references frames. The telescope sites form part of the terrestrial reference frame on a constantly rotating and shifting Earth, while quasars detected by the VLBI technique help form the fixed celestial reference frame. “By observing quasars all around the sky and measuring the delays for each one of them on each baseline, you can use a method of triangulation to solve for where the quasar is, where the Earth is, what the Earth orientation is,” Gordon said.
Earth Orientation Parameters
In the 1970s, NASA helped develop VLBI because accurate and repeated observations could discern motion in Earth’s crust. By 1979, NASA had established the Crustal Dynamics Project (CDP) at Goddard, and created NASA's Crustal Dynamics Data and Information Service (CDDIS) to archive and distribute CDP data. Early achievements of VLBI include measuring the rate of tectonic spreading between North America and Europe, as well as tracking tectonic deformation along the San Andreas fault in the southwestern US. The VLBI technique has also measured earthquake motion in Alaska, California, Hawaii, Chile, and Japan. Researchers continue to rely on VLBI and the ICRF to study tectonic activity, sea level rise, interactions between Earth’s core and mantle, and post-glacial land rebound and subsidence.
The VLBI technique also increased the accuracy of Earth Orientation Parameters (EOP), measurements that precisely characterize irregularities in Earth’s rotation, critical for space missions. This includes polar motion, or slight offsets in the axis around which Earth rotates—its wobble. Any significant motion or mass change on Earth’s surface can affect its axis or the velocity of its rotation, like earthquakes, large tides or ocean currents, or even melting ice.Another parameter involves time-keeping standards that measure a day as one rotation of Earth. Because Earth’s spin rate varies, the length of each day slightly varies. Of all the space geodetic techniques, only VLBI accurately measures UT1, a form of Universal Time based on the precise rotational position of the Earth. UT1 provides a correction to Coordinated Universal Time (UTC), on which civil time is based. “The UT1 correction changes the most rapidly of the EOP's, so it is necessary to measure it daily,” Gordon said.
Accounting for these tiny motions, along with precise time keeping, improve GPS positioning. In fact, without the UT1 measurements provided by VLBI, GPS satellites would not be able to provide accurate locations, Gordon said. Several NASA Earth Science missions depend on the EOP input from VLBI, in particular UT1. For instance, the Ice, Cloud and land Elevation Satellite 2 (ICESat-2) relies on VLBI-supported data for precise orbit determination.
More radio sources, more accuracy
The first version of this reference frame, the ICRF1, was completed by researchers at a host of international agencies. After being approved by the International Astronomical Union, the ICRF1 was adopted in 1998 and relied on the positions of 608 distant celestial objects. In 1999, the International VLBI Service for Geodesy and Astrometry (IVS) was formed to bring under one roof the operational activities of the geodetic and astrometric VLBI disciplines and to standardize the data flow. The central bureau of the service is hosted at GSFC and Behrend functions as its secretary.In 2009, the ICRF2 was adopted, using 3,414 sources. The ICRF3 becomes official in January 2019, based on 4,536 sources from observations dating to 1979. “The ICRF3 precision is about 30 micro-arc seconds,” Gordon said. “For an analogy, that’s about the size of a billiard ball on the moon as seen from Earth.” Gordon served as a key member of the ICRF3 working group. VLBI data used for the ICRF are archived at CDDIS, and at mirror sites in Europe.
Over the decades, radio telescopes have advanced observations, precisely capturing minute quasar motion. Not only is ICRF3 more accurate, it corrects for aberration: a phenomenon where a stationary object appears to change as you are moving relative to it. This correction accounts for the solar system rotating around the Milky Way, completing a circuit every 225 million years, resulting in a slow drift of distant quasars as seen from Earth. “The motion is only 5.8 micro-arc seconds per year, which is an extremely tiny number, like seeing a penny on the surface of the moon,” Gordon said.
To generate these increasingly accurate terrestrial and celestial references frames, researchers rely on radio waves that have travelled across vast distances of not only space, but time. “The quasars that we are using, they are several billions of light years away. So the signals that we use for the VLBI technique are actually older than the Earth itself,” Behrend said. “I think that’s an amazing thing, that we use something now that was produced so many billions of years ago.”
For more information
NASA Crustal Dynamics Data Information System (CDDIS)
International Celestial Reference Frame (ICRF)
Very Long Baseline Interferometry (VLBI)
Gordon, D. 2017. Impact of the VLBA on reference frames and Earth orientation studies. Journal of Geodesy 91(7): 735-742. doi: 10.1007/s00190-016-0955-0.
Nothnagel, A., T. Artz, D. Behrend, and Z. Malkin. 2017. International VLBI service for geodesy and astronomy. Journal of Geodesy 91: 711-721. doi: 10.1007/s00190-016-0950-5.
Crustal Dynamics Data Information System (CDDIS). 2018. Very Long Baseline Interferometry (VLBI), International VLBI Service for Geodesy and Astrometry (IVS) products. Available on-line https://cddis.nasa.gov/Data_and_Derived_Products/VLBI/VLBI_data_holdings.html from NASA EOSDIS CDDIS, Greenbelt, MD, U.S.A.
|About the remote sensing data|
||Various radio telescopes|
Very Long Baseline Interferometry (VLBI), International VLBI Service for Geodesy and Astrometry (IVS) products https://cddis.nasa.gov/Data_and_Derived_Products/VLBI/VLBI_data_holdings.html
|Parameter||Very Long Baseline Interferometry (VLBI)
|DAAC||NASA Crustal Dynamics Data Information System (CDDIS)|
Page Last Updated: Jan 6, 2020 at 12:37 PM EST | 0.861947 | 3.932683 |
(CN) – The question of how clouds form in Mars’ atmosphere may have been answered in a new study released Monday: meteors.
The study, published in the journal Nature Geoscience, discovered that “meteoric smoke” – icy dust created by meteorites impacting on the surface – accumulates in the red planet’s middle atmosphere about 18 miles above the surface.
The astronomers behind the findings said it is a “good reminder that planets and their weather patterns aren’t isolated from the solar systems around them.”
“We’re used to thinking of Earth, Mars and other bodies as these really self-contained planets that determine their own climates,” said Victoria Hartwick, lead author and graduate student at the University of Colorado Boulder. “But climate isn’t independent of the surrounding solar system.”
Hartwick said two to three tons of space debris hurtle to Mars’ surface every day, injecting large amounts of dust as they fall apart in the atmosphere. Using massive computer simulations to emulate the planetary atmosphere, the team discovered the formation of clouds after they added meteors to the simulations.
“Our model couldn’t form clouds at these altitudes before,” Hartwick said. “But now, they’re all there, and they seem to be in all the right places.”
Despite the formation of clouds in the Martian atmosphere, Hartwick said “you shouldn’t expect to see gigantic thunderheads forming above the surface of Mars anytime soon.” She compared the clouds on Mars to “much more like bits of cotton candy” rather than those on Earth that can cover the sky.
“But just because they’re thin and you can’t really see them doesn’t mean they can’t have an effect on the dynamics of the climate,” Hartwick said.
Some of the clouds her team observed in the simulation could cause temperatures at high altitudes to increase or decrease by up to 18 degrees. Study team member Brian Toon said the study could help astronomers determine how the red planet once support liquid water at the surface.
“More and more climate models are finding that the ancient climate of Mars, when rivers were flowing across its surface and life might have originated, was warmed by high altitude clouds,” Toon said. “It is likely that this discovery will become a major part of that idea for warming Mars.” | 0.800104 | 3.669359 |
Stunning image of two interacting galaxies caught by Hubble Space Telescope, known as UGC 2369, destined to become a single galaxy.
The illustrious Hubble Space Telescope recorded for the first time two galaxies that passed by making contact. The duo featured, known as UGC 2369, is destined to merge one day and become a single galaxy. But the two galaxies are only getting to know each other for now.
In the picture below, as their mutual attraction (read: gravity) draws them closer together, the pair can be seen swirling around each other. According to the European Space Agency (ESA), all that the two galaxies presently connect is a “tenuous bridge of gas, dust and stars,” almost as if holding hands.
Galaxies are extroverts-most of them belong to groups or galactic clusters. Interaction between two or more members in such close quarters is not unusual. The intense gravitational pull can still bend a galaxy out of shape even if a collision is somehow avoided.
Also Read: The Great Collision is Coming
In many respects, this is what makes it so amazing to observe galactic interactions. For example, galaxy fly-bys — where no contact is made — can create permanent warps, bars, and tidal tails that stretch out from the centre of the galaxy, morphing it into unusual shapes, and inducing new star formation bursts.
On the other hand, mergers are much more destructive, and this is particularly true when galaxies are about the same size. These larger events are less prevalent than minor fusions, but it thought that our galaxy has one coming in its future.
The in which we reside right now is busy shredding and absorbing two neighbouring dwarf galaxies, called Sagittarius and Canis Major. But one day it’s our galaxy that might turn into the meal.
Astronomers are quite certain that in the future, at some point, the Milky Way and the Andromeda galaxies will collide billions of years. It’s still up for discussion exactly when that might be and how it’s going to play out.
Despite the fresh look of the UGC 2369 merger, this galactic duo is regarded to be in a comparatively advanced phase. Therefore, training Hubble’s eye on such interactions could offer us a glimpse of the destiny of our galaxy. | 0.836865 | 3.691834 |
Astronomical year numbering is based on AD/CE year numbering, but follows normal decimal integer numbering more strictly. Thus, it has a year 0 and the years before that are designated with a minus sign '−'. The era designations AD/CE are dropped. So the year 1 BC(Before Christ) is numbered 0, the year 2 BC (Before Christ) is numbered −1, and in general the year n BC(E) is numbered (1−n). The numbers of AD/CE years are not changed, but AD/CE is not used, being replaced by either no sign or a positive sign. For normal calculation a number zero is often needed, here most notably when calculating the number of years in a period that spans the epoch; the end years need only be subtracted from each other.
The system is so named due to its use in astronomy. Few other sciences outside history deal with the time before year 1, exceptions being dendrochronology, archaeology and geology, the latter two of which use 'years before the present'. Although the absolute numerical values of astronomical and historical years only differ by one before year 1, this difference is critical when calculating astronomical events like eclipses or planetary conjunctions to determine when historical events which mention them occurred.
A zero year was first used by the eighteenth century French astronomers Philippe de La Hire (1702) and Jacques Cassini (1740). However, both of these astronomers used the applicable AD/BC designations of Latin and French with their year zero, thus near the epoch the years were designated 2 BC, 1 BC, 0, 1 AD, 2 AD, etc. They did not use −/0/+. During the nineteenth century, astronomers designated years with either BC/0/AD or −/0/+. Astronomers did not exclusively use the −/0/+ system until the mid twentieth century. | 0.856802 | 3.1797 |
A large diameter telescope provides two new basic capabilities that are not available with existing ground based telescopes and that cannot be delivered by the small telescopes in space or planned for the future:
- Improved spatial resolution, as long as the distorting effects of the Earth’s atmosphere are corrected for with an adaptive optics system; and
- Increased sensitivity
Sharper images allow us to see smaller objects and more detail; thus TMT will provide three times better resolution and detail than other telescopes. One example of new science that can be achieved with TMT’s tripled resolution is finding planets around other stars in the “habitable zone,” where the separation between the star and the exoplanet is similar to Earth and allows for liquid water on the planet’s surface. Many other areas of science that TMT will explore require finer spatial resolution than is currently available. TMT will have a high-performance adaptive optics system from day one.
TMT will also deliver a huge increase in sensitivity or image depth, thanks both to the larger area of the telescope and the sharper images. Increased sensitivity will finally allow us to detect the faintest, most distant galaxies and the smallest stars and planets. High sensitivity also means the properties of stars and galaxies are measured more quickly, allowing more objects to be studied and more rare objects to be found. The sensitivity for standard forms of observations is proportional to the telescope’s diameter (D) multiplied by itself 4 times (DxDxDxD). Today, large telescopes are typically 8 meters in diameter; in comparison, the TMT will be 200 times more sensitive, up to 200 times faster or able to detect objects 200 times fainter.
The TMT will be a general-purpose telescope, able to carry out different scientific investigations across many areas of astronomy, planetary science, and physics. The telescope will support a variety of instruments that work at different wavelengths of light (optical or infrared) and take images or spectral measurements. The instruments selected for early operations are versatile in nature.
A few key science areas that TMT will address far better than any existing facility include:
DARK MATTER AND DARK ENERGY:
TMT will study very distant “standard candle” supernovae that are magnified by the strong gravity of nearby galaxy clusters. The properties of these supernovae will allow TMT to test competing theories of Dark Energy and to determine how Dark Energy and Dark Matter have governed the evolution of our universe over cosmic time. | 0.885917 | 3.781213 |
Pluto’s ‘heart’ sheds light on a possible buried ocean
Ever since NASA’s New Horizons spacecraft flew by Pluto last year, evidence has been mounting that the dwarf planet may have a liquid ocean beneath its icy shell. Now, by modeling the impact dynamics that created a massive crater on Pluto’s surface, a team of researchers has made a new estimate of how thick that liquid layer might be.
The study, led by Brown University geologist Brandon Johnson and published in Geophysical Research Letters, finds a high likelihood that there’s more than 100 kilometers of liquid water beneath Pluto’s surface. The research also offers a clue about the composition of that ocean, suggesting that it likely has a salt content similar to that of the Dead Sea.
“Thermal models of Pluto’s interior and tectonic evidence found on the surface suggest that an ocean may exist, but it’s not easy to infer its size or anything else about it,” said Johnson, who is an assistant professor in Brown’s Department of Earth, Environmental and Planetary Sciences. “We’ve been able to put some constraints on its thickness and get some clues about composition.”
The research focused on Sputnik Planum, a basin 900 kilometers across that makes up the western lobe the famous heart-shaped feature revealed during the New Horizons flyby. The basin appears to have been created by an impact, likely by an object 200 kilometers across or larger.
The story of how the basin relates to Pluto’s putative ocean starts with its position on the planet relative to Pluto’s largest moon, Charon. Pluto and Charon are tidally locked with each other, meaning they always show each other the same face as they rotate. Sputnik Planum sits directly on the tidal axis linking the two worlds. That position suggests that the basin has what’s called a positive mass anomaly — it has more mass than average for Pluto’s icy crust. As Charon’s gravity pulls on Pluto, it would pull proportionally more on areas of higher mass, which would tilt the planet until Sputnik Planum became aligned with the tidal axis.
But a positive mass anomaly would make Sputnik Planum a bit of an odd duck as craters go.
“An impact crater is basically a hole in the ground,” Johnson said. “You’re taking a bunch of material and blasting it out, so you expect it to have negative mass anomaly, but that’s not what we see with Sputnik Planum. That got people thinking about how you could get this positive mass anomaly.”
Part of the answer is that, after it formed, the basin has been partially filled in by nitrogen ice. That ice layer adds some mass to the basin, but it isn’t thick enough on its own to make Sputnik Planum have positive mass, Johnson says.
The rest of that mass may be generated by a liquid lurking beneath the surface.
Like a bowling ball dropped on a trampoline, a large impact creates a dent on a planet’s surface, followed by a rebound. That rebound pulls material upward from deep in the planet’s interior. If that upwelled material is denser than what was blasted away by the impact, the crater ends up with the same mass as it had before the impact happened. This is a phenomenon geologists refer to as isostatic compensation.
Water is denser than ice. So if there were a layer of liquid water beneath Pluto’s ice shell, it may have welled up following the Sputnik Planum impact, evening out the crater’s mass. If the basin started out with neutral mass, then the nitrogen layer deposited later would be enough to create a positive mass anomaly.
“This scenario requires a liquid ocean,” Johnson said. “We wanted to run computer models of the impact to see if this is something that would actually happen. What we found is that the production of a positive mass anomaly is actually quite sensitive to how thick the ocean layer is. It’s also sensitive to how salty the ocean is, because the salt content affects the density of the water.”
The models simulated the impact of an object large enough to create a basin of Sputnik Planum’s size hitting Pluto at a speed expected for that part in the solar system. The simulation assumed various thicknesses of the water layer beneath the crust, from no water at all to a layer 200 kilometers thick.
The scenario that best reconstructed Sputnik Planum’s observed size depth, while also producing a crater with compensated mass, was one in which Pluto has an ocean layer more than 100 kilometers thick, with a salinity of around 30 percent.
“What this tells us is that if Sputnik Planum is indeed a positive mass anomaly —and it appears as though it is — this ocean layer of at least 100 kilometers has to be there,” Johnson said. “It’s pretty amazing to me that you have this body so far out in the solar system that still may have liquid water.”
As researchers continue to look at the data sent by New Horizons, Johnson is hopeful that a clearer picture of Pluto’s possible ocean will emerge. | 0.852008 | 3.876066 |
Donkeys, lard, and a telescope: eclipse exploration in 1878 and 1900
Something borrowed, something blue—that is what Samuel P. Langley, director of the Allegheny Observatory in Pennsylvania, was counting on in July 1878 as he waited on Pikes Peak, Colorado, for the wedding of light and shadow displayed by a total eclipse of the sun. At his eye was a telescope borrowed from the U.S. Naval Observatory. Over his head, a sky he reported to be a "deep and transparent blue."
The stint of fair weather was a welcome contrast to the preceding seven days of rain and hail, during which Langley had to transport all his equipment, including this five-inch equatorial refractor made by Alvan Clark & Sons, up Pikes Peak. The scope wasn't exactly light, a fact with which the donkeys tasked with hauling it up to some 14,000 feet would have surely agreed. In a desperate measure to protect the steel components of the telescope from water damage, Langley poured lard over it. If that weren't enough to turn one's stomach, the altitude was. Langley and others in his party severely suffered from "mountain sickness." He described the condition in his report to the U.S. Naval Observatory as a caution to future researchers who sought to obtain clearer observations in the thinner mountain air.
All this fuss over equipment is ironic considering Langley would spend the bulk of his time observing the total phase of the solar eclipse with his unaided eye. (Learn about eclipse safety.) As soon as the moon completely blocked the bright disk of the sun, he sketched his impression of the shape and extent of the suddenly visible solar atmosphere, or corona. Because the corona is so much dimmer than the sun, an eclipse provides one of the easiest ways to observe it. Langley was surprised that the corona appeared dimmer and far more extended than he had seen before. In a coordinated effort organized by the U.S. Naval Observatory, many other observers at multiple locations also created sketches of the corona and submitted them for study and publication.
Sketches of the corona during the 1878 eclipse by various observers. Courtesy of Astronomical and Meteorological Observations, XXII, U.S. Naval Observatory.
The real surprise came after Langley finished his sketch and looked through the telescope. He had only five seconds to observe an "extraordinary sharpness of filamentary structure" of the corona before the sun started to reappear. This structure would haunt him. Photographs taken during this and later eclipse expeditions failed to reproduce what he saw. Was it a figment of his imagination? One has but to look at the variety of drawings from the 1878 eclipse to see how questions of subjectivity could come to play.
When Langley had a chance to witness another eclipse in May 1900, he decided to capture images of the corona with "photography upon a greater scale than any hitherto attempted." By then, he was the Secretary of the Smithsonian and head of its Astrophysical Observatory. He had considerably more resources at his disposal, including $4,000 from the government to study the eclipse. Langley formed the party from staff at the Smithsonian, Catholic University, the U.S. Coast and Geodetic Survey, Williams College, and the U.S. Patent Office. And this time there would be no need to worry about steep mountain hiking, sickness, and freezing rain. The eclipse path crossed the small town of Wadesboro, North Carolina, about 400 miles from Washington, D.C., and accessible by train.
Since Wadesboro was an ideal place to observe the eclipse, other expeditions chose it, which meant a serious influx of astronomers. As "some slight return" for the hospitality extended to the team, the Smithsonian observers invited townspeople to look through a five-inch visual telescope to view the stars on clear nights. That scope was the same one that Langley had borrowed from the U.S. Naval Observatory for the 1878 eclipse. He borrowed it again.
This time, Langley wanted to record the detail he had glimpsed before. So the team made a really big camera. I mean big. The glass plate negatives it exposed were 30 by 30 inches. The camera lens was 12 inches in diameter and required 135 feet to focus. This "great lens" was borrowed from E. C. Pickering, director of Harvard College Observatory. (If you want to see the original, check out Harvard's Collection of Historical Scientific Instruments.)
Borrowed telescope, borrowed lens—and this from the head of the Astrophysical Observatory of the Smithsonian? What a mooch! Well, hold on a second. Let's not be hasty to judge. It makes sense that Langley would want to use the same telescope in Wadesboro that he had used on Pikes Peak. That is good science. Minimize the variables so you can confidently ascribe any observed change. Borrowing large lenses and other telescopes also makes sense because his Astrophysical Observatory was more concerned with studying the various wavelengths of light from the sun than with making pictures of it. Langley was especially interested in parts of the solar spectrum that were not visible to the naked eye. He developed an instrument to measure infrared radiation, the bolometer. And the Wadesboro expedition was an early attempt to use such an instrument to study the solar corona. While Langley enjoyed the view through his borrowed telescope, two other researchers sat in a small hut and took readings from the bolometer.
Perhaps the excitement of this unfolding field of study was enough to cheer Langley up after he finished watching the 1900 eclipse. "To the writer's view with the 5-inch telescope the inner corona was filled with detail, but far less sharp and definite than he saw it on Pikes Peak in 1878," Langley later wrote. "Having in mind the wonderful structure seen with the same instrument in the clear mountain air twenty-two years before, the impression was a disappointing one." Humidity could have been to blame, or even changes in the sun itself. Whatever the cause of his disappointment, it is hard to believe that anyone could look upon this telescope, learn about the eclipse expeditions it was used for, and be disappointed.
Kristen Frederick-Frost is curator of modern science in the Division of Medicine and Science. Planning to view the total solar eclipse this summer? The Smithsonian Eclipse app is your interactive guide to the big event. | 0.805085 | 3.535713 |
November 18, 2016 – The ExoMars orbiter is preparing to make its first scientific observations at Mars during two orbits of the planet starting next week.
The Trace Gas Orbiter, or TGO, a joint endeavour between ESA and Roscosmos, arrived at Mars on October 19. It entered orbit, as planned, on a highly elliptical path that takes it from between 230 and 310 km above the surface to around 98,000 km every 4.2 days.
The main science mission will only begin once it reaches a near-circular orbit about 400 km above the planet’s surface after a year of ‘aerobraking’ – using the atmosphere to gradually brake and change its orbit. Full science operations are expected to begin by March 2018. But next week provides the science teams with a chance to calibrate their instruments and make the first test observations at Mars.
In fact, the neutron detector has been on for much of TGO’s cruise to Mars and is currently collecting data to continue calibrating the background flux and checking that nothing changed after the Schiaparelli module detached from the spacecraft. It will measure the flow of neutrons from the martian surface, created by the impact of cosmic rays. The way in which they are emitted and their speed on arriving at TGO will tell scientists about the composition of the surface layer. In particular, because even small quantities of hydrogen can cause a change in the neutron speed, the sensor will be able to seek out locations where ice or water may exist, within the planet’s top 1–2 m.
The orbiter’s other three instruments have a number of test observations scheduled between November 20–28.
During the primary science mission two instrument suites will make complementary measurements to take a detailed inventory of the atmosphere, particularly of gases that are present only in trace amounts. Of high interest is methane, which on Earth is produced primarily by biological activity or geological processes such as some hydrothermal reactions.
The measurements will be carried out in different modes: pointing through the atmosphere towards the Sun, at the horizon at sunlight scattered by the atmosphere, and looking downwards at sunlight reflected from the surface. By looking at how the sunlight is influenced, scientists can analyse the atmospheric constituents.
In the upcoming orbits there are only opportunities for pointing towards the horizon or directly at the surface. This will allow the science teams to check the pointing of their instrument to best prepare for future measurements. There is a possibility that they might detect some natural nightside airglow – an emission of light in the upper atmosphere produced when atoms broken apart by the solar wind recombine to form molecules, releasing energy in the form of light.
During the second orbit, the scientists have also planned observations of Phobos, the larger and innermost of the planet’s two moons.
Finally, the camera will take its first test images at Mars next week. In each of the two orbits, it will first point at stars to calibrate itself for measuring the planet’s surface reflectance. Then it will point at Mars.
Given the current elliptical orbit, the spacecraft will be both closer to and further from the planet than during its main science mission. Closest to the planet, it will be travelling faster over the surface than in its final circular orbit, which presents some challenges in timing when the images should be taken.
The camera is designed to capture stereo pairs: it takes one image looking slightly forwards, and then the camera is rotated to look ‘back’ to take the second part of the image, in order to see the same region of the surface from two different angles. By combining the image pair, information about the relative heights of the surface features can be seen. Several components from Cobham Semiconductor Solutions in Colorado Springs, Colorado, were used in the design of the CaSSIS instrument.
Next week, the camera team will be checking the internal timing to help program commands for future specific scientific observations. The high speed and changing altitude of the elliptical orbit will make stereo reconstruction challenging, but the team will be able to test the stereo rotation mechanism and the various different camera filters, as well as how to compensate for spacecraft orientation with respect to the ground track.
There are no specific imaging targets in mind, although near the closest approach of the first orbit the orbiter will be flying over the Noctis Labyrinthus region and it will attempt to obtain a stereo pair. In the second orbit, it has the opportunity to capture images of Phobos.
Ultimately, the camera will be used to image and analyse features that may be related to the trace gas sources and sinks, to help better understand the range of processes that may be producing the gases. The images will also be used for looking at future landing sites.
“We’re excited we will finally see the instruments perform in the environment for which they were designed, and to see the first data coming back from Mars,” said Håkan Svedhem, ESA’s TGO Project Scientist.
After this brief science instrument demonstration period, which also serves as a test for relaying this data back to Earth, along with data from NASA’s Curiosity and Opportunity rovers, the focus turns back to operations and the preparations required for aerobraking next year. | 0.809072 | 3.818118 |
What is the most distant object humans have ever seen in the known Universe? The latest record-holder is a galaxy that is about 13.4 billion light-years away! Or, is it? Something screwy is going on when we talk about distances in an our ever-expanding Universe.
The Universe itself is roughly 13.8 billion years old, so this distant galaxy (MACS0647-D) is indeed old, since its light has been traveling to us for 13 billion years.
In comparison, our Solar System is only about 4.6 billion years old. (Our Solar System consists of our Sun and the orbiting planets and objects. Our Sun is one of many stars in the Milky Way Galaxy which is one among the billions of galaxies in what makes up the total known Universe!)
The object that we see, however, is very young, since it took so many years to travel to us. It’s from the time when the Universe itself was still an infant, just 420 million years old or 3 percent of its present age! So, we can look back into the very formation of the Universe.
The Crab Nebula, a six-light-year-wide remnant of a star’s supernova
Is it really 13.4 billion light-years away?
So, is the farthest object in the Universe really 13.4 billion light-years away, as the news articles claim? Well, when the image we now see left that galaxy, we were much closer together because the entire expanding Universe was much smaller back then.
Since those very first minutes of the Universe, it has been expanding. In 1998, the Hubble Space Telescope revealed that the expansion of the Universe is actually accelerating due to dark energy, which is still a mystery.
Since it was only 3 billion light-years away when its light started toward us, that galaxy should logically look large, since a photograph’s dimensions don’t change just because it took a long time to get delivered here. Amazingly, that galaxy does look four times larger than we’d expect for something so far away. It appears much closer than it is!
In size, that is. But its brightness is the opposite. It’s far dimmer than we’d expect a 13.4 billion light-year object to be. Space has been stretching all the time that this image traveled, dramatically reshifting it. It now exhibits the ultra-faintness of a galaxy at the impossible distance of 263 billion light-years!
Kepler’s Supernova Remnant is a cloud from an exploded star in our Milky Way galaxy
Could things get any weirder? You bet. Science articles say that it’s 13.4 billion light-years from here—but that’s merely how long its light took to reach us. During all that time, that farthest-of-all galaxies has meanwhile been madly receding in this expanding universe. It is now actually 30 billion light-years away. Got all that?
Anyway, it’s clear that the simple question, “How far is it, really?” has no simple answer. Don’t ask! You can’t get there from here! | 0.812339 | 3.614729 |
Meet the new low-cost, reliable approach to sampling planetary surfaces
With the help of Planetary Society members, donors, and Honeybee Robotics, we brought to life a new citizen-funded sampling technology that will help us do science on other planets. It’s called PlanetVac.
Taking samples of other worlds is an important step towards discovery, but it is an expensive and complex process. Honeybee Robotics and The Planetary Society teamed up to solve this problem. This is PlanetVac.
How does it work?
Some of the biggest discoveries we make in planetary science rely on picking up pieces of other worlds. Soil sampled by the Curiosity rover showed us Mars had liquid water conducive to life for an extended period of time. Rocks brought back to Earth by Apollo astronauts taught us the Moon is almost 4.6 billion years old. And grains of dust captured by the Stardust spacecraft contained amino acids, confirming comets can carry the building blocks of life.
Despite the fact that we've been scooping samples of planetary bodies since the 1960s, sample collection is still hard—and expensive. Robot arms are heavy, complicated, and power hungry, and they don't work on low-gravity worlds.
That’s where PlanetVac—short for Planetary Vacuum—changes the game.
PlanetVac Sample Collection
Attached to a lander leg, PlanetVac collects a surface sample by using an inert gas to move regolith into the sample container.
In practice it actually blows materials up tubes using compressed gas, which by the way, is usually available on landers already because it is used to pressurize the fuel tanks. The PlanetVac sampling devices would be built into the lander legs themselves. This technique can conceptually be used to feed surface dirt to science instruments and/or feed it into sample return rockets on landers on Mars, asteroids, or the Moon. Because of the low pressures on all those bodies, the technique is extremely efficient because the efficiency is related to the ratio of the pressure of the gas you are using to the ambient pressure.
PlanetVac Sampling System
The PlanetVac sampling installed on a (1) lander leg, includes (2) a sampler cone, (3) air nozzles, (4) a sample container, (5) a filter, and (6) pneumatic tubing.
In 2013, we helped fund a successful test of this next-generation system in the lab, and in May 2018, we took it out for a successful test flight on a rocket called Xodiac.
Bruce Betts / The Planetary Society
PlanetVac Xodiac takes flight
PlanetVac planetary sampling test flight on a Xodiac rocket, May 2018. PlanetVac can be seen as the left foot of the rocket in this picture.
Xodiac, built by Masten Space Systems, takes off and lands vertically in California's Mojave Desert. This allows space hardware developers to test new equipment and make sure prototypes can survive the stresses of a rocket launch and landing—all without actually flying to space.
PlanetVac wouldn’t have happened without the generosity of our members and donors.
Richard Chute / The Planetary Society
Bill Nye and donors
Planetary Society CEO Bill Nye and donors to PlanetVac Xodiac pose in front of the Xodiac rocket following a successful sampling test flight. Front row, shown left to right: Scott Purdy, Lauren Roberts, Dustin Roberts, Brian Pope, Shirley Ginzburg and Allen Ginzburg. Back row, shown left to right: Pendleton Ward, Bill Nye (CEO), Martin Schmitt, and Sue Ganz-Schmitt. For more information, visit the PlanetVac homepage.
We’re always working on new technologies that will further our understanding of the Cosmos. Sign up and get involved in citizen space exploration.
Some of the biggest discoveries we make in planetary science rely on the seemingly simple act of picking up and analyzing pieces of other worlds. When things go awry, scientists and engineers can sometimes squeeze amazing science out of a tough situation. | 0.817637 | 3.429873 |
This animation shows the distribution of the dark matter, obtained from a numerical simulation, at a redshift z~2, or when the Universe was about 3 billion years old.
The first frame displays the continuous distribution of dark matter particles, showing the typical wispy structure of the cosmic web, with a network of sheets and filaments that developed out of tiny fluctuations in the early Universe.
The second frame provides a simplified view of the complex network of dark matter structure according to the so-called halo model, a statistical approach used to describe the distribution of dark matter on both large and small scales. Within this framework, the dark matter distribution is viewed as an ensemble of discrete objects, the dark matter halos, corresponding to the densest knots of the cosmic web.
The last frame highlights the dark matter halos (shown in yellow) that represent the most efficient cosmic sites for the formation of galaxies. Only halos with a mass above a certain threshold can trigger the ignition of intense bursts of star formation, thus creating a starburst galaxy. According to the latest measurements achieved with Herschel, the minimum mass needed by a halo for a starburst galaxy to form within it is 3 x 10^11 times that of the Sun. | 0.840699 | 3.654432 |
The Chandra Space Telescope, an X-ray observatory, was the third in NASA's collection of "Great Observatories" orbiting Earth. The Great Observatories were designed to send back detailed information about space.
The Chandra X-ray Observatory is currently in orbit around Earth, peering out into the universe in search of extremely high-temperature events in space. These events give off X-rays, which are a highly energized form of light that cannot be seen by human eyes. X-rays can't make it through the Earth's atmosphere, so for astronomers to study them, X-ray telescopes like the Chandra must be based in space. The Chandra collects X-rays, some from as far as ten billion light years away, and uses a high resolution camera (HRC) to interpret them into images. The Chandra also contains scientific instruments that can measure the strength and temperature of X-rays.
Because X-rays would be absorbed right into the dish-shaped mirrors typically used in telescopes that measure visible light, the Chandra contains barrel-shaped mirrors with reflecting surfaces that run almost parallel to the X-rays. The X-rays barely bounce off the mirrors and are focused onto a point about half the width of a human hair, where they are recorded and measured.
X-ray telescopes are important because they allow us to see events in space that would normally be invisible to us. High-energy events such as huge explosions, black holes and neutron stars can be seen in much greater detail with an X-ray telescope, and X-ray telescope images can add an extra dimension to objects in space that also give off visible light.
The Chandra, which is named after Nobel prize winner Subrahmanyan Chandrasekhar, orbits up to 200 times higher above Earth than the Hubble—about a third of the distance to the moon! Chandra is the third in NASA's series of four great observatories designed to explore the universe from Earth's orbit.
The Science Center's Chandra Space Telescope
The Chandra telescope on display in the gallery is a 1/5th-scale model on loan from TRW. | 0.833446 | 3.773705 |
Like its twin that's busy exploring Mars aboard the rover Curiosity, the device known as SAM II spends its days as if it were 200 million miles away, in a very different environment than our own.
Temperatures around the instrument plunge to minus 130ºF (-90°C), the air pressure is one percent of Earth's, and the atmosphere it sits in consists largely of carbon dioxide.
But this second SAM—short for Sample Analysis on Mars—resides in suburban Maryland, inside a tightly controlled chamber where it plays a little-known but essential role as a test instrument for the Curiosity mission to Mars. (Watch: How Curiosity took a self-portrait.)
And for a short time last month, this microwave-size "test bed" SAM was out of its deep freeze for repairs and upgrades, offering a rare peak into exactly what it takes to keep a rover and its scientific instruments alive and well on Mars.
Simply put, SAM is the most complex and sophisticated suite of scientific equipment to ever land on another celestial body.
The gold-covered box holds two tiny cylinder ovens that can vaporize Mars's rocks and soil at temperatures up to 1800°F (1,000 °C). Three instruments (spectrometers) then identify and analyze the gases produced by the ovens, as well as those collected from the Martian atmosphere. Some six miles (nine kilometers) of electrical wire connect these and many other parts together.
SAM's task constitutes a primary aim of Curiosity's mission: investigating whether Mars preserves the chemical ingredients needed for life, including organic carbon. (Related: Intriguing new evidence of a watery past on Mars.)
SAM has already analyzed some Martian soil and will very soon get its first taste of Martian rock, dug out with a drill last week and crushed into powder. A pre-programmed examination of that rock powder—a first-of-its-kind procedure—is scheduled to begin inside SAM shortly. (Related: Curiosity completes first full drill for Martian rock samples.
Maryland SAM in the Operating Room
But for the SAM on Mars to operate safely and properly, it needs the Maryland SAM (a 99 percent duplicate) as a test bed.
Every command sent to the instrument on Mars must first be run through the twin on Earth to make sure it doesn't confuse the operating system, doesn't open a wrong valve, doesn't set into motion a fatal cascade of events. So keeping the test-bed SAM in near-perfect shape is essential to Curiosity's success.
Yet some parts or connections have failed in recent months, requiring less-than-ideal work-arounds. And when the SAM team recently devised additional ways to further improve their creation, they decided to bring it in for repairs.
Which is why test-bed SAM was out of its chamber last month, laid out on a gurney in a clean room at the NASA Goddard Space Flight Center in Greenbelt, Maryland.
Several days before, the liquid nitrogen piped into SAM II's chamber to keep it cold had been turned off. Myriad pipes and tubes going in were shut down. The near-vacuum pressure inside the chamber—which is the size of a washing machine and wrapped in aluminum foil—had been changed to Earth conditions.
The big chamber door (which would have exerted some 10,000 pounds, or about 4,500 kilograms, of force) was swung open.
SAM II's lustrous gold plating, needed to regulate temperatures and keep the instrument as clean as possible, had been removed, exposing the warren of intricately packed equipment and wiring inside.
In a Mylar-draped section of the room, two of the men who put both SAMs together were poking and prodding, vacuuming and tightening its insides. In their head-to-toe white cover-ups, they looked like surgeons in the OR.
One of them, Oren Sheinman, is a lead designer and builder of the two SAMs. His repair involved a heat pipe for the tunable laser spectrometer—an instrument Sheinman designed to sniff the Mars air for gases such as carbon-based methane, which could be a sign of past or present life.
Problems with SAM's heat pipe had made it difficult to ensure that the new computer instructions going up to Mars were accurate and effective, so Sheinman and colleague Bob Arvey had to find a work-around.
Speaking from behind the Mylar screen, Sheinman said that what they had created was actually similar to some spacecraft he had worked on. "Not in terms of guidance and propulsion," he said, "but in terms of system issues and sheer complexity."
"With SAM, the difficult part mechanically was packaging, because it isn't really an instrument, but an instrument suite," he said.
Discovery Requires Complexity
SAM was already the largest and heaviest instrument that Curiosity would carry, but it needed to be as small as possible to make room for Curiosity's other equipment.
Fortunately, the hardware Sheinman was working on sat near the outside of the SAM configuration; fixing a piece deeper inside would have required what he called an "excavation."
For Arvey, the primary repair job involved his specialty, the miles of wire. Because SAM has high-temperature wires to supply the ovens and low temperature wires for the instruments, all the wiring had to be crimped together rather than connected with welds.
One of those crimps, or "getters," had failed some time ago, and it too had to be replaced.
Arvey said he needed all of his 40-plus years of experience in wiring space-bound equipment (to Venus, Jupiter, Titan, and Mars) to lay out the electrical rigging of SAM.
"Everything we did in building SAM had to be made up new," he said.
It was SAM principal investigator Paul Mahaffy who decided to open up the chamber, and he says his rationale was more improvement than repair.
While the several malfunctioning parts were making life difficult, his primary goal was to better stabilize the test-bed SAM so the team could send up commands that would allow Mars SAM to make more sensitive measurements.
Curiosity is a "discovery-driven" mission, Mahaffy said, and that means demands placed on the faraway rover and its instruments are ever changing. The result is a constant process of tweaking, upgrading, and modifying as scientists and engineers learn about Mars and look to devise ways to follow new leads.
Everyone Needs a Test Bed
The Goddard test bed is hardly the only one used for Curiosity.
The home institutions of the principal investigator for all ten Curiosity instruments have their test beds, and their results have to be squared with the entire Curiosity system, headquartered at the Jet Propulsion Laboratory in Pasadena, California.
JPL has its "Mars yard," where duplicate Curiosity rovers are put through their paces—everything from climbing a steep incline to approaching and drilling a rock.
Using the drill, for instance, involves more than a hundred discrete commands, and they have been put through their paces at the yard in advance of Curiosity's first ever Mars drilling.
"It's kind of unexpected and occasionally funny, but the test beds tend to come up with more problems than the actual equipment on Mars," said Curiosity mission manager Michael Watkins.
Since the equipment and instruments are virtual duplicates, Watkins said it's not an issue of quality. Rather, problems arise because the equipment is made to operate under Mars atmospheric and gravity conditions, which are difficult to entirely reproduce on Earth.
The test equipment is also used far more frequently and aggressively than what's on the actual Curiosity.
The constant testing slows a mission down at times, and after six months on Mars the rover has traveled only about a quarter mile, or less than half a kilometer.
But it has been a productive trip. Since landing on Mars in early August, Curiosity has identified a once fast-flowing stream bed on the planet, found tantalizing but unconfirmed signs of organic materials, and has drilled into low-lying bedrock and found gray (rather than the usual Martian red) rock inside.
The rover's travels on Mars are officially set to continue until the summer of 2014, but if Curiosity and its instruments remain healthy, all involved expect it will operate for several years beyond that.
With that kind of time frame in mind, the SAM team recently arranged to have its busy test bed moved to a building that has a supply of liquid nitrogen just outside a back door.
Before that, researchers and technicians had to roll large, heavy canisters of the gas long distances into a different test room. Hardly ideal for a test bed that's likely to be busy for a long time to come.
Marc Kaufman is working on a book about Curiosity and Mars for National Geographic Books. | 0.809897 | 3.634141 |
Hubble's discovery “made as great a change in man’s conception of the universe as the Copernican revolution 400 years before." -Dictionary of Scientific Biography
FIRST EDITION OF HUBBLE'S DISCOVERY OF THE EXPANSION OF THE UNIVERSE.
Edwin Hubble’s landmark paper documented what would later become known as Hubble’s Law, stating that there is a proportional relationship between a galaxy’s recession velocity and its distance from the Earth. One of the most profound discoveries in science, Hubble’s data provided evidence of an expanding universe, thereby providing the essential argument for the Big Bang theory, proving the natural implications of Einstein’s General Theory of Relativity, and ultimately allowing for the determination of the age of the universe.
By the early 1920’s advances in spectroscopy had allowed for the observance of a curious “redshifting” of galaxies, indicating that the majority of galaxies seemed to be receding from the Milky Way. The evidence was rudimentary and inconclusive and “various weird and wonderful explanations were put forward, but there was no consensus. The case of the receding galaxies remained a mystery until Edwin Hubble applied his mind and his telescope to the problem. When he entered the debate he saw no point in wild theorizing, particularly when the power of the mighty 100-inch Mount Wilson telescope held the promise of new data.”
To solve the redshift mystery, Hubble and his assistant Milton Humason “divided the work between them. Humason would measure the Doppler shifts of numerous galaxies, and Hubble set about measuring their distances... By 1929 Hubble and Humason had gauged the redshifts and distances for forty-six galaxies.” Using only the twenty that were within an acceptable margin of error for their measurements, Hubble plotted velocity versus distance for each galaxy. “In almost every case the galaxies were redshifted, implying they were receding. Also, the points on the graph seemed to indicate that the velocity of a galaxy strongly depended on its distance. Hubble drew a straight line through the data, suggesting that the velocity of a given galaxy was proportional to its distance from the Earth...
“If Hubble was right, the repercussions were immense. The galaxies were not randomly dashing through the cosmos, but instead their speeds were mathematically related to their distances, and when scientists see such a relationship they search for a deeper significance. In this case, the significance was nothing less than the realization that at some point in history all the galaxies in the universe had been compacted into the same small region. This was the first observational evidence to hint at what we now call the Big Bang. It was the first clue that there might have been a moment of creation.” (Simon Singh, Big Bang).
Two additional implications of Hubble’s discovery were that, through the use of Hubble’s Law and the accurate determination of Hubble’s proportionality constant, the age of the universe could be determined; also, it confirmed the natural result of Einstein’s General Theory of Relativity which predicted an expanding universe (before Einstein added his “cosmological term” to prevent this seemingly impossible conclusion). After Hubble’s discovery proved the unnecessary and incorrect inclusion of the forced “cosmological term” in Einstein’s theory, Einstein sought out Hubble to congratulate him, later calling his cosmological term “the biggest blunder he ever made in his life.”
In Proceedings of the National Academy of Sciences, Vol. 15, No. 3. [Washington, D.C.]: Carnegie Institution, 1929. The entire volume offered. Quarto, elegant modern three-quarter morocco. A few stamps to outer corner of a few pages (none to Hubble paper). Binding and Hubble paper in fine condition. | 0.815574 | 4.021702 |
Monday, July 30 – Today’s history celebrates the 2001 flyby of the Moon by the Wilkinson Microwave Anisotropy Probe (WMAP) on its way to Lagrange Point 2 to study the cosmic microwave background radiation. Tonight we’ll also fly right by the Full Buck Moon as we continue our studies to have a look at Mu 1 and Mu 2 Scorpii about two fingerwidths north of Zeta.
Very close to the same magnitude and spectral type, the twin Mu stars are easy to separate visually and most definitely worth a look in telescopes or binoculars. They are considered an actual physical pair because they share the exact same distance and proper motion, but they are separated by less than one light-year.
Hanging out in space some 520 light-years away, western Mu 1 is a spectroscopic binary – the very first discovered to have double lines. This Beta Lyrae-type star has an orbiting companion that eclipses it around every day and a half, yet causes no significant visual drop in magnitude – even though the orbiting companion is only 10 million kilometers away from it! While that sounds like plenty of distance, when the two pass, their surfaces would nearly touch each other!
Now, relax and enjoy the peak of the Capricornid meteor shower. Although it is hard for the casual observer to distinguish these meteors from the Delta Aquarids, no one minds. Again, face southeast and enjoy! The fall rate for this shower is around 10 to 35 per hour, but unlike the Aquarids, this stream produces those great “fireballs” known as bolides. Enjoy…
Tuesday, July 31 – Tonight with the slightly later rise of the Moon, we’ll take the opportunity to look at two multiple star systems – Nu and Xi Scorpii.
Starting with Nu about a fingerwidth east and slightly north of bright Beta, we find a handsome duo of stars in a field of nebulosity that will challenge telescopic observers much the way that Epsilon Lyrae does. With any small telescope, the observer will easily see the widely separated A and C stars. Add just a little power and take your time… The C star has a D companion to the southwest! For larger telescopes, take a very close look at the primary star. Can you separate the B companion to the south?
Now let’s hop to Xi about four fingerwidths north of Beta.
Discovered by Sir William Herschel in 1782, this 80 light-year distant system poses a nice challenge for mid-sized scopes. The yellow-hued A and B pair share a very eccentric orbit about the same distance as Uranus is from our Sun. During the 2007 observing year they should be fairly well spaced, and the slightly fainter secondary should appear to the north. Look a good distance away for the 7th magnitude orange C component and south for yet another closely-matched double of 7th and 8th magnitude – the D and E stars.
For the larger scope, this multiple star system does display a little bit of color. Most will see the A and B components as yellow/white, the C star as slightly orange, and the D/E pair as slightly tinged with blue. Be sure to mark your observations for this is one of the finest!
Wednesday, August 1 – Today is the birthdate of Maria Mitchell. Born in 1818, Mitchell became the first woman to be elected as an astronomer to the American Academy of Arts and Sciences. She later rocketed to worldwide fame when she discovered a bright comet in 1847.
Tonight, let’s continue our exploration of globular clusters. These gravitationally bound concentrations of stars contain anywhere from ten thousand to one million members and attain sizes of up to 200 light-years in diameter. At one time, these fantastic members of our galactic halo were believed to be round nebulae. Perhaps the very first to be discovered was M22 in by Abraham Ihle in 1665. This particular globular is easily seen in even small binoculars and can be located just slightly more than two degrees northeast of the “teapot’s lid,” Lambda Sagittarii.
Ranking third amongst the 151 known globular clusters in total light, M22 is probably the nearest of these incredible systems to our Earth with an approximate distance of 9600 light-years, and it is also one of the nearest globulars to the galactic plane. Since it resides less than a degree from the ecliptic, it often shares the same eyepiece field with a planet. At magnitude 6, the class VII M22 will begin to show individual stars to even modest instruments and will burst into stunning resolution for larger aperture. About a degree west-northwest, mid-sized telescopes and larger binoculars will capture smaller 8th magnitude NGC 6642. At class V, this particular globular will show more concentration toward the core region than M22. Enjoy them both!
Thursday, August 2 – As we know, most globular clusters congregate around the galactic center in the Ophiuchus/Sagittarius region. Tonight let’s explore what creates a globular cluster’s form… We’ll start with the “head of the class,” M75.
Orbiting the galactic center for billions of years, globular clusters endured a wide variety of disturbances. Their component stars escape when accelerated by mutual encounters and the tidal force of our own Milky Way pulls them apart when they are near periapsis, that is, closest to the galactic center. Even close encounters with other masses, such as other clusters and nebulae, can affect them! At the same time, their stellar members are also evolving and this loss of gas can contribute to mass loss and deflation of these magnificent clusters. Although this happens far less quickly than in open clusters, our observable globular friends may only be the survivors of a once larger population, whose stars have been spread throughout the halo. This destruction process is never-ending, and it is believed that globular clusters will cease to exist in about 10 billion years.
Although it will be later evening when M75 appears on the Sagittarius/Capricornus border, you will find the journey of about 8 degrees southwest of Beta Capricorni worth the wait. At magnitude 8, it can be glimpsed as a small round patch in binoculars, but a telescope is needed to see its true glory. Residing around 67,500 light-years from our solar system, M75 is one of the more remote of Messier’s globular clusters. Since it is so far from the galactic center – possibly 100,000 light-years distant – M75 has survived almost intact for billions of years to remain one of the few Class I globular clusters. Although resolution is possible in very large scopes, note that this globular cluster is one of the most concentrated in the sky, with only the outlying stars resolvable to most instruments.
Friday, August 3 – Tonight let’s return to earlier evening skies as we continue our studies with one of the globulars nearest to the galactic center – M14. Located about sixteen degrees (less than a handspan) south of Alpha Ophiuchi, this ninth magnitude, class VIII cluster can be spotted with larger binoculars, but will only be fully appreciated with the telescope.
When studied spectroscopically, globular clusters are found to be much lower in heavy element abundance than stars such as own Sun. These earlier generation stars (Population II) began their formation during the birth of our galaxy, making globular clusters the oldest of formations that we can study. In comparison, the disk stars have evolved many times, going through cycles of starbirth and supernovae, which in turn enrich the heavy element concentration in star forming clouds and may cause their collapse. Of course, as you may have guessed, M14 breaks the rules. It contains an unusually high number of variable stars – in excess of 70 – with many of them known to be the W Virginis type. In 1938, a nova appeared in M14, but it was undiscovered until 1964 when Amelia Wehlau of the University of Ontario was surveying the photographic plates taken by Helen Sawyer Hogg. The nova was revealed on eight of these plates taken on consecutive nights, and showed itself as a 16th magnitude star – and was believed to be at one time almost 5 times brighter than the cluster members. Unlike 80 years earlier with T Scorpii in M80, actual photographic evidence of the event existed. In 1991, the eyes of the Hubble were turned its way, but neither the suspect star nor traces of a nebulous remnant were discovered. Then six years later, a carbon star was discovered in M14.
To a small telescope, M14 will offer little to no resolution and will appear almost like an elliptical galaxy, lacking in any central condensation. Larger scopes will show hints of resolution, with a gradual fading towards the cluster’s slightly oblate edges. A true beauty!
Saturday, August 4 – As we explore globular clusters, we simply assume them all to be part of the Milky Way galaxy, but that might not always be the case. We know they are basically concentrated around the galactic center, but there may be four of them that actually belong to another galaxy. Tonight we’ll look at one such cluster being drawn into the Milky Way’s halo. Set your sights just about one and a half degrees west-southwest of Zeta Sagittarii for M54.
At around magnitude 7.6, M54 is definitely bright enough to be spotted in binoculars, but its rich class III concentration is more notable in a telescope. Despite its brightness and deeply concentrated core, M54 isn’t exactly easy to resolve. At one time we thought it to be around 65,000 light-years distant, and rich in variables – with 82 known RR Lyrae types. We knew it was receding, but when the Sagittarius Dwarf Elliptical Galaxy was discovered in 1994, it was noted that M54 was receding at almost precisely the same speed! When more accurate distances were measured, we found M54 to coincide with the SagDEG distance of 80-90,000 light-years, and M54’s distance is now calculated to be 87,400 light-years. No wonder it’s hard to resolve – it’s outside our galaxy!
Sunday, August 5 – Today we celebrate the 76th birthday of Neil Armstrong, the first human to walk on the moon. Congratulations! Also on this date in 1864, Giovanni Donati made the very first spectroscopic observations of a comet (Tempel, 1864 II). His observations of three absorption lines led to what we now know as the Swan bands, from a form of the carbon radical C2.
Our study continues tonight as we move away from the galactic center in search of a remote globular cluster that can be viewed by most telescopes. As we have learned, radial velocity measurements show us the majority of globulars are involved in highly eccentric elliptical orbits, which take them far outside the plane of the Milky Way. These orbits form a sort of spherical “halo” which tends to be more concentrated toward our galactic center. Reaching out several thousands of light-years, this halo is actually larger than the disk of our own galaxy. Since globular clusters aren’t involved in our galaxy’s disk rotation, they may possess very high relative velocities. Tonight let’s head toward the constellation of Aquila and look at one such globular – NGC 7006.
Located about half a fist’s width east of Gamma Aquilae, NGC 7006 is speeding towards us at a velocity of around 345 kilometers per second. At 150,000 light-years from the center of our galaxy, this particular globular could very well be an extra-galactic object. At magnitude 11.5, it’s not for the faint of heart, but can be spotted in scopes as small as 150mm, and requires larger aperture to look like anything more than a suggestion.
Given its tremendous distance from the galactic center, it’s not hard to realize this is a class I – although it is quite faint. Even the largest of amateur scopes will find it unresolvable! | 0.895707 | 3.615968 |
A star twirling in a tight orbit around the centre of our galaxy has finally pinned down the existence of a monstrous black hole.
The size of the orbit and estimated mass of the star S2 rules out all but the most exotic possibilities for the relatively small but massive object lurking at the heart of the Milky Way.
Previous observations of X-ray radiation, as well as the movement of other central stars, have strongly suggested that the compact radio source known as Sagittarius A* is a supermassive black hole. But other explanations, such as a cluster of smaller black holes, neutron stars or a ball of heavy neutrinos, could not be ruled out until now.
“Most astronomers were pretty much convinced, but with this orbit we can exclude that it is a neutrino ball or some very dense cluster of normal-sized black holes or neutron stars,” says Rainer Schödel, at the Max Planck Institute for Extraterrestrial Physics in Germany, who led the research. “It really settles the issue.”
The only remaining alternative is an star made of elementary particles called bosons, but even this would eventually collapse into a black hole says Schödel’s colleague Reinhard Genzel.
3.7 million Suns
The researchers used data on S2 gathered at various observatories over 10 years and also captured new images of the star using Adaptive Optics NAOS-CONICA instrument at Paranal Observatory in Chile. This provided images of unprecedented quality by correcting for the distortion caused by the Earth’s atmosphere.
S2 orbits Sagittarius A* every 15.6 years at a distance of between 17 light hours and five light days. The orbit and estimated mass of the star allow researchers to calculate that the Milky Way’s black hole has a mass 3.7 million times that of our Sun. The black hole’s Schwarzschild radius, equivalent to the “size” of its event horizon, was found to be 11 times the radius of the Sun at 7.7 million kilometres.
Astronomer Paul O’Brien of the UK’s Leicester University says this approach is much better than previous methods, such as observing X-rays. “It’s a technique that no one will argue with,” he says.
James Binney, a theoretical astrophysicist at Oxford University, UK, adds that confirming the black hole’s existence will mean detailed analysis of it can now begin.
He told New Scientist: “We have now entered the era of precision measurements when the issue is determination of its spin and exactly what is going on in its environment.” He says the discovery will also shed new light on the general relationship between black holes and galaxies.
Journal reference: Nature (vol 419, p 694) | 0.837063 | 3.951675 |
Image credit: Subaru Telescope
The Subaru telescope, based in Japan, has detected the most distant galaxy ever recorded at 12.8 billion light-years away. The Subaru Deep Field project team uncovered 70 candidate distant objects, by using a special filter which only allows light of a very specific wavelength to pass through – one that corresponds to objects which are approximately 13 billion light-years away.
Subaru telescope has found a galaxy 12.8 billion light years away (a redshift of 6.58; see note 1), the most distant galaxy ever observed. This discovery is the first result from the Subaru Deep Field Project, a research project of the Subaru Telescope of the National Astronomical Observatory of Japan which operates the Subaru telescope. The Subaru Deep Field (SDF) project team found approximately 70 distant galaxy candidates by attaching a special filter designed to detect galaxies around 13 billion light years away on a camera with a wide field of view. Follow-up observations with a spectrograph confirmed that two out of nine of the candidates are in fact distant galaxies. One of these is the most distant galaxy ever observed. This discovery raises the expectation that the project will be able to find a large number of distant galaxies that will help unravel the early history of the universe in a statistically meaningful manner.
The SDF project is an observatory project of the National Astronomical Observatory of Japan designed to showcase the abilities of Subaru telescope and to resolve fundamental astronomical questions that are difficult to address through Subaru’s regular time allocation system. Most research programs on Subaru telescope are selected through a competitive time allocation process called Open Use, which is open to all astronomers but allows a maximum of only three observing nights every six months. By pooling together observing nights reserved for the observatory and astronomers that contributed to the establishment of Subaru Telescope, an observatory project can address questions that require greater telescope resources than the typical research proposal. The SDF project’s main goal is to detect a large number of the most distant galaxies detectable and to understand their properties and their impact on the evolution of the universe. The speed of light is the fundamental limit to how fast information can travel (see note 2). When we detect light from a galaxy 13 billion light years away, that means we are seeing the galaxy as it was 13 billion years ago. Looking for ever more distant galaxies means looking at galaxies at earlier and earlier times in the universe.
The SDF observations took advantage of the fact that light from distant galaxies have a characteristic wavelength and shape. Astronomers think that the earliest galaxies rapidly formed stars from hydrogen, the dominant form of matter in the universe. The light from these stars would have excited any hydrogen remaining around them to higher energy states and even ionize it. When excited hydrogen returns to lower energy states, it emits light at several distinct wavelengths. However, most of this light would escape the young galaxy as an emission line at 122 nanometers because “bluer” light with shorter wavelengths and higher energy can re-excite other hydrogen atoms. Since the universe is expanding, the farther away a galaxy is from us, the faster it is moving away from us. Because of this movement, light from distant galaxies are doppler shifted to longer, or redder wavelengths, and this emission line is “redshifted” to a longer wavelength that is characteristic of the galaxy’s distance and the galaxy itself appears redder. As the light travels the long distance from its origin to Earth, light at the higher energy side, or blue side of the emission line, can be absorbed by the neutral hydrogen in intergalactic space. This absorption gives the emission line a distinctive asymmetrical look. A overall red appearance and a strong emission line at a particular wavelength with a particular asymmetrical shape is the signature of a distant new born galaxy.
To detect the most distant galaxies ever observed, the SDF team developed a special filter that only passes light with the narrow wavelength range of 908 to 938 nanometers. These wavelengths correspond to the 122 nanometer emission line after travelling a distance of 13 billion light years. The team installed the special filter, and two other filters at shorter and longer wavelengths bracketing the special filter, on Subaru telescope’s Suprime-Cam, Subaru Prime Focus Camera, and carried out an extensive observing program from April through May 2002. Suprime-Cam has the capability of imaging an area of the sky as large as the full moon in one exposure, a unique capability among instruments on 8-m class and larger telescopes, and is extremely well suited for surveys of very faint objects over large areas of the sky. By observing an area of the sky the size of the moon for up to 5.8 hours in each filter, the team was able to detect over 50,000 objects, including many extremely faint galaxies. By selecting galaxies that were bright only in the special filter and preferentially red, the team found 70 candidates for galaxies at a redshift of 6.6 (or a distance of 13 billion light years; see figure 1).
In June 2002, the team used FOCAS, the Faint Object Camera and Spectrograph on Subaru telescope, to observe 9 of the 70 candidates, and confirmed the generally red appearance and an emission line with a distinctive asymmetry in 2 objects (see figure 2), and determined that their redshifts are 6.58 and 6.54. The light from these galaxies was emitted 12.8 billion years ago when the universe was only 900 million years old. The previously observed most distant galaxy, with a redshift of 6.56, was discovered by looking at a large cluster of galaxies that can amplify light from more distant galaxies with a gravitational lensing effect. (See our press release from May 2002, http://www.naoj.org/Latestnews/200205/UH/index.html.)The SDF observations is the first time multiple galaxies at such a great distance have been observed, and without the help of gravitational lensing. The galaxy with a redshift of 6.58 is the most distant galaxy ever observed.
The SDF team expects to find many more distant galaxies through continued observations. Before the first stars and galaxies formed, the universe was in a stage that Astronomers call “the dark ages of the universe”. Determining when the dark ages ended is one of the most important astronomical questions of our time. Core members of the team, Keiichi Kodaira from the Graduate University of Advanced Studies in Japan, Nobunari Kashikawa from the National Astronomical Observatory of Japan, and Yoshiaki Taniguchi from Tohoku University hope that by detecting a statistically significant number of distant galaxies, they can begin to characterize the galaxies that heralded the end of the universe’s dark ages.
Original Source: Subaru News Release | 0.860348 | 3.985496 |
Throughout the final week of August 1835, a long article appeared in serial form on the front page of the New York Sun
. It bore the headline:
GREAT ASTRONOMICAL DISCOVERIES
BY SIR JOHN HERSCHEL, L.L.D. F.R.S. &c.
At the Cape of Good Hope
[From Supplement to the Edinburgh Journal of Science]
The article started by triumphantly listing a series of stunning astronomical breakthroughs the famous British astronomer, Sir John Herschel, had made "by means of a telescope of vast dimensions and an entirely new principle." Herschel, the article declared, had established a "new theory of cometary phenomena"; he had discovered planets in other solar systems; and he had "solved or corrected nearly every leading problem of mathematical astronomy." Then, almost as if it were an afterthought, the article revealed Herschel's final, stunning achievement. He had discovered life on the moon.
The article was an elaborate hoax. Herschel hadn't really observed life on the moon, nor had he accomplished any of the other astronomical breakthroughs credited to him in the article. In fact, Herschel wasn't even aware until much later that such discoveries had been attributed to him. However, the announcement caused enormous excitement throughout America and Europe. To this day, the moon hoax is remembered as one of the most sensational media hoaxes of all time.
Front page of the NY Sun: August 25, 1835
The moon hoax began on Friday, 21 August 1835, when a small, teaser notice appeared on the second page of the Sun
. Ostensibly copied from the Edinburgh Courant
, the announcement read, "We have just learnt from an eminent publisher in this city [Edinburgh] that Sir John Herschel, at the Cape of Good Hope, has made some astronomical discoveries of the most wonderful description, by means of an immense telescope of an entirely new principle."
This initial notice elicited no comments from rival papers. It merely served as a setup for the more elaborate series of articles (the lunar narrative) that appeared the next week, published over the course of six days as a series of extracts purportedly reprinted from a supplement to the Edinburgh Journal of Science
The entire lunar narrative, all six parts of it, ran to approximately 17,000 words in length. It consisted primarily of a long, rambling, and fanciful telescopic tour across the surface of the moon. It didn't have a plot or directional storyline, as such. Instead, it maintained the reader's attention by unveiling one miraculous discovery after another, constantly promising that revelations even more stupendous than those already made would soon be disclosed. It relied heavily on the premise that it was a true narrative for its sensational effect.
printed the first extract
on Tuesday, August 25. The text of the extract occupied three-quarters of the front page. The paper's editor wrote a short note on the second page explaining to his readers what he was presenting them with:
We this morning commence the publication of a series of extracts from the new Supplement to the Edinburgh Journal of Science, which have been very politely furnished us by a medical gentleman immediately from Scotland, in consequence of a paragraph which appeared on Friday last from the Edinburgh Courant. The portion which we publish to day is introductory to celestial discoveries of higher and more universal interest than any, in any science yet known to the human race.
This first extract only briefly mentioned that Herschel had discovered any form of life on the moon. Instead, it was principally devoted to establishing the premise upon which the entire hoax depended: that Herschel had created an immense new telescope so powerful that it could be used to view astronomical objects with great clarity at previously unheard-of magnifications or as the text said, it could be used to study "even the entomology of the moon, in case she contained insects upon her surface."
Such a telescope would, of course, have to be massive, and according to the text, it was. It measured 24 feet in diameter. By contrast, the modern telescope at California's Mt. Palomar observatory measures only 17 feet in diameter. However, its true power lay in the fact that it contained a special, second lens, the "hydro-oxygen microscope," that further magnified, illuminated, and projected the telescopic image onto a canvas screen. It was this second lens that gave the instrument its power. It did so by solving the problem of distant objects losing their light and becoming dimmer when magnified a problem that had long plagued astronomers. By adding illumination to the telescopic image, the hydro-oxygen microscope supposedly allowed the magnification of even the most distant objects with absolute clarity.
Finally, the first extract introduced the supposed author of the narrative, a man identified as Dr. Andrew Grant, a former pupil of Sir William Herschel (Sir John Herschel's famous father, discoverer of the planet Uranus) and now the travelling companion and amanuensis of the younger Herschel. Dr. Grant, it was claimed, had written this popular account of Herschel's discoveries for the Edinburgh Journal of Science
to complement a more scholarly account that Herschel himself had transmitted to the Royal Society.
The lunar tour began in earnest in the second extract
. The narrative described the moment when, on January 10, 1835, Herschel first trained his telescope upon the moon. What appeared before his eyes was "a beautifully distinct, and even vivid representation of basaltic rock... their articulations similar to those of the basaltic formation at Staffa." Shifting the view a little bit, Herschel then perceived that the rock was "profusely covered with a dark red flower."
Having thus established that the moon contained plant life, the central question remaining was whether the moon also supported animal life. That day's narrative soon answered this question when it reported that the scientists saw herds of brown quadrupeds similar to bison, a goat "of a bluish lead color," and "a strange amphibious creature, of a spherical form, which rolled with great velocity across the pebbly beach.
The third extract
began with a description of more geological formations (oval-shaped mountains and extinct volcanoes). Dr. Grant offered a list of the variety of lunar flora and fauna seen by the astronomers up to that point: 38 species of trees, twice this number of plants, nine species of mammalia, and five of ovipara. However, the highlight of this extract was the discovery of the first sign of intelligent, though primitive, lunar life — the biped beaver. These extraordinary beavers walked on two feet and bore their young in their arms. They lived in huts "constructed better and higher than those of many tribes of human savages." And signs of smoke above the huts of the beavers indicated that these advanced animals had even mastered the use of fire.
The fourth extract
proved to be the highpoint of the entire narrative. The scientists discovered human-like creatures living inside a ring of red hills they dubbed the "Ruby Colosseum." Unlike earth-bound humans, these creatures were "covered, except on the face, with short and glossy copper-colored hair, and had wings composed of a thin membrane, without hair, lying snugly upon their backs." The faces of these creatures, Dr. Grant remarked, being "of a yellowish flesh color, was a slight improvement upon that of the large orang outang."
Further observation of these curious creatures, whom Herschel dubbed the "Vespertilio-homo, or man-bat," followed. The astronomers watched them engage in what appeared to be animated conversations and "hence inferred that they were rational creatures." The very proper Dr. Grant also noted that "some of their amusements would but ill comport with our terrestrial notions of decorum." Apparently the Vespertilio-homo were mating with each other out in the open.
An old print of the moon hoax showing the Vespertilio-Homo (center) and the Biped Beavers (right)
Anticipating that some readers would find the existence of such creatures too incredible to believe, Dr. Grant assured skeptics that a forthcoming volume would provide certificates from "several Episcopal, Wesleyan, and other ministers, who, in the month of March last, were permitted, under stipulation of temporary secrecy, to visit the observatory, and become eye-witnesses of the wonders which they were requested to attest."
The author of the lunar narrative (whoever he really was) now faced a challenge. Having revealed the existence of intelligent lunar life, how could he produce even greater wonders to maintain the interest of readers? His solution in the fifth extract
was to present readers with a mystery: the discovery of an apparently abandoned temple, built of polished sapphire. The roof of this temple was constructed out of a yellow metal and fashioned to look like a mass of flames rising upwards and licking at a large sphere of clouded copper, "as if hieroglyphically consuming it."
1835 print sold by the Sun showing the Sapphire Temple
The astronomers pondered what was meant by this globe surrounded by flames. Did the makers of the globe "by this record any past calamity of their world, or predict any future one of ours?" Unable to answer this question, the astronomers decided to refrain from "indulging in speculative theories, however seductive to the imagination."
The lunar narrative concluded on Monday, August 31. In the final extract
the astronomers discovered a superior order of Vespertilio-homo living in close proximity to the mysterious sapphire temple. These new creatures were "of a larger stature than the former specimens, less dark in color, and in every respect an improved variety of the race."
While observing these creatures — who spent their time collecting fruit, flying, bathing, and conversing — the astronomers realized that there reigned a "universal state of amity among all classes of lunar creatures." They couldn't remember having observed any "carnivorous or ferocious species." (Apparently they had forgotten watching birds catching fish earlier in the narrative.)
Print showing lunar creatures living peacefully side-by-side in the "Ruby Colosseum" (unknown date)
With this thought in mind, Herschel and his companions temporarily ended their observations. However, when they returned to the telescope the next day they were presented with a minor setback. They had accidentally left the telescope's lens in a position where it had caught the Sun's
rays and burned down a wall of the observatory. A week later, after having completed the repairs, the moon was no longer visible.
Dr. Grant noted that he did get a chance to briefly observe the moon again the following month, at which time he discovered a still superior species of the Vespertilio-homo who "were of infinitely greater beauty, and appeared in our eyes scarcely less lovely than the general representations of angels by the more imaginative schools of painters." But having said this much, Dr. Grant then declined to say any more, explaining to his readers that they would find a more detailed account of the highest order of Vespertilio-homo in the upcoming publication of "Dr. Herschel's authenticated natural history of this planet." With this, the narrative ended.
By all accounts, the news that life had been found on the moon generated enormous popular excitement. People throughout New York City debated whether or not the story was true and, if true, what its implications were.
Several people described this excitement in their diaries. On August 30, a young New Yorker named Michael Floy wrote in his diary, "A great talk concerning some discoveries in the moon by Sir John Herschel; not only trees and animals but even men have been discovered there." Philip Hone, the former mayor of New York, also wrote a long summary of the lunar narrative in his diary, remarking on how admirably it was written.
But we know of the excitement most of all from all the newspapers and magazines that gave it extensive coverage. By the end of August, most of the other New York papers began reprinting the narrative, in response to their readers' intense interest in it. Meanwhile, word of the discoveries quickly spread to the rest of the country, within days reaching the other major eastern cities — Baltimore, Philadelphia, and Boston. In a little less than two weeks it had travelled as far west as Cincinnati. Within a month, it had crossed the Atlantic to Europe. Everywhere the news caused the same buzz of interest and speculation.
A full month after the hoax had first seen the light of day, the New York Herald
main rival) reported that the "ingenious hoax is going the rounds still. Every paper that we receive from the West brings it back again. The Bowery Theatre has dramatized it, and now Hannington [a New York museum] has actually put it on canvas, and placed it for exhibition in his diorama."
Many accounts of the moon hoax claim that popular interest in it was so great that it caused a dramatic rise in the paper's circulation, almost overnight. For instance, science writer Willy Ley wrote in Watchers of the Skies
(1963) that the hoax caused the Sun's
circulation to rise from 8000 to 19,360 copies, within the span of a few days. Similarly, a 1984 journalism textbook, The Press and America: An Interpretive History of the Mass Media
, claims that the circulation of the Sun
"nearly trebled" because of the moon hoax.
These assertions derive from a boast the Sun
made about its circulation on Friday, August 28 (the fourth day of the lunar narrative). It stated that its total circulation had reached 19,360 and then said:
We do not hesitate to say that our circulation is the greatest of any daily paper in the world, (the daily edition of the London Times being only 17,000.) Our only present difficulty is to strike off a sufficient number for the demand.
Taken alone, this statement seems to confirm that the hoax had a dramatic effect on the Sun's
circulation. However, the Sun
had made similar claims about its large circulation in the weeks before the hoax. For instance, on 13 August 1835, two weeks before publishing the moon hoax, the Sun
boasted that its circulation had reached 26,000:
Enormous Circulation — At the time of penning this paragraph—5 P.M. Wednesday afternoon—the enormous number of twenty-six thousand copies of yesterday's edition of the Sun had been issued to carriers and sold at our counter, and our publishing office is still thronged with persons waiting to be supplied:—our press, though a double cylinder, not being able to print them as fast as they have been demanded. We may safely assert that no other one paper in the Union, nor in the world, ever sold as many papers in one day, as we did yesterday.
Two statements from the Sun about its circulation. Left: Aug. 13, 1835. Right: Aug 28, 1835.
So according to the figures provided by the Sun
itself, its circulation actually dropped during the moon hoax — from a high of 26,000 before it, to 19,360 during it. However, this drop needs to be taken in context. The 26,000 copies it sold on August 13 were probably related to a one-time event — a fire that swept through parts of downtown New York City, destroying the printing press of its fiercest competitor, the NY Herald
. So people who would normally have bought the Herald may temporarily have been buying the Sun
. There had also been riots in Baltimore, which people were anxious to read about.
But although 26,000 may have represented a circulation that was higher than normal, the evidence indicates that the Sun
was regularly selling around 19,000 or 20,000 copies a day by August, 1835, and it maintained this rate during the moon hoax, apparently without experiencing a dramatic circulation spike. In its August 29 boast, the Sun
noted specifically that its circulation had been rising "within the last two months." It didn't attribute the rise to the printing of the lunar discoveries.
In fact, people didn't need to buy copies of the Sun
to read the lunar narrative because almost every paper in New York reprinted the text, making it widely available. This meant some lost sales for the Sun
, but it could hardly complain about the reprinting because it, in turn, claimed to have reprinted the narrative from the Edinburgh Journal of Science
Nevertheless, the Sun
did make a large profit from the moon hoax. It did so by selling the complete text of the lunar discoveries as a special-edition pamphlet that it put on sale on August 31 for one shilling. It also sold various lithographic prints showing fanciful scenes of Herschel's lunar discoveries, such as the lunar animals and the Ruby Colosseum. It commissioned the production of these prints from the Wall Street lithographers Norris & Baker.
never shared sales figures for the pamphlet and prints, but according to William Gowans, writing in 1859, it sold 60,000 pamphlets in less than a month. This would have been a huge financial windfall for the paper. These pamphlets are now collector's items. Only sixteen of them are known to still exist, and they sell for as much as $2000 each.
The idea that the popularity of the moon hoax led to a rise in the Sun's
circulation has become a standard part of the story of the hoax. However, it turns on its head what actually happened and obscures the historical significance of the event. In fact, as Mario Castagnaro (2009) has argued, it was the Sun's
already high circulation and broad reach that ensured the success of the moon hoax — not the other way around.
high circulation was made possible by its use of steam-powered printing presses
. Such presses, which had only recently become available, allowed papers to print tens of thousands of copies at a cheap rate, thereby broadening their readership and turning them into a medium of truly mass communication. In addition, the Sun
used an innovative means of distribution that further broadened its reach — newsboys who sold issues on the street, shouting out the headlines for everyone to hear. The Sun
was the first paper anywhere to use newsboys to sell copies. It had started using them in 1833, less than two years before the moon hoax, so their presence on city streets was still a relatively new part of the urban environment.
Source: American Heritage (1969)
The combination of the Sun's
high circulation and the newsboys meant that everyone throughout the city, spanning all social classes, heard about the lunar discoveries at the same time. They experienced it as a shared social event in a way that was entirely new.
The importance of the Sun's
circulation can be demonstrated by comparing the lunar narrative to a similar hoax that occurred just two months prior but failed to have a similar impact. In June of 1835 Edgar Allan Poe had published a story in the first issue of a new magazine, The Southern Literary Messenger
, about a man from Rotterdam named Hans Pfall who supposedly built a balloon that carried him to the moon. Poe assured readers that his story was a factual narrative of a true event.
When the Sun's
moon hoax debuted in August, Poe became convinced that the Sun
had stolen his idea. As he later pointed out, both stories were astronomical hoaxes that had the moon as their main subject, both claimed to have obtained exclusive information from a foreign country, and both relied upon scientific detail to lend an air of plausibility. However, while the Sun's
moon hoax caused enormous excitement, Poe's story elicited hardly any interest.
One of the central reasons for the different way in which the stories were received is that the Southern Literary Messenger
had few readers whereas the Sun
had many. The Sun
broadcast its hoax out to a mass audience, and its reach was amplified when almost every paper in the city reprinted the story. Within a week close to 100,000 copies of the lunar narrative had been printed — at a time when New York City only had a population of around 300,000.
The manner in which the hoax reached such a wide audience so quickly, pushed by the power of the mass media, fascinated people. They recognized it as a great novelty. Poe himself observed:
The hoax was circulated to an immense extent, was translated into various languages — was even made the subject of (quizzical) discussion in astronomical societies... and was, upon the whole, decidedly the greatest hit in the way of sensation — of merely popular sensation — ever made by any similar fiction either in America or in Europe.
The moon hoax was the first truly sensational demonstration of the power of the mass media that had come into existence after the introduction of steam-powered printing presses. Before the 1830s, such a hoax would not have been possible.
The moon hoax foreshadowed what would eventually became a central concern about the mass media: its ability, because of its enormous reach, to shape and influence popular belief. Later hoaxes, such as the 1938 War of the Worlds "panic broadcast,"
would provide even more dramatic and disturbing examples of this power. But in 1835 the mass media was still new enough that most people seemed intrigued rather than concerned by this display of its power.
Lunar scene published in the Sun, September 1835
The lunar narrative wouldn't have caused as much excitement as it did if many people hadn't been willing to consider the possibility that it might be true. But how many people actually accepted it, at face value, as factual? That is, how many people fell for it outright?
It's difficult to answer this question. But accounts of the hoax, written by people who lived through it, all agreed that the overwhelming majority of the public initially appeared to accept the reality of the lunar discoveries.
Asa Greene, editor of the New York Transcript
(one of the Sun's
rivals), included one of the first published recollections of the hoax in a travel-guide to New York City
he published in 1837. According to Greene:
"The credulity was general. All New York rang with the wonderful discoveries of Sir John Herschell... There were, indeed, a few sceptics; but to venture to express a doubt of the genuineness of the great lunar discoveries, was considered almost as heinous a sin as to question the truth of revelation."
A year later, Dr. Meredith Reese, a respectable New York physician, wrote a work titled Humbugs of New York: Being a Remonstrance against Popular Delusion whether in Science, Philosophy, or Religion
, in which he included similar remarks
about the widespread belief in the hoax:
In relation to philosophical humbugs, an illustrious example is furnished by the celebrated moon story, ingeniously fabricated by a shrewd and intelligent practitioner on public gullibility, and the success of which proved, that he had rightly judged of the character of our population in regard to their readiness to swallow the most sublimated nonsense, when dignified by the name of science... There are very many in our city, who to the present hour, regard those revelations with more of reverence and confidence than any of the established truths in physics or morals.
Harriett Martineau, an English writer who was travelling through America at the time of the hoax, recorded her impressions of the event
"I happened to be going the round of several Massachusetts villages when the marvellous account of Sir John Herschel's discoveries in the moon was sent abroad. The sensation it excited was wonderful. As it professed to be a republication from the Edinburgh Journal of Science, it was some time before many persons, except professors of natural philosophy, thought of doubting its truth. The lady of such a professor, on being questioned by a company of ladies as to her husband's emotions at the prospect of such an enlargement of the field of science, excited a strong feeling of displeasure against herself. She could not say that he believed it, and would gladly have said nothing about it; but her inquisitive companions first cross-examined her, and then were angry at her skepticism. A story is going, told by some friends of Sir John Herschel (but whether in earnest or in the spirit of the moon story I cannot tell), that the astronomer has received at the Cape a letter from a large number of Baptist clergymen of the United States, congratulating him on his discovery, informing him that it had been the occasion of much edifying preaching and of prayer-meetings for the benefit of brethren in the newly-explored regions; and beseeching him to inform his correspondents whether science affords any prospects of a method of conveying the Gospel to residents in the moon. However it may be with this story, my experience of the question with regard to the other, 'Do you not believe it?' was very extensive."
While Martineau remembered that professors saw through the deception, Edgar Allan Poe, writing in 1846
, recalled the exact opposite:
Not one person in ten discredited it, and (strangest point of all!) the doubters were chiefly those who doubted without being able to say why — the ignorant, those uninformed in astronomy, people who would not believe because the thing was so novel, so entirely 'out of the usual way.' A grave professor of mathematics in a Virginian college told me seriously that he had no doubt of the truth of the whole affair!
William Griggs published the longest, near-contemporary analysis of the moon hoax
in 1852, seventeen years after the event. He recalled being present in New York when the hoax was first printed and standing outside the offices of the Sun
as crowds gathered there, clamoring to purchase copies of the lunar discoveries. According to Griggs, the public greeted the hoax with "voracious credulity". While he conceded there were some skeptics, most notably the Sun's
main rival, the New York Herald
, he insisted that, "the almost universal impression and expression of the multitude was that of confident wonder and insatiable credence."
Griggs added one other curious detail. According to him, not only did the public readily believe the hoax, but they were encouraged in their belief by people who came forward of their own free will to corroborate the story's details. He referred to this phenomenon as "instances of spontaneous mendacity." For instance, a Quaker gentleman apparently told the crowds gathered outside the offices of the Sun
that while he had been in London, he had personally witnessed Herschel's telescope being loaded into a ship bound for South Africa. Still others, according to Griggs, claimed to have in their possession copies of the supplement to the Edinburgh Journal of Science
and assured the doubtful that the Sun
had accurately reproduced the text of the lunar discoveries.
Finally, in 1852 an anonymous contributor to the Southern Quarterly Review
recalled the scene at Yale College when news of the lunar discoveries broke:
Yale College was alive with staunch supporters. The literati — students and professors, doctors in divinity and law — and all the rest of the reading community, looked daily for the arrival of the New York mail with unexampled avidity and implicit faith. Have you seen the accounts of Sir John Herschel's wonderful discoveries? Have you read the Sun? Have you heard the news of the man in the Moon? These were the questions that met you every where. It was the absorbing topic of the day. Nobody expressed or entertained a doubt as to the truth of the story.
From an historical point of view, these recollections represent an important source of information about the hoax, but they should be taken with a grain of salt. The "voracious credulity" of the public quickly became part of the mythology of the event and strongly influenced subsequent recollections. After all, this was a period of time in American history characterized by a rambunctious spirit of popular democracy — the Jacksonian era. While this spirit of democracy was celebrated, it simultaneously sparked fears about the credulity of the democratic masses and their ability to govern. Much of the fascination of the moon hoax lay in the fact that it dramatized these tensions and concerns.
In addition, the idea that almost everyone believed the lunar discoveries provided a dramatic punchline to the story of the moon hoax that satisfied both the supporters of the Sun
(for whom it represented the Sun's
ingenuity and wit) and its detractors (for whom it represented the lack of critical judgement of the general public). So as the story of the moon hoax was told and retold, there was little incentive for anyone to try to impartially assess the extent of belief in it. To the contrary, there was a strong incentive to exaggerate the extent of belief because this made the story far more sensational. And so the legend of the moon hoax grew.
The suspicion that belief in the lunar discoveries was not quite as widespread as frequently reported is supported when we look at the media response to the hoax, in which we find more skepticism and bemused sarcasm than voracious credulity.
On 1 September 1835, the day after printing the final extract of the lunar narrative, the Sun
made some remarks about how other newspapers had responsed to the news of the lunar discoveries. It conceded there were some skeptics, singling out the Journal of Commerce
as one of them. But it dismissed such skepticism with the comment, "Consummate ignorance is always incredulous to the higher order of scientific discoveries, because it cannot possibly comprehend them."
then provided its readers with a list of eleven comments about the discoveries culled from other papers whom it deemed to be "competent judges of the great scientific questions now before the community." This list appeared to demonstrate widespread belief within the news community about the authenticity of the narrative. For instance, (according to the Sun
) the Daily Advertiser
wrote, "Sir John has added a stock of knowledge to the present age that will immortalize his name, and place it high on the page of science." The Mercantile Advertiser
stated, "It [the lunar narrative] appears to carry intrinsic evidence of being an authentic document." At the end of the list, the Sun
"These are but a handful of the innumerable certificates of credence and of complimentary testimonials with which the universal press of the country is loading our tables. Indeed we find very few of the public papers express any other opinion."
Subsequent accounts of the moon hoax, particularly those written during the 20th Century, took these "certificates of credence" at face value as valid evidence of the media response to the moon hoax. It was only towards the end of the 20th Century that a historian, Michael Crowe (1986), questioned the validity of the list. Crowe wondered whether the quotations were genuine, or if the Sun
had simply invented them.
An examination of archival newspaper sources reveals that the Sun's
accurate. However, it also partially confirms Crowe's suspicions because many of the quotations were taken misleadingly out of context. For instance, the Sun
quoted the N.Y. Commercial Advertiser
as saying, "We think we can trace in it marks of transatlantic origin." It omitted the previous line where the Commercial Advertiser
declared, "We can hardly understand how any man of common sense should read it without at once perceiving the deception."
Similarly, the Sun
quoted the N.Y. Evening Post
as saying, "It is quite proper that the Sun
should be the means of shedding so much light on the Moon." It failed to mention that the Post
also wrote (in the same paragraph), "We publish the article as we find it, and do not know that it is necessary that we should accompany it with any comments to shake the faith which credulous readers may be disposed to place in its authenticity."
An analysis of New York City's leading newspapers in 1835 produces the following breakdown of moon-hoax skeptics vs. believers, which indicates that at least half of the papers greeted the lunar discoveries with skepticism:
- New York Herald: (James Gordon Bennett, editor). Extremely skeptical. Discussed in greater detail below.
- New York Transcript: (Asa Greene, editor). Openly skeptical. Responded with satire, claiming that through sources of their own (a "Captain Tarbox") they had obtained additional details about Herschel's lunar discoveries — namely that the lunar inhabitants were infested by nits and lice "of a bright amber color, with azure eyes, and seemed to be of a smaller species than that which infests human beings on our planet."
- New York Commercial Advertiser: (William Leete Stone, editor). Politely skeptical. Pointed out that such a massive telescope could hardly have been built without the British press commenting on it, but nevertheless praised the ingenuity of the narrative.
- Journal of Commerce: Openly skeptical. Declared, "There is no doubt but the article was manufactured in this country, and that it belongs to the same school as Robinson Crusoe and Gulliver's Travels."
- Courier and Enquirer: (James Watson Webb, editor). This was the only major New York paper that completely ignored the lunar discoveries. Given that Webb had a history of open antagonism towards the Sun, this act has to be interpreted as skepticism.
- New York Evening Post: (William Cullen Bryant, editor). Politely skeptical, stated, "[we] commend the article to our readers as one from which they will derive much entertainment whether they wholly believe it or not."
- New York Sunday News: As quoted by the Sun, it wrote, "Our doubts and incredulity may be a wrong to the learned astronomer, and the circumstances of this wonderful discovery may be correct. Let us do him justice, and allow him to tell his story in his own way." The admission of "doubts and incredulity" seems more skeptical than not.
- Daily Advertiser: This was the oldest daily newspaper in New York City. It hasn't been possible to examine the Daily Advertiser itelf, but we know it professed belief on the basis both of the quotation attributed to it by the Sun, and because the Journal of Commerce mocked "the 'respectable Daily' and the Mercantile Advertiser, each of whom, besides copying so much of the article as they could get in type for yesterday's paper, have honored it with a paragraph, expressing unbounded admiration at the discoveries it announces."
- Mercantile Advertiser: See explanation for the Daily Advertiser.
- New Yorker: (Horace Greeley, editor). According to the Sun, it stated that, "The promulgation of these discoveries creates a new era in astronomy and science generally." This seems to indicate belief.
- New York Times: Not the same NY Times as the present-day one. The Sun quoted it as saying, "the account of the wonderful discoveries in the moon, &c., are all probable and plausible, and have an air of intense verisimilitude." A little ambiguous, but we'll place it in the believers category.
- Evening Star: (Mordecai Noah, editor). Response unknown.
- U.S. Gazette: As quoted by the Sun, "The article is said to be an extract from a supplement to the Edinburgh Journal of Science. It sets forth difficulties encountered by Sir John, on obtaining his glass castings for his great telescope, with magnifying powers of 42,000. The account, excepting the magnifying power, has been before published."
- New York Spirit of '76: A minor New York paper. As quoted by the Sun, "Our enterprising neighbors of the Sun, we are pleased to learn, are likely to enjoy a rich reward from the late lunar discoveries. They deserve all they receive from the public — 'they are worthy.'"
As the hoax spread around the nation (and world), papers tended to take their cues from whatever New York City papers they received first. For instance, on August 29 the New Haven Daily Herald
published, without editorial comment, a condensed summary of the "New Discoveries in the Moon" that it took from the Daily Advertiser
. But by August 31, having received more papers, it had become aware that the lunar discoveries might be false and noted, "Some of our editorial brethren, especially in N.York, treat the late wonderful discoveries, purporting to be made by the celebrated Herschel, as mere matter of moonshine, a complete hoax."
Among the believers were the Albany Daily Advertiser
, whose support of the Sun
was so over-the-top as to lead Ormond Seavey (1975) to suspect that the two papers were in collusion.
But nationwide, there appear to have been more skeptics than believers. The Boston Morning Post
scolded that it seemed "strange that men of sense and knowledge can have any doubt respecting this palpable hoax, or more properly imposition." The Vermont State Paper
suggested the lunar discoveries would "certainly afford amusing reading to those not disposed to yield it full credence." In South Carolina, the Charleston Courier
simply reprinted the skeptical remarks of the Journal of Commerce
under the heading, "News from the Moon — A Consummate Hoax."
By the end of September, news of the "lunar discoveries" had reached Europe. William Griggs (1852) described the reaction of European papers:
"whether they were hoaxed themselves or not, they too well knew the value of the narrative, as matter of interest to their readers, to expose its American origin, even if they were really apprised of it. As evidence of this conclusion, even the Edinburgh papers, where it must instantly have been known as a hoax, published it with all the gravity and reserve of a synod or council of sages.
From England and France these glorious and astounding discoveries sped their welcome way through Germany, Italy, Switzerland, Spain, and Portugal, and were translated into all the languages. We have recently been assured, in the most serious manner, that in many of the interior parts of Germany, and of the Continent generally, they remain uncontradicted to the present day, and are believed like sacred and delightful truths by vast numbers of the population."
However, Griggs' account seems unlikely. The few European papers from 1835 in which discussions of the lunar narrative have been found all describe it as an American hoax. For instance, the Liverpool Mercury
first reported about the narrative on September 25, 1835, under the headline: "Alleged Discovery of Men, Animals, Vegetables, &c., In The Moon." It compared the narrative to several famous eighteenth-century hoaxes, the Native of Formosa
and the Shakespeare forgeries of William Henry Ireland
A peculiar feature of the media response, from a modern perspective, was the relative lack of anger directed at the Sun
. Even among papers that expressed disbelief, almost none criticized the Sun
for deceiving its readers. Many actually praised the artistry and ingenuity of the narrative.
Mario Castagnaro (2009) notes, "Because readers did not yet have fixed expectations about what news was as a commodity or assumptions that it needed to be reported objectively, the fact that these stories were hoaxes did not outrage the public. Most publishers were curiously neutral, leaving it up to their readers to decide on the story's authenticity."
Castagnaro also offers this elaboration: "The early nineteenth-century was a culture of curiosity, one in which readers did not have clear-cut expectations about truth and fiction and the two usually blended together on newspaper pages; credibility was not the chief reason people picked up newspapers."
The one significant exception to the lack of outrage was the Sun's
main rival, the New York Herald
, edited by James Gordon Bennett. As noted above, the Herald's
printing press had been destroyed by fire in mid-August. But by the end of the month, Bennett had managed to find a new printer, and he returned to print on August 31, immediately calling out the Sun
in a column titled, "The Astronomical Hoax Explained."
James Gordon Bennett
When the Sun
failed to confess the hoax, Bennett's anger grew, and he began to hurl invective at the Sun
, in hyperbolic terms:
"We mean now to show up the Sun — the impudent Sun — the unprincipled Sun —the mercenary Sun — the low bred Sun — the Sun that hoaxes the public — that tells untruths for money — that makes fools of the wine [sic] — that cheats the whole city and country. The revulsion of public sentiment, is fast accumulating. Its astronomical hoax will touch the Sun yet to the quick." (N.Y. Herald, Sep. 3, 1835: 2)
The next day Bennett declared the Sun's
hoax to be, "highly improper, wicked, and in fact a species of impudent swindling." Bennett only calmed his attack when he sensed that his righteous indignation was being met by public indifference.
It's unlikely that the real source of Bennett's anger was offense at the Sun's
deception. Rather, he was probably annoyed that he hadn't thought up the hoax himself. His paper (which in Sep 1835 had only been in print for three months) later became notorious for its sensationalism. He had no problem twisting the truth when it served his purpose.
The media response to the moon hoax has to be understood within the context of the newspaper business in the 1830s — specifically that there were two kinds of newspapers, penny papers and six-cent papers.
At the start of the 1830s, only six-cent papers existed, so-called because they cost six-cents an issue or ten dollars a year. They catered to a relatively narrow audience, and they had small circulations, typically lower than 2000. There were, in turn, two main kinds of six-cent papers: political papers funded by political parties, and financial papers that catered to the business community.
But as the 1830s progressed, a new kind of newspaper emerged: the penny paper. In fact, the Sun
was the very first successful penny paper in the world, started in 1833 by Benjamin Day, when he was only 23-years-old.
As the name suggests, penny papers cost a penny, which made them affordable to far more people. Two factors allowed for the creation of the penny press: urbanization (that created large potential markets for newspapers in cities), and the steam-powered printing press (that made it possible to print large quantities of papers very cheaply).
Unlike the six-cent papers, which got their money from subscriptions or through political funding, penny papers relied on high circulations and advertising for income. They boasted that this made them more politically independent.
To attract readers, the penny papers published content that was considered far more sensational and low-brow than what the six-cent papers were willing to run — content such as crime reports and local gossip. They also used newsboys to sell copies directly on the street. This focus on catering to the reading tastes of the average person attracted the scorn of the six-cent papers. James Watson Webb, editor of the six-cent Courier and Enquirer
, referred to the penny papers as "penny trash".
The penny papers also introduced a new policy towards advertising. The editors of the six-cent papers felt an obligation to stand behind the claims of any advertisement that appeared in their pages, but the editors of the penny press felt no such sense of obligation. They adopted a laissez-faire attitude towards advertising. They printed the ads of anyone who had the money to pay, and they left it up to their readers to decide whether an advertised claim was true or false.
What this meant, in practice, was that all variety of bizarre products soon appeared for sale in the columns of the penny press: leeches, real Indian hair restoratives, balsam of liver wort (promised to cure tightness of the chest), infallible remedies for the piles, Compound syrup of iceland moss for the cure of whooping cough, and Genuine Hygeian Vegetable Universal Medicine (whose virtues, according to its promoter, were "too well known" to require explanation). Even personal ads, placed by men attempting to meet wives, first made their appearance in the penny press.
The "penny system" (as it came to be called) eventually prevailed over the six-cent system and grew into the modern newspaper industry. But in late 1835 — by which time New York City had two other penny papers in addition to the Sun
: Bennett's New York Herald
and the New York Transcript
— the success of the penny system seemed far from guaranteed. All three penny papers were doing well, with circulations of around 15,000 to 20,000 each — far higher than their six-cent rivals. But most New York papers were still six-cent papers. This was the context in which the moon hoax appeared.
Dan Schiller (1981) has argued that Day printed the moon hoax in order to embarrass the six-cent papers, hoping they might try to steal his scoop by reprinting the story without crediting him. As it turned out, none of the six-cent papers took this bait. Although they did reprint the story, they all credited the Sun
. Nevertheless, the hoax did dramatize the difference between the conservative six-cent papers and the more rambunctious penny papers, casting the penny papers as more sharp-witted (and entertaining) than their rivals. And for this reason, the hoax proved to be a smart business move on Day's part.
Even Bennett, when he wasn't raging at the Sun
for deceiving the public, paused to note that the moon hoax reflected favorably on the penny papers as a whole:
"The Difference. — The sixpenny papers think and talk as if they were philosophers, critics, learned, intelligent men. Now mark the test. Not one of the penny papers ever believed the moon hoax — one half the sixpenny were hoaxed. The Herald at the jump was the only paper that explained the whole humbug." (N.Y. Herald, Oct. 27, 1835: 2)
The moon hoax holds a special place in the history of journalism, because its success has been widely credited with ensuring the success of the Sun
itself, and therefore, by extension, the success of the penny system and modern journalism. This may be going a bit far. The penny system would certainly have eventually overshadowed the six-cent system anyway, and it's debatable how much the hoax really helped the Sun's
circulation (see above). Nevertheless, the hoax definitely did make make a name for the Sun
, and since the public responded favorably to the hoax, viewing it as a clever joke rather than a malicious deception, it served as an excellent advertisement for the paper, and for the laissez-faire values of the penny system.
Vespertilio-Homo, from an Italian edition of the moon hoax
Although the lunar narrative may not have been met with credulity as widespread as most accounts of the hoax suggest, it certainly wasn't dismissed as a fraud out of hand. It was plausible enough to give most people pause.
This may seem strange to modern readers, since today the narrative reads like rather far-fetched science fiction. (The moon hoax is considered to be one of the first science fiction stories ever published.) So what was it about the narrative that gave it the appearance of (possible) truth? It wasn't anyone one thing, but rather a variety of factors.
The central claim of the moon hoax was that life had been discovered on the moon. Today such a claim sounds absurd — especially life of the kind described in the narrative, biped beavers and man-bats — but in 1835 there was still genuine debate about the possibility of lunar life. The scientific community was beginning to lean towards the conclusion that the moon couldn't support life, but there was no consensus on the matter yet. So on the issue of lunar life, science didn't provide the public with any clear guidance by which to judge the lunar narrative.
Throughout the eighteenth century, prominent scientists such as Gottfried Wilhelm Leibniz, Edmond Halley, and William Herschel (father of John) had strongly supported the idea that extraterrestrial life existed, even on the moon (as well as inside the hollow earth according to Halley, and on the sun according to Herschel Sr.). But by the 1830s, many astronomers had grown far more skeptical about the possibility of lunar life.
The primary reason for their skepticism was the observation that the moon sharply occulted stars. That is, when the moon passed in front of stars, the image of the stars didn't appear fuzzy as they neared the edge of the moon. Such sharp occultation
indicated that the moon lacked an atmosphere, and therefore lacked air to sustain life. As the German astronomer Friedrich Wilhelm Bessel put it in an 1834 lecture, "The moon has no air; thus also no water, because without the pressure of air, water at least in the liquid state would evaporate; thus also no fire, for without air nothing can burn."
However, the apparent lack of a lunar atmosphere hadn't convinced all scientists that the moon didn't support life. After all, what if unseen areas of the moon, such as caves, held an atmosphere? Or what if the lunar inhabitants didn't require an atmosphere to survive? For these reasons, some astronomers continued to insist that only direct telescopic observation of the moon would settle the question of lunar life, and they had been diligently scanning the surface of the moon to find any signs of life. They even believed they had met with some success.
In 1824, Franz von Paula Gruithuisen, professor of Astronomy at Munich University, had published a paper titled "Discovery of Many Distinct Traces of Lunar Inhabitants, Especially of One of Their Colossal Buildings." In this paper, he noted the existence not only of different shades of color on the lunar surface, which he correlated with climate and vegetation zones, but also lines and geometrical shapes, which he felt indicated the existence of roads, walls, fortifications, and cities.
Other prominent German astronomers during the 1820s and 30s shared Gruithuisen's belief in the existence of lunar life. Carl Friedrich Gauss (director of the Göttingen Observatory), Johann Joseph von Littrow (director of the Vienna Observatory), and Wilhelm Olbers (a Bremen astronomer) all seriously discussed ways of communicating with the inhabitants of the moon, such as the construction of gigantic geometrical symbols on the surface of the Earth that would be visible from the moon. These discussions were described in the October 1826 issue of the Edinburgh New Philosophical Journal
Sir John Herschel himself, to whom the moon hoax credited the supposed lunar discoveries, hadn't ruled out the possibility of lunar life. In his Treatise on Astronomy
, published in America in 1834 (one year before the moon hoax), Herschel had reviewed the arguments for and against the possibility of lunar life, but took no side in the debate. After concluding his review, he simply remarked, "Telescopes... must yet be greatly improved, before we could expect to see signs of inhabitants, as manifested by edifices or by changes on the surface of the soil."
Moon hoax scene, created by artist Don Davis for Sky and Telescope magazine (1981).
The first installment of the lunar narrative described the "immense telescope of an entirely new principle" that Sir John Herschel had supposedly invented and constructed. The telescope consisted of a 24-foot diameter lens, whose power was amplified by a second lens, the "hydro-oxygen microscope". It was the extraordinary power of this telescope that allowed Herschel a clear view of the lunar inhabitants. (Perhaps the author of the moon hoax had read the passage in Herschel's book, quoted above, about improving telescopes to spy on lunar inhabitants.) This was a specific technological claim, whose plausibility readers could judge independent of the claims about lunar life.
For some readers (the more technologically astute ones) the improbability of such a telescope immediately undermined the plausibility of the entire narrative. William Leete Stone, editor of the Commercial Advertiser
, pointed out that if such a massive piece of equipment had been built, the British press would certainly have written about it before. And Michael Floy, the young New York businessman who wrote about the hoax in his diary, noted that such a telescope was impossibly far beyond the limits of optical technology:
The author of these wonders says that an enormous lens of 30 feet diameter was constructed. He thought that would be a big enough lie in all conscience, but he should have said a lens of 100 feet diameter, as it is shown by writers on optics that such a diameter would be required to ascertain if any inhabitants in the Moon. Why not make a good lie at once? But it is utterly impossible to construct a lens of half that diameter, and therefore we may despair of ever ascertaining whether the moon be inhabited.
Ironically, two years before the moon hoax, Day had run an article in the Sun
about lunar science, in which he too had pointed out that a telescope couldn't be built powerful enough to see life on the moon:
"Some of the German astronomers gave out a few years since that they had discovered cities and regular fortifications in the moon. This we may doubt without fear of being sceptical, but is recorded in works of credit that a lunar volcano was seen at midday with the naked eye in the streets of London. It is now ascertained that no telescope can be made, in the present state of science or art, which will enable us in the way of further discoveries to 'Pluck bright honor from the pale-faced moon.'" (N.Y. Sun, Sep. 11, 1933: 1.)
However, no one remembered Day's earlier article. And few people were sufficiently well versed in optics to know that a telescope of the kind described was impossible. And moreover, such skeptical considerations tended to be swept aside by the enormous faith that Americans placed in the promise of technological advance.
The first decades of the nineteenth century had produced numerous technological wonders such as steamboats, canals, railroads, the cotton gin, and improved printing presses. Soon to appear were the telegraph and the daguerrotype. It was an age when people were prepared to believe that any invention, no matter how remarkable, was possible. This technological optimism was particularly strong in New York state, home of the recently completed Erie Canal, a marvel of engineering in its own right. And people were particularly willing to accept that Sir John Herschel might have been able to construct such a telescope, since he and his father were famous throughout the world for the remarkable telescopes they built, and their astronomical discoveries.
So while for some readers the technological claims posed by the lunar narrative immediately marked it out as a hoax, to others the claims were simply more evidence of the wonder of the age in which they lived.
For many readers of the lunar narrative, scientific and technological considerations were inseparable from religious ones. In particular, there was widespread acceptance of the arguments of Natural Theology, whose proponents had been arguing for decades in favor of the existence of extraterrestrial (and lunar) life. This was an important part of the frame of reference by which readers judged the narrative.
Natural Theology was a religious philosophy which taught that the study of nature provided not only direct evidence of the existence of God, but also insight into his divine plan. This philosophy had been articulated in works such as William Paley's Natural Theology
(1801) and the Bridgewater Treatises
of the 1830s. Natural Theology was extremely popular, both among scientists and the general public, and actually served as the dominant framework for the study of nature during the first half of the nineteenth century.
The divine plan that seemed evident to most Natural Theologians, as they dug deeper into the secrets of Nature, was that God intended, through his creation, to promote life. This conclusion was strengthened as scientists realized that the more they searched, the more they found life crammed into every obscure corner of the globe. Microscopes, for instance, revealed small, life-filled worlds even inside drops of water.
Natural theologians concluded that God was clearly bountiful and plentitudinous in his Creation. He had evidently created a universe full of life. This made it seem illogical that the Creator would have surrounded the Earth with a universe full of dead planets. After all, if God's purpose was to support life, what role could lifeless planets serve in this plan? It was this logic that convinced many that the moon must indeed be inhabited, despite its apparent lack of an atmosphere.
The astronomical implications of natural theology reached a wide audience through the writings of Thomas Dick. Dick, also known as the 'Christian Philosopher'
after the title of his first book, was a Scottish astronomer whose works were suffused with the concepts of Natural Theology. Like an early, Christian version of Carl Sagan, he campaigned tirelessly as both a writer and a lecturer to popularize astronomy and the concept of a "plurality of worlds."
Thomas Dick, the 'Christian Philosopher'
One of Dick's more notorious achievements was his estimate of the population of the solar system. According to his calculations, the solar system contained 21,894,974,404,480 inhabitants. In fact, the moon alone, by his count, contained 4,200,000,000 inhabitants (Source: Crowe, 1997). His writings were enormously popular in the United States, with his fans including intellectual luminaries such as Ralph Waldo Emerson.
Rev. Timothy Dwight
America also had its own, homegrown proponents of Natural Theology. The most influential of these was Rev. Timothy Dwight, who served as president of Yale from 1795 until his death in 1817. He tirelessly promoted the tenets of Natural Theology. In his sermons, Dwight frequently referred to the concept of a plurality of worlds, using the idea as a means to illustrate the omnipotence of the Creator. He talked about an infinity of worlds, all governed by divinely ordained laws. He even referred in one sermon to the 'Herschellian Telescope' (meaning Sir William Herschel, not his son Sir John Herschel), and the grandeur of the inhabited universe that it revealed. Though deceased by the time of the moon hoax, Dwight's influence lived on through the students whose scientific training he had encouraged and supported. These students included Benjamin Silliman, editor of the American Journal of Science and Arts
, and Josiah Holbrook, founder of the American Lyceum movement.
Because of the popularity and influence of men such as Dwight and Dick, the Natural Theology movement laid the groundwork that made the moon hoax plausible to many people.
Perhaps the most compelling aspect of the lunar narrative had nothing to do with optics or the ongoing debate about extraterrestrial life. It was that the narrative came wrapped in the authority of European science, which Americans were very much in awe of. The discoveries were said to have been made by the renowned Sir John Herschel and had been published in the prestigious Edinburgh Journal of Science
. If this was true, then Americans were willing to consider that the narrative might be true, no matter how ridiculous it sounded. After all, who were they to question the great Herschel?
The question was, was any of this true? Had Herschel really claimed to make such discoveries? Had the narrative really been published in the Edinburgh Journal of Science
? Or was the narrative of American origin (in which case it would be obviously false)? In 1835, these questions weren't that easy to answer. It wasn't possible to pick up a telephone and call Herschel. Instead, people tried to look for clues in the narrative itself to determine its authenticity, but often these clues were misleading.
First, the narrative did pass the simplest level of fact-checking, in that people knew there really was an Edinburgh Journal of Science
, and that Herschel definitely was in South Africa, where he was charting the stars of the Southern Hemisphere. His departure from London to South Africa had been widely reported in 1833.
Herschel's twenty-foot reflector in Feldhausen, South Africa. Lithograph by G.H. Ford.
Second, people assessed the language and style of the story, to determine whether it sounded like something a genuine scientist would write — and here again the internal evidence proved misleading.
The narrative displayed an ornate style that included numerous scientific allusions extremely obscure to the lay reader. It did sound convincing, and it was generally doubted that any American possessed the intellectual background to have composed such a piece. In reality, quite a few Americans possessed the breadth of education and scientific experience necessary to have written it, but the general perception among Americans was that their countrymen intellectually lagged far behind the Europeans. This sense of cultural inferiority helped to convince readers that the narrative had to be of European origin, which lent credibility to the hoax.
Ironically, the fact that the narrative first appeared in the Sun
also lent weight to the belief that it was of European origin, because many people doubted that a lowbrow penny paper could have produced such an erudite text.
Third, the Sun's
explanation of how it had obtained the lunar narrative, and why they had the sole American copy, was plausible. The Sun
explained that it had obtained the journal from a "medical gentleman immediately from Scotland." European science journals were notoriously difficult to obtain copies of in America. American scientists were always struggling to get the latest journals. Because newspapers cultivated connections with dock employees in order to obtain the first news from Europe, it wasn't considered odd that the Sun
possessed the only copy of the journal in America.
Finally, there was no transatlantic cable linking America and Europe in 1835. People had to wait weeks for the mail to be shipped back and forth across the ocean. This provided the Sun
with a long window of time in which it simply wasn't possible for anyone in America to confirm whether such an article had appeared in the Edinburgh Journal of Science
. They had to take the Sun's
word for it.
took full advantage of this window of doubt. As public suspicion grew concerning the authenticity of the discoveries, it adopted a stance of wounded innocence, claiming that it had merely published what it had received from Europe and that therefore, if there was a hoax, it was a European one. It insisted that, to settle the matter, it had to wait for the mail from Europe like everyone else:
"Certain correspondents have been urging us to come out and confess the whole to be a hoax; but this we can by no means do, until we have the testimony of the English or Scotch papers to corroborate such a declaration." (NY Sun, Sep. 16, 1835)
Lunar scene, from a Welsh edition of the moon hoax
insisted it had to wait for the mail from Europe to arrive in order to determine whether the lunar narrative was a hoax. However, it supposedly had a copy of the relevant issue of the Edinburgh Journal of Science
. Why didn't it share this journal with others — show it around — in order to quell suspicions that there was no such journal? This question did occur to people at the time, and there was a report of an attempt to examine the Sun's
copy of the journal.
During the first two weeks of September 1835, a rumor spread among New York City's editors alleging that a small party of scientific gentlemen from Yale College had shown up unannounced at the Sun's
office on Nassau Street. Day asked how he could help them, and they explained that they wanted to see the Sun's
copy of the Edinburgh Journal of Science
. They said they were considering reprinting portions of the lunar narrative in a scientific publication of their own, but before they did so, they wished to verify its authenticity. Day explained that he couldn't show it to them:
"They were informed that we could not then show them the original, as it was partly divided among a number of compositors, and the remainder of it was in the hands of the lithographic artist. Dissatisfied with this answer, one of the gentlemen went, as we believe, to the office of the Journal of Commerce, and advised the editors not to insert the article [i.e. the lunar narrative] without denying or at least questioning its authenticity." (NY Sun, Sep 22, 1835: 2)
In 1852, William Griggs retold the story of the visitors from Yale, but he included new details that added a touch of comedic farce to it. According to him, after being rebuffed at the Sun
, the men headed to the printer on Spruce Street to obtain the journal there. But Day sent a messenger boy ahead of them to tell the printer to shut his office, so that the men's search for the journal was "rendered fruitless".
By the twentieth century, the story had been embellished further. Not only were the gentlemen said to be from Yale, but the deputation supposedly included the two most esteemed astronomers in America, Yale professors Denison Olmstead and Elias Loomis.
Denison Olmsted (left) and Elias Loomis (right)
It would be amusing if America's top astronomers were taken in by the lunar narrative to the extent that they traveled from New Haven to New York City to verify its authenticity. But there are reasons to doubt the story.
On September 20, the Evening Star
published a letter it had received from a correspondent identifying himself as "Yalensis". This correspondent insisted that no professors from Yale had visited the Sun
. The Sun
responded to this letter with equivocation, saying it wasn't sure the men were from Yale, only that they were from New Haven.
Perhaps the Sun
did receive a group of visitors from New Haven. However, it's just as likely the Sun
invented the story of the visit as a boast that had populist appeal — i.e., look how the lowbrow Sun
fooled the fancy professors from Yale!
It's also unlikely that Olmsted and Loomis would have been taken in by the lunar narrative. If anyone could have recognized its implausibility, it would have been them. Moreover, at the time of the moon hoax they were engaged in an important project of their own, preparing to observe the return of Halley's Comet.
In early September, Olmsted and Loomis sent a short letter to the New Haven Daily Herald
announcing that they had finally observed the comet:
"Yesterday morning, August 31st, we had the satisfaction of first observing this interesting body, in the field of Clark's great telescope. The possibility of confounding it with a nebula, induced us to wait for another observation, in order to ascertain whether it changed its place among the stars, in which case no doubt would remain of its being a comet. The approach of the twilight prevented our ascertaining this point yesterday; but observations repeated this morning, plainly indicated a proper motion; and being very near the place assigned to Halley's comet, we recognized it as the long expected visitant." (New Haven Daily Herald, Sep. 3, 1835: 2)
It's highly improbable that the two astronomers would have taken an entire day away from their observations at such a time to travel to New York City in an attempt to verify the reality of lunar biped beavers and man-bats.
The Journal of Commerce
is widely credited with being the first newspaper to suggest the lunar discoveries were a hoax. But it did so in a very general way, merely stating, "There is no doubt but the article was manufactured in this country, and that it belongs to the same school as Robinson Crusoe and Gulliver's Travels." It probably published this statement on Friday, August 28, 1835. (It hasn't been possible to find archived copies of the Journal of Commerce
from before September 1835, but its remarks were subsequently reprinted by other papers such as the Charleston Courier
The hoax was much more thoroughly debunked by James Gordon Bennett when he resumed publication of the New York Herald
on August 31, 1835. In an article titled, "The Astronomical Hoax Explained," Bennett offered clear evidence that the lunar narrative had to be a hoax, and he also identified its author.
Bennett noted, "the town has been agape two or three days at the very ingenious astronomical hoax." Then he revealed a glaring mistake that revealed the whole to be a hoax. The narrative had supposedly been published in the Edinburgh Journal of Science
. But Bennett pointed out that there was, "no work of that kind being now published. A few years ago there was such a work, but it merged into another journal published in London."
Bennett was correct. The Edinburgh Journal of Science
had ceased publication in 1833. Therefore, it was impossible that it could have published the lunar narrative in 1835. Bennett's revelation should have ended the debate about whether the narrative was a hoax, but instead his disclosure was ignored by the rest of the media community.
But as for the author of the hoax, Bennett pointed the finger at a well-educated British writer, recently arrived in America, whom Benjamin Day had hired two months before to serve as the new editor of the Sun
— a man named Richard Adams Locke. This disclosure wasn't ignored.
Richard Adams Locke
During the Summer of 1835, a small-time religious leader named 'Matthias the Prophet' had been put on trial for the murder of one of his followers. It was a sensational trial, full of scandalous revelations, and the penny papers had given it extensive coverage. Bennett recalled meeting Locke during this trial, who was there to cover it for the Sun
. Bennett claimed that he had struck up a casual conversation with Locke during which Locke "told me he was engaged on some scientific studies. He mentioned optics, and I think astronomy, as the particular branches." Bennett offered this remembered conversation as proof that Locke had to be the author of the moon hoax.
Bennett also shared a bit of scandal from Locke's past, revealing that the man had originally considered dedicating his life to the Church, "but in consequence of some youthful love affair, getting a chambermaid in some awkward plight, abandoned religion for astronomy."
Bennett's evidence implicating Locke as the author of the lunar narrative was a bit flimsy. But on the other hand, Locke was the natural suspect. There were only two people working at the Sun
: Benjamin Day and Locke. Of the two, Locke was far more highly educated. He claimed to have graduated from Cambridge, and to be a direct descendant of the famous 17th-century philosopher John Locke. So, if one assumed that the lunar narrative was a hoax, it wasn't hard to guess which of the two men at the Sun
must have written it.
Locke didn't reply to Bennett's accusations in the Sun
. Instead, he sent a letter to the Evening Star
in which he declared, "I beg to state, as unequivocally as the words can express it, that I did not make those discoveries." He also complained that the story about him and a chambermaid was "as untrue as it is impertinent."
Bennett responded by pointing out, correctly, that he never claimed Locke had made the discoveries: "We only said he did the writing part." Bennett added:
"He need not be ashamed of it, neither need he squint so awfully at us about the chamber-maid. We can return the look with seven per cent interest. We still persist in our belief." (NY Herald, Sep.1, 1835)
Over the next few weeks, a battle of words raged between the Sun
and the Herald
. Locke and Day refused to admit that the lunar narrative was a hoax. Even by late September, when the mails from Europe had confirmed that the narrative was pure fiction, the two men maintained their innocence. This infuriated Bennett, who took every opportunity he could find to goad and ridicule Locke, in an attempt to get him to lose his composure and confess.
For instance, in late September Bennett declared that, "Mr. R.A. Locke, the ingenious author of the 'Moon Hoax,' is preparing a series of lectures on Astronomy, to be delivered at as early a day as possible, in the lecture-room of the Clinton Hall." Of course, Locke wasn't preparing any such lectures, but Bennett kept up the joke for weeks, constantly asking when Locke would be ready with his astronomy lectures.
In mid-November, Bennett claimed he had received a confession from Locke, in the form of a letter signed, "Richard Adams Locke, Author of the Lunar Discoveries." Locke responded that the letter was "an outrageous and felonious forgery." To which, Bennett retorted:
"Master Richard Adams and his associates of the Sun, bawl out 'an outrageous and felonious forgery'—'most malicious and libelous.' Oh! oh! oh! Why did you not think of morals when you forged the name of Herschell? Come forward good people all ye that believed in the Lunar Hoax—won't you sympathise with the Sun and Sir Richard Adams Locke in this new calamity? Will no one move? no one budge? No indeed, every one seems most inclined to laugh." (NY Herald, Nov.17, 1835).
Even in December, almost four months after the hoax, Bennett was still inserting snide comments about Locke and the moon hoax into his columns. When New York City was in the grip of a fierce ice storm, Bennett joked:
"Sir Richard Adams Locke is preparing a magnificent burning glass of one hundreds tons for the purpose of melting the ice in the North River and canals, and permitting the embargoed flour to reach the city.—A benefactor of the human race!" (NY Herald, Dec.10, 1835)
And still Locke and Day refused to confess.
Locke was born on September 22, 1800 in the county of Somerset, England to a well-to-do family. His grandfather, Richard Locke, had acquired a sizeable fortune through farming, by buying poor land and using scientific techniques to improve it. Locke would later claim that he was a direct descendant of the philosopher John Locke, but this wasn't true. He was a collateral descendant. His great-great-great-grandfather was John Locke's uncle.
As a young gentleman, it was expected that Locke should attend attend either Oxford or Cambridge (his father went to Oxford) and then take on the responsibility of managing the family estate. But at a young age Locke adopted radical Republican political views, and he decided not to follow the career his family had planned for him, for which reason his father disowned him.
Instead, Locke chose to be a writer. He first wrote for a radical newspaper, the Republican
, and several literary journals. Then he briefly served as editor of a small Somerset paper, the Bridgwater and Somersetshire Herald
, but was fired because of his politics.
Locke struggled along working as a freelance writer, but his responsibilities increased when he married in 1826 and in 1830 his wife gave birth to a daughter. Still finding it difficult to find work because of his political views, in 1831 Locke decided to move his family to America, where his politics would be a non-issue. He arrived in New York City with his wife and daughter on January 13, 1832.
In New York, Locke initially found occasional work as a legal reporter and stenographer. He also began telling people he had graduated from Cambridge, in an apparent effort to make himself appear more distinguished, and thus employable. Matthew Goodman (2008) has determined that Locke never attended Cambridge. However, because he had an extremely intellectual demeanor and was highly knowledgeable about a range of subjects, historical and scientific,
everyone in America accepted his claim about his education. A description of Locke written by Edgar Allan Poe demonstrates how he was viewed by his American colleagues:
He is about five feet seven inches in height, symmetrically formed; there is an air of distinction about his whole person — the air noble of genius. His face is strongly pitted by the small-pox, and, perhaps from the same cause, there is a marked obliquity in the eyes; a certain calm, clear luminousness, however, about these latter, amply compensates for the defect, and the forehead is truly beautiful in its intellectuality. I am acquainted with no person possessing so fine a forehead as Mr. Locke.
In 1834, Locke landed his first regular job in New York City as the metropolitan reporter for the Courier and Enquirer
. He also authored a small pamphlet, The History of the Polish Revolution
During the following summer, 1835, Locke was covering the trial of Matthias the Prophet, and it was here that he first met Benjamin Day, who was looking for someone to cover the trial for the Sun
. Locke agreed to provide him with a series of articles, provided his name didn't appear on them as the author, since he was still working for the Courier and Enquirer
. Day agreed.
Locke's Matthias articles proved so popular with the Sun's
readers that Day issued them as a sixteen-page pamphlet, which sold 10,000 copies. This proved to be an eye-opening experience for Day, who realized that a great deal of money could be made by reissuing material from his paper in pamphlet form — though it had to be the right kind of material. He told Locke that he would pay him for any other long articles he might write, and Locke set to work thinking of other topics he could write about in serial form. He came up with the idea of an astronomical satire detailing the discovery of life on the moon.
At the end of June, Day's co-editor on the Sun
, George Wisner, quit, and Day hired Locke as his replacement. Two months later, the Sun
published Locke's lunar narrative.
When Bennett exposed Locke as the author of the lunar narrative, Locke responded by publicly denying the charge. But according to a story first told by Frank O'Brien (1928) in his history of the Sun
newspaper, Locke admitted to a fellow reporter in private that he had written it.
According to O'Brien, Locke was having a drink in the taproom of the Washington Hotel with a fellow reporter named Finn, who worked at the Journal of Commerce
. Finn mentioned that the Journal was planning to reprint the lunar narrative. Locke said, "Don't print it right away. I wrote it myself."
The story, though anecdotal, is plausible because Locke had a reputation as a heavy drinker, and it might be the reason why the Journal of Commerce
was among the first papers to identify the lunar narrative as a hoax.
However, this wasn't the only time Locke confessed.
Locke left the Sun
in the Fall of 1836 to work at the New Era
, a new penny paper. In an article (about poetry) that he wrote soon after arriving at the New Era
, he added the title "Author of the Moon Hoax" to his byline. This was the first time he publicly acknowledged being the author of the hoax.
While at the New Era
, in the winter of 1838, Locke also attempted to perpetrate another hoax. He claimed to have discovered the lost diary of Mungo Park, the Scottish explorer who had disappeared in Africa in 1806. However, this hoax fell entirely flat. No other papers bothered to mention it. As Edgar Allan Poe later noted, "Mr. Locke's columns were a suspected district."
Locke left the New Era
in October 1839 and returned to freelancing. While looking for work, he responded to an invitation offered by Park Benjamin, editor of the New World
, to tell his side of the moon hoax. He did so in a long letter that appeared on the front page of the New World
on May 16, 1840. This was his fullest and most public confession.
Locke explained that he had intended the lunar narrative to be a satire, not a hoax at all, and that the object of his satire was the unchecked influence of religion upon science. This influence led, he believed, to an "imaginative school of philosophy" that substituted airy fancies, pleasing to religion, for hard fact. For Locke, such "theological and devotional encroachments upon the legitimate province of science" were particularly evident in the works of Thomas Dick, the 'Christian Philosopher' who had calculated the population of the solar system, as well as those German astronomers such as Gruithuisen who had claimed to see signs of life on the moon.
Locke's direct inspiration appears to have been the October 1826 issue of the Edinburgh New Philosophical Journal
in which there was a discussion of the lunar-life beliefs of the German astronomers, as well as an article by Thomas Dick in which he described his invention of a new telescope that he called the "Aërial Reflector".
Thomas Dick was aware of the moon hoax and (probably sensing that it was a joke aimed largely at himself) he offered his thoughts on it in a book he published in 1838, Celestial Scenery; or, the Wonders of the Planetary System Displayed, Illustrating the Perfections of Deity and a Plurality of Worlds
. Dick scolded the author of the moon hoax for taking liberties with the truth:
"It ought to be remembered that all such attempts to deceive are violations of the laws of the Creator, who is the 'God of Truth,' and who requires 'truth in inward parts;' and, therefore, they who wilfully and deliberately contrive such impositions ought to be ranked in the class of liars and deceivers."
In his letter to the New World
, Locke, in turn, responded to Dick:
"I think it quite laudable in any man to satirize, as I did, that school of crude speculation and cant of which he is so eminent a professor... But what has Dr. Dick to say in defence of his own hoaxes, which were chiefly instrumental in preparing the way for mine, and without which I cannot conceive that it could have obtained so instantaneous and extraordinary a circulation?"
In 1842, Locke gave up journalism and took a job with the Customs Service in New York. To get the job, he had to tell another lie: that he was born in America. He worked there until 1862, and then he spent the final years of his life living in retirement on Staten Island. He died on February 16, 1871. The following, brief obituary for him ran on the front page of the Sun
"Richard Adams Locke died on Staten Island on Thursday, in his 71st year. Mr. Locke was the author of the 'Moon Hoax,' the most successful scientific joke ever published, which originally appeared in The Sun. The story was told with a minuteness of detail and dexterous use of technical phrases that not only imposed upon the ordinary reader, but deceived and puzzled men of science to an astonishing degree." (NY Sun, Feb. 18, 1871: 1)
One of the features of the lunar narrative that was often remarked upon and admired was the way it wove together accurate (and often quite obscure) astronomical references with more farcical elements. It appeared to have been written by someone with a good background in astronomy. For instance, David Evans (1981) singled out the following passage, from the second day's extract of the narrative, for comment:
They arrived, after an expeditious and agreeable passage, and immediately proceeded to transport the lens, and the frame of the large observatory, to its destined site, which was a piece of table-land of great extent and elevation, about thirty-five miles to the north-east of Capetown; and which is said to be the very spot on which De La Caille, in 1750, constructed his invaluable solar tables, when he measured a degree of the meridian, and made a great advance to exactitude in computing the solar parallax from that of Mars and the Moon.
Evans noted that it's actually true that the French astronomer Nicolas De La Caille
had an observation station located about 35 kilometers northeast of Cape Town on the summit of Riebeeck Casteel mountain. However, this is an extremely obscure piece of information, which suggests that Locke was familiar with De La Caille's account of his observations, published (in French) in the Histoire de l'Académie Royale des Sciences
in 1755. It's not clear how Locke came by this information, nor how he acquired the familiarity with astronomy in general that informs the entire narrative.
The mystery of Locke's astronomical knowledge led to speculation that he wasn't the true author of the lunar narrative, or that he wasn't the sole author. But it was only after Locke died that the names of other possible authors began to be suggested.
In 1872, the mathematician Augustus De Morgan published A Budget of Paradoxes
in which he suggested that a French scientist, Jean-Nicolas Nicollet
, authored the lunar narrative. Nicollet was living in America at the time of the publication of the moon hoax, having left France, apparently because he was fleeing creditors. According to De Morgan:
"There is no doubt that it [the lunar narrative] was produced in the United States, by M. Nicollet, an astronomer, once of Paris, and a fugitive of some kind... The moon-story was written, and sent to France, chiefly with the intention of entrapping M. Arago, Nicollet's especial foe, into the belief of it. And those who narrate this version of the story wind up by saying that M. Arago was entrapped, and circulated the wonders through Paris, until a letter from Nicollet to M. Bouvard explained the hoax."
De Morgan offered no evidence to back up the theory of Nicollet's authorship, but the case for Nicollet was later taken up by S.A. Mitchell, in an article in Popular Astronomy
(1900). Mitchell argued that Locke simply didn't have the astronomical knowledge or creative skill necessary to have come up with the moon hoax:
Besides the great fluency of style and the masterful command of the English language shown by the 'Moon Hoax,' there is evinced in this article so accurate a knowledge of astronomical facts, even to the most scientific details, that it is evident none but an astronomer of more than ordinary ability could have written it. This Locke certainly was not. After severing his connection with the Sun, Locked edited the New Era, and soon after there appeared in this periodical another hoax, 'The Lost Manuscript of Mungo Park,' also by Locke. This, however, while showing the same peculiarities in style as the 'Moon Hoax,' lacked greatly the bold and daring conception in the plot of the latter, and as a result secured very little notoriety. It would seem, therefore, that there had been some bolder and more learned spirit than Locke's which had conceived the plot of the 'Moon Hoax,' and supplied the editor of the Sun with the astronomical facts necessary for the construction of the article... We seem to find this man in the person of M.J.N. Nicollet, a noted French astronomer, who, for some unknown causes, had been compelled to leave France and seek refuge in America.
This astronomer, in connection with MM. Brosseaud and Bouvard, was the author of an important memoir, 'Sur la Libration de la Lune'; and in Amer. Phil. Soc. Trans. Vol. VIII, 1842, pp. 306-310, we have a work of his published under the name of 'Observations made at several places in the United States.' With Nicollet as the author we find an explanation of the precise astronomical knowledge shown in our article, and especially the frequent use of the term 'libration' in his descriptions of the moon.
The problem with the theory of Nicollet's authorship is that it's unlikely that Nicollet, whose first language was French, could have written a text that displayed such a mastery of English. At the very least, he must have had someone (probably Locke) translate it. But there's no evidence that Locke and Nicollet ever met or communicated. Nor was Nicollet anywhere near New York in 1835. He was living in St. Louis.
Lewis Gaylord Clark
Another theory, put forward by Benson Lossing in 1884 in his History of New York City
, was that Lewis Gaylord Clark, editor of the Knickerbocker Magazine
, helped Locke write the lunar narrative. Lossing wrote:
"Clark was the real inventor of the incidents, the imaginative part, while to Locke was intrusted the ingenious task of unfolding the discoveries. Messrs. Beach, Clark, and Locke were in daily consultation while the hoax was in preparation. It was thus a joint product."
The 'Beach' referred to by Lossing was Moses Beach, who purchased the Sun
from Benjamin Day in 1837. But in 1835, Beach wasn't involved with the Sun
, which suggests that Lossing's theory is mistaken. Also, it's not clear why Clark would have had a better knowledge of astronomy than Locke.
Overall, there's no compelling evidence to indicate that anyone but Locke wrote the moon hoax. After all, Locke confessed to it. Neither Nicollet nor Clark ever did. And Benjamin Day never hinted that anyone else might be involved. Nor did first-hand observers of the hoax, such as James Gordon Bennett and Edgar Allan Poe, ever suggest that they suspected anyone else's participation.
We can attribute Locke's knowledge of astronomy to his wide reading. As Goodman (2008) points out, even from a young age Locke demonstrated a "seemingly bottomless capacity for knowledge." He chose to become a writer, but he definitely had an aptitude for the sciences and scholarship, and he might have excelled in these fields if he had made different choices early in his career.
Sir John Herschel
An innocent victim of the moon hoax was Sir John Herschel, to whom the lunar discoveries were attributed. At the time of the publication of the lunar narrative, he was in South Africa, charting the stars of the Southern Hemisphere, unaware of the liberties being taken with his name.
According to William Griggs (1852), an American showman named Caleb Weeks, who traveled to Africa in late 1835 in order to collect animals for his New York menagerie, first presented the Sun's
lunar narrative to Herschel. Weeks handed the paper to Herschel, telling him only, in vague language, that it was an American paper containing a report of some of his "great astronomical discoveries." Herschel thanked Weeks for the gift, retired to his room in the Cape Town hotel where they both were staying, only to burst forth minutes later exclaiming, "This is a most extraordinary affair! Pray, what does it mean?"
After receiving a full description of the hoax, Herschel laughed and said he "feared the actual results of his telescopic observations at the Cape would be very humble, in popular estimation, at least, in comparison with those ascribed to him in the American account."
Herschel’s good humor concerning the hoax apparently didn't last too long. Two years later he complained in a letter to his Aunt Caroline, "I have been pestered from all quarters with that ridiculous hoax about the Moon — In English French Italian & German!!"
And in May 2001, an unsent letter was discovered in the private archives of Herschel's descendants. It was written by Herschel, dated 21 August 1836, and addressed to the editor of the Athenaeum
magazine. If published, it would have been Herschel's longest official response to the moon hoax:
As I perceive by an Advertisement in one of the London Newspapers now before me that the nonsense alluded to in the heading of this letter after running the round of the American and French journals has at last found a London editor, it appears to me high time to disclaim all knowledge of or participation in the incoherent ravings under the name of discoveries which have been attributed to me. I feel confident that you will oblige me therefore by inserting this my disclaimer in your widely circulated and well conducted paper, not because I have the smallest fear that any person possessing the first elements of optical Science (to say nothing of Common Sense) could for a moment be misled into believing such extravagancies, but because I consider the precedent a bad one that the absurdity of a story should ensure its freedom from contradiction when universally repeated in so many quarters and in such a variety of forms. Dr. Johnson Indeed used to say that there was nothing, however absurd or impossible which if seriously told a man every morning at breakfast for 365 days he would not end in believing — and it was a maxim of Napoleon that the most effective figure in Rhetoric is Repetition. Now I should be sorry, for my own sake as well as for that of truth, that the world or even the most credulous part of it, should be brought to believe in my personal acquaintance with the man in the moon — well knowing that I should soon be pestered to death for private anecdotes of himself and his family, and having little intention and less inclination to humour the hoax, should come to be looked on as a very morose and uncommicative sort of person when it was found that I could or would say no more about him than what is already known to all the world — vis that he
'eats powdered beef turnip & carrot'
and that 'a cup of old Malaya Sack'
'Will fire the pack at his back.'
I am Sir
John F. Wm Herschel
Near Wynberg C.G.H.
- The text of Locke's lunar narrative was translated into many languages, including French, German, Italian, and Welsh. There was even a shorthand version of it, published in 1886.
Left: Shorthand edition of the moon hoax. Right: Welsh edition of the moon hoax.
- During the remainder of the nineteenth century, the moon hoax became a byword for deception. Anything suspicious would be compared to the moon hoax, or it might be called "moon hoaxy" — a term used by Poe in his short story Von Kempelen and his Discovery.
- During the nineteenth century, the moon hoax was popular enough to inspire the creation of various forms of moon-hoax-themed merchandise. For instance, the Nantucket Historical Association has what appears to be a fragment of Moon Hoax Wallpaper that decorated a house in Nantucket. And Oxford's Museum of the History of Science has a Moon Hoax Snuff Box.
- In 1891, when workmen were tearing down the old Brooklyn Institute Building, they discovered a lead box beneath the cornerstone. It had been placed there when the cornerstone was laid, on 31 October 1835. Upon opening the box, it was found to contain some coins, several newspapers dated 31 October 1835, and two large engravings of "Lunar animals and other objects discovered by Sir John Herschel in his observatory at the Cape of Good Hope."
- A complete copy of the original lunar narrative published in the Sun (not the pamphlet that the Sun subsequently published) was sold in July 1969 for $160. It was bought by Walter R. Benjamin, an autograph dealer, on behalf of a private client. In December 2011, a set of the articles was offered for sale on eBay for $488.
- Griggs, W.N. (1852), The Celebrated 'Moon Story,' Its Origin And Incidents. New York: Bunnell & Price.
- Locke, R.A. (1859), The Moon Hoax; or, A Discovery that the Moon has a vast population of human beings. New York: William Gowans.
- De Morgan, A. (1872), A Budget of Paradoxes. London: Longmans, Green, and Co.
- Proctor, R.A. (July/Oct 1876), "The Lunar Hoax," Belgravia: An Illustrated London Magazine, 30: 177-194.
- Mitchell, S.A. (May 1900), "The Moon Hoax", Popular Astronomy, 8(5): 256-267.
- O'Brien, F.M. (1928), The Story of The Sun. New York: D. Appleton and Company.
- Barton, W.H. (Feb 1937), "The Moon Hoax: The Greatest Scientific Fraud Ever Perpetrated," Sky, 1: 6-10, 22; March 1937: 10-11, 23-5; April 1937: 10-11, 22-4, 28.
- Reaves, G. (Nov 1954), "The Great Moon Hoax of 1835," The Griffith Observer, 17(11): 126-134.
- Price, G.R. (July 1958), "The Day they Discovered Men on the Moon." Popular Science, 173: 61-64.
- Ley, W. (1963), Watchers of the Skies: An Informal History of Astronomy from Babylon to the Space Age. London: Sidgwick & Jackson Ltd.
- Morrison, J.L. (1969), "A View of the Moon from the Sun: 1835." American Heritage. 20(3): 80-82.
- Seavey, O. ed. (1975), The Moon Hoax, Or, A Discovery That The Moon Has A Vast Population of Human Beings. Boston: Gregg Press.
- Evans, D.S. (Sep 1981), 'The Great Moon Hoax', Sky and Telescope: 196-198; Oct 1981: 308-311.
- Crowe, M.J. (Nov. 1981), "New Light on the Moon Hoax", Sky and Telescope: 428-429.
- Crowe, M.J. (1986), The Extraterrestrial Life Debate, 1750-1900. New York: Cambridge University Press.
- Cohan, P. (Apr/May 1986), "Heavenly Hoax", Air & Space Smithsonian, 1(1): 86-95.
- Fernie, D.J. (Mar/Apr 1993), "The Great Moon Hoax", American Scientist, 81: 120-122.
- Crowe, M.J. (June 1997), 'A History of the Extraterrestrial Life Debate', Zygon, 32(2): 147-162.
- Ruskin, S.W. (2002), 'A Newly-Discovered Letter of J.F.W. Herschel Concerning the Great Moon Hoax', Journal for the History of Astronomy, 33: 71-74.
- Copeland, D.A. (Fall 2007), 'A Series of Fortunate Events: Why People Believed Richard Adams Locke's Moon Hoax', Journalism History, 33(3): 140-150.
- Goodman, M. (2008), The Sun and the Moon: The Remarkable True Account of Hoaxers, Showmen, Dueling Journalists, and Lunar Man-Bats in Nineteenth-Century New York. New York: Basic Books.
- Castagnaro, M. (2009), Embellishment, Fabrication, and Scandal: Hoaxing and the American Press. Carnegie Mellon University. Ph.D. Dissertation. | 0.811135 | 3.105117 |
Astronomers find best evidence for elusive mid-sized black hole
Pic credit: IANS
Washington: Astronomers have found the best evidence for a black hole of an elusive class known as “intermediate-mass” by using the combined power of two X-ray observatories and the keen vision of NASA’s Hubble Space Telescope.
Weighing in at about 50,000 times the mass of our Sun, the black hole is smaller than the supermassive black holes (at millions or billions of solar masses) that lie at the cores of large galaxies, but larger than stellar-mass black holes formed by the collapse of a massive star, according to the study published in The Astrophysical Journal Letters.
These so-called intermediate-mass black holes (IMBHs) are a long-sought “missing link” in black hole evolution.
Though there have been a few other IMBH candidates, researchers consider these new observations the strongest evidence yet for mid-sized black holes in the universe.
“Intermediate-mass black holes are very elusive objects, and so it is critical to carefully consider and rule out alternative explanations for each candidate. That is what Hubble has allowed us to do for our candidate,” said principal investigator of the study Dacheng Lin of the University of New Hampshire in the US.
Lin and his team used Hubble to follow up on leads from NASA‘s Chandra X-ray Observatory and ESA’s (the European Space Agency) X-ray Multi-Mirror Mission (XMM-Newton).
In 2006 these satellites detected a powerful flare of X-rays, but they could not determine whether it originated from inside or outside of our galaxy.
Researchers attributed it to a star being torn apart after coming too close to a gravitationally powerful compact object, like a black hole.
Surprisingly, the X-ray source, named 3XMM J215022.4-055108, was not located in a galaxy’s centre, where massive black holes normally would reside.
This raised hopes that an intermediate-mass black holes was the culprit, but first another possible source of the X-ray flare had to be ruled out: a neutron star in our own Milky Way galaxy, cooling off after being heated to a very high temperature.
Neutron stars are the crushed remnants of an exploded star.
Hubble was pointed at the X-ray source to resolve its precise location. Deep, high-resolution imaging provided strong evidence that the X-rays emanated not from an isolated source in our galaxy, but instead in a distant, dense star cluster on the outskirts of another galaxy — just the type of place astronomers expected to find an IMBH.
The star cluster that is home to 3XMM J215022.4-055108 may be the stripped-down core of a lower-mass dwarf galaxy that has been gravitationally and tidally disrupted by its close interactions with its current larger galaxy host, said the study. | 0.84035 | 3.947154 |
Galileo Galilei found what came to be known as the Galilean moons around December 1609 or January 1610. As a result of improvements he made to the telescope, Galileo was able to see celestial bodies better than ever before in human history. Using his improved telescope, Galileo was the first to see four moons of Jupiter.
On January 7, 1610, Galileo wrote a letter containing the first mention of Jupiter’s moons. At the time, he only saw three of them, and he believed them to be fixed stars near Jupiter. He continued to look at them from January 8 through March 2. In these observations, he found a fourth body, and also observed that the four were not fixed stars, but rather were orbiting Jupiter.
Galileo’s discovery proved the importance of the telescope as a tool for astronomers. It showed there were objects in space to be found, which were not seen by the naked eye. More importantly, the discovery of celestial bodies orbiting something other than the Earth dealt a blow to the then-accepted Ptolemaic world system. This held that the Earth was at the center of the universe and all other celestial bodies revolved around it. That Jupiter has four moons while Earth has only one further undercut the near-universal belief that the Earth was the center of the universe both in position and in importance. Galileo's Sidereus Nuncius (Starry Messenger), which announced celestial observations through his telescope, does not mention Copernican heliocentrism, a theory that placed the Sun at the center of the universe. Nevertheless, Galileo believed in the Copernican theory.
Galileo also developed a method of determining longitude based on the timing of the orbits of the Galilean moons.
Galileo called his discovery the Cosmica Sidera ('Cosimo's stars'), in honour of Cosimo II de' Medici (1590–1621), grand-duke of Tuscany, whose patronage he wanted. At the grand-duke's suggestion, Galileo changed the name to Medicea Sidera ('the Medici stars'), honouring all four Medici brothers (Cosimo, Francesco, Carlo, and Lorenzo). The discovery was announced in the Sidereus Nuncius ('Starry Messenger'), published in Venice in March 1610, less than two months after the first observations.
Other names put forward, but the names which eventually prevailed were chosen by Simon Marius. Marius claimed to have found the moons at the same time as Galileo: he named them after lovers of the god Zeus (the Greek equivalent of Jupiter): Io, Europa, Ganymede and Callisto, in his Mundus Jovialis, published in 1614.
Galileo refused to use Marius's names and invented the numbering scheme that is still used nowadays, in parallel with proper moon names. The numbers run from Jupiter outward, thus I, II, III and IV for Io, Europa, Ganymede and Callisto respectively. Galileo used this system in his notebooks but never actually published it.
The Galilean moons are, in order from closest to Jupiter to farthest away:
Seeing the moonsEdit
All four Galilean moons are bright enough that they could, if they were farther away from Jupiter, be seen without a telescope. They have apparent magnitudes between 4.6 and 5.6 when Jupiter is in opposition with the Sun, and about one unit of magnitude dimmer when Jupiter is in conjunction. The main thing that is hard in observing them is due to the fact that they are very close to Jupiter, and are masked by its brightness. Their maximum angular separations from Jupiter are between 2 and 8 minutes of arc, close to the limit of human visual acuity. Ganymede and Callisto, at their maximum separation, are the likeliest targets for possible naked-eye observation. The easiest way to observe them is to cover Jupiter with an object, e.g. a tree limb or a power line that is perpendicular to the plane of moons' orbits.
- Galilei, Galileo, Sidereus Nuncius. Translated and prefaced by Albert Van Helden. Chicago & London: University of Chicago Press 1989, 14-16.
- Galilei/Helden, 15-16.
- Xi Zezong 1982. "The discovery of Jupiter's satellite made by Gan De 2000 years before Galileo," Chinese Physics 2: 664-667. | 0.845473 | 3.919699 |
Astronomers have captured the best image ever of planet formation around an infant star as part of the testing and verification process for the Atacama Large Millimeter/submillimeter Array’s (ALMA) new high-resolution capabilities.
This revolutionary new image reveals in astonishing detail the planet-forming disk surrounding HL Tau, a Sun-like star located approximately 450 light-years from Earth in the constellation Taurus.
ALMA uncovered never-before-seen features in this system, including multiple concentric rings separated by clearly defined gaps. These structures suggest that planet formation is already well underway around this remarkably young star.
“These features are almost certainly the result of young planet-like bodies that are being formed in the disk. This is surprising since HL Tau is no more than a million years old and such young stars are not expected to have large planetary bodies capable of producing the structures we see in this image,” said ALMA Deputy Director Stuartt Corder.
The new ALMA image reveals these striking features in exquisite detail, providing the clearest picture to date of planet formation. Images with this level of detail were previously only seen in computer models and artist concepts. ALMA, living up to its promise, has now provided direct proof that nature and theory are very much in agreement.
“This new and unexpected result provides an incredible view of the process of planet formation. Such clarity is essential to understand how our own Solar System came to be and how planets form throughout the Universe,” said Tony Beasley, director of the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia, which manages ALMA operations for astronomers in North America. (Credit: Charles E. Blue)via public.nrao.edu | 0.898497 | 3.384381 |
At the 6,400-acre Plum Brook Field Station complex near Sandusky, Ohio, stands five large test facilities operated by NASA to test various aspects of space flight. Most of these were built decades ago at a time when the country’s space program was of national importance. But now, these million-dollar facilities have fell into disuse and some are so rundown they would require millions of dollars more to repair. Out of the five still-standing facilities, four have seen no use in the recent past. Two are slated for demolition, one is not fully functional and one has never been used. Only a large vacuum chamber, called the Space Power Facility, is in use with a long queue of customers booked through at least 2021. One of its most recent customers was SpaceX.
The Space Power Facility (SPF) is the world’s largest vacuum chamber measuring 30 meters tall and 37 meters across. It is used to simulate conditions existing in outer space so that rocket hardware could be tested before they are actually sent into space. It does that by pumping out the nearly 30 tons of air contained in the chamber until there is only about 20 milligrams left. It takes about eight hours to pump down to this level. Inside, an array of quartz heat lamp simulates solar radiation and a 400 kilowatt arc lamp simulates the solar spectrum. A cryogenic cold shroud brings the temperature down to minus one hundred sixty degree centigrade.
The facility was built in 1969 originally for nuclear-electric power studies under vacuum conditions, but was later adopted for testing spacecraft propulsion systems. The entire chamber is made of aluminum, which isn’t the most toughest metal to withstand the enormous pressure produced when the air is pumped out. The strange choice of metal is owing to the fact that the chamber was originally designed for testing nuclear devices and aluminum has radiation shielding properties. To provide strength to the structure, the entire aluminum chamber is encased in concrete which provides additional radiation shielding.
The SPF is not the most extreme vacuum chamber but it’s definitely the largest. Some vacuum chambers can achieve ultra vacuum conditions where air pressure goes down to as low as 100 nanopascals, or about 2,500 times lower than the strongest vacuum achieved by the SPF, but those vacuum chambers are generally small, and used for things like X-Ray spectroscopy and gravitational wave detectors. The SPF, on the other hand, is big enough to swallow a spacecraft. The airbag landing systems for the Mars Pathfinder were tested inside this vacuum chamber, and the Mars Exploration Rovers, Spirit and Opportunity, were stress-tested under simulated Mars atmospheric conditions here. In 2013, the most exciting private space venture, SpaceX, utilized the services of the SPF to test their payload fairing—the nose cone that protects a spacecraft from pressure and heat during launch through the atmosphere.
In 2013, BBC physically demonstrated one of the most famous thought experiments inside the SPF. They took a bowling ball and a bunch of feathers, raised it by a crane to the roof of the chamber and dropped them at the same time. Without air resistance to slow the feathers down, both objects fell at the same rate and touched the floor of the chamber at precisely the same moment. Here is the video of the experiment.
H/T: Amusing Planet | 0.845165 | 3.026638 |
The dazzling Orionid meteor shower is expected to peak tonight and you don't want to miss out on the much anticipated celestial event.
The annual shower has been called "one of the most beautiful showers of the year" by Bill Cooke, head of NASA's Meteoroid Environment Office, and is a popular celestial event for stargazers everywhere.
Here are 11 things you need to know about the 2019 Orionid meteor shower:
Why are these meteor showers called Orionids?
The meteors radiate (or originate) from a region close to the constellation Orion the Hunter.
What causes the meteor shower?
According to Space.com, the meteors' particles come from Comet 1P, also known as Halley's Comet, which zips by the planet every 75 to 76 years.
As the comet passes Earth, it leaves behind “a trail of comet crumbs” and every now and then, Earth’s orbit around the sun crosses paths with the comet’s debris.
What’s the difference between a meteoroid, meteor and meteorite. anyway?
Cooke told Space.com that a meteoroid is essentially space debris. For example, the crumbs from Halley's Comet are meteoroids.
Once the meteoroids enter Earth’s atmosphere, they become meteors (or shooting stars).
Though most meteors disintegrate before hitting the ground, meteors that do strike the surface of the planet are called meteorites, Cooke said.
How fast will the Orionids be?
According to Cooke, some will zoom at speeds up to 148,000 mph in relative speed — less than 4 mph slower than the Leonids.
When will it peak?
The Orionid shower will peak early morning hours of Oct. 22 with as many 20 meteors per hour during its peak.
Orionid meteors usually fly between Oct. 2 to Nov. 7 each year.
How many meteors will I see?
According to EarthSky.org, you can expect to see up to 15-20 meteors per hour during peak time.
Where do I have to go to watch the meteor showers?
The meteor shower will be visible from anywhere on the planet, but be sure to go somewhere far from city lights.
How to find the shape of Orion the Hunter
The meteor shower will radiate from Orion’s sword, which is slightly north of the star Betelgeuse.
According to Space.com, it could be helpful or just educational to find the shape of Orion the Hunter as you get settled for the show.
But staring straight at the point of origin won’t do much for you, Cooke said. That’s because “meteors close to the radiant have short trails and are harder to see — so you want to look away from Orion.”
Your best bet is to simply look up at the vast, dark sky.
GLOBE at Night has a nifty Orion Finder Chart that will show you Orion based on your location, for anyone interested.
The easiest way to find Orion is to go outside in the evening and look in the southwest sky if you are in the Northern Hemisphere or the northwestern sky if you are in the Southern Hemisphere. If you live on or near the equator, he will be visible in the western sky. You are looking for three bright stars close together in an almost-straight line. These three stars represent Orion's belt. The two bright stars to the north are his shoulders and the two to the south are his feet.
Do I need binoculars?
According to Space.com, binoculars and telescopes won’t actually help. That’s because those tools are designed to magnify and focus on stationary objects in the sky.
The naked eye will do just fine.
How to safely watch the shower
Space.com recommends heading outdoors around 1:30 a.m. and letting your eyes adjust to the darkness for about 20 minutes.
© 2020 Cox Media Group | 0.816984 | 3.539181 |
Owing to radio’s aptitude in transporting information, our planet is endlessly peppered by man-made low-frequency radiation. Phone conversations, computer data, text messages, radar echoes, sitcoms, and morning DJ chatter are all electromagnetically belched in every direction at the speed of light— including straight up into outer space.
Purveyors of science fiction are fond of exploring the ramifications of this radio leakage, suggesting that someday an advanced alien race might materialize to befriend, enslave, or destroy humanity after a little electromagnetic eavesdropping from afar. Indeed, if there happen to be any radio-savvy civilizations within 114 light years of Earth— an area which encompasses roughly fifteen thousand stars— humanity’s earliest meaningful transmissions will have already reached them.
Similar speculation appears in science non-fiction, such as the Search for Extra-Terrestrial Intelligence (SETI) project, which strains its giant radio ears for extraterrestrial signals. When consulting the wisdom of probability, one finds that the universe ought to be teeming with technology-toting aliens; but aside from a couple of interesting-but-inconclusive detections, no discernibly intelligent patterns have ever been observed by Earth’s space-listening instruments. One might surmise that the conspicuous silence is “evidence of absence,” but such a conclusion might be a bit premature under the circumstances.
Outer space, as it was aptly put by the late Douglas Adams, is vastly, hugely, mind-bogglingly big. Astronomy’s most up-to-date observations and calculations number the stars in the visible universe at somewhere around seventy sextillion (7 x 1022), an incomprehensible value which is seldom welcome in polite company. This figure is so formidable that any attempt to scale it for human consumption results in such impotent analogies as “ten times as many stars as grains of sand on all the world’s beaches and deserts;” or, “ten trillion stars for every man, woman, and child on Earth.”
At least two hundred billion of these stars reside within our own 13-billion-year-old galaxy, along with millions or billions of planets and moons. Considering the abundance of potential habitats and the amount time our galaxy has been around, it seems inconceivable that our ordinary planet is the only one which has produced intelligent, signal-radiating life. Even if a solar system’s odds of developing intelligent life is only one-in-a-billion, that means that the Milky Way should be home to two hundred or so past or present civilizations, in addition to some seventy billion amongst the other galaxies.
In 1950, famed physicist Enrico Fermi was one of the first to popularize the discrepancy between probable and observable life in the universe. While lunching with colleagues and discussing the notion of interstellar neighbors, Fermi summed up the question by wondering aloud, “Where is everybody?” Thereafter the inconsistency was known as the Fermi Paradox. The paradox is a product of science’s mediocrity principle, the observation that the Earth seems to be an ordinary planet orbiting an ordinary star within an ordinary galaxy. It follows, therefore, that Earth-like planets are probably somewhat common.
In 1961, a collection of ten distinguished scientists and engineers known as The Order of the Dolphin set upon a quest to remedy this astronomical shortcoming in our knowledge. They pondered the possibility of employing massive radio telescopes to scan the sky for stray extraterrestrial signals, a concept which eventually evolved into SETI. During these early discussions, astronomer Dr. Frank Drake first described a formula intended to estimate the number of technologically advanced civilizations within the galaxy at a given time. To this day the Drake Equation remains as a framework for extraterrestrial speculation. The equation is essentially an elaborate “what if” question, and there is much fist-shaking and spittle-making debate regarding most correct inputs, but as we gradually increase our knowledge of the universe, our guesses for these values become increasingly educated, and the equation helps us to imagine how much life the universe might contain.
Editor’s Note: This interactive predates mobile browsers, so it may not work correctly in small viewports.
Even when using somewhat conservative inputs, the Drake Equation suggests that our own humble galaxy is home to at least one other advanced civilization at present, along with the lingering physical and electromagnetic remains of many others. Massive radio telescopes have scoured the sky for such alien signals, including efforts by the Big Ear Observatory in Ohio; the Very Large Array (VLA) in New Mexico; and the famous Arecibo Observatory in Puerto Rico, the largest single-aperture telescope ever constructed. In forty-seven years of signal-seeking, SETI twice detected signals of possibly intelligent origins— The “Wow!” signal in 1977, and Radio Source SHGb02+14a in 2004. But both had plausible Earthly explanations, so science must assume for now that they were not of extraterrestrial origin. The failure to find any stray radio evidence is taken by some as an indication there may indeed be something special about our planet and its location in the cosmos.
The Rare Earth hypothesis is the antithesis to the mediocrity principle, suggesting that complex life requires an extremely uncommon combination of astrophysical and geological events and circumstances: a slightly tilted planet with just the right chemistry, a large moon, a suitably metallic sun, and an orbit at just the right distance.
The hypothesis also advances the notion that there is a narrow galactic habitable zone where radiation levels are survivable, rogue meteors are few, and gravitational perturbations from neighboring stars are negligible. If all life relies upon such factors, then Rare Earth resolves the Fermi Paradox. The hypothesis carries the faint odor of anthropomorphic bias, however, since it assumes that all complex life must be very much like humans.
All these factors aside, there is one additional daunting obstacle which complicates any effort to tune in to intergalactic radio. Even if the universe is thick with signal-slinging civilizations, including some old enough that their indiscriminate electromagnetism has had sufficient time to reach Earth, not even the most massive and sensitive equipment of science is currently capable of plucking the signal from the static. When any non-focused electromagnetic signal is generated— such as a television broadcast or a cell phone conversation— the energy propagates as a spherical wavefront at the speed of light. When a sphere is doubled in diameter, its surface area increases by a factor of four; but in a spherical wave the “surface area” is the energy itself. This means the signal’s energy is spread over four times more area at twice the distance, resulting in a 75% loss in intensity. To put it another way, in order for a broadcasting tower to double its effective range for a given receiver, it must quadruple its transmitting power.
To demonstrate the degrading effect of distance on an everyday omnidirectional signal, one might imagine a spacecraft equipped with an Arecibo-style radio receiver directed towards the Earth. If this hypothetical spacecraft were to set out for the interstellar medium, its massive 305-meter wide dish would lose its tenuous grip on AM radio before reaching Mars. Somewhere en route to Jupiter, the UHF television receivers would spew nothing but static. Before passing Saturn, the last of the FM radio stations would fade away, leaving all of Earth’s electromagnetic chatter behind well before leaving our own solar system. If a range-finding radar beam from Earth happened to intersect the ship’s path, it would be observable from a much greater distance; though its short duration and smooth, Gaussian meaninglessness would make it an inconclusive detection— much like the Wow! signal and Radio Source SHGb02+14a. A highly focused beam such as that used to communicate with space probes would also remain detectable for some distance beyond the edge of the solar system.
If, hypothetically, A) a race of extra-intelligent extraterrestrials happened to reside in the nearby Alpha Centauri star system, B) they happened to broadcast a 5 Megawatt UHF television signal, and C) we were fortunate enough to be pointing the mighty Arecibo telescope directly towards the source when it arrived four years later, we would still be unable to enjoy the zany capers of the Alpha Centauri equivalent of Mork & Mindy.
In order to detect such a signal from this relatively proximate star, a dish with a diameter of 33,000 kilometers would be required. Even using Very Long Baseline Interferometry to link two Arecibo-style radio telescopes on opposite sides of the planet— thereby providing a virtual radio telescope the size of the entire Earth— our antenna area would still be 20,244 kilometers too small.
By coupling the laws of probability with our best current observations, we can be reasonably confident that some fraction of the 70,000,000,000,000,000,000,000 star systems in the visible universe are home to radio-sending species. It may indeed be that our planet is subjected to an unending spray of alien TV and radio signals, though they’d be attenuated beyond our best hardware’s receiving extremes. Unless we dramatically improve our interstellar listening skills, or some alien race makes a specific and vigorous attempt to send us a message, there is little chance that we Earthlings will be trading messages with our astronomical neighbors anytime soon. | 0.919594 | 3.511495 |
By examining Antarctic snow, researchers have discovered, for the first time, interstellar dust that recently fell to Earth, a new study finds.
These findings may shed light on the mysterious interstellar clouds the solar system flies through regularly, scientists said. Tons of extraterrestrial dust — created by passing comets, asteroid collisions and exploding stars — falls on Earth daily. But scientists may not find it until long after it has fallen, and so lack details about the solar system’s recent interactions with its surroundings.
By contrast, this new study analyzes relatively fresh interstellar dust, and the findings may reveal insight into mysterious interstellar clouds and their relationship with our solar system.
"Scientists might be able to use our results to figure out how the solar neighborhood was shaped," study lead author Dominik Knoll, an experimental nuclear physicist at the Australian National University in Canberra, told Space.com. "We know something about distant galaxies and stars and a lot about our solar system, but the nearby surroundings of our solar system need more investigation."
To look for potentially pristine samples of interstellar dust, scientists collected about 1,100 lbs. (500 kilograms) of Antarctic snow that was less than 20 years old. It was collected several hundred miles from the coast of the frozen continent, near Germany's Kohnen Station.
To identify the snow's components, the researchers brought it to Munich, melted it, filtered out the solids, incinerated the residue and analyzed the pattern of light it gave off. They discovered the presence of two rare, mildly radioactive isotopes: iron-60 and manganese-53. (Isotopes of an element vary in how many neutrons they possess in their nuclei; so for example, the most naturally abundant iron isotope, iron-56, has 30 neutrons, whereas iron-60 has 34 neutrons.)
According to the researchers, the most likely source of the iron-60 was a supernova, a powerful explosion from a gigantic dying star that is bright enough to briefly outshine all of the other stars in its host galaxy. Other natural ways of creating iron-60 produce only up to one-tenth as much. However, iron-60 and manganese-53 also can be produced when atom fragments called cosmic rays strike interplanetary dust. Nonetheless, the researchers found a greater ratio of iron-60 to manganese-53 than they would have expected from this mechanism.
The researchers also investigated whether the iron-60 came as fallout from nuclear weapons or power plants. However, they found that the production of iron-60 and manganese-53 from these sources should be negligible.
So the scientists concluded that these radioactive isotopes were most likely forged in a nearby supernova that went on to seed interstellar clouds of gas and dust. In the study, the researchers suggested that, as the solar system passes through such clouds, this dust rains down on Earth's surface.
Future examination of interstellar dust in older snow and ice could shed light on the origins and structure of nearby interstellar clouds and the history of their interactions with the solar system, the researchers said.
The scientists detailed their findings online Aug. 12 in the journal Physical Review Letters.
- Rho Ophiuchi: A Brilliantly Colored Interstellar Cloud (Photo)
- Spectacular Photo Reveals Bright Nebula Near Orion's Belt
- Telescope Reveals Spectacular 'Fiery Ribbon' in Orion Nebula (Photos) | 0.87987 | 3.960468 |
Why do we always see the same side of the Moon?
The Moon also rotates about its own axis just as the earth is doing. But it does so much slower. One rotation actually takes the same time as it takes the Moon the complete one orbit around the Earth. And the Moon orbits the Earth in the same direction as the Earth is rotating (towards the east if you want to call it that), and the Moon rotates about its own axis again in the same direction. All this means that we are always looking at the same side of the Moon.
That is no accident and happens quite often with spherical Moons. The gravitational pull between Earth and Moon causes the Moon (and the Earth to a lesser extent) to bulge out in the direction of the Earth as well as on the opposite side of the Moon. The solid Moon resists this deformation and tends to make it constant, in the sense that the bulge always stays at the same position in the Moon’s body. It can do so by adjusting its own rotation to become synchronous with its orbital period about the Earth. This is called tidal locking.
In this animation the closer moon is in tidal locking with the central planet. The moon that is further out has its own independent rotation.
Thus both the rotation of the Moon about its own axis (the "Moon day") and its revolution around Earth (Lunar cycle) take the same time, called the Synodic month of 29.53 days. | 0.861194 | 3.268285 |
one relatively newer goal of modern astronomy is to describe and characterize objects in the distant universe, with the Milky Way galaxy being recognized as a distinct and related group of stars only in the 20th century. This realization was followed by recognition of the expansion of the universe as described by Hubble's law, as well as distant objects such as quasars, pulsars, radio galaxies, black holes, and neutron stars.
The field of observational astronomy is based on data received from electromagnetic radiation from celestial objects and is divided into different sub-fields based on the wavelengths being studied. Radio astronomy deals with interpreting radiation received from celestial objects where the radiation has a wavelength greater than one millimeter, and is commonly used to study supernovae, interstellar gas, pulsars, and galactic nuclei. Radio astronomy uses wave theory to interpret these signals, since these long wavelengths are more easily assigned wavelengths and amplitudes than shorter wavelength forms of radiation. Most radio emissions from space received on Earth are a form of synchrotron radiation, produced when electrons oscillate in a magnetic field, although some is also associated with thermal emission from celestial objects, and interstellar gas is typically associated with 21-cm radio waves.
Infrared astronomy works with infrared wavelengths (longer than the wavelength of red light) and is used primarily to study areas such as planets and circumstellar disks that are too cold to radiate in the visible wavelengths of the electromagnetic spectrum. The longer infrared wavelengths are able to penetrate dust clouds, so infrared astronomy is also useful for observing processes such as star formation in molecular clouds and galactic cores blocked from observations in the visible wavelengths. Infrared astronomy observatories must be located in outer space or in high dry locations since the Earth's atmosphere is associated with significant infrared emissions.
optical astronomy, the oldest form of observational astronomy, uses light recorded from the visible wavelengths. Most optical astronomy is now completed by using digital recording apparatus, speeding analysis. ultraviolet astronomy (observations in the ultraviolet wavelengths) is used to study thermal radiation and the emission of spectral lines from hot blue stars, planetary nebula, supernova, and active galactic nuclei. Like infrared observatories, ultraviolet observation stations must be located in the upper atmosphere or in space, since ultraviolet rays are strongly absorbed by Earth's atmosphere.
The study and analysis of celestial objects at X-ray wavelengths is known as X-ray astronomy. X-ray emitters include some binary star systems, pulsars, supernova remnants, elliptical galaxies, galaxy clusters, and active galactic nuclei. X-rays are produced by celestial objects by thermal and synchrotron emission (generated by the oscillation of electrons around magnetic fields), but are absorbed by the Earth's atmosphere, so they must be observed from high-altitude balloons, rockets, or space. The study of the shortest wavelengths of the electromagnetic spectrum, known as gamma-ray astronomy, can so far be observed only by indirect observations of gamma ray bursts from objects including pulsars, neutron stars, and black holes near galactic nuclei.
See also astrophysics; black holes; constellation; cosmology; galaxies; galaxy clusters; origin and evolution of the universe; universe.
Chaisson, Eric, and steve McMillan. Astronomy Today. 6th ed. upper saddle River, N.J.: Addison-Wesley, 2007.
Comins, Neil F. Discovering the Universe. 8th ed. New
York: W. H. Freeman, 2008. snow, Theodore P. Essentials of the Dynamic Universe: An Introduction to Astronomy. 4th ed. st. Paul, minn.: West Publishing Company, 1991.
astrophysics Astrophysics is the branch of astronomy that examines the behavior, physical properties, and dynamic processes of celestial objects and phenomena. Astrophysics includes study of the luminosity, temperature, density, chemical composition, and other characteristics of celestial objects and aims at understanding the physical laws that explain these characteristics and behavior of celestial systems. Astrophysics is related to observational astronomy, as well as cosmology, the study of the theories related to the very large-scale structure and evolution of the universe. Astrophysicists study these systems using principles from different subfields in physics and astronomy, including thermodynamics, mechanics, electromagnetism, quantum mechanics, relativity, nuclear and particle physics, and atomic and molecular physics.
much of astrophysics is founded on formulating theories based on observational astronomy using principles of quantum mechanics and relativity. Theoretical astrophysicists use analytical models and complex computational and numerical models of the behavior of celestial systems to understand better the origin and evolution of the universe and to test for unpredicted phenomena. In general theoretical models of celestial behavior are tested with the observations and constraints from astronomical studies, and the agreement (or lack thereof) between the model and the observed behavior is used to refine the models of celestial evolution.
Current topics of research in astrophysics include celestial and stellar dynamics and evolution, the large-scale structure of the universe, cosmology and the origin and evolution of the universe, models for galaxy formation, the physics of black holes, quasars, and phenomena such as gravity waves, and implications and tests of models of general relativity.
See also astronomy; black holes; constellation; cosmology; galaxies; galaxy clusters; origin and evolution of the universe; universe.
Chaisson, Eric, and Steve McMillan. Astronomy Today. 6th ed. Upper Saddle River, N.J.: Addison-Wesley,
Comins, Neil F. Discovering the Universe. 8th ed. New
York: W. H. Freeman, 2008. Encyclopedia of Astronomy and Astrophysics. CRC Press, Taylor and Francis Group. Available online. URL: http://eaa.crcpress.com/. Accessed October 24, 2008. ScienceDaily. "Astrophysics News." ScienceDaily LLC. Available online. URL: http://www.sciencedaily.com/ news/space_time/astrophysics/. Accessed October 24,
Snow, Theodore P. Essentials of the Dynamic Universe: An Introduction to Astronomy. 4th ed. St. Paul, Minn.: West Publishing Company, 1991.
atmosphere Thin sphere around the Earth consisting of the mixture of gases we call air, held in place by gravity. The most abundant gas is nitrogen (78 percent), followed by oxygen (21 percent), argon (0.9 percent), carbon dioxide (0.036 percent), and minor amounts of helium, krypton, neon, and xenon. Atmospheric (or air) pressure is the force per unit area (similar to weight) that the air above a certain point exerts on any object below it. Atmospheric pressure causes most of the volume of the atmosphere to be compressed to 3.4 miles (5.5 km) above the Earth's surface, even though the entire atmosphere is hundreds of kilometers thick.
The atmosphere is always moving, because the equator receives more of the Sun's heat per unit area than the poles. The heated air expands and rises to where it spreads out, then it cools and sinks, and gradually returns to the equator. This pattern of global air circulation forms Hadley cells that mix air between the equator and midlatitudes. similar circulation cells mix air in the middle to high latitudes, and between the poles and high latitudes. The effects of the Earth's rotation modify this simple picture of the atmosphere's circulation. The Coriolis effect causes any freely moving body in the Northern Hemisphere to veer to the right, and toward the left in the southern Hemisphere. The combination of these effects forms the familiar trade winds, easterlies and westerlies, and doldrums.
The atmosphere is divided into several layers, based mainly on the vertical temperature gradients that vary significantly with height. Atmospheric pressure and air density both decrease more uniformly with height, and therefore are not a useful way to differentiate between different atmospheric layers.
The lower 36,000 feet (11,000 m) of the atmosphere, the troposphere, is where the temperature generally decreases gradually, at about 70°F per mile
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Structure of the atmosphere showing various layers and temperature profile with height
(6.4°C per km), with increasing height above the surface. This is because the Sun heats the surface, which in turn warms the lower part of the troposphere. Most of the familiar atmospheric and weather phenomena occur in the troposphere.
Above the troposphere is a boundary region known as the tropopause, marking the transition into the stratosphere. The stratosphere in turn continues to a height of about 31 miles (50 km). The base of the stratosphere contains a region known as an isothermal, where the temperature remains the same with increasing height. The tropopause is generally at higher elevations in summer than winter and is also the region where the jet streams are located. Jet streams are narrow, streamlike channels of air that flow at high velocities, often exceeding 115 miles per hour (100 knots). Above about 12.5 miles (20 km), the isothermal region gives way to the upper stratosphere, where temperatures increase with height, back to near surface temperatures at 31 miles (50 km). The heating of the stratosphere is due to ozone at this level absorbing ultraviolet radiation from the sun.
The mesosphere lies above the stratosphere, extending between 31 and 53 miles (50-85 km). An isothermal region known as the stratopause separates the stratosphere and mesosphere. The air temperature in the mesosphere decreases dramatically above the stratopause, reaching a low of -130°F (-90°C) at the top of the mesosphere. The mesopause separates the mesosphere from the thermosphere, a hot layer where temperatures rise to more than 150°F (80°C). The relatively few oxygen molecules at this level absorb solar energy and heat quickly, and temperatures may change dramatically in this region in response to changing solar activity. The thermosphere continues to thin upward, extending to about 311 miles (500 km) above the surface. Above this level, atoms dissociate from molecules and are able to shoot outward and escape the gravitational pull of Earth. This far region of the atmosphere is sometimes referred to as the exosphere.
In addition to the temperature-based division of the atmosphere, it is possible to divide the atmosphere into different regions based on their chemical and other properties. Using such a scheme, the lower 46.5-62 miles (75-100 km) of the atmosphere may be referred to as the homosphere, which contains a well-mixed atmosphere with a fairly uniform ratio of gases from base to top. In the overlying hetero-sphere, the denser gases (oxygen and nitrogen) have settled to the base, whereas lighter gases (hydrogen and helium) have risen to greater heights, resulting in chemical differences with height.
The upper parts of the homosphere and the heterosphere contain a large number of electrically charged particles known as ions. Also called the ionosphere, this region strongly influences radio transmissions and the formation of the aurora borealis and aurora australis.
The production and destruction or removal of gases from the atmospheric system occur at approximately equal rates, although some gases are gradually increasing or decreasing in abundance, as described below. soil bacteria and other biologic agents remove nitrogen from the atmosphere, whereas decay of organic material releases nitrogen back to the atmosphere. However, decaying organic material removes oxygen from the atmosphere by combining with other substances to produce oxides. Animals also remove oxygen from the atmosphere by breathing, whereas photosynthesis returns oxygen to the atmosphere.
Water vapor is an extremely important gas in the atmosphere, but it varies greatly in concentration (0-4 percent) from place to place and from time to time. Though water vapor is normally invisible, it becomes visible as clouds, fog, ice, and rain when the water molecules coalesce into larger groups. In the liquid or solid state, water constitutes the precipitation that falls to Earth and is the basis for the hydro-logic cycle. Water vapor is also a major factor in heat transfer in the atmosphere. A kind of heat known as latent heat is released when water vapor turns into solid ice or liquid water. This heat, a major source of atmospheric energy, is a major contributor to the formation of thunderstorms, hurricanes, and other weather phenomena. Water vapor may also play a longer-term role in atmospheric regulation, as it is a greenhouse gas that absorbs a significant portion of the outgoing radiation from the Earth, causing the atmosphere to warm.
Carbon dioxide (C02), although small in concentration, is another very important gas in the Earth's atmosphere. Carbon dioxide is produced during decay of organic material, from volcanic out-gassing, deforestation, burning of fossil fuels, and cow, termite, and other animal emissions. Plants take up carbon dioxide during photosynthesis, and many marine organisms use it for their shells, made of CaC03 (calcium carbonate). When these organisms (for instance, phytoplankton) die, their shells can sink to the bottom of the ocean and be buried, removing carbon dioxide from the atmospheric system. Like water vapor, carbon dioxide is a greenhouse gas that traps some of the outgoing solar radiation reflected from the earth, causing the atmosphere to warm up. Because carbon dioxide is released by the burning of fossil fuels, its concentration is increasing in the atmosphere as humans consume more fuel. The concentration of Co2 in the atmosphere has increased by 15 percent since 1958, enough to cause considerable global warming. Estimates predict that the concentration of C02 will increase by another 35 percent by the end of the 21st century, further enhancing global warming.
other gases also contribute to the greenhouse effect, notably methane (CH4), nitrous oxide (N02) and chlorofluorocarbons (CFCs). Methane concentration is increasing in the atmosphere and is produced by the breakdown of organic material by bacteria in rice paddies and other environments, termites, and the stomachs of cows. Produced by microbes in the soil, No2 is also increasing in concentration by 1 percent every few years, even though it is destroyed by ultraviolet radiation in the atmosphere. Chlorofluo-rocarbons have received much attention since they are long-lived greenhouse gases increasing in atmospheric concentration as a result of human activity. Chlorofluorocarbons trap heat like other greenhouse gases, and also destroy ozone (03), a protective blanket that shields the Earth from harmful ultraviolet radiation. Chlorofluorocarbons were used widely as refrigerants and as propellants in spray cans. Their use has been largely curtailed, but since they have such a long residence time in the atmosphere, they are still destroying ozone and contributing to global warming, and will continue to do so for many years.
ozone is found primarily in the upper atmosphere where free oxygen atoms combine with oxygen molecules (02) in the stratosphere. The loss of ozone has been dramatic in recent years, even leading to the formation of "ozone holes" with virtually no ozone present above the Arctic and Antarctic in the fall. There is currently debate about how much of the ozone loss is human-induced by chlorofluorocarbon production, and how much may be related to natural fluctuations in ozone concentration.
Many other gases and particulate matter play important roles in atmospheric phenomena. For instance, small amounts of sulfur dioxide (S02) produced by the burning of fossil fuels mixes with water to form sulfuric acid, the main harmful component of acid rain. Acid rain is killing the biota of many natural lake systems, particularly in the northeastern United States in areas underlain by granitic-type rocks, and it is causing a wide range of other environmental problems across the world. other pollutants are major causes of respiratory problems and environmental degradation, and the major increase in particulate matter in the atmosphere in the past century has increased the hazards and health effects from these atmospheric particles.
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Your Alternative Fuel Solution for Saving Money, Reducing Oil Dependency, and Helping the Planet. Ethanol is an alternative to gasoline. The use of ethanol has been demonstrated to reduce greenhouse emissions slightly as compared to gasoline. Through this ebook, you are going to learn what you will need to know why choosing an alternative fuel may benefit you and your future. | 0.887033 | 4.155107 |
You can breathe easily. The Moon is slowly receding away from the Earth at a rate of 3.7 cm/year (1.5 in/yr). But the Martians aren’t so lucky. Their moon Phobos is known to be doing exactly the opposite. It’s spiraling inward, and in the distant future it will crash into the surface of Mars. Researchers originally thought that Phobos has about 50 million years to go, but an Indian researcher has re-run the calculations and thinks Phobos only has about a quarter of that time to live.
It was originally believed that Phobos would take about 50 million years to crash into the surface of Mars, but according to Bijay Kumar Sharma, an Assistant Professor at the National Institute of Technology in Bihar, India, it might happen much more quickly. Dr. Sharma has revised the calculations for Phobos’ destruction in his new paper, Theoretical Formulation of the Phobos, moon of Mars, rate of altitudinal loss.
According to Sharma, Phobos will actually be destroyed about 10.4 million years from now, and not the 50 million years the researchers had previously calculated.
Phobos is believed to be an asteroid that Mars captured early on in its history. it’s one of the least-reflective objects in the Solar System, and thought to be similar to a D-type asteroid. It currently orbits Mars at an altitude of about 9,380 km (or about 6,000 km above the Martian surface).
Why does the Earth’s moon spiral outward, while Phobos is spiraling inward to Mars?
The Moon formed billions of years ago when a Mars-sized object crashed into Earth and sprayed material into orbit. This material pulled back together from mutual gravity to form the Moon, and this debris received a gravitational slingshot from the Earth.
They key is that the material was tossed into a high enough orbit, above what’s known as the synchronous orbit. This is where the Moon completes an orbit slower than the Earth takes to rotate once. Since the Moon ended up higher than this orbit, it’s spiraling outward. If its orbit was less than the length of a day, it would spiral inward.
And this is what has happened to Phobos. It orbits below this synchronous orbit, where it completes an orbit around Mars faster than the planet itself turns. It’s spiraling inward instead of outward.
Once Phobos gets down to an altitude of only 7000 km above the center of Mars (or 3,620 km above its surface), it will enter what’s known as the Roche limit. At this point, the tidal forces of Mars will tear Phobos apart, turning it into a ring that will continue to spiral into Mars. According to Dr. Sharma, this will happen in only 7.6 million years from now.
To know exactly how long Phobos has to live, Dr. Sharma suggests that a mission should be sent to Phobos to land on its surface and then use radar to measure the changing distance to Mars.
Original Source: Arxiv | 0.832783 | 3.724587 |
Liquid found on Titan: Saturn in science and mythology
NASA’s Cassini spacecraft finds liquid for the first time on Saturn’s moon, Titan, but why was Saturn venerated in mythology throughout the ancient world?
NASA has completed analysis on data provided by Cassini’s flyby of Titan in 2013, and has found for the very first time, liquid hydrocarbons in canyons hundreds of meters deep on Saturn’s moon.
What is remarkable is that the formation of the canyons are very similar to how canyons are formed on our terrestrial abode, Earth, and that our planet’s canyons were carved by water and ice.
“Earth is warm and rocky, with rivers of water, while Titan is cold and icy, with rivers of methane. And yet it’s remarkable that we find such similar features on both worlds,” said Alex Hayes, a Cassini radar team associate at Cornell University, Ithaca, New York.
According to Space.com, “The new discovery further cements the intriguing similarity between Earth and Titan, the only two worlds in the solar system that are known to harbor stable liquid on their surfaces. (Titan also has a thick atmosphere dominated by nitrogen, as does Earth).”
How is that the most distant planet visible with the naked eye, Saturn, can have a moon so similar to Earth? At 746 million miles or 1.2 billion kilometers from Earth, has Saturn always maintained this distance in the heavens, or did our ancient sky used to look a whole lot different in our ancestors’ past?
Mythological evidence backed by modern science suggests that Saturn used to be the dominate celestial body in the night sky as it was much, much closer to Earth than it is today.
The Saturn Myth
In his groundbreaking book “The Saturn Myth” (1980), researcher David Talbott analyzed myths from ancient cultures throughout the world and found that they all described the same phenomenon surrounding the planet Saturn.
Not only is the symbolism for Saturn the same throughout ancient Mesopotamia, Egypt, India, Greece, and the Americas, but there is evidence that Saturn’s ancient near-proximity to Earth caused unbelievably electromagnetic disturbances upon our planet that were actually visible to the naked eye in antiquity.
Talbott claims that Saturn was located at a fixed point above our North Pole in the night’s sky. To ancient peoples living on Earth, the heavenly body appeared as a dot within a circle, or as a type of spoked-wheel radiating cosmic energy.
The introduction to “The Saturn Myth” describes “such diverse symbols as the Cross, “sun”-wheels, holy mountains, crowns of royalty and sacred pillars grew out of ancient Saturn worship. Talbott contends that Saturn’s appearance at the time, radically different from today, inspired man’s leap into civilization, since many aspects of early civilization can be seen as conscious efforts to re-enact or commemorate Saturn’s organization of his “celestial” kingdom.”
Most scholars of antiquity attribute the cross, spoked-wheel, chariot-in-the-sky, or crescent as being symbols related to our Sun. However, they don’t take into account that all those symbols would point to Saturn, not the Sun, as it may have once looked in our sky, which would bring a whole new scientific understanding to something that has been long-regarded as mere mythology.
The Electric Universe
Apart from ancient symbols depicting what Saturn actually looked like, there are thousands of other inexplicable symbols that don’t make any sense unless viewed with modern, scientific eyes.
Have a look at the following rock paintings from around the world.
While the popular TV show “Ancient Aliens” would have you believe that these are respresentations of extraterrestrials, modern physics can explain their appearance quite easily.
What these “squatting man” symbols represent is an electrical phenomenon known as a High-Current, Z-Pinch Aurora.
According to one study on these ancient symbols, “It is found that a great many archaic petroglyphs can be classified according to plasma stability and instability data. As the same morphological types are found worldwide, the comparisons suggest the occurrence of an intense aurora, as might be produced if the solar wind had increased between one and two orders of magnitude, millennia ago.”
Below we can see what a natural plasma configuration looks like alongside one of the ancient glyphs (left) and what it may have looked like in the ancient sky, similar to our Northern Lights (right).
There are countless examples of ancient myth depicting electricity, plasma, and the heavens that there is no way to cover them all in a single article, let alone dozens of books.
Coming full circle
As modern science sheds more light on ancient mythology, or vice versa, the question of Saturn becomes more clear. There is mounting evidence that what we see when we look at the stars at night is not the same sky as what our ancestors saw only a few thousands years in the past.
Their symbolism describes phenomenon that so far can only be accounted for by applying modern physics. Our ancestors didn’t have to understand how or why, but they documented what they actually saw. How else would these symbols be so universal and depicted by civilizations oceans apart with no apparent contact with one another?
Now that NASA has confirmed the presence of liquid on Titan and the formation of Earth-like canyons, is it that far of a stretch to believe that Saturn was once closer to Earth and thus closer to the liquid water-providing warmth of the Sun? | 0.899397 | 3.412994 |
August 6, 2015 – Visit a 2-mile-deep crater, weird bright spots, and a 4-mile-tall mountain in the video narrated by mission director Marc Rayman. Get your red/blue glasses ready for the finale – a global view of Ceres in 3D.
A prominent mountain with bright streaks on its steep slopes is especially fascinating to scientists. The peak’s shape has been likened to a cone or a pyramid. It appears to be about 4 miles (6 kilometers) high, with respect to the surface around it, according to the latest estimates. This means the mountain has about the same elevation as Mount McKinley in Denali National Park, Alaska, the highest point in North America.
“This mountain is among the tallest features we’ve seen on Ceres to date,” said Dawn science team member Paul Schenk, a geologist at the Lunar and Planetary Institute, Houston. “It’s unusual that it’s not associated with a crater. Why is it sitting in the middle of nowhere? We don’t know yet, but we may find out with closer observations.”
Also puzzling is the famous Occator (oh-KAH-tor) crater, home to Ceres’ brightest spots. A new animation simulates the experience of a close flyover of this area. The crater takes its name from the Roman agriculture deity of harrowing, a method of pulverizing and smoothing soil.
In examining the way Occator’s bright spots reflect light at different wavelengths, the Dawn science team has not found evidence that is consistent with ice. The spots’ albedo–a measure of the amount of light reflected–is also lower than predictions for concentrations of ice at the surface.
“The science team is continuing to evaluate the data and discuss theories about these bright spots at Occator,” said Chris Russell, Dawn’s principal investigator at the University of California, Los Angeles. “We are now comparing the spots with the reflective properties of salt, but we are still puzzled by their source. We look forward to new, higher-resolution data from the mission’s next orbital phase.”
An animation of Ceres’ overall geography, also available in 3-D, shows these features in context. Occator lies in the northern hemisphere, whereas the tall mountain is farther to the southeast (11 degrees south, 316 degrees east).
“There are many other features that we are interested in studying further,” said Dawn science team member David O’Brien, with the Planetary Science Institute, Tucson, Arizona. “These include a pair of large impact basins called Urvara and Yalode in the southern hemisphere, which have numerous cracks extending away from them, and the large impact basin Kerwan, whose center is just south of the equator.”
Ceres is the largest object in the main asteroid belt between Mars and Jupiter. Thanks to data acquired by Dawn since the spacecraft arrived in orbit at Ceres, scientists have revised their original estimate of Ceres’ average diameter to 584 miles (940 kilometers). The previous estimate was 590 miles (950 kilometers).
Dawn will resume its observations of Ceres in mid-August from an altitude of 900 miles (less than 1,500 kilometers), or three times closer to Ceres than its previous orbit.
On March 6, 2015, Dawn made history as the first mission to reach a dwarf planet, and the first to orbit two distinct extraterrestrial targets. It conducted extensive observations of Vesta in 2011-2012.
Dawn’s mission is managed by NASA’s Jet Propulsion Laboratory for NASA’s Science Mission Directorate in Washington. Dawn is a project of the directorate’s Discovery Program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team. | 0.879595 | 3.50543 |
Pluto may have a subsurface ocean thanks to layer of gas insulation
If there is a subsurface sea on Pluto, why hasn't it frozen solid? According to computer simulations devised by researchers from Japan's Hokkaido University and elsewhere, it may be that the hypothetical Plutonian sea may remain liquid thanks to an insulating gas layer keeping in the heat.
When NASA's New Horizons robotic probe flew by Pluto in July 2015, it changed many of our ideas about the dwarf planet as well as other celestial bodies in the cold outer reaches of the solar system. One fascinating discovery was that the nature of the equatorial, Texas-sized, white, ellipsoidal basin called Sputnik Planitia is such that is may have a slushy ocean located beneath its icy surface.
It's an intriguing idea, but it raises the question of how could it exist on a world so far from the Sun like Pluto, which doesn't have a molten core and isn't in the vicinity of a giant planet that could heat it through tidal forces. According to the math, such an ocean should have frozen solid billions of years ago, and if there ever was a sea beneath Sputnik Planitia, then it should also have frozen and the ice cap above it collapsed flat on top of it.
However, the new study that includes scientists from the Tokyo Institute of Technology, Tokushima University, Osaka University, Kobe University, and the University of California, Santa Cruz, suggests that the presence of a layer of gas hydrates between the cap and the slushy ocean could keep the Plutonian sea liquid.
Gas hydrates are a special form of water where ice forms crystalline cages that trap in gases like methane. Such hydrates are highly viscous, and have low thermal conductivity. In other words, they keep in heat very well. Hydrates are very common on Earth, where there are 6.4 trillion tonnes of methane hydrates in the deep ocean floor.
What the new study found was that computer simulations covering a timescale of 4.6 billion years, or about the time since the formation of the solar system, showed that without a gas hydrate layer the interior of Pluto would have frozen solid hundreds of millions of years ago, but with it, the subsurface sea would stay liquid. In addition, the gas hydrates would keep the sea free of a uniformly thick ice cap for one billion years, instead of just one million years without a gas hydrate insulating layer.
According to the team, the simulations suggest that the methane for the hydrates came from the rocky core of Pluto and may be part of the reason why the Plutonian atmosphere is poor in methane and rich in nitrogen. In addition, these sorts of capped subsurface seas may be very common.
"This could mean there are more oceans in the universe than previously thought, making the existence of extraterrestrial life more plausible," says team leader Shunichi Kamata of Hokkaido University.
The research was published in Nature Geoscience.
Source: Hokkaido University | 0.809747 | 3.648437 |
Venus is the second planet from the binary star at the centre of the SOL star system, the sun. Orbiting it every 224.7 Earth days. It has no natural satellite (moon) though the asteroid 2002 VE68 presently maintains a quasi-orbital relationship with it, which becomes relevant in relation to the explanations presented in contact 150. Its elongation reaches a maximum of 47.8°. It is named after the Roman goddess of love and beauty.
After Earth's Moon, it is the brightest natural object in the night sky (of Earth), reaching an apparent magnitude of −4.6 (in the night sky), bright enough to cast shadows under the right conditions. Venus reaches its maximum brightness shortly before sunrise or shortly after sunset (as seen on Earth), for which reason it has been referred to by ancient cultures as the Morning Star or Evening Star. Such as the Mayan culture, even though its a planet, not a star, nor a planet-planet (such as Jupiter).
Venus is a terrestrial planet, which means its primarily composed of silicate rocks and metals. Its sometimes called Earth's "sister planet" by academics in the current age and level of understanding because of their similar size, gravity, and bulk composition, furthermore pointing out that Venus is both the closest planet to Earth and the planet closest in size to Earth in the star system. While the Plejaren reference the now destroyed planet Malona as Earth's sister planet. Current understanding additionally points out that it has also been shown to be very different from Earth in other respects undermining the academic conclusions. It has the densest atmosphere of the four terrestrial planets in this star system, consisting of more than 96% carbon dioxide. The atmospheric pressure at the planet's surface is 92 times that of Earth's. With a mean surface temperature of 735 K (Kelvin) (462 °C; 863 °F), making it by far the hottest planet in the Solar System (Sol star system). It has no carbon cycle to lock carbon back into rocks and surface features, nor does it have any organic life to absorb it into biomass. Venus is shrouded by an opaque layer of highly reflective clouds of sulphuric acid, preventing its surface from being seen from space via the visible light spectrum at least. Venus may have possessed oceans in the past but these would have vaporized as the temperature rose due to a runaway greenhouse effect (Also see Akart). The water has most probably photo-dissociated and because of the lack of a planetary magnetic field, the free hydrogen has been swept into interplanetary space by the solar wind from the local star. Venus's surface is a dry desert scape interspersed with slab-like rocks and periodically refreshed by volcanism.
In Block 13 of the Contact Notes in German (page 2542): On the 238th contact, 18th May, 1991, Ptaah told Billy that there existed a planet circling the Sun where today Venus has its orbit. It was a planet called "Skill" (as called by the Plejaran). It was 6,100 kilometres in diameter, which is roughly half the size of Earth. Earth is 12,756.2 kilometres.
- Planet Skill collided with the Destroyer Comet and was hurled into SOL, our sun.
- Skill means "Oede" in German, that in English means: "desertion, desolateness, abandonment, barrenness, forsaken, neglected.
Which incidentally fits the description of current day Venus, in the same orbit. Which is to be expected for any planet with a diameter of 12,104 km at a distance of 108,200,000 km from a star (the sun) with a diameter of 1,391,000 km. Also see Transit of Venus
Titius-Bodes law, often considered a rule rather than a natural law but that has yet to be thoroughly tested on other star systems nor revised with the futurological understanding of Dark Matter (the 5th fundamental force of the universe, as described in contact 544). Is a formula that indicates the bodies in an orbital system, orbit at semi-major axes in a function of planetary sequence. Which reflect a combination of orbital resonance, resonance-driven commensurabilities and a shortage of degrees of freedom. This particular hypothesis supports the concept presented in contact 150 of Venus having been repulsed into its current orbit from its original orbit around Uranus. As this particular formula places it at 0.7 AU (Astronomical Units) while its actual distance is currently 0.72 AU. While all planetary orbits are elliptical, Venus's orbit is the closest to circular, with an eccentricity of less than 0.01. All the planets of the Solar System orbit the Sun in an anti-clockwise direction as viewed from above the Sun's north pole. Most planets also rotate on their axes in an anti-clockwise direction, but Venus rotates clockwise (retrograde rotation) once every 243 Earth days—the slowest rotation period of any planet (there are 224.7 days in a Venusian year).
In this way Titius-Bodes law appears to reflect the turbulent past of all the planets in our star system. With the exception of Earth and Jupiter which are exactly where this formula predicts them to be. Earth's relative stability up until this time may have something to do with the events that proceeded the destruction of Atlantis. While Jupiter being the largest and a gas giant may explain why it has been less affected by cosmic influences. While it interestingly points towards Ceres, a rock now in the orbit of where the planet Malona was destroyed. Uranus in contact 150 being pushed out of its orbit of 19.6 AU to its current 19.2 AU by the same force that brought Venus to its current orbital rotation to replace the planet Skill found in the 238th contact. Which presumably had an elliptic orbit of 0.7 AU having become accustomed to the binary dark star over the duration of this planets evolution unlike Venus. While Neptune and Plutos inconsistency with the formula may again have something to do with this same star, our suns dark binary star, as discussed in contact 544. Though in Pluto's case it could be due to its moon Charon.
Venus in contact 31 is flown past in a beamship when Billy jokes about photographing a Venusian, which spurs a conversation about fraudulent contactees, because no one lives there. Its another desolate and uninhabitable planet.
Chronology Of Venus
- 6,339.5 BCE - The Destroyer rips Venus out of its orbit around Uranus and "tows" it behind itself in the direction of the earth's orbital path.
- 6,104 BCE - Venus breaks into earth's orbital path which disturbs Venuses rotation in such a way that a new rotational period is created around the sun. Bringing gigantic earthquakes, volcanic eruptions, floods and elemental storms to Earth at that time.
- 4,006 BCE - Venus crosses again into the earth's path and lightly disturbs the earth again, but without bringing about large catastrophes this time.
- 3,545 BCE - Venus finally stabilizes itself and sets itself into its own path around the sun.
*note, this information was taken from the FIGU forum and does not mirror contact 150, so will need to be revised.
- Destroyer Planet/Comet
- [Elliptic Orbit]
- [Kepler Orbit]
- [Gravitational two body problem]
- [Bertrands theorem]
- [Titius-Bode Law]
- [Dermotts Law]
- [Axial precession]
- [Roman Mythology] | 0.888881 | 3.867829 |
Nature loves to riff on existing motifs, even in the most unearthly of environments.
The most interesting worlds are those that are most varied and vibrant. Consider Earth. Lying between its churning interior and solar-driven atmosphere, its surface is constantly reworked, producing infinite diversity and beauty. Maybe I’m biased, but that winning combination of vigorous internal and atmospheric activity makes for the best of planetary exteriors.
Fortunately, we keep finding more places where the fertile interface between geology and meteorology cooks up marvels. Such features are often a beguiling mix of the familiar and the exotic, with recognizable forms assembled from available materials that are malleable in the extreme (to us) conditions found on other worlds. On Titan, for example, a hydrological cycle creates recognizable fractal rivers and lakeshores, but the working fluid is methane, not water.
Pluto, as revealed to us by the New Horizons encounter of 2015, sports precipitous water-ice mountains capped with methane snow, ringing a vast nitrogen glacier called Sputnik Planitia. Upon seeing that massive smooth plain, clear and fresh and free of craters, we were consumed by the mystery of its self-erasing surface. What is happening below to drive that sea of solid nitrogen to turn itself over? It may simply be that the radioactive decay of the rocky interior generates enough heat to churn the soft nitrogen ice.
There’s no new physics here — simply common materials found in such otherworldly scales and conditions that our pre-encounter imaginations were not quite up to the task. This is why we explore rather than simply stay home and construct models.
Yet it’s not just internally driven activity that gives Pluto its dazzling variety and complexity. Our favorite Kuiper Belt orb, we find, is another place where many of the grandest enigmas and most exquisite features arise from the interaction between surface and atmosphere.
The wonderful discovery of dunes on the western flanks of Sputnik confirms this. Among the discoverers is Jani Radebaugh, a planetary geologist at Brigham Young University, who was instrumental in gathering the international, multi-disciplinary team that produced the June 1st Science paper that made the case for Plutonian dunes.
I admit I was skeptical when I first heard about potential dunes on Pluto. I assumed its wispy atmosphere, 100,000 times thinner than Earth’s at the surface, would be far too rarefied to blow around material in the way needed to fashion dunes.
But Jani knows dunes through and through, on our planet and elsewhere. Applying her physical intuition, honed from years of hiking over, measuring, and comparing geologic features, she recognized the telltale forms of surface landscapes formed by windblown deposits of fine materials. “When I first saw the high-resolution images of those areas, I realized that these were dunes,” she told me. “I knew there had to be an atmosphere that could produce them.”
The rare Plutonian air hosts strong breezes, but what generates the initial force to lift the small particles of methane snow that seem to be forming these drifts? One possibility: As the solid nitrogen surface heats up in the Sun, it vaporizes, launching particles skyward. Alternatively, the dunes could have formed in the past when Pluto’s changeable atmosphere was thicker.
Nitrogen glaciers, ice mountains, methane snowcaps, and now — apparently — methane “sand” dunes. Wonders never cease.
This article originally appeared in print in Sky & Telescope's September 2018 issue. | 0.885006 | 3.754039 |
Arguably the biggest astronomy story of the year was the hullabaloo about Pluto, and whether it should be classified as a planet. Astronomers were outraged, children cried, and late-night comedians joked. But in the end, the solar system shrugged. Although the International Astronomical Union voted to officially remove Pluto from the ranks of full-fledged planetdom, and the Minor Planet Center gave the world an asteroid number, we can be sure that the issue isn't over yet. Regardless of its status, Pluto will remain in the gaze of astronomers. Its two new moons were named in June. And the world will have a visitor — NASA's New Horizons probe launched on January 19th and will make a flyby in 2015. Hopefully by then, astronomers will settle on what Pluto is.
The Pluto uproar of August was the loudest part of a yet another year of astronomical triumph and disappointment. Nowhere was this more apparent but on the Red Planet, where the multimission exploration continues. Excitement peaked several weeks ago when researchers found surface changes that may indicate events of contemporary flowing water. Curiously, the announcement came a month after the spacecraft that led to the discovery, Mars Global Surveyor, fell silent. Nevertheless, the planetary invasion continues, with the arrival of Mars Reconnaissance Orbiter last March. It joined Mars Express, whose camera has dazzled earthlings with high-resolution orbital images of the robotic landers of past and present.
Elsewhere in the solar system, Jupiter developed a new junior Red Spot, Periodic Comet Schwassmann-Wachmann 3 crumbled in front of our telescopes, and the Cassini spacecraft continued to reveal discoveries, from detail on the surface of Titan to curiosities in Saturn's rings.
At the start of the year, the Stardust probe returned back to Earth after spending months collecting interplanetary debris. Scientists pore over the
minute bits it captured for clues to the solar system's formation.
Meanwhile, on the ground, Hawaiian observatories rocked and rolled in a large earthquake but suffered no major damage. Tremors of a budgetary nature propagated as research projects and facilities faced cancellation or closure. The Hubble Space Telescope will be rescued from the brink. And SOFIA was saved from the budget ax and will soon get off the ground. While Wisconsin's venerable Yerkes Observatory may have changed owners, it will remain an institution of research. But the future remains cloudy for other facilities, including Arecibo Observatory's giant radio telescope, whose ear may become deaf because of cuts by the National Science Foundation.
This sampling of astronomical events during the past 12 months represent just a fraction of the stories we've covered on SkyandTelescope.com and in Sky & Telescope. The pace of celestial discoveries will surely continue, and we'll be bringing them to you through 2007 and beyond.
Happy New Year! | 0.910334 | 3.321441 |
Goddard Space Flight Center
NASA’s Goddard Space Flight Center (GSFC) in the oldest and largest space research center in the United States. GSFC builds spacecraft, satellites, and technologies to study the sun, outer space, and other planets in the local solar system. It was founded on May 1, 1959, and is currently home to Hubble space telescope operations. GSFC will also be home to the headquarters of the James Webb Space Telescope. GSFC is primarily focused with the operation and study of the known universe rather than satcom or FSO.
Hubble Space Telescope
The Hubble Space Telescope, launched in 1990, is the world’s most famous satellite. It has operated for over 20 years and has produced an incredible amount of finds relevant to both astrophysics and astronomy, such as the rate of expansion of the universe. The satellite operates in the ultraviolet to near-infrared waveband. GSFC operates and controls the satellite while the Space Telescope Space Institute (STScI) chooses Hubble’s targets and processes the data.
James Webb Space Telescope
The James Webb Space Telescope (JWST) will be the successor to the Hubble Space Telescope. Its primary function and purpose will be to observe light from distant galaxies to understand the nature of the beginning of the universe. JWST will observe the creation of life, the birth of stars, and the assembly of galaxies using infrared light. It will have the capability to observe light up to the helium ionization period of the universe’s formation, answering key questions about the Big Bang.
ICESat-2 (Ice, Cloud, and land Elevation Satellite 2) is a satellite operated by GSFC that uses free-space optics time-of-flight calculations to measure and detect the elevation differences on Earth’s surface. ICESat-2 operates at 10kHz, sending a laser pulse to the ground once every 10 microseconds, allowing the satellite to map the ground once every 28 inches. The key focus of the satellite is to measure the elevation of ice sheets, sea ice, and other frozen areas of the globe collectively called the cryosphere. ICESat-2 also measures the stock of vegetation in the planet’s forests. It was launched in 2018 and has a three year lifespan.
The satellite has incredible precision, capable of measuring the change in ice thickness over time to within 4 millimeters. After combining data from ICESat-2 and ICESat-1, research scientists will be able to predict cryosphere behavior for 16 years. | 0.818038 | 3.32254 |
Hey Pluto, Sedna, Haumea, Makemake Et al.: You’ve got company!
While searching for distant galaxies and supernovae, the Dark Energy Survey’s powerful 570-megapixel digital camera spotted a few other moving “dots” in its field of view. Turns out, the DES has found more than 100 previously unknown trans-Neptunian objects (TNOs), minor planets located in Kuiper Belt of our Solar System.
A new paper describes how the researchers connected the moving dots to find the new TNOs, and also says this new approach could help look for the hypothetical Planet Nine and other undiscovered worlds.
Guess you never know what you’ll find once you start looking!
The gas giant Jupiter, which was named in honor of the king of the gods in the Roman pantheon, has always lived up to its name. In addition to being the largest planet in the Solar System – with two and a half times the mass of all the other planets combined – it also has an incredibly powerful magnetic field and the most intense storms of any planet in the Solar System.
What’s more, it is home to some of the largest moons in the Solar System (known as the Galilean Moons), and has more known moons than any other planet. And thanks to a recent survey led by Scott S. Sheppard of the Carnegie Institution of Science, twelve more moons have been discovered. This brings the total number of known moons around Jupiter to 79, and could provide new insight into the history of the Solar System.
The team was led by Scott S. Sheppard and included Dave Tholen (University of Hawaii) and Chad Trujillo (Northern Arizona University). It was this same team that first suggested the existence of a massive planet in the outer reaches of the Solar System (Planet 9 or Planet X) in 2014, based on the unusual behavior of certain populations of extreme Trans-Neptunian Objects (eTNOs).
Curiously enough, it was while Sheppard and his colleagues were hunting for this elusive planet that they spotted the first of these new moons in 2017. As Sheppard explained in a recent Carnegie press release:
“Jupiter just happened to be in the sky near the search fields where we were looking for extremely distant Solar System objects, so we were serendipitously able to look for new moons around Jupiter while at the same time looking for planets at the fringes of our Solar System.”
The orbits of the newly-discovered moons were then calculated by Gareth Williams of the International Astronomical Union’s Minor Planet Center (MPC), based on the team’s observations. “It takes several observations to confirm an object actually orbits around Jupiter,” he said. “So, the whole process took a year.”
As you can see from the image above, two of the newly-discovered moons (indicated in blue) are part of the inner group that have prograde orbits (i.e. they orbit in the same direction as the planet’s rotation). They complete a single orbit in a little less than a year, and have similar orbital distances and angles of inclination. This is a possible indication that these moons are fragments of a larger moon that was broken apart, possibly due to a collision.
Nine of the new moons (indicated in red) are part of the distant outer group that have retrograde orbits, meaning they orbit in the opposite direction of Jupiter’s rotation. These moons take about two years to complete a single orbit of Jupiter and are grouped into three orbital groups that have similar distances and inclination. As such, they are also thought to be remnants of three larger moons that broke apart due to past collisions.
The team observed one other moon that does not fit into either group, and is unlike any known moon orbiting Jupiter. This “oddball moon” is more distant and more inclined than the prograde moons and takes about one and a half years to orbit Jupiter, which means its orbit crosses the outer retrograde moons. Because of this, head-on collisions are much more likely to occur with the retrograde moons, which are orbiting in the opposite direction.
The orbit of this oddball moon was also confirmed by Bob Jacobson and Marina Brozovic at NASA’s Jet Propulsion Laboratory in 2017. This was motivated in part to ensure that the moon would not be lost before it arrived at the predicted location in its orbit during the recovery observations made in 2018. As Sheppard explained,
“Our other discovery is a real oddball and has an orbit like no other known Jovian moon. It’s also likely Jupiter’s smallest known moon, being less than one kilometer in diameter…This is an unstable situation. Head-on collisions would quickly break apart and grind the objects down to dust.”
Here too, the team thinks that this moon could be the remains of a once-larger moon; in this case, one that had a prograde orbit that formed some of the retrograde moons through past collisions. The oddball moon already has a suggested name for it – Valetudo, after the Jupiter’s great-granddaughter, the goddess of health and hygiene in the Roman pantheon.
In addition to adding to Jupiter’s overall moon count, the study of what shaped these moon’s orbital histories could teach scientists a great deal about the earliest period of the Solar System. For instance, the fact that the smallest moons in Jupiter’s various orbital groups (prograde, retrograde) are still abundant suggests that the collisions that created them occurred after the era of planet formation.
According to the Nebular Hypothesis of Solar System formation, the Sun was still surrounded by a rotating protoplanetary disk at this time – i.e. the gas and dust from which the planets formed. Because of their sizes – 1 to 3 km – these moons would have been more influenced by surrounding gas and dust, which would have placed a drag on their orbits and caused them to fall inwards towards Jupiter.
The fact that these moons still exist shows that they likely formed after this gas and dust dissipated. In this respect, these moons are much like time capsules or geological records, preserving pieces of Jupiter’s (and the Solar Systems) history of formation and evolution.
Zoomed-in image from the Dark Energy Camera of the barred spiral galaxy NGC 1365, about 60 million light-years from Earth. (Dark Energy Survey Collaboration)
The ongoing search for dark energy now has a new set of eyes: the Dark Energy Camera, mounted on the 4-meter Victor M. Blanco telescope at the National Science Foundation’s Cerro Tololo Inter-American Observatory in Chile. The culmination of eight years of planning and engineering, the phone-booth-sized 570-megapixel Dark Energy Camera has now gathered its very first images, capturing light from cosmic structures tens of millions of light-years away.
Eventually the program’s survey will help astronomers uncover the secrets of dark energy — the enigmatic force suspected to be behind the ongoing and curiously accelerating expansion of the Universe.
Zoomed-in image from the Dark Energy Camera of the Fornax cluster
“The Dark Energy Survey will help us understand why the expansion of the universe is accelerating, rather than slowing due to gravity,” said Brenna Flaugher, project manager and scientist at Fermilab.
The most powerful instrument of its kind, the Dark Energy Camera will be used to create highly-detailed color images of a full 1/8th of the night sky — about 5,000 square degrees — surveying thousands of supernovae, galactic clusters and literally hundreds of millions of galaxies, peering as far away as 8 billion light-years.
The survey will attempt to measure the effects of dark energy on large-scale cosmic structures, as well as identify its gravitational lensing effects on light from distant galaxies. The images seen here, acquired on September 12, 2012, are just the beginning… the Dark Energy Survey is expected to begin actual scientific investigations this December.
Full Dark Energy Camera composite image of the Small Magellanic Cloud
“The achievement of first light through the Dark Energy Camera begins a significant new era in our exploration of the cosmic frontier,” said James Siegrist, associate director of science for high energy physics with the U.S. Department of Energy. “The results of this survey will bring us closer to understanding the mystery of dark energy, and what it means for the universe.”
Images: Dark Energy Survey Collaboration. Inset image: the 4-meter Blanco Telescope dome at CTIO (NOAO)
The Dark Energy Survey is supported by funding from the U.S. Department of Energy; the National Science Foundation; funding agencies in the United Kingdom, Spain, Brazil, Germany and Switzerland; and the participating DES institutions. | 0.893064 | 3.727136 |
GREENBELT, Md. (NASA PR) — 5:32 p.m. Eastern Time on June 18, 2019, marks 10 years since the launch of the Lunar Reconnaissance Orbiter (LRO). Its contributions to the fields of lunar science and exploration are unmatched: it has provided the largest volume of data ever collected by a planetary science mission.
The diverse suite of instruments aboard LRO include a laser altimeter that fires pulses of light about 28 times per second, creating one of the most accurate topographic maps of any celestial body. LRO measured the coldest known temperatures in the solar system at the Moon’s poles. Observations of tectonic features across the lunar surface indicated the Moon’s gradual shrinkage — LRO showed us not a dead but rather a dynamic and intriguing Moon.
LRO’s original mission duration was supposed to be one to two years, not 10. “We’ve just submitted our fourth extended mission proposal,” said Noah Petro, project scientist of LRO at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “With the national focus on the Moon as part of NASA’s Moon to Mars strategy, the data from LRO has been instrumental in Artemis planning and the mission will continue to be a major player going forward in finding more landing sites for humans and robotic explorers. The work that we’re doing is meaningful to the science community, to NASA and to the world.”
The Allure of the Moon
In the months leading up to its launch, LRO received submissions of over a million names as part of an initiative to involve the public in NASA’s return to the Moon. The names, encoded on a microchip, launched with LRO. “It gave people a sense of not just belonging but also of being part of a mission,” Petro said.
Why does Earth’s largest satellite have such a widespread impact upon human imaginations? Beyond the invaluable science and data that LRO gave and continues to give to benefit the onward march of scientific advancement, LRO personifies the investigation of all that is utterly extraordinary about the Moon.
As part of NASA’s 60th anniversary celebration last year, the National Symphony Orchestra played Claude Debussy’s “Clair de Lune” at the Kennedy Center in Washington set to projections of digital images of a lunar day. Science visualizer Ernie Wright, also of Goddard, created this breathtaking view of the Moon’s landscape entirely with LRO data.
The stunning video produced a palpable reaction among those who were at the live performance. “People came up to me during the intermission and asked if I was the photographer,” Wright said. “They didn’t understand completely what I’d made, but they had an emotional reaction to the visual and the way it was combined with the music.”
Wright has been fascinated by the Moon since he saw, live on television, the first humans to step foot on the Moon with the Apollo 11 mission. His connection to the Moon persevered for decades. “I feel especially lucky to be specifically involved with LRO and with data rendering of the Moon because the lunar landing was my first memory of a major space event,” he said. A return to the Moon could inspire a new generation of people motivated, like Ernie Wright, by their specific lunar connection.
LRO’s Figurative Shortening of the Lunar Distance
LRO is a major source of information about the moon for NASA. “When they want someone to talk about the Moon, they call the LRO team,” Petro said. “LRO’s continuation is a direct result of NASA’s interest in the Moon.”
NASA is obviously not the only entity with an interest in the Moon — yet one particular factor seems to shape humanity’s fascination.
“The Moon is very accessible,” said Molly Wasser, planetary science and LRO digital media lead from Goddard. “Anyone can see it, no matter where you are — from the brightest cities to the most remote communities. It’s a way to introduce children to space since little kids can see it and observe it changing over time. There’s something very romantic about it. Everyone loves the Moon.”
The rise of social media over the span of LRO’s lifetime further satiates the public desire for lunar information, but images get the most attention. Having collected over a petabyte (one billion megabytes) of data, LRO has millions of photos of stark geological features lit sharply by unfiltered sunlight. “That content gets the most traction,” Wasser said.
The Moon is visible and it is the largest object in Earth’s night sky. “The Moon has that immediacy,” Petro said. “There’s a connection that people can have which puts it at the forefront of our consciousness.” Even if they are unaware of the mission, LRO brings the Moon to humans in detail precise enough to see the sites of previous lunar missions — a feat beyond impossible for the naked eye.
Apollo, LRO and Artemis
The Moon’s scientific value is not to be understated. The history of the solar system’s evolution is almost indelibly pounded into the lunar surface, providing data over billions of years that mirrors Earth’s history. The Moon exists without the protective effects of an atmosphere or the erasure of geological history as rocks cycle through the processes of plate tectonics.
“We use the Moon as a template for understanding how any solid object in the solar system formed, and by extension, solid objects anywhere in the universe,” Petro said. “There’s an important reason why we study the Moon — it’s not only the Moon for the Moon’s sake. It’s an extension of the Earth.”
Observation of the Moon long predates LRO and Apollo. “So many people don’t notice it or think anything of it,” Petro said. “But the Moon is a part of our consciousness.” The Moon, however, isn’t merely ingrained into cultural memory: it is also part of humanity’s future.
NASA recently announced its commitment to return to the Moon by 2024 with the Artemis program. Named for the mythological Greek Moon goddess and twin of Apollo, Artemis carries humanity back to our largest satellite — this time, for good — before we launch to Mars and to the unexplored beyond. | 0.805914 | 3.02315 |
Origin Of Solar System The Origin of the Solar System One of the most intriguing questions in astronomy today is the how our solar system formed. Not only does the answer add insight to other similarly forming systems, but also helps to satisfy our curiosity about the origin of our species. Although it is highly unlikely that astronomers will ever know with absolute scientific certainty how our system originated, they can construct similar theoretical models with the hopes gaining a better understanding. A basic understand of the current physical aspects of our solar system are helpful when trying to analyzing its origin. Our solar system is made of the Sun, nine major planets, at least sixty planetary satellite, thousands of asteroids and comets that all span an immense distance.
Each planet has its own individual characteristics and seven of which have one or more satellites. There are thousands of asteroids, mainly congested in the area between Mars and Jupiter, as well as countless comets that all travel in a spherical orbit around our Sun. The Sun contains approximately 99 percent of the mass in the solar system, but only 2 percent of the systems angular momentum. It lies in the center of our system while all planets, asteroids and alike rotate in elliptical orbits around it in the same plane. The smaller inner planets have solid surfaces, lack ring systems and have far fewer satellites then the outer planets. Atmospheres of most of the inner planets consist of large quantities of oxidized compounds such as carbon dioxide. While on the other hand, the outer planets are far more massive then the inner terrestrial planets, and have gigantic atmospheres composed mainly of hydrogen and helium.
Asteroids and comets make up the smallest portion of the solar systems entities and are composed of the remnants left behind while planets were forming. For over 300 years, there has been a very long history of conjecture on the origin of the solar system. These many theories stem from two general categories. The first category called monistic, involves the evolution of the Sun and planets as an isolated system. The second group of theories called dualistic, suggested that the solar system formed as a result of the interaction between two individual stars. The dualistic formation theory has been almost entirely dropped and monistic formation has become the general consensus on the basic formation of our solar system.
Most modern theories of the origin of the solar system hypothesize that all bodies in the solar system, including the sun accreted from the formation and evolution of a single primordial solar nebula. It is believed that our solar system began to form around 4.56 billion years ago from a dense interstellar cloud of gas. Because of the conservation of angular momentum, the cloud of gas formed a rotating flattened disk approximately the size of the planetary system. It was this flattened disk that is referred to as the primitive solar nebula and from which our current solar system evolved. Ordinarily, the internal pressures of the cloud are sufficient to prevent if form collapsing.
However, from time to time local increases in pressure of the interstellar medium cause the additional compression of interstellar clouds. These compressions caused the clouds to reach their threshold of gravitational collapse. Once the gravitational attraction of matter is greater then any tendency to expand due to internal pressures the cloud begins to collapse inward. Theoretical models suggest that the presolar nebula continued to collapse until the center of the cloud became so dense that heat started to form. This heat increased the thermal pressure of the cloud until the collapse was eventually halted.
The existence of our system of planets is entirely due to the angular momentum of the initial cloud. If there were no angular momentum, then the interstellar cloud would have collapsed to from a single star. While at the same time, if the collapse had occurred under a system with too much angular momentum then a binary star would have resulted from our system. Our system formed under intermediate conditions allowing the planets to evolve. The fact that the Sun contains 99 percent of the solar systems mass but only 2 percent of its angular momentum raises questions about the distribution of masses during the early formation of the solar system.
It is suggested that certain processes transported nebula mass inward to form the Sun, and angular momentum outward to the preplanetary region. Thus decreasing the total angular momentum of the Sun. Three separate hypothesizes have been suggested to explain the processes for such a transport. The main theories suggest that gravitational torques, viscous stress, and magnetic fields may have acted individually or in some combination to produce our present system. The first theory including gravitational torques arises from the gravitational forces between segments of asymmetric mass. One example of this case would be between inner and outer regions of the trailing spiral arms of the nebula.
Assuming there is a source of asymmetry, then these torques can result in significant outward transportation of angular momentum. Viscous stresses are another possible source of the shift in angular momentum of the solar system during its evolution. Viscous stresses are caused by the friction between adjacent fluid parcels trying to move past each other with different speeds. These stresses result in the outward transport of angular momentum and are one more possible explanation to the outward spread of momentum. The third theory postulates that magnetic fields are the source of this momentum transfer.
Magnetic fields may have been produced during the collapse of the initial cloud or even electrically generated between the proto-Sun and the solar nebula. This would eventually end in the same result of an outward spread of angular momentum. Therefore the evolution of the solar nebula involved both the transportation of mass into the central proto-Sun region and the increased angular momentum in the planetary regions. This meant that most of the primitive clouds mass fell in to the proto-Suns region while the remainder formed the planets. It is not only important to study the evolution of the solar nebula, but also the formation of the planets.
There is a general consensus that once the solar nebula settled to rest that solid dust particles began to move toward the central plane of the nebula. It was at this stage that the planets began to form. There are two current theories that resulted in the development of the planets. The first theory suggests that the planets formed in a very basic process where dust particles accumulated into planetesimals which in turn grew to the present planets. The second theory proposes that planetesimals resulted from a gravitational instability in the gaseous portion of the solar nebula.
The first theory states process of planet formation began with the settling of dust in into the central plane of the nebular disk. Soon after, the first dust particles began to coagulate into small solid bodies. These bodies then accumulated through a collective gravitational instability in of the dust disk. The thin dust disk became more massive through continual sedimentation and resulted in its breakup into a large number of planetesimals. Through a process of random collisions these planetesimal continued to grow and accumulate mass. There are two possible extremes that ended this process of accumulation.
The first involved runaway accreting where one object grows extremely large through the collection of all smaller planetesimals within its area. The alternative extreme would involve the uniform growth of a number of masses resulting in a many equal mass planetesimals. It is currently believed that the formation of the planets resulted from a combination of these two processes. The equal mass accumulation is presumed to have dominated during the early stages of planet formation while the run away accumulation is suggested to have taken over during the latter stages. However, there is one substantial problem with this explanation of the planet’s formation.
The accumulation theory fails to take into account the rapid formation of the giant planets. By the slow process of coagulation, it would take much longer then the lifetime of the solar system to form the giant planets of Jupiter and Saturn. This incorrectness in the first theory led scientists to contrive the second theory. The second theory of planetary evolution involves a gravitational instability of the gaseous portion of the solar nebula. It is suggested that if the solar system were massive enough then the instability would lead to the fragmentation of the gaseous nebula and the formation of giant gaseous protoplanets.
This theory allows plenty of time for the formation of the very large planets Jupiter and Saturn. The one flaw of this theory is its contingency on a very massive planetary nebula, one much larger than ours. Because of this problem many cosmogonists have begun to doubt that the gaseous disk instability led to planet formation in our solar system. Although many of the details on the theories of our solar system will most likely change in the near future, the fundamental concept of solar system formation appear to remain the same. The Sun and planets began forming approximately 4.56 billion years ago out of a solar nebula produced by the collapse of a rotating interstellar cloud of gas and dust. Following soon after, the terrestrial and Jovian planets eventually formed from the collision and accumulation of smaller planetesimals.
While there is significant evidence supporting the formation of the Sun and planets in this way, it is not likely that scientist will know with complete certainty about the solar systems origin for some time. It is highly likely that the details in the theory of the solar system will change. With continued improvements in technology and significant advances in astronomical fields of observation, further understanding of our solar system will undoubtedly come. In recent years, the idea that the Solar System formed from the evolution of a primodial solar nebula, has received significant conformation. The use of satellites such as the Infrared Astronomical Satellite (IRAS) have detected disks of solid particles around several nearby stars, including Formalhaut, Beta Pictoris and Vega.
The uses of satellites have provided scientists with most of the information they currently have on the systems origin. Another source of information lies in our neighboring planets. Investigations of the other planets in the solar system by means of interplanetary spacecraft have provided a wealth of data pertaining to the origin and history of the solar system. Through the observation of solar-type stars in the Galaxy, we can learn critical information about the properties of the interstellar cloud that collapsed to form our own solar nebula. It is likely that future explorations and observations will help to solidify our understanding of the solar system. | 0.858667 | 3.85373 |
Our Spectacular California Sky
By Christy Milan
A Galaxy Far, Far Away
By Christy Milan
NORTHERN CALIFORNIA PROVIDES BEAUTY and excellent places to explore throughout all seasons. However, sometimes one area is often missed – the big, beautiful California sky. March is a great time to look up! This month provides many events happening just outside your door. We can delight in two full moons, Mercury at elongation, the spring equinox and a planetary parade. All these celestial wonders can be found just by looking up.
The full moon in March is traditionally called the Full Worm Moon by Native Americans, who would use the moon phases to track the seasons. During this time, the earth is awakening from its winter nap. Earthworm casts reappear among the soft earth, inviting birds to return from migrating. The roots of once-dormant plants begin to push their way up through the soil in a display of re-birth. The full moon in March has also been named the sap moon in different regions in reference to the maple flowing and the tapping of maple trees.
The next big event begins early in
late February and into early March, when the planets slip into alignment. For those who rise early, they only need to look into the southeastern sky at dawn to discover Saturn, Mars and Jupiter positioned near one another. Over the next few nights, the waning moon appears with the planetary parade.
Arriving mid-month is the planet Mercury. The planet is at elongation during its orbit, which means it has reached the greatest distance from the sun. “Planets don’t orbit the sun in perfect circles but rather eclipses,” says Greg Williams of the Shasta Astronomy Club. “Think of an egg shape.” This allows the best viewing of Mercury since it has fewer glares from the sun and is at its highest point above the horizon. Look low in the western sky just after the sun sets.
The spring equinox arrives March 20. The name equinox comes from the Latin words aequus (equal) and nox (night). It was once thought that the equinox meant everyone on Earth could experience a day and night that is equal – 12 hours of daylight and 12 hours of night.
Now, we understand that most places on Earth see more daylight than night. This is due to how the sunset and sunrise are defined, and the atmospheric refraction of sunlight. On this day, many cultures around the world celebrate with festivals and grand events. The Mayans celebrate the vernal equinox with the Return of the Sun Serpent at the El Castillo pyramid. During the spring and autumn equinox, the late afternoon sun casts a shadow on the pyramid that creates the illusion of a snake moving down the pyramid.
The second full moon of the month is called a blue moon. The moon is not actually blue and it is not a term used by early Native Americans. The term blue moon is not even an astronomical term. It is believed it was first used in the 1940s in an astronomy magazine – it was a mistake that went viral and gave us this term used to describe two full moons in a month. This year is unique in that both January and March have two full moons and February has no full moon at all.
March in the North State is sure to bring about wonder and amazement if you know when and where to look. Now that winter has gone, we can embrace the renewal of a season and bask in its energy. The blooms of flowers celebrate spring by stretching toward the sun in an embrace of warmth and growth. We have all grown in one way or another through the season. Now is the time to venture outdoors, and don’t forget to look up! •
Sky viewing with Shasta Astronomy Club
March 10- 6 pm
March 17 – 7 pm
Oak Bottom at Whiskeytown Lake
Shasta Astronomy Club
Find them on Facebook
1644 Magnolia Ave., Redding
March 1: Full Moon, Full Worm Moon
March 7-8: Planetary Parade
March 15: Mercury Elongation
March 20: Spring Equinox
March 31: Blue Moon | 0.884446 | 3.29884 |
Shu is known for pioneering theoretical work in a diverse set of fields of astrophysics, including the origin of meteorites, the birth and early evolution of stars and the structure of spiral galaxies. One of his most highly-cited works is a 1977 seminal paper Self-similar collapse of isothermal spheres and star formation describing the collapse of a dense giant molecular cloud core which forms a star. This model (commonly referred to as the “inside-out” collapse model or the “singular isothermal sphere” model) helped provide the basis for much later work on the formation of stars and planetary systems, although it has been criticized for its shortcomings. Shu has also performed calculations on the structure of planet-forming disks around very young stars, the jets and winds that these stars and their disks generate, and the production of chondrules, inclusions in meteorites. Much of this work has been done in collaboration with his postdocs and graduate students, many of whom have gone on to successful academic careers in their own right.
* – Academy-Springer Nature Chair Professor Public Lecture
⁺ – Colloqium
Astrophysics Of Molten Salt Breeder Reactors
Astron Solutions Corporation
Many experts believe that a solution for climate change, especially in nations that are still trying to develop their economies, is not possible without nuclear power. However, among the general public there is discomfort about the four S’s:
Under the leadership of its top nuclear scientists, India has a far-sighted program to address these concerns by switching from the current fuel cycle of light-water reactors burning uranium-235 to an alternative fuel cycle that would burn uranium-233 bred from thorium-232 (the only form of thorium found in the world, and for which India has rich deposits). From the perspective of theoretical astrophysics, we argue in this talk that the best reactor to achieve the four-S goal uses, not solid fuel elements, but liquid fuel elements in the form of molten salts. Knowledge of how specific isotopes are produced in the big bang, in advanced stages of stellar evolution, and in cosmic rays, help in the choice of the composition of the salts and the materials used in the construction of molten-salt breeder reactors (MSBRs). The exchange of the kinetic energies of neutrons and atomic nuclei in a spherical reactor is akin to similar interactions among low-mass and high-mass stars in a globular cluster, the basic equations for which were formulated by S. Chandrasekhar in the 1940s. Tailoring the nuclear reactions to favour the formation of certain isotopes versus competitors has an analogy with the s- and r-processes of neutron-capture transformations in pre-supernova stars. Achieving economic superiority relative to other sources of energies relies on a basic understanding of energy hierarchies in the natural world. Managing the decay heat in fuel salt dumped into metal tanks in severe emergencies benefits from knowing how white dwarf stars cool by stages to a final inert state as a solid. If the world adopts sustainable, secure, superior, and safe thorium-MSBRs as the primary clean replacement for coal and natural gas, halting climate change could be a solved problem by the end of the twenty-first century without destroying the aspirations of future generations for a better life.
Six decades of Spiral density – Wave Theory
University Professor Emeritus
UC Berkeley and UCSD
The theory of spiral density waves had its origin approximately six decades ago in an attempt to reconcile the winding dilemma of material spiral arms in flattened disk galaxies. Our review begins with the earliest calculations of linear and nonlinear spiral density waves in disk galaxies, in which the hypothesis of quasi-stationary spiral structure (QSSS) plays a central role. The earliest success was the prediction of the nonlinear compression of the interstellar medium and its embedded magnetic field; the earliest failure, seemingly, was not detecting colour gradients associated with the migration of OB stars whose formation is triggered downstream from the spiral shock front. The reasons for this apparent failure are understood with an update on the current status of the problem of OB star formation, including its relationship to the feathering substructure of galactic spiral arms. Infrared images can show two-armed, grand design spirals, even when the optical and UV images show flocculent structures. We suggest how the nonlinear response of the interstellar gas, coupled with overlapping subharmonic resonances, might introduce chaotic behaviour in the dynamics of the interstellar medium and Population I objects, even though the underlying forces to which they are subject are regular. We then move to a discussion of resonantly forced spiral density waves in a planetary ring and their relationship to the ideas of disk truncation, and the shepherding of narrow rings by satellites orbiting nearby. The back reaction of the rings on the satellites led to the prediction of planet migration in protoplanetary disks, which has had widespread application in the exploding data sets concerning hot Jupiters and extrasolar planetary systems. We then return to the issue of global normal modes in the stellar disk of spiral galaxies and its relationship to the QSSS hypothesis, where the central theoretical concepts involve waves with negative and positive surface densities of energy and angular momentum in the regions interior and exterior, respectively, to the corotation circle; the consequent transmission and over-reflection of propagating spiral density waves incident on the corotation circle; and the role of feedback from the central regions. Lastly, we discuss how the amplitude modulation predicted for the destructive interference of oppositely propagating waves that form standing wave patterns may have been observed in deep infrared images of nearby spiral galaxies. We also present without comment the tantalising ALMA image of spiral structure in the protoplanetary disk around the forming star Elias 2–27.
Challenges Of Traveling To And Living On Mars
Founder, Astron Solutions Corporation
As the challenges of living sustainably on Earth grow ever more dire because of environmental constraints on the unlimited growth of population and demand for energy and material resources, many visionaries promote the idea of a new start for a subset of humans by colonising Mars. But is getting to Mars and living there as feasible as portrayed by certain captains of industry and directors of science-fiction movies? Earth and Mars differ in their surface gravities and in their distance from the Sun, which results in many disadvantages for Mars settlers:
Many of these disadvantages can be overcome by having access to nuclear power on Mars. Indeed, travelling to and surviving on Mars for many months at a time, without ready access to fresh water or air, is a problem similar to surviving in a sea-faring submarine that stays submerged under the ocean for months at a time. Unlike a nuclear submarine, the optimum nuclear reactor uses molten salt rather than water as a coolant and is a breeder that runs on the thorium fuel cycle rather than uranium-235 or plutonium-239. It is carried on board the spacecraft as a fission-fragment rocket engine, rather than as a driver of a turbine that can propel a payload from low-Earth orbit to Mars orbit that more resembles the spacious International Space Station than a cramped automobile. We outline how access to ample nuclear heat and electricity can help terraform Mars to be more like Earth, and how the spin-off application of such a development for space can help save civilisation on Earth from the ravages of climate change.
Formation Of Sunlike Stars And Planetary Systems
University Professor Emeritus
University of California at Berkeley and Sandiego
We discuss the main events in the birth and evolution of a sunlike star from the collapse of a cloud of molecules, to the accretion of a magnetized disk of material from which planets form, to the appearance of jets and bipolar outflows from young stellar objects. We relate how this sequence of events corresponds to the classification scheme from infrared and radio astronomy of class 0, I, II, and III objects. A recurring theme is the outward transport of angular momentum and the inward transport of mass that produce configurations where most of the mass of the system ends up as a ball at the center, and most of the angular momentum ends up in a flattened protoplanetary disk that revolves about the central ball that is the host star. From the disk, the dust separates from the gas to aggregate into planetesimals that grow to become protolanets and planets. Radio astronomical observations in spectral lines and the continuum will be crucial to deciphering how this separation of gas and solids occurs, and the likely crucial role played by water ice in forming icy giant planets relative to rocky terrestrial planets.
Reversing Climate Change With Molten Salt Technologies
Founder, Astron Solutions Corporation
Rational people agree that climate change poses an existential threat to civilisation. How do we mitigate its effects so that the global surface temperature does not rise by more than two degrees Celsius from pre-industrial levels to the end of the twenty-first century? Decarbonization is the buzz-word, but many experts believe that the two-degree goal is currently unachievable without technologies that can deliver negative carbon emissions. We present two molten salt approaches, especially suitable to the situation of India, which have considerable potential to halt and to begin to reverse the effects of climate change within this century. The first technology is supertorrefaction: the immersion of waste biomass under hot molten salt for a minute or so to sequester its carbon in a porous form for improving agricultural yields as well as for water filtration and the removal of industrial toxins. The second technology is two-fluid molten-salt breeder-reactors that can transform the nuclear power industry in a fundamental fashion by addressing societal concerns about its sustainability (against the depletion of uranium-235), security (against weapons proliferation), safety (against accidental release of massive amounts of radioactivity to the local environment), and superiority (against the economics of burning coal or natural gas for dispatchable electricity generation). With these two technologies, nations that bear little historical responsibility for the buildup of greenhouse gases in the atmosphere can continue to develop their economies while bequeathing to future generations a healthier and cleaner environment.
RECENT ARTICLES OF GENERAL INTEREST AUTHORED BY FELLOWS AND ASSOCIATES OF THE ACADEMY
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July 15, 2015
New close-up images of a region near Pluto’s equator reveal a giant surprise — a range of youthful mountains rising as high as 11,000 feet (3,500 meters) above the surface of the icy body. Credits: NASA/JHU APL/SwRI
Icy mountains on Pluto and a new, crisp view of its largest moon, Charon, are among the several discoveries announced Wednesday by the NASA’s New Horizons team, just one day after the spacecraft’s first ever Pluto flyby.
“Pluto New Horizons is a true mission of exploration showing us why basic scientific research is so important,” said John Grunsfeld, associate administrator for NASA’s Science Mission Directorate in Washington. “The mission has had nine years to build expectations about what we would see during closest approach to Pluto and Charon. Today, we get the first sampling of the scientific treasure collected during those critical moments, and I can tell you it dramatically surpasses those high expectations.”
“Home run!” said Alan Stern, principal investigator for New Horizons at the Southwest Research Institute (SwRI) in Boulder, Colorado. “New Horizons is returning amazing results already. The data look absolutely gorgeous, and Pluto and Charon are just mind blowing.”
A new close-up image of an equatorial region near the base of Pluto’s bright heart-shaped feature shows a mountain range with peaks jutting as high as 11,000 feet (3,500 meters) above the surface of the icy body.
The mountains on Pluto likely formed no more than 100 million years ago — mere youngsters in a 4.56-billion-year-old solar system. This suggests the close-up region, which covers about one percent of Pluto’s surface, may still be geologically active today.
“This is one of the youngest surfaces we’ve ever seen in the solar system,” said Jeff Moore of the New Horizons Geology, Geophysics and Imaging Team (GGI) at NASA’s Ames Research Center in Moffett Field, California.
Unlike the icy moons of giant planets, Pluto cannot be heated by gravitational interactions with a much larger planetary body. Some other process must be generating the mountainous landscape.
“This may cause us to rethink what powers geological activity on many other icy worlds,” says GGI deputy team leader John Spencer at SwRI.
The new view of Charon reveals a youthful and varied terrain. Scientists are surprised by the apparent lack of craters. A swath of cliffs and troughs stretching about 600 miles (1,000 kilometers) suggests widespread fracturing of Charon’s crust, likely the result of internal geological processes. The image also shows a canyon estimated to be 4 to 6 miles (7 to 9 kilometers) deep. In Charon’s north polar region, the dark surface markings have a diffuse boundary, suggesting a thin deposit or stain on the surface.
New Horizons also observed the smaller members of the Pluto system, which includes four other moons: Nix, Hydra, Styx and Kerberos. A new sneak-peak image of Hydra is the first to reveal its apparent irregular shape and its size, estimated to be about 27 by 20 miles (43 by 33 kilometers).
The observations also indicate Hydra’s surface is probably coated with water ice. Future images will reveal more clues about the formation of this and the other moon billions of years ago. Spectroscopic data from New Horizons’ Ralph instruments reveal an abundance of methane ice, but with striking differences among regions across the frozen surface of Pluto.
The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland designed, built and operates the New Horizons spacecraft and manages the mission for NASA’s Science Mission Directorate. SwRI leads the mission, science team, payload operations and encounter science planning. New Horizons is part of NASA’s New Frontiers Program, managed by the agency’s Marshall Space Flight Center in Huntsville, Alabama.
For more information on the New Horizons mission, including fact sheets, schedules, video and all the new images, visit: http://www.nasa.gov/newhorizons and http://solarsystem.nasa.gov/planets/plutotoolkit.cfm. | 0.888884 | 3.682091 |
The objectives of the mission are extremely ambitious, and it’s all about to happen this year and next.
So I thought it a good idea to prime everyone with a timely preview of
what’s on the ‘menu’ of events for 2014/15.
The mission objectives of the Rosetta spacecraft are to chase a comet, rendezvous with it, orbit it and deploy an instrument package to land on its surface. The comet orbiting and landing phases have never been attempted before, and if ESA can pull this off it will be a truly historic and remarkable achievement.
giant dirty snowballs (typically 1 to 10 km in diameter), usually in highly eccentric closed orbits or open near-parabolic trajectories around the Sun. So why is a load of dusty
iceballs so interesting? This is because they are generally believed to be the remnants of material left over from the formation of the Sun and planets – and as such are samples of very old (and generally uncontaminated) material left over from the original solar nebula dating from about 5 billion years ago. Consequently, analysis of the comet’s composition will hopefully tell us a good deal about the beginning of the Solar System. Also it is generally assumed that comets were the original source of the abundance of water found on planet Earth. During the formative years of the Earth, the Solar System was full of debris (including comets), and all of the larger bodies in the Solar System were subjected to violent bombardment. Obvious evidence of
this period can be seen on the cratered surfaces of many planets and moons throughout the Solar System. The
majority of the craters formed on the Earth during this period have not survived the extensive processes of erosion that occur on Earth, but the ocean’s of water are believed to be evidence of cometary impacts over time.
Also long-range analysis of comets shows evidence of organic molecules, which raises the question about whether comets had anything to do with the rise of life on planet Earth. All of these issues, and many others, will be addressed by the instrument package to be deployed on the comet’s surface.
Rosetta (see picture, and image heading up the ‘External links’ page of this website) is a large spacecraft, with a box-like central structure of approximate dimensions 2.8 m x 2.1 m x 2.0 m. Stretching either side of this structure are two large solar array panels with an area of 64 square meters presented to the Sun to raise power (840 Watts at a distance from the Sun of 3.4 AU – you may recall from the book How Spacecraft Fly that an Astronomical Unit (AU) is the average Earth-Sun distance of around 150 million km). This gives a 32 meter total span across the spacecraft. Communications with Earth are facilitated by a 2.2 m high-gain antenna. The
total launch mass of Rosetta is about 3,000 kg, of which 2,900 kg comprises the comet orbiter and 100 kg the comet lander. To undertake the various manoeuvres required during the mission, this mass budget includes 1,670 kg of rocket propellant.
The Rosetta was to be lofted by the European Ariane 5 launch vehicle, with the launch scheduled for January 2003. At that time the target comet was identified as 46P/Wirtanen. However, due to an Ariane 5 launch failure during 2002, the Rosetta launch was delayed to March 2004, and a new target comet had to be selected. Consequently, the comet now subject to Rosetta’s scrutiny is 67P/Churnyumov-Gerasimenko.
The table below gives a concise summary of the main Rosetta mission events. Watch this space for Part 2 of the Rosetta mission preview.
2 March 2004
4 March 2005
25 February 2007
13 November 2007
5 September 2008
13 November 2009
10 July 2010
8 June 2011
20 January 2014
13 August 2015
31 December 2015
First Earth gravity assist
Mars gravity assist
Second Earth gravity assist
Asteroid Steins flyby
Third Earth gravity assist
Asteroid Lutetia flyby
Enter deep space hibernation
Exit deep space hibernation
Comet rendezvous manoeuvre
Arrive at comet
Start global mapping of comet | 0.87103 | 3.756445 |
During a high profile news conference in March 2014, the BICEP2 radio astronomy team announced purported direct evidence for inflation— an important part of the modern Big Bang model.1
In Big Bang cosmology, inflation is a hypothesized "growth spurt" in which the universe enormously increased in size. Inflation was an ad hoc addition to the Big Bang model intended to solve some very serious theoretical difficulties, including the Big Bang's own version of the seeing-distant-starlight-in-a-young- universe problem.2 Inflation was originally thought to have occurred shortly after the Big Bang, although secular cosmologists have since begun to view inflation as the actual cause of this alleged cosmic explosion.3 Hence, finding evidence for this hypothesized inflationary process is quite important to Big Bang proponents.
Nearly uniform radiation comes to Earth from all directions. Because this radiation has its peak intensity in the microwave portion of the electromagnetic spectrum, it's called the cosmic microwave background (CMB) radiation. Secular cosmologists interpret this radiation as an afterglow from a time about 400,000 years after the supposed Big Bang.
The BICEP2 team found swirly patterns in the CMB radiation called B-mode polarization. These were thought to have been imprinted on the CMB by primordial "gravity waves" during the inflationary process.
Big Bang advocates were of course jubilant at the time. However, mere months after the big announcement, other scientists noticed a flaw in the analysis: the BICEP2 team had seriously underestimated the amount of B-mode polarization that could be caused by microwaves emitted by dust within our own galaxy.4 Hence, the CMB polarization patterns cited as "smoking gun" evidence for the Big Bang quite possibly had nothing to do with this hypothesized inflationary process. One prominent theoretical physicist even called this embarrassing episode a "Big Bang blunder."5
However, the BICEP2 radio telescope was not the only source of information regarding this microwave background radiation. CMB measurements had also been obtained by the Planck satellite, and initial results of the Planck data analysis were released in 2013.6 But this preliminary report did not include a study of the B-mode polarization within the CMB causing some to hold out hope that analysis of the Planck CMB data would provide the needed evidence for inflation, apart from the flawed BICEP2 analysis. That claim has not been realized.
Analysis of polarization patterns within the CMB, obtained from the Planck data, has now been presented in a paper submitted for publication last month.7 Its authors concluded that the "noise" caused by dust within our own galaxy is about the same size as the signal detected by the BICEP2 team. Hence, analysis of the Planck data has confirmed that the signal detected by the BICEP2 team is likely to have been caused by dust within our own Milky Way galaxy.
To make matters even worse for Big Bang proponents, researchers from King's College London have argued that accepting the BICEP2 claim at face value would imply that the universe should have collapsed in on itself shortly after the supposed Big Bang. Hence, if the BICEP2 results were correct, our universe should not even exist!8
As we noted at the time of the initial BICEP2 announcement, this is not the first sensationalistic "proof" of secular stories about origins that has been walked back by secular scientists, nor will it be the last.9 With so many such defeated proofs littering the scientific landscape (Piltdown Man, vestigial organs, the supposed missing link "Ida," smoking gun evidence for the Big Bang, etc.), one would think that Christians would learn not to be so intimidated by the dogmatic claims of secular scientists. Yet many Christians are still reluctant to question the scientific "high priests" of the new secular religion and can only bring themselves to meekly suggest, against all logic and common sense, that perhaps such claims don't really contradict the Bible after all! This recent debacle should encourage Christians to toughen up and exhibit a little hard-nosed skepticism the next time scientists announce the latest "proof" for their theories. After all, aren't secular scientists always telling us that skepticism is a virtue?
- Overbye, D. 2014. Space Ripples Reveal Big Bang's Smoking Gun. New York Times. Posted on nytimes.com March 17, 2014, accessed March 17, 2014.
- Lisle, J. 2003. Light-travel time: a problem for the big bang. Creation. 25 (4): 48-49.
- Guth, A. The Inflationary Universe: Alan Guth. Edge. Posted on edge.org November 19, 2002, accessed March 17, 2014.
- Cho, Adrian. Doubts Shroud Big Bang Discovery. Science. Posted on sciencemag.org May 19, 2014 accessed May 21, 2014.
- Steinhardt, P. 2014. Big Bang blunder bursts the multiverse bubble. Nature. 510 (7503): 9.
- Hebert, J. 2013. The Planck Data and the Big Bang. Creation Science Update. Posted on icr.org April 3, 2013, accessed September 24, 2014.
- Adam, R. et al. 2014. Planck intermediate results. XXX. The angular power spectrum of polarized dust emission at intermediate and high Galactic latitudes. Submitted to Astronomy and Astrophysics. Pre-print submitted to arxiv.org on September 19, 2014, accessed September 24, 2014.
- Parnell, B. A. Higgs Boson Seems to Prove that the Universe Doesn't Exist. Forbes.com. Posted on forbes.com June 24, 2014, accessed September 24, 2014.
- Hebert, J. 2014. 'Smoking Gun' Evidence of Inflation? Creation Science Update. Posted on icr.org March 21, 2014, accessed September 24, 2014.
Image credit: ESA/NASA/JPL-Caltech
* Dr. Hebert is Research Associate at the Institute for Creation Research and received his Ph.D. in physics from the University of Texas at Dallas.
Article posted on October 13, 2014. | 0.850286 | 3.875921 |
At CCRG, we are interested in studying the final fate of the inner cores of stars. Stellar cores also known as protostars form from the gravitational collapse of dense molecular clouds. The protostars rotational speed increases causing an increase in temperature and a protoplanetary disk to form around it. Later on, hydrogen is converted to helium inside the core, and then a main sequence star is formed. Once the core hydrogen is depleted, the core shrinks, and the internal temperature increases and causes the outer shell of hydrogen to ignite. The helium core contracts and increases in temperature. The star then becomes a red giant, until the core is hot enough to turn helium into carbon. What happens next depends on the mass of the star. If the star is lower mass, a white dwarf will form. If it is massive, a supernova may occur and leave behind a neutron star or just collapse into a black hole if it is even more massive.
Few events match the grandeur of supernovae and none surpass their raw power. Viewed on a cosmic scale, supernovae light up galaxies in spectacular explosions that mix the interstellar and intergalactic media. They make most of the elements in the universe, including those that form our own planet and bodies, and they give birth to the most exotic states of matter known - neutron stars and black holes. However, though supernovae have been at the forefront of astronomical research for the better part of a century, the mechanism by which they explode is not known. Supernovae are inherently multi-dimensional objects in which convection, hydrodynamic instabilities, and neutrino transport play central roles. The image on the is from a 3D core-collapse supernova simulation.
Computational work at CCRG in this area focuses on both the modeling both isolated and binary star systems which requires the use of very sophisticated, scalable software based on complex hydrodynamical models deployed on large multi-core machines. | 0.859505 | 3.802111 |
Astrophysicists have developed AI software to help scientists automatically detect and describe galaxies snapped by telescopes surveying the distant sky.
The program, known as Morpheus, was built over a two-year period by a computer scientist and an astrophysicist at the University of California, Santa Cruz.
Morpheus employs a range of computer vision algorithms, including a neural network, that segments objects in the image from the empty background of space, and analyses each detected galaxy pixel-by-pixel to classify its type, whether it’s disk, spheroidal, or irregular shaped. The goal is to trawl through petabytes of images, picking out faraway systems, far faster than humans can.
A paper detailing the code was published in The Astrophysical Journal this week.
The software supports images in the Flexible Image Transport System (FITS) format widely used for astronomical data. That means Morpheus can directly analyse a telescope’s data without having to convert it to other formats, like JPEG or PNG, first.
The programmers trained their system on 7,600 galaxy images snapped by NASA’s Hubble Space Telescope and checked by human astronomers. Brant Robertson, who worked on the code, told The Register it has high accuracy rates for galaxies that are more well-defined.
“When expert astronomers agree on the galaxy classification, Morpheus is 82 to 98 per cent accurate depending on the class of object," he said. "When detecting objects, Morpheus recovers over 98 per cent of the galaxies in the survey data used to train the model.” It may struggle if a galaxy appears blurry or is particularly oddly shaped, in other words.
AI beats astroboffins at sniffing out fast radio bursts amid the universe's clutterREAD MORE
The code for Morpheus is available here, though it probably won't run that quickly unless you have a supercomputer to hand. Luckily, the folks over at UC Santa Cruz have Lux, a system that contains "dozens of nodes that each have two 32GB Nvidia V100 GPUs."
"We are trying to make the code easy to use. We've provided tutorials in the form of Jupyter notebooks that show how to use Morpheus on existing data," Robertson told El Reg.
"The code will work on CPUs if needed, but it's optimized for use with GPUs. If people have an Nvidia GPU on their home system for gaming and access to the GPU enabled version of TensorFlow, then they can get pretty good performance from the model."
Robertson, a professor of astronomy and astrophysics, worked with Ryan Hausen, a computer science graduate student, to build the framework, which they hope can be used with data from the future Legacy Survey of Space and Time (LSST). That survey will start in 2022 when the Vera C. Rubin Observatory, under construction in Chile, has been built.
The LSST will employ a large eight-metre telescope attached to a 3.2 gigapixel camera to capture the entire southern hemisphere every three days over ten years. It’s expected to haul in 200 petabytes of data. Pictures of space may be pretty to look at, when there’s billions of objects to study in the images, it starts to slip into tedium, hence the need for AI automation.
Humans won’t be able to manually look through each image, anyway. “There are some things we simply cannot do as humans, so we have to find ways to use computers to deal with the huge amount of data that will be coming in over the next few years from large astronomical survey projects," said Robertson.
And that's where Morpheus comes in handy, automatically detecting galaxies among stars and planets, and classifying each one by its type, leaving boffins enough spare time to put on a cuppa at least. ®
Sponsored: Ransomware has gone nuclear | 0.852697 | 3.62648 |
The brilliant flash of light created by Deep Impact as it smashed into Tempel 1. Image credit: NASA/JPL. Click to enlarge.
The hyper-speed demise of NASA’s Deep Impact probe generated an immense flash of light, which provided an excellent light source for the two cameras on the Deep Impact mothership. Deep Impact scientists theorize the 820-pound impactor vaporized deep below the comet’s surface when the two collided at 1:52 am July 4, at a speed of about 10 kilometers per second (6.3 miles per second or 23,000 miles per hour).
“You can not help but get a big flash when objects meet at 23,000 miles per hour,” said Deep Impact co-investigator Dr. Pete Schultz of Brown University, Providence, R.I. “The heat produced by impact was at least several thousand degrees Kelvin and at that extreme temperature just about any material begins to glow. Essentially, we generated our own incandescent photo flash for less than a second.”
“They say a picture can speak a thousand words,” said Deep Impact Project Manager Rick Grammier of NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “But when you take a look at some of the ones we captured in the early morning hours of July 4, 2005 I think you can write a whole encyclopedia.”
At a news conference held later on July 4, Deep Impact team members displayed a movie depicting the final moments of the impactor’s life. The final image from the impactor was transmitted from the short-lived probe three seconds before it met its fiery end.
“The final image was taken from a distance of about 30 kilometers (18.6 miles) from the comet’s surface,” said Deep Impact Principal Investigator Dr. Michael A’Hearn of the University of Maryland, College Park. “From that close distance we can resolve features on the surface that are less than 4 meters (about 13 feet) across. When I signed on for this mission I wanted to get a close-up look at a comet, but this is ridiculous? in a great way.”
The Deep Impact scientists are not the only ones taking a close look at their collected data. The mission’s flight controller team is analyzing the impactor’s final hours of flight. When the real-time telemetry came in after the impactor’s first rocket firing, it showed the impactor moving away from the comet’s path.
“It is fair to say we were monitoring the flight path of the impactor pretty closely,” said Deep Impact navigator Shyam Bhaskaran of JPL. “Due to the flight software program, this initial maneuver moved us seven kilometers off course. This was not unexpected but at the same time not something we hoped to see. But then the second and third maneuvers put us right where we wanted to be.”
The Deep Impact mission was implemented to provide a glimpse beneath the surface of a comet, where material from the solar system’s formation remains relatively unchanged. Mission scientists hoped the project would answer basic questions about how the solar system formed, by providing an in-depth picture of the nature and composition of the frozen celestial travelers known as comets. The University of Maryland is responsible for overall Deep Impact mission science, and project management is handled by JPL. The spacecraft was built for NASA by Ball Aerospace & Technologies Corporation, Boulder, Colo.
For information about Deep Impact on the Internet, visit http://www.nasa.gov/deepimpact.
Original Source: NASA News Release | 0.860623 | 3.365684 |
Spectrum indicating atmosphere over rings. Image credit: NASA/JPL/SSI/SWRI/UCL Click to enlarge
Data from the NASA/ESA/ASI Cassini spacecraft indicate that Saturn’s majestic ring system has its own atmosphere – separate from that of the planet itself.
During its close fly-bys of the ring system, instruments on Cassini have been able to determine that the environment around the rings is like an atmosphere, composed principally of molecular oxygen.
This atmosphere is very similar to that of Jupiter’s moons Europa and Ganymede.
The finding was made by two instruments on Cassini, both of which have European involvement: the Ion and Neutral Mass Spectrometer (INMS) has co-investigators from USA and Germany, and the Cassini Plasma Spectrometer (CAPS) instrument has co-investigators from US, Finland, Hungary, France, Norway and UK.
Saturn’s rings consist largely of water ice mixed with smaller amounts of dust and rocky matter. They are extraordinarily thin: though they are 250 000 kilometres or more in diameter they are no more than 1.5 kilometres thick.
Despite their impressive appearance, there is very little material in the rings – if the rings were compressed into a single body it would be no more than 100 kilometres across.
The origin of the rings is unknown. Scientists once thought that the rings were formed at the same time as the planets, coalescing out of swirling clouds of interstellar gas 4000 million years ago. However, the rings now appear to be young, perhaps only hundreds of millions of years old.
Another theory suggests that a comet flew too close to Saturn and was broken up by tidal forces. Possibly one of Saturn’s moons was struck by an asteroid smashing it to pieces that now form the rings.
Though Saturn may have had rings since it formed, the ring system is not stable and must be regenerated by ongoing processes, probably the break-up of larger satellites.
Water molecules are first driven off the ring particles by solar ultraviolet light. They are then split into hydrogen, and molecular and atomic oxygen, by photodissocation. The hydrogen gas is lost to space, the atomic oxygen and any remaining water are frozen back into the ring material due to the low temperatures, and this leaves behind a concentration of oxygen molecules.
Dr Andrew Coates, co-investigator for CAPS, from the Mullard Space Science Laboratory (MSSL) at University College London, said: “As water comes off the rings, it is split by sunlight; the resulting hydrogen and atomic oxygen are then lost, leaving molecular oxygen.
“The INMS sees the neutral oxygen gas, CAPS sees molecular oxygen ions and an ?electron view? of the rings. These represent the ionised products of that oxygen and some additional electrons driven off the rings by sunlight.”
Dr Coates said the ring atmosphere was probably kept in check by gravitational forces and a balance between loss of material from the ring system and a re-supply of material from the ring particles.
Last month, Cassini-Huygens mission scientists celebrated the spacecraft’s first year in orbit around Saturn. Cassini performed its Saturn Orbit Insertion (SOI) on 1 July 2004 after its six-year journey to the ringed planet, travelling over three thousand million kilometres.
The Cassini-Huygens mission is a co-operative project of NASA, ESA and ASI, the Italian space agency.
Original Source: ESA Science | 0.856533 | 4.015042 |
Some very clever people have figured out how to use MSL Curiosity’s navigation sensors to measure the gravity of a Martian mountain. What they’ve found contradicts previous thinking about Aeolis Mons, aka Mt. Sharp. Aeolis Mons is a mountain in the center of Gale Crater, Curiosity’s landing site in 2012.
Gale Crater is a huge impact crater that’s 154 km (96 mi) in diameter and about 3.5 billion years old. In the center is Aeolis Mons, a mountain about 5.5 km (18,000 ft) high. Over an approximately 2 billion year period, sediments were deposited either by water, wind, or both, creating the mountain. Subsequent erosion reduced the mountain to its current form.
Now a new paper published in Science, based on gravity measurements from Curiosity, shows that Aeolis Mons’ bedrock layers are not as dense as once thought.
Curiosity’s gravity measurements recall earlier days in Solar System exploration, when Apollo 16 astronauts used their Moon buggy, or Lunar Roving Vehicle, to measure the Moon’s gravity. That was way back in 1972. In our time, its robots instead of astronauts that are setting foot on distant worlds, but the spirit of exploration, and the science, is the same.
The new study is based on gravimetry, the measurement of very small changes in gravitational fields. It can only be done on the ground, versus large-scale gravimetry done from an orbiting spacecraft. To take these measurements, the research team re-purposed Curiosity’s accelerometers, instruments onboard the rover that are used for navigation.
When coupled with gyroscopes, accelerometers tell the rover where it is on Mars and which way it’s facing. Smart phones have them too, and they’re used by apps that allow you to point your phone at the sky and read the names of stars. Of course, Curiosity’s gyroscopes and accelerometers are far more accurate than anything inside a smart phone.
“I’m thrilled that creative scientists and engineers are still finding innovative ways to make new scientific discoveries with the rover.”
Study co-author Ashwin Vasavada, Curiosity’s project scientist, NASA’s Jet Propulsion Laboratory, Pasadena, California.
The team measured the change in the gravitational field of Mt. Sharp as the rover climbed it. Gravity weakens with altitude, and Curiosity’s instruments were re-calibrated to measure these tiny changes. From those changes, the density of the underlying rock was inferred.
The gravimetric measurements showed that the rock under the mountain is less dense than thought, meaning it is relatively porous. This goes against previous research showing that the crater floor used to be buried under several kilometers of rock.
“The lower levels of Mount Sharp are surprisingly porous,” said lead author Kevin Lewis of Johns Hopkins University. “We know the bottom layers of the mountain were buried over time. That compacts them, making them denser. But this finding suggests they weren’t buried by as much material as we thought.”
In their paper, the researchers show that their measurements include bedrock to a depth of several hundred meters, not mere surface rock. They measured an average density of 1680 ± 180 kg m -3. That’s much less dense than typical sedimentary rocks. Since sedimentary rocks gain density by being compacted underneath a greater accumulation of rock, their low density suggests they weren’t buried that deeply.
In a way, these findings only add to the mystery of Mt. Sharp’s formation, structure, and erosion. For instance, we still don’t know if Gale Crater was once completely filled with sediment, and that sediment was eroded to the modern shape of Mt. Sharp. It may be that only a portion of the crater was ever filled with sediment.
On the other hand, the summit of Mt. Sharp is higher than the rim of the crater. Based on that, other research has proposed Gale Crater was completely filled with sediment, and that Mt. Sharp is the remnant of a much taller mountain than we see now. But if that’s the case, then these new findings go counter to that. If these rocks at the lower reaches of Mt. Sharp were buried so deeply, their measured density would be much higher.
Another line of reasoning relies on Aeolian sedimentation. Aeolian means wind-driven. In this hypothesis, the wind carried sediment into the crater, depositing it onto Mt. Sharp and building it up into more or less the form it takes now. In that case, the rocks measured by Curiosity would never have been compacted. That would explain their low-density when compared to other buried, sedimentary rocks.
“There are still many questions about how Mount Sharp developed, but this paper adds an important piece to the puzzle,” said study co-author Ashwin Vasavada, Curiosity’s project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “I’m thrilled that creative scientists and engineers are still finding innovative ways to make new scientific discoveries with the rover,” he added.
This study won’t solve the debate over Gale Crater and Mt. Sharp, but it does add some clarity. It also shows the usefulness of rover-based gravimetric measurements in understanding the history of Mars.
Plus, it’s just really cool.
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Mars, otherwise known as the “Red Planet”, is the fourth planet of our Solar System and the second smallest (after Mercury). Named after the Roman God of war, its nickname comes from its reddish appearance, which has to do with the amount of iron oxide prevalent on its surface. Every couple of years, when Mars is at opposition to Earth (i.e. when the planet is closest to us), it is most visible in the night sky.
Because of this, humans have been observing it for millennia, and its appearance in the heavens has played a large role in the mythology and astrological systems of many cultures. And in the modern era, it has been a veritable treasure trove of scientific discoveries, which have informed our understanding of our Solar System and its history.
Size, Mass and Orbit:
Mars has a radius of approximately 3,396 km at its equator, and 3,376 km at its polar regions – which is the equivalent of roughly 0.53 Earths. While it is roughly half the size of Earth, it’s mass – 6.4185 x 10²³ kg – is only 0.151 that of Earth’s. It’s axial tilt is very similar to Earth’s, being inclined 25.19° to its orbital plane (Earth’s axial tilt is just over 23°), which means Mars also experiences seasons.
At its greatest distance from the Sun (aphelion), Mars orbits at a distance of 1.666 AUs, or 249.2 million km. At perihelion, when it is closest to the Sun, it orbits at a distance of 1.3814 AUs, or 206.7 million km. At this distance, Mars takes 686.971 Earth days, the equivalent of 1.88 Earth years, to complete a rotation of the Sun. In Martian days (aka. Sols, which are equal to one day and 40 Earth minutes), a Martian year is 668.5991 Sols.
Composition and Surface Features:
With a mean density of 3.93 g/cm³, Mars is less dense than Earth, and has about 15% of Earth’s volume and 11% of Earth’s mass. The red-orange appearance of the Martian surface is caused by iron oxide, more commonly known as hematite (or rust). The presence of other minerals in the surface dust allow for other common surface colors, including golden, brown, tan, green, and others.
As a terrestrial planet, Mars is rich in minerals containing silicon and oxygen, metals, and other elements that typically make up rocky planets. The soil is slightly alkaline and contains elements such as magnesium, sodium, potassium, and chlorine. Experiments performed on soil samples also show that it has a basic pH of 7.7.
Although liquid water cannot exist on Mars’ surface, owing to its thin atmosphere, large concentrations of ice water exist within the polar ice caps – Planum Boreum and Planum Australe. In addition, a permafrost mantle stretches from the pole to latitudes of about 60°, meaning that water exists beneath much of the Martian surface in the form of ice water. Radar data and soil samples have confirmed the presence of shallow subsurface water at the middle latitudes as well.
Like Earth, Mars is differentiated into a dense metallic core surrounded by a silicate mantle. This core is composed of iron sulfide, and thought to be twice as rich in lighter elements than Earth’s core. The average thickness of the crust is about 50 km (31 mi), with a maximum thickness of 125 km (78 mi). Relative to the sizes of the two planets, Earth’s crust (averaging 40 km or 25 mi) is only one third as thick.
Current models of its interior imply that the core region measures between 1,700 – 1850 kilometers (1,056 – 1150 mi) in radius, consisting primarily of iron and nickel with about 16–17% sulfur. Due to its smaller size and mass, the force of gravity on the surface of Mars is only 37.6% of that on Earth. An object falling on Mars falls at 3.711 m/s², compared to 9.8 m/s² on Earth.
The surface of Mars is dry and dusty, with many similar geological features to Earth. It has mountain ranges and sandy plains, and even some of the largest sand dunes in the Solar System. It also has the largest mountain in the Solar System, the shield volcano Olympus Mons, and the longest, deepest chasm in the Solar System: Valles Marineris.
The surface of Mars has also been pounded by impact craters, many of which date back billions of years. These craters are so well preserved because of the slow rate of erosion that happens on Mars. Hellas Planitia, also called the Hellas impact basin, is the largest crater on Mars. Its circumference is approximately 2,300 kilometers, and it is nine kilometers deep.
Mars also has discernible gullies and channels on its surface, and many scientists believe that liquid water used to flow through them. By comparing them to similar features on Earth, it is believed these were were at least partially formed by water erosion. Some of these channels are quite large, reaching 2,000 kilometers in length and 100 kilometers in width.
Mars has two small satellites, Phobos and Deimos. These moons were discovered in 1877 by the astronomer Asaph Hall and were named after mythological characters. In keeping with the tradition of deriving names from classical mythology, Phobos and Deimos are the sons of Ares – the Greek god of war that inspired the Roman god Mars. Phobos represents fear while Deimos stands for terror or dread.
Phobos measures about 22 km (14 mi) in diameter, and orbits Mars at a distance of 9234.42 km when it is at periapsis (closest to Mars) and 9517.58 km when it is at apoapsis (farthest). At this distance, Phobos is below synchronous altitude, which means that it takes only 7 hours to orbit Mars and is gradually getting closer to the planet. Scientists estimate that in 10 to 50 million years, Phobos could crash into Mars’ surface or break up into a ring structure around the planet.
Meanwhile, Deimos measures about 12 km (7.5 mi) and orbits the planet at a distance of 23455.5 km (periapsis) and 23470.9 km (apoapsis). It has a longer orbital period, taking 1.26 days to complete a full rotation around the planet. Mars may have additional moons that are smaller than 50- 100 meters (160 to 330 ft) in diameter, and a dust ring is predicted between Phobos and Deimos.
Scientists believe that these two satellites were once asteroids that were captured by the planet’s gravity. The low albedo and the carboncaceous chondrite composition of both moons – which is similar to asteroids – supports this theory, and Phobos’ unstable orbit would seem to suggest a recent capture. However, both moons have circular orbits near the equator, which is unusual for captured bodies.
Another possibility is that the two moons formed from accredit material from Mars early in its history. However, if this were true, their compositions would be similar to Mars itself, rather than similar to asteroids. A third possibility is that a body impacted the Martian surface, who’s material was ejected into space and re-accreted to form the two moons, similar to what is believed to have formed the Earth’s Moon.
Atmosphere and Climate:
Planet Mars has a very thin atmosphere which is composed of 96% carbon dioxide, 1.93% argon and 1.89% nitrogen along with traces of oxygen and water. The atmosphere is quite dusty, containing particulates that measure 1.5 micrometers in diameter, which is what gives the Martian sky a tawny color when seen from the surface. Mars’ atmospheric pressure ranges from 0.4 – 0.87 kPa, which is equivalent to about 1% of Earth’s at sea level.
Because of its thin atmosphere, and its greater distance from the Sun, the surface temperature of Mars is much colder than what we experience here on Earth. The planet’s average temperature is -46 °C (-51 °F), with a low of -143 °C (-225.4 °F) during the winter at the poles, and a high of 35 °C (95 °F) during summer and midday at the equator.
The planet also experiences dust storms, which can turn into what resembles small tornadoes. Larger dust storms occur when the dust is blown into the atmosphere and heats up from the Sun. The warmer dust filled air rises and the winds get stronger, creating storms that can measure up to thousands of kilometers in width and last for months at a time. When they get this large, they can actually block most of the surface from view.
Trace amounts of methane have also been detected in the Martian atmosphere, with an estimated concentration of about 30 parts per billion (ppb). It occurs in extended plumes, and the profiles imply that the methane was released from specific regions – the first of which is located between Isidis and Utopia Planitia (and the second in Arabia Terra .
It is estimated that Mars must produce 270 tonnes of methane per year. Once released into the atmosphere, the methane can only exist for a limited period of time (0.6 – 4 years) before it is destroyed. Its presence despite this short lifetime indicates that an active source of the gas must be present.
Several possible sources have been suggested for the presence of this methane, ranging from volcanic activity, cometary impacts, and the presence of methanogenic microbial life forms beneath the surface. Methane could also be produced by a non-biological process called serpentinization involving water, carbon dioxide, and the mineral olivine, which is known to be common on Mars.
The Curiosity rover has made several measurements for methane since its deployment to the Martian surface in August of 2012. The first measurements, which were made using its Tunable Laser Spectrometer (TLS), indicated that there were less than 5 ppb at its landing site (Bradbury Landing). A subsequent measurement performed on September 13th detected no discernible traces.
On December 16th, 2014, NASA reported that the Curiosity rover had detected a “tenfold spike”, likely localized, in the amount of methane in the Martian atmosphere. Samples measurements taken between late 2013 and early 2014 showed an increase of 7 ppb; whereas before and after that, readings averaged around one-tenth that level.
Ammonia was also tentatively detected on Mars by the Mars Express satellite, but with a relatively short lifetime. It is not clear what produced it, but volcanic activity has been suggested as a possible source.
Earth astronomers have a long history of observing the “Red Planet”, both with the naked eye and with instrumentation. The first recorded mentions of Mars as a wandering object in the night sky were made by Ancient Egyptian astronomers, who by 1534 BCE were familiar with the planet’s “retrograde motion”. In essence, they deduced that the planet, though it appeared to be a bright star, moved differently than the other stars, and that it would occasionally slow down and reverse course before returning to its original course.
By the time of the Neo-Babylonian Empire (626 BCE – 539 BCE), astronomers were making regular records of the position of the planets, systematic observations of their behavior and even arithmetic methods for predicted the positions of the planets. For Mars, this included detailed accounts of its orbital period and its passage through the zodiac.
By classical antiquity, the Greeks were making additional observations on Mars’ behavior that helped them to understand its position in the Solar System. In the 4th century BCE, Aristotle noted that Mars disappeared behind the Moon during an occultation, which indicated it was farther away than the Moon.
Ptolemy, a Greek-Egyptian astronomer of Alexandria (90 CE – ca. 168 CE), constructed a model of the universe in which he attempted to resolve the problems of the orbital motion of Mars and other bodies. In his multi-volume collection Almagest, he proposed that the motions of heavenly bodies were governed by “wheels within wheels”, which attempted to explain retrograde motion. This became the authoritative treatise on Western astronomy for the next fourteen centuries.
Literature from ancient China confirms that Mars was known by Chinese astronomers by at least the fourth century BCE. In the fifth century CE, the Indian astronomical text Surya Siddhanta estimated the diameter of Mars. In the East Asian cultures, Mars is traditionally referred to as the “fire star”, based on the Five elements.
The Ptolemaic model of the Solar System remained canon for western astronomers until the Scientific Revolution (16th to 18th century CE). Thanks to Copernicus’ heliocentric model, and Galileo’s use of the telescope, Mars proper position relative to Earth and the Sun began to become known. The invention of the telescope also allowed astronomers to measure the diurnal parallax of Mars and determine its distance.
This was first performed by Giovanni Domenico Cassini in 1672, but his measurements were hampered by the low quality of his instruments. During the 17th century, Tycho Brahe also employed the diurnal parallax method, and his observations were measured later by Johannes Kepler. During this time, Dutch astronomer Christiaan Huygens also drew the first map of Mars which included terrain features.
By the 19th century, the resolution of telescopes improved to the point that surface features on Mars could be identified. This led Italian astronomer Giovanni Schiaparelli to produce the first detailed map of Mars after viewing it at opposition on September 5th, 1877. These maps notably contained features he called canali – a series of long, straight lines on the surface of Mars – which he named after famous rivers on Earth. These were later revealed to be an optical illusion, but not before spawning a wave of interest in Mars’ “canals”.
In 1894, Percival Lowell – inspired by Schiaparelli’s map – founded an observatory which boasted two of the largest telescopes of the time – 30 and 45 cm (12 and 18 inch). Lowell published several books on Mars and life on the planet, which had a great influence on the public, and the canals were also observed by other astronomers, like Henri Joseph Perrotin and Louis Thollon of Nice.
Seasonal changes like the diminishing of the polar caps and the dark areas formed during Martian summer, in combination with the canals, led to speculation about life on Mars. The term “Martian” became synonymous with extra-terrestrial for quite some time, though telescopes never reached the resolution needed to provide any proof. Even in the 1960s, articles were published on Martian biology, putting aside explanations other than life for the seasonal changes on Mars.
Exploration of Mars:
With the advent of the space age, probes and landers began to be sent to Mars by the late 20th century. These have yielded a wealth of information on the geology, natural history, and even the habitability of the planet, and increased our knowledge of the planet immensely. And while modern missions to Mars have dispelled the notions of there being a Martian civilization, they have indicated that life may have existed there at one time.
Efforts to explore Mars began in earnest in the 1960s. Between 1960 and 1969, the Soviets launched nine unmanned spacecraft towards Mars, but all failed to reach the planet. In 1964, NASA began launching Mariner probes towards Mars. This began with Mariner 3 and Mariner 4, two unmanned probes that were designed to carry out the first flybys of Mars. The Mariner 3 mission failed during deployment, but Mariner 4 – which launched three weeks later – successfully made the 7½-month long voyage to Mars.
Mariner 4 captured the first close-up photographs of another planet (showing impact craters) and provided accurate data about the surface atmospheric pressure, and noted the absence of a Martian magnetic field and radiation belt. NASA continued the Mariner program with another pair of flyby probes – Mariner 6 and 7 – which reached the planet in 1969.
During the 1970s, the Soviets and the US competed to see who could place the first artificial satellite in orbit of Mars. The Soviet program (M-71) involved three spacecraft – Cosmos 419 (Mars 1971C), Mars 2 and Mars 3. The first, a heavy orbiter, failed during launch. The subsequent missions, Mars 2 and Mars 3, were combinations of an orbiter and a lander, and would be the first rovers to land on a body other than the Moon.
They were successfully launched in mid-May 1971 and reached Mars about seven months later. On November 27th, 1971, the lander of Mars 2 crash-landed due to an on-board computer malfunction and became the first man-made object to reach the surface of Mars. In December 2nd, 1971, the Mars 3 lander became the first spacecraft to achieve a soft landing, but its transmission was interrupted after 14.5 seconds.
Meanwhile, NASA continued with the Mariner program, and scheduled Mariner 8 and 9 for launch in 1971. Mariner 8 also suffered a technical failure during launch and crashed into the Atlantic Ocean. But the Mariner 9 mission managed to not only make it to Mars, but became the first spacecraft to successfully establish orbit around it. Along with Mars 2 and Mars 3, the mission coincided with a planet-wide dust storm. During this time, the Mariner 9 probe managed to rendezvous and take some photos of Phobos.
When the storm cleared sufficiently, Mariner 9 took photos that were the first to offer more detailed evidence that liquid water might have flowed on the surface at one time. Nix Olympica, which was one of only a few features that could be seen during the planetary duststorm, was also determined to be the highest mountain on any planet in the entire Solar System, leading to its reclassification as Olympus Mons.
In 1973, the Soviet Union sent four more probes to Mars: the Mars 4 and Mars 5 orbiters and the Mars 6 and Mars 7 fly-by/lander combinations. All missions except Mars 7 sent back data, with Mars 5 being most successful. Mars 5 transmitted 60 images before a loss of pressurization in the transmitter housing ended the mission.
By 1975, NASA launched Viking 1 and 2 to Mars, which consisted of two orbiters and two landers. The primary scientific objectives of the lander mission were to search for biosignatures and observe the meteorologic, seismic and magnetic properties of Mars. The results of the biological experiments on board the Viking landers were inconclusive, but a reanalysis of the Viking data published in 2012 suggested signs of microbial life on Mars.
The Viking orbiters revealed further data that water once existed on Mars, indicating that large floods carved deep valleys, eroded grooves into bedrock, and traveled thousands of kilometers. In addition, areas of branched streams in the southern hemisphere, suggest that surface once experienced rainfall.
Mars was not explored again until the 1990’s, at which time, NASA commenced the Mars Pathfinder mission – which consisted of a spacecraft that landed a base station with a roving probe (Sojourner) on the surface. The mission landed on Mars on July 4th, 1987, and provided a proof-of-concept for various technologies that was would be used by later missions, such as an airbag landing system and automated obstacle avoidance.
This was followed by the Mars Global Surveyor (MGS), a mapping satellite that reached Mars on September 12th, 1997 and began its mission on March 1999. From a low-altitude, nearly polar orbit, it observed Mars over the course of one complete Martian year (nearly two Earth years) and studied the entire Martian surface, atmosphere, and interior, returning more data about the planet than all previous Mars missions combined.
Among key scientific findings, the MGS took pictures of gullies and debris flows that suggest there may be current sources of liquid water, similar to an aquifer, at or near the surface of the planet. Magnetometer readings showed that the planet’s magnetic field is not globally generated in the planet’s core, but is localized in particular areas of the crust.
The spacecraft’s laser altimeter also gave scientists their first 3-D views of Mars’ north polar ice cap. On November 5th, 2006, MGS lost contact with Earth, and all efforts by NASA to restore communication ceased by January 28th, 2007.
In 2001, NASA’s Mars Odyssey orbiter arrived at Mars. Its mission was to use spectrometers and imagers to hunt for evidence of past or present water and volcanic activity on Mars. In 2002, it was announced that the probe had detected large amounts of hydrogen, indicating that there are vast deposits of water ice in the upper three meters of Mars’ soil within 60° latitude of the south pole.
On June 2, 2003, the European Space Agency’s (ESA) launched the Mars Express spacecraft, which consisted of the Mars Express Orbiter and the lander Beagle 2. The orbiter entered Martian orbit on December 25th, 2003, and Beagle 2 entered Mars’ atmosphere on the same day. Before the ESA lost contact with the probe, the Mars Express Orbiter confirmed the presence of water ice and carbon dioxide ice at the planet’s south pole, while NASA had previously confirmed their presence at the north pole of Mars.
In 2003, NASA also commenced the Mars Exploration Rover Mission (MER), an ongoing robotic space mission involving two rovers – Spirit and Opportunity – exploring the planet Mars. The mission’s scientific objective was to search for and characterize a wide range of rocks and soils that hold clues to past water activity on Mars.
The Mars Reconnaissance Orbiter (MRO) is a multipurpose spacecraft designed to conduct reconnaissance and exploration of Mars from orbit. The MRO launched on August 12th, 2005, and attained Martian orbit on March 10th, 2006. The MRO contains a host of scientific instruments designed to detect water, ice, and minerals on and below the surface.
Additionally, the MRO is paving the way for upcoming generations of spacecraft through daily monitoring of Martian weather and surface conditions, searching for future landing sites, and testing a new telecommunications system that will speed up communications between Earth and Mars.
The NASA Mars Science Laboratory (MSL) mission and its Curiosity rover landed on Mars in the Gale Crater (at a landing site named “Bradbury Landing”) on August 6th, 2012. The rover carries instruments designed to look for past or present conditions relevant to the habitability of Mars, and has made numerous discoveries about atmospheric and surface conditions on Mars, as well as the detection of organic particles.
NASA’s Mars Atmosphere and Volatile EvolutioN Mission (MAVEN) orbiter was launched on November 18th, 2013, and reached Mars on September 22nd, 2014. The purpose of the mission is to study the atmosphere of Mars and also serve as a communications relay satellite for robotic landers and rovers on the surface.
Most recently, the Indian Space Research Organisation (ISRO) launched the Mars Orbiter Mission (MOM, also called Mangalyaan) on November 5th, 2013. The orbiter successfully reached Mars on September 24th, 2014, and was the first spacecraft to achieve orbit on the first try. A technology demonstrator, who’s secondary purpose is to study the Martian atmosphere, MOM is India’s first mission to Mars, and has made the ISRO the fourth space agency to reach the planet.
Future missions to Mars include NASA’s Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSIGHT) lander. This mission, which is planned for launch in 2016, involves placing a stationary lander equipped with a seismometer and heat transfer probe on the surface of Mars. The probe will then deploy these instruments into the ground to study the planets interior and get a better understanding of its early geological evolution.
The ESA and Roscosmos are also collaborating on a large mission to search for biosignatures of Martian life, known as Exobiology on Mars (or ExoMars). Consisting of an orbiter that will be launched in 2016, and a lander that will be deployed to the surface by 2018, the purpose of this mission will be to map the sources of methane and other gases on Mars that would indicate the presence of life, past and present.
The United Arab Emirates also has a plan to send an orbiter to Mars by 2020. Known as Mars Hope, the robotic space probe will be deployed in orbit around Mars for the sake of studying its atmosphere and climate. This spacecraft will be the first to be deployed by an Arab state in orbit of another planet, and is expected to involve collaboration from the University of Colorado, the University of California, Berkeley and Arizona State University, as well the French space agency (CNES).
Numerous federal space agencies and private companies have plans to send astronauts to Mars within the not-too-distant future. For instance, NASA has confirmed that it plans to conduct a manned mission to Mars by 2030. In 2004, human exploration of Mars was identified as a long-term goal in the Vision for Space Exploration – a public document released by the Bush administration.
In 2010, President Barack Obama announced his administration’s space policy, which included increasing NASA funding by $6 billion over five years and completing the design of a new heavy-lift launch vehicle by 2015. He also predicted a U.S.-crewed orbital Mars mission by the mid-2030s, preceded by an asteroid mission by 2025.
The ESA also has plans to land humans on Mars between 2030 and 2035. This will be preceded by successively larger probes, starting with the launch of the ExoMars probe and a planned joint NASA-ESA Mars sample return mission.
Robert Zubrin, founder of the Mars Society, plans to mount a low-cost human mission known as Mars Direct. According to Zubrin, the plan calls for the use of heavy-lift Saturn V class rockets to send human explorers to the Red Planet. A modified proposal, known as “Mars to Stay”, involves a possible one-way trip, where the astronauts would become Mars’ first colonists.
Similarly, MarsOne, a Netherlands-based non-profit organization, hopes to establish a permanent colony on the planet beginning in 2027. The original concept included launching a robotic lander and orbiter as early as 2016 to be followed by a human crew of four in 2022. Subsequent crews of four will be sent every few years, and funding is expected to be provided in part by a reality TV program that will document the journey.
SpaceX and Tesla CEO Elon Musk has also announced plans to establish a colony on Mars. Intrinsic to this plan is the development of the Mars Colonial Transporter (MCT), a spaceflight system that would rely of reusable rocket engines, launch vehicles and space capsules to transport humans to Mars and return to Earth.
As of 2014, SpaceX has begun development of the large Raptor rocket engine for the Mars Colonial Transporter, and a successful test was announced in September of 2016. In January 2015, Musk said that he hoped to release details of the “completely new architecture” for the Mars transport system in late 2015.
In June 2016, Musk stated in the first unmanned flight of the MCT spacecraft would take place in 2022, followed by the first manned MCT Mars flight departing in 2024. In September 2016, during the 2016 International Astronautical Congress, Musk revealed further details of his plan, which included the design for an Interplanetary Transport System (ITS) – an upgraded version of the MCT.
Mars is the most studied planet in the Solar System after Earth. As of the penning of this article, there are 3 landers and rovers on the surface of Mars (Phoenix, Opportunity and Curiosity), and 5 functional spacecraft in orbit (Mars Odyssey, Mars Express, MRO, MOM, and MAVEN). And more spacecraft will be on their way soon.
These spacecraft have sent back incredibly detailed images of the surface of Mars, and helped discover that there was once liquid water in Mars’ ancient history. In addition, they have confirmed that Mars and Earth share many of the same characteristics – such as polar icecaps, seasonal variations, an atmosphere, and the presence of flowing water. They have also shown that organic life can and most likely did live on Mars at one time.
In short, humanity’s obsession with the Red Planet has not waned, and our efforts to explore its surface and understand its history are far from over. In the coming decades, we are likely to be sending additional robotic explorers, and human ones as well. And given time, the right scientific know-how, and whole lot of resources, Mars may even be suitable for habitation someday.
We have written many interesting articles about Mars here at Universe Today. Here’s How Strong Is The Gravity On Mars?, How Long Does It Take To Get To Mars?, How Long Is A Day On Mars?, Mars Compared To Earth, How Can We Live On Mars? | 0.879443 | 3.820931 |
Hubble Maps the Cosmic Web of 'Clumpy' Dark Matter in 3-D
An international team of astronomers using NASA’s Hubble Space Telescope has created the first three-dimensional map of the large-scale distribution of dark matter in the universe.
Image right: The top "sliced" image shows how dark matter evolved from 6.5 billion to 3.5 billion years ago. Dark Matter is an invisible form of matter that accounts for most of the universe’s mass. The bottom image shows dark matter "clumping" together over time confirming theories of how structure formed in our evolving universe. Click image to enlarge. + High resolution Credit: NASA, ESA, CalTech
Dark matter is an invisible form of matter whose total mass in the universe is roughly five times that of “normal” matter (i.e., atoms). It can be thought of as the scaffolding of the universe. The visible matter we see collects inside this scaffolding in the form of stars and galaxies. The first direct detection of dark matter was made this past year through observations of the Bullet Cluster of galaxies.
The new map provides the best evidence yet that normal matter, including all stars and galaxies, collect within the densest concentrations of dark matter.
Mapping dark matter’s distribution in space and time is fundamental to understanding how galaxies grew and clustered over billions of years.
The map stretches halfway back in time to the beginning of the universe, and reveals a network of dark matter filaments, collapsing under the relentless pull of gravity and growing clumpier over time.
Image left: These two false-color images compare the distribution of normal matter (red, left) with dark matter (blue, right) in the universe. The brightness of clumps corresponds to
the density of mass. The comparison will provide insight on how structure formed in the evolving universe under the relentless pull of
gravity. Click image to enlarge. + High resolution Credit: NASA, ESA, CalTech
This is consistent with conventional theories of how structure formed in our evolving universe, which has transitioned from a smooth distribution of matter at the time of the Big Bang.
The researchers used data from Hubble Space Telescope’s largest survey to date of the universe, the Cosmic Evolution Survey (“COSMOS”). The COSMOS field covers a sufficiently wide area of sky – eight times the area of the full Moon – for the large-scale filamentary structure of dark matter to be clearly evident. To add 3-D distance information, the Hubble observations were combined with data from Europe’s Very Large Telescope in Chile, Japan’s Subaru Telescope in Hawaii, the U.S.’s Very Large Array radio telescope in New Mexico, as well as the European Space Agency’s orbiting XMM-Newton X-ray Observatory.
The dark matter map was constructed by measuring the shapes of half a million faraway galaxies.
To reach Hubble, their light has had to travel through intervening dark matter, and the path of the light is slightly deflected by the dark matter’s gravity. The observed, subtle distortion of the galaxies’ shapes was used to reconstruct the distribution of intervening mass along Hubble’s line of sight – a method called weak gravitational lensing.
For astronomers, the challenge of mapping the universe has been similar to mapping a city from nighttime aerial snapshots showing only streetlights. Dark matter is invisible, so only the galaxies can be seen directly.
This new map is equivalent to seeing a city for the first time during the day, where the major arteries and intersections of the asphalt roadways become evident, and a variety of neighborhoods are revealed. Because the survey looks back in time the deeper it looks into the universe, it is also like a time-lapse view of the growth of a city over decades.
Goddard Space Flight Center | 0.822762 | 4.065918 |
Why is the universe being ripped apart? It’s a question that has plagued astronomers since the discovery in the 1990s that the expansion of the universe is accelerating. The story is only further complicated by new observations of distant exploding stars that cast doubt on the leading explanation, called the cosmological constant.
Whatever is causing the universe’s acceleration has been named dark energy, but its origins remain mysterious. Back when Albert Einstein was formulating his general theory of relativity he added a repulsive force to his equations called the cosmological constant, which was meant, at the time, to cause the theory to predict a static universe. Without it, his calculations showed gravity would not result in a steady-state universe, but rather would have caused it to collapse upon itself. When it was later discovered that the universe isn’t static, but expanding, Einstein dropped the constant, reportedly calling it his “biggest blunder.” Decades later, however, when it was revealed that the universe was not merely expanding, but that its dilation was accelerating, scientists retrieved the discarded constant and added it back to the general relativity equations to predict a universe that’s flying apart at increasing speed. The cosmological constant is now the leading idea to account for dark energy, but it only works if what is known as the dark energy equation of state parameter (relating pressure and density), called w, equals –1.
But that is not what the latest experiment, Pan-STARRS (for Panoramic Survey Telescope and Rapid Response System), found. Based on cosmological measurements from other projects combined with Pan-STARRS observations of a special type of stellar explosion called a type Ia supernova, which can be used as a cosmic ruler for measuring astronomical distances, researchers calculated w’s value at −1.186. “If w has this value, it means that the simplest model to explain dark energy is not true,” says Armin Rest of the Space Telescope Science Institute (STScI) in Baltimore, lead author of a paper reporting the results posted October 22 to the astrophysics preprint Web site arXiv. Rest cautioned, however, that the results are too preliminary to seriously doubt the cosmological constant at this point. “I don’t think we can say now that we’ve really found a discrepancy. We still have to look if this is due to some issues with any of these projects.”
The calculation is based on observations of about 150 type Ia supernovae made between 2009 and 2011 by the Pan-STARRS telescope PS1 in Hawaii. This class of supernova occurs when a particular type of star called a white dwarf reaches its maximum mass limit, which is the same for all white dwarfs, and explodes with a standard brightness. By comparing a supernova’s apparent brightness with its known intrinsic brightness, astronomers can deduce how far away it is. Follow-up spectroscopic observations of the supernova, which break light down to its constituent colors, reveal how much the light’s wavelength has been stretched by the expansion of the universe. With these parameters in hand, the Pan-STARRS researchers combined their data with the findings from other probes of dark energy, such as the observations of the cosmic microwave background light from the European Planck satellite, to calculate the dark energy equation of state parameter.
How much to read into the calculation depends on how uncertain it is, and whether systematic errors associated with the telescope and the analysis skewed the result. “It’s generally accepted that telescope calibration, supernova physics and galaxy properties are big sources of uncertainties, so everyone’s trying to figure these out in different ways,” says Daniel Scolnic of Johns Hopkins University, who led an accompanying paper estimating the data’s uncertainties. “I think that Dan did an excellent job characterizing their systematics,” says Alexander Conley of the University of Colorado at Boulder who worked on a different supernova study called the Supernova Legacy Survey that found similar results. “They still have a lot of work to do to improve the characterization for future papers, but they know that and are working on it.” However, another survey researcher, Julien Guy of University Pierre and Marie Curie in Paris, says the team may have underestimated their systematic error by ignoring an extra source of uncertainty from supernova light-curve models. He’s been in touch with the Pan-STARRS researchers, who are looking into that factor. Ultimately, most experts say the new results are tantalizing, but don’t prove the existence of new physics. “The Pan-STARRS paper presents a very thorough, careful analysis and a solid result, but it doesn't qualitatively change our view of the cosmological parameters,” says Joshua Frieman, an astrophysicist at Fermilab in Batavia, Ill., who was not involved in the research.
The fact that multiple cosmology experiments are producing values of w that diverge from –1, however, is causing many to take notice. “This paper is now the third survey of distant supernovae that’s coming to this conclusion,” says STScI astronomer Adam Riess, a member of the Pan-STARRS team who won the 2011 Nobel Prize in Physics for the discovery of dark energy. “We can’t just say this survey or that survey screwed up. It could be something fundamental to one of these measurements. Or it could be that dark energy is more interesting in a way that actually we hope.” Whereas the cosmological constant explains dark energy mathematically, it does not elucidate why such a force exists. An alternative value of w might indicate that dark energy hasn’t been constant over time, but varies—an idea called quintessence. Either way, more data from Pan-STARRS and other surveys are expected soon to either support or refute the latest value of w. “I expect in the next year or two this will probably either become definitive, or go away,” Riess says. | 0.875103 | 4.080119 |
2I Borisov comet to pass close to Earth and the sun.
A shining comet from beyond our solar system is due to reach its closest point to the sun (and to Earth) on Sunday.
The landmark object is named comet 2I/Borisov because it’s just the second interstellar anything ever spotted in our cosmic neighborhood (hence 2-I) and it was discovered by Crimean amateur astronomer Gennady Borisov, who has a track record of spotting new comets.
In 2017, an interstellar object was seen in our solar system for the first time when the bizarre, oblong Oumuamua was discovered. Its odd shape and apparent acceleration as it disappeared into deep space led to all kinds of theories about its origin, prompting a prominent Harvard astronomer to even suggest it might be a product of some alien intelligence.
Unlike comet Borisov, Oumuamua was first seen after it had already made its closest pass by Earth, so there was little opportunity to study it closely. Comet Borisov was observed in August and scientists have already been able to determine it’s very different from Oumuamua. It’s basically the same as most comets within our own solar system.
Hopefully this latest interstellar interloper will continue to be visible for several more weeks as it continues on its journey. That is, if it doesn’t break up and disintegrate as it passes by the sun. That’s what happened with eagerly anticipated comet ISON in 2013, which was supposed to be the celestial sight of a lifetime, but fizzled on approach as it was broken apart by the sun’s radiation.
Unfortunately, Borisov isn’t going to be bright enough for most backyard astronomers to observe, but the pros have already begun to capture some pretty brilliant images on approach, like the one above. If you have access to a telescope with at least a 30-centimeter (12-inch) aperture, you can try hunting for it in the direction of the constellations Corvus the crow and Crater the cup over the next few nights.
Researchers will continue to gather as much data as they can on Borisov in the coming months. Astronomers poring over old observations were able to find the comet hiding in data from almost a year ago as it came nearer.
The hope is to eventually trace the comet back to its source, but that could be difficult, as Borisov may be a semi-permanent wanderer, bouncing from one solar system to another. | 0.892938 | 3.573944 |
Spotting transiting planets is what missions like CoRoT and Kepler are all about. The next step, getting a read on what’s in the atmosphere of any transiting, terrestrial world, is going to be tricky. The biomarkers like ozone and methane, so crucial for determining whether there’s life on a distant planet, are beyond the range of existing spacecraft. But the the next generation James Webb Space Telescope is also in the works, scheduled for launch in 2013.
For nearby Earth-class worlds, JWST may be up to the task, at least for terrestrial planets that transit. In fact, if Alpha Centauri A turns out to have a transiting Earth-like planet (a major if!), it would take only a few transits to study the light filtering through its atmosphere to look for signs of life. Alpha Centauri is problematic in any case, but a recent study shows that the method — breaking down the star’s light during a transit to look for the characteristic markers — could be extended to other stars, provided enough transits can be measured.
Image: This artist’s conception shows a hypothetical twin Earth orbiting a Sun-like star. A new study shows that characterizing a distant Earth’s atmosphere will be difficult, even using next-generation technology like the James Webb Space Telescope. If an Earth-like world is nearby, though, then by adding observations of a number of transits, astronomers should be able to detect biomarkers like methane or ozone. Credit: David A. Aguilar (CfA).
Lisa Kaltenegger (Harvard-Smithsonian Center for Astrophysics) and Wesley Traub (Jet Propulsion Laboratory) have been studying JWST in this context. Says Kaltenegger:
“We’ll have to be really lucky to decipher an Earth-like planet’s atmosphere during a transit event so that we can tell it is Earth-like. We will need to add up many transits to do so – hundreds of them, even for stars as close as 20 light-years away.”
If we’re looking at a planet in an Earth-like orbit around a G-class star, then a ten-hour transit once a year is the best we can expect, meaning that collecting a hundred hours of transit data would take ten years. But the same world orbiting in the habitable zone of a red dwarf would make many more transits in the same amount of time because of its proximity to the primary star, which is why Kaltenegger says nearby M-dwarfs “…offer the best possibility of detecting biomarkers in a transiting Earth’s atmosphere.”
The paper is Kaltenegger and Traub, “Transits of Earth-like Planets,” accepted by The Astrophysical Journal and available online. | 0.874428 | 4.036054 |
Osiris-Rex is a near-Earth asteroid sample return mission. The NASA spacecraft was launched on 8 September 2016 on an Atlas V rocket. Heading to asteroid Bennu.
What is Osiris-Rex?
Osiris-Rex is a spacecraft NASA is sending a space probe to near earth asteroid Bennu.
Astronomers have found that the asteroid Bennu crosses Earth’s orbit once every six years and is getting closer. In 2135 it will pass between the moon and earth. According to scientists the chance of an Earth impact is small.
What is Osiris-Rex Name Stand for?
Osiris-Rex stands for the Origins Spectral Interpretation Resource Identification Security – Regolith Explorer.
- To map every detail of the asteroid Bennu. It will descend and hover about the surface to pick up some rubble before returning to Earth.
- To study the geology of asteroid Bennu.
- To assist scientists investigate how planets formed and how life began.
- To help improve our understanding of asteroids that could impact Earth.
- To study and measure the Yarkovsky effect.
The Yarkovsky effect is a force on an asteroid when it absorbs sunlight and then radiates it back into space as heat. It acts like a small thruster, constantly changing an asteroid’s course. As of 2016 Bennu’s position has shifted 160km since 1999.
Osiris-Rex spacecraft is being built by Lockheed Martin Space Systems in Denver, USA.
Overall mission management is provided by NASA’s Goddard Space Flight Center in Greenbelt, Maryland, USA.
Osiris-Rex spacecraft was launched on 8 September 2016 on an Atlas V rocket from Space Launch Complex (SLC)-41 at Cape Canaveral Air Force Station, Florida.
OSIRIS-REx was the 65th launch of an Atlas V and the fourth in the 411 configuration. 411 configuration adds a single strap-on solid booster rocket to the first stage.
This was United Launch Alliance’s (ULA) 111th launch since the company was formed in 2006.
Mass (without fuel): 880 Kg (1,940 pounds)
Mass (fueled): 2110 Kg (4,650 pounds)
Length: 6.2 m (20.25 ft) with solar arrays deployed
Width: 2.43 m (8 ft)
Height: 3.15 m (10.33 ft)
Asteroid Bennu is a carbonaceuos near Earth Asteroid. It was formerly called 1999 RQ36. The asteroid was discovered in 1999 and has been studied intensively partly because of the potential threat it poses to earth and also due to its huge scientific interest.
Bennu is about 488 metres in diameter and travels around the sun at an average of 101,000kph.
Bennu is an ancient relic from the early solar system that is filled with organic molecules. Asteroids like Bennu may have seeded the early Earth with organic molecules.
Gravity of Bennu is so small, forces like solar radiation and thermal pressure from Bennu’s surface can push the spacecraft around in its orbit much more than if it were orbiting around Earth or Mars.
September 2016: Launch of Osiris-Rex spacecraft.
The spacecraft’s journey involves an initial year of orbiting the sun to build up speed before it slingshots back around the earth. It will use Earth’s gravity to align its orbit with the asteroid Bennu.
August 2018: Osiris-Rex spacecraft arrives at asteroid Bennu to start a year-long detailed survey.
December 2018: NASA’s OSIRIS-REx spacecraft went into orbit around asteroid Bennu for the first time on 31 December 2018.
July 2020: Osiris-Rex spacecraft descends to the surface to recover up to 5 pounds of rocks. When its scoop hits the surface a blast of gas should force material into its collector.
September 2023: Osiris-Rex flies back to Earth and returns samples.
Did you know?
- OSIRIS-REx is the third mission in NASA’s New Frontiers Program. New Horizons was the first mission and Juno was the second mission.
- Earth has been hit by asteroids and meteorites many times in the past. There are theories that an Earth-Asteroid collision formed our Moon and an asteroid may have wiped out the dinosaurs.
- Asteroids have featured in many films such as Armageddon movie and Deep Impact movie where they try to save Earth.
- The Atlas V rocket uses a Russian-built RD-180 to power its first stage and an American-built RL10 engine to power its Centaur upper stage.
Osiris- Rex Links:
OSIRIS-REx Mission: Home
OSIRIS-REx | NASA
NASA’s OSIRIS-REx Spacecraft Enters Close Orbit Around Bennu, Breaking Record:
By Lonnie Shekhtman (asteroidmission.org)
Any comments or suggestions, then click on Contact Info. | 0.834382 | 3.405097 |
Everyone’s favorite red supergiant star is bright again. The American Association of Variable Star Observers (AAVSO) has been tracking Betelgeuse as it has gradually returned to its more normal brilliance. As of this writing, it is about 95% of its typical visual brightness. Supernova fans will have to wait a bit longer.
Betelgeuse created quite a stir back in February when it became particularly dim. So dim that experienced observers could easily tell with the naked eye. As a variable star, Betelgeuse does go through bright and dim periods, but it was unusual enough that many wondered what might have been the cause.
There are several ways a star can vary in brightness. Cepheid variable stars, for example, vary because they expand and contract. As helium in the star’s outer layer is heated it expands, causing the star to swell. The helium then cools and the star shrinks again. This pulsation effect is so regular that astronomers can use Cepheids as standard candles to measure the distances of nearby galaxies.
Betelgeuse is a semiregular variable star, so it’s mechanism is different. As a red supergiant star, its diameter is wider than the orbit of Mars, but its outer layer is very diffuse. This means the layer is convective. Gas in the interior is heated and flows up to the surface. It then cools and sinks into the star again. This type of convection occurs in the Sun as well, but they are small compared to the Sun as a whole. On Betelgeuse, a single convection region can occupy a large part of the star’s surface.
So one popular idea is that the recent dimming was caused by an unusually large convective region. As a huge pocket of gas burst to the surface and cooled, Betelgeuse would dim more than usual. But a new study shows that wasn’t the case.1
Rather than simply measuring the brightness of Betelgeuse, the team looked at its spectrum. The spectral lines of starlight are often used to determine the chemical composition of a star because each type of element and molecule has a unique pattern of spectral lines. But these are affected by their environment. They shift slightly depending on their pressure and temperature. So the team used the spectral lines to measure the surface temperature of Betelgeuse. They then compared it to a 2004 measurement when Betelgeuse was bright.
They found that Betelgeuse might have gotten a bit cooler, from 3650 K in 2004 to 3600 K in 2020. This could be due to surface convection, but it is nowhere near large enough to account for its dimming. A similar change of temperature would have been seen if the star’s atmosphere has a whole swelled similar to a Cepheid star, so that isn’t the answer either. That leaves one other likely culprit: dust.
What likely happened is that Betelgeuse belched up a cloud of gas and dust. As this dust expanded in front of Betelgeuse from our point of view, it blocked some of the starlight, making Betelgeuse appear dimmer than it is. This idea is consistent with 2009 observations that observed a plume of gas near the star.2
Betelgeuse will eventually become a supernova, but not any time soon. But before that day Betelgeuse will continue to give us plenty of information about how dying stars meet their end.
Levesque, Emily M., and Philip Massey. “Betelgeuse Just Is Not That Cool: Effective Temperature Alone Cannot Explain the Recent Dimming of Betelgeuse.” The Astrophysical Journal Letters 891.2 (2020): L37. ↩︎
Kervella, Pierre, et al. “The close circumstellar environment of Betelgeuse-Adaptive optics spectro-imaging in the near-IR with VLT/NACO.” Astronomy & Astrophysics 504.1 (2009): 115-125. ↩︎ | 0.897011 | 4.018631 |
Most people hate winter, but for those of us who watch the sky, there’s no better time to witness some of nature’s most dazzling optical displays, like the one you see here.
The image was taken by Joshua Thomas in Red River, New Mexico on January 9, 2015, at where I am guessing might be the Red River Ski resort. The arcs and halos are light passing through ice crystals, which act like tiny prisms of varying shapes. They refract and reflecting light rays into the patterns seen here. More often than not, viewing conditions only show perhaps just one or two of these patterns, but Joshua’s photo shows several rare patterns happening all at once.
Let me stipulate that I’m hardly an expert at this but with the help of the atmospheric optics site I’ve been able to identify – or at least make an educated guess – at some of these arcs. Let’s take them one at a time.
At the center is the Sun, washed out in this view., though perhaps there is a Sun Pillar formed by light reflecting off small, plate-like crystals. It is immediately surrounded by the 22° halo. These halos are fairly common, and you may have noticed them surrounding the full moon on a winter’s night. If you look closely at the photo, you’ll notice that there is a reddish color on the inside and a bluish color toward the outside. This is exactly what you’d expect to see if the light were being refracted by the ice crystals.
To the left and right of the Sun are Parhelia, or sundogs. We only see the right sundog in this photo, the left being obscured by the mountain range. Typically, these are teardrop-shaped, but sometimes they extend to form long streamers called Parhelic Circles. It looks like we have a nice Parhelic Circle going horizontally to the right. I imagine there would be one stretching outward from the left if the mountain wasn’t in the way. These circles run parallel to the horizon and can even wrap 360° around the horizon if you have a clear enough view!!
The gull wing-shaped structure is called the Tangent Arc which, as its name implies, is just grazing the 22° halo. Notice that the wingtips are connected by a “capping” arc, called the Parry Arc.
Piercing the Perry arc is a “V”-shaped sunvex Perry Arc, which is a very rare phenomenon. Sunvex Perry Arcs are caused by light passing through hexagonal column ice crystals in high and cold cirrus cloud. These ice crystals are suspended nearly perfectly horizontal in the sky, as if that weren’t cool enough.
Surrounding the structures is what appears to be a giant rainbow. At first, I assumed this was the 46° halo, because it appears circular and seems to be about 46° across. But I learned that 46° halos are rare and typically very dim. Now I’m thinking that this must in fact be a Supralateral Arc, which are brighter than 46° halos and show up at the same location. Supralateral Arcs are sometimes accompanied by Infralateral arcs, and at first I thought that may be what see poking up from the treetops on the left from the edge of the arc on the right at a 45° angle from the Parhelic Circle. But on further inspection, I’m not convinced that’s really what those are. Still stumped on this.
By way of illustrating my guesses, I color-coded the different arcs according to the types I think they are. Please let me know if I got any of them wrong!
Comet Lovejoy (C/2014 Q2) has been making its way higher into the northern sky these last few weeks and is nearing its peak brightness. Already demonstrating a fully formed coma and an increasingly long tail, Lovejoy has been turning up on the interwebs in some spectacularphotos.
Chances are you don’t live in a location with zero light pollution and a powerful telescope, but Lovejoy is bright enough that a decent pair of binoculars will easily reveal the coma (the “head” of the comet). Here’s a pic to give you an idea of what to look for:
My friend Tom Wolf took this image last night from his home in southern Pennsylvania with his camera and tripod. Cameras are great for picking up details and colors that we cannot see with our eyes. Binoculars or even a small telescope won’t reveal a greenish color, nor will the comet appear quite so bright (unless, perhaps, you have a really nice set of binoculars). But this does give you an idea of the comet’s shape and relative “size”, depending on your binocular’s/telescope’s field of view.
Best of all, the comet is relatively easy to spot in the early evening after dark, making its way from Orion into the constellation of Taurus. It will soon be passing by some bright stars which will make it even easier to locate in the next couple of days. Sites like Sky and Telescope and Earth Sky have some handy viewing guides. In fact, I’ve been making use of this finder chart published by Sky and Telescope to find the comet each night:
So bundle up, grab your binoculars, and find this comet. It will take a few tries but believe me, it’s a very cool feeling when you finally “bag” it in your binoculars. Enjoy Lovejoy!
My friend Padi Boyd is an astronomer at NASA’s Goddard Spaceflight Center. She’s also a singer, songwriter, and founding member of The Chromatics, an A Capella group who sing about, among other things, astronomy. So I was happy to hear their latest number, Dance of the Planets, got made into a nice little video. Check it out:
It’s a lovely song and a reminder of how much of our perception has changed in such a short amount of time. Just 25 years ago, there was not a single known exoplanet – instead, we could only speculate about them and take a guess as to how what percentage of stars have planets, their number, and whether or not any of them might even have potentially habitable worlds.
Today, it’s a completely different story. We now know of more than 1800 worlds orbiting other stars, with thousands more waiting to be confirmed. We can confidently state that every star, regardless of its type, likely has at least one planet orbiting it. The Kepler Space Telescope showed us that planets do in fact orbit other suns in their host star’s habitable zone, can have stable orbits in binary star systems, and come in a variety of sizes around stars very different than our Sun. The upcoming Transiting Exoplanet Survey Satellite will identify even more interesting targets for future telescopes, and get us started down the path of understanding what their atmospheres are made of.
It’s an exciting time to be discovering new worlds beyond our solar system, and Padi sums it up best with these lyrics:
At the dawn of the twenty-first century,
The dream has become a reality
We’re not quite as alone as we used to be,
There are planets around the stars | 0.905736 | 3.386865 |
ESA’s Solar Orbiter mission lifted off on an Atlas V 411 from Cape Canaveral, Florida, at 05:03 CET on 10 February on its mission to study the Sun from new perspectives.
Signals from the spacecraft were received at New Norcia ground station at 06:00 CET, following separation from the launcher upper stage in low Earth orbit.
Facing the Sun
Solar Orbiter, an ESA-led mission with strong NASA participation, will provide the first views of the Sun’s uncharted polar regions, giving unprecedented insight into how our parent star works.
It will also investigate how intense radiation and energetic particles being blasted out from the Sun and carried by the solar wind through the Solar System impact our home planet, to better understand and predict periods of stormy ‘space weather’. Solar storms have the potential to knock out power grids, disrupt air traffic and telecommunications, and endanger space-walking astronauts, for example.
“As humans, we have always been familiar with the importance of the Sun to life on Earth, observing it and investigating how it works in detail, but we have also long known it has the potential to disrupt everyday life should we be in the firing line of a powerful solar storm,” says Günther Hasinger, ESA Director of Science.
“By the end of our Solar Orbiter mission, we will know more about the hidden force responsible for the Sun’s changing behaviour and its influence on our home planet than ever before.”
“Solar Orbiter is going to do amazing things. Combined with the other recently launched NASA missions to study the Sun, we are gaining unprecedented new knowledge about our star,” said Thomas Zurbuchen, NASA’s associate administrator for Science at the agency’s headquarters in Washington.
“Together with our European partners, we’re entering a new era of heliophysics that will transform the study of the Sun and help make astronauts safer as they travel on Artemis program missions to the Moon.”
At its closest, Solar Orbiter will face the Sun from within the orbit of Mercury, approximately 42 million kilometres from the solar surface. Cutting-edge heatshield technology will ensure the spacecraft’s scientific instruments are protected as the heatshield will endure temperatures of up to 500ºC – up to 13 times the heat experienced by satellites in Earth orbit.
“After some twenty years since inception, six years of construction, and more than a year of testing, together with our industrial partners we have established new high-temperature technologies and completed the challenge of building a spacecraft that is ready to face the Sun and study it up close,” adds César García Marirrodriga, ESA’s Solar Orbiter project manager.
New perspectives on our parent star
Solar Orbiter will take just under two years to reach its initial operational orbit, making use of gravity-assist flybys of Earth and Venus to enter a highly elliptical orbit around the Sun. The spacecraft will use the gravity of Venus to slingshot itself out of the ecliptic plane of the Solar System, which is home to the planetary orbits, and raise its orbit’s inclination to give us new views of the uncharted polar regions of our parent star.
The poles are out of view from Earth and to other spacecraft but scientists think they are key to understanding the Sun’s activity. Over the course of its planned five-year mission, Solar Orbiter will reach an inclination of 17º above and below the solar equator. The proposed extended mission would see it reach up to 33º inclination.
“Operating a spacecraft in close proximity of the Sun is an enormous challenge,” says Sylvain Lodiot, ESA’s Solar Orbiter spacecraft operations manager.
“Our team will have to ensure the continuous and accurate pointing of the heatshield to avoid the potential damage from the Sun’s radiation and thermal flux. At the same time, we will have to ensure a rapid and flexible response to the requests of the scientists to adapt their instruments’ operations according to the most recent observations of the Sun surface.”
Solar Orbiter will use a combination of 10 in situ and remote-sensing instruments to observe the turbulent solar surface, the Sun’s hot outer atmosphere and changes in the solar wind. Remote-sensing payloads will perform high-resolution imaging of the Sun's atmosphere – the corona – as well as the solar disc. In situ instruments will measure the solar wind and the solar magnetic field in the vicinity of the orbiter.
“The combination of remote-sensing instruments, which look at the Sun, and in situ measurements, which feel its power, will allow us to join the dots between what we see at the Sun and what we experience while soaking up the solar wind,” says Daniel Müller, ESA’s Solar Orbiter project scientist.
“This will provide unprecedented insight into how our parent star works in terms of its 11-year solar activity cycle, and how the Sun creates and controls the magnetic bubble – the heliosphere – in which our planet resides.”
We are all Solar Orbiters
Solar Orbiter will be one of two complementary spacecraft studying the Sun at close proximity: it will join NASA’s Parker Solar Probe, which is already engaged in its mission.
Solar Orbiter and Parker Solar Probe have each been designed and placed into a unique orbit to accomplish their different, if complementary, goals. Parker Solar Probe ‘touches’ our star at much closer distances than Solar Orbiter, to study how the solar wind originates – but does not have cameras to view the Sun directly. Solar Orbiter flies at an ideal distance to achieve a comprehensive perspective of our star, including both remote images and in situ measurements, and will view the Sun’s polar regions for the first time.
Beyond accomplishing its own science goals, Solar Orbiter will provide contextual information to improve the understanding of Parker Solar Probe’s measurements. By working together in this way, the two spacecraft will collect complementary data sets that will allow more science to be distilled from the two missions than either could manage on its own.
“Solar Orbiter is the newest addition to the NASA Heliophysics System Observatory, joining Parker Solar Probe in an extraordinary adventure to unlock the biggest mysteries of the Sun and its extended atmosphere,” says Holly Gilbert, NASA Solar Orbiter Project Scientist.
“The powerful combination of these two missions and their awe-inspiring technology advancements will thrust our understanding to new heights.”
Solar Orbiter is set to build on the legacy of missions such as the joint ESA/NASA Ulysses and Solar and Heliophysics Observatory (SOHO), to give us the most advanced look yet at our star, and its influence on Earth.
About Solar Orbiter
Solar Orbiter is an ESA-led mission with strong NASA participation. The prime contractor is Airbus Defence and Space in Stevenage, UK. Solar Orbiter is the first ‘medium’-class mission implemented in the Cosmic Vision 2015-25 programme, the current planning cycle for ESA’s space science missions.
More information about Solar Orbiter: http://www.esa.int/solarorbiter
In-depth information about Solar Orbiter: http://sci.esa.int/solar-orbiter
Follow on social media: @ESASolarOrbiter, #SolarOrbiter and #WeAreAllSolarOrbiters
Solar Orbiter launch media kit: https://esamultimedia.esa.int/docs/science/solar_orbiter_media_kit.pdf
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Perseids meteor shower peaks under moonless skies
The revelations by New Horizons at Pluto were certainly the highlight for July, showing that even small ice-bound worlds far from the Sun can have an active and fascinating geology. No doubt we are in for further surprises as the data from the encounter are downloaded over the narrow-bandwidth link to the probe over the coming months.
August sees our attention return to Comet 67P/Churyumov–Gerasimenko which is due to experience its peak activity as it sweeps through perihelion, its closest to the Sun, on the 15th. We should enjoy a grandstand view courtesy of Europe’s Rosetta probe in orbit around the comet’s icy nucleus, but it is far from certain that Philae will be able to relay further measurements from the surface. The comet’s perihelion occurs 26 million km outside the Earth’s orbit so none of the icy debris being driven from its nucleus is destined to reach the Earth.
The Earth does, though, intersect the orbit of Comet 109P/Swift-Tuttle with the result that its debris or meteoroids plunge into the upper atmosphere to produce the annual Perseids meteor shower. Its meteors diverge from a radiant point in Perseus which lies in the north-east at our star map times and climbs to stand just east of the zenith before dawn. Note that the shower’s meteors appear in all parts of the sky, with many of them bright and leaving persistent trains in their wake as they disintegrate at 59 km per second.
According to the British Astronomical Association (BAA), the premiere organisation for amateur astronomers in Britain, the shower is active from July 23 until August 20 and, for an observer under ideal conditions, reaches a peak of 80 or more meteors per hour at about 07:00 on the 13th. This is obviously after our daybreak, but rates should be high throughout the night of the 12th-13th and particularly before dawn, and respectable on the preceding and following nights too. With the Moon new on the 14th and causing no interference, the BAA puts the Perseids’ prospects this year as very favourable, an accolade it shares with the Geminids shower in December.
The Sun dips 10° southwards during August as sunrise/sunset times for Edinburgh change from 05:16/21:21 BST on the 1st to 06:14/20:11 on the 31st. The duration of nautical twilight at dawn and dusk shrinks from 121 to 89 minutes. The Moon is at first quarter on the 7th, new on the 14th, at first quarter on the 22nd and full again on the 29th.
After the twilit nights during the weeks around the solstice, August should bring (if the weather ever improves!) a chance to reacquaint ourselves with the best of what the summer skies can offer. The Summer Triangle formed by Vega in Lyra, Deneb in Cygnus and Altair in Aquila stands high in the south at our star map times, somewhat squashed by the map projection used. After the Moon leaves the scene, look for the Milky Way as it flows diagonally through the Triangle, its mid-line passing between Altair and Vega and close to Deneb as it arches over the sky from the south-south-west towards Cassiopeia, Perseus and Auriga in the north-east.
The main stars of Cygnus the Swan are sometimes called the Northern Cross, particularly when the cross appears to stand upright in our north-western sky later in the year. The Swan’s neck stretches south-westwards from Sadr to Albireo, the beak, which is one of the finest double stars in the sky. A challenge for binoculars, almost any telescope shows Albireo as a contracting pair of golden and bluish stars.
The brightest star on the line between Sadr and Albireo is usually the magnitude 3.9 Eta. However, just 2.5° south-west of Eta is the star Chi Cygni which pulsates in brightness every 407 days or so and belongs to the class of red giant variable stars that includes Mira in Cetus. Chi is a dim telescopic object at its faintest, but it can become easily visible to the naked eye at its brightest. Last year, though, it only reached magnitude 6.5, barely visible to the naked eye. Now approaching maximum brightness again and as bright as magnitude 4.2 in late July, it may surpass Eta early in August, so is worth a look.
Venus and Jupiter have dominated our evening sky over recent months but are now lost in the Sun’s glare to leave Saturn as our only bright planet as the night begins. Although it dims slightly from magnitude 0.4 to 0.6, it remains the brightest object low down in the south-west as the twilight fades. Indeed, it stands only 5° or so above Edinburgh’s horizon at the end of nautical twilight and sets thirty minutes after our map times, so is now poorly placed for telescopic study. Catch it 2° below-right of the first quarter Moon on the 22nd when Saturn’s rings are tipped at 24° and span 38 arcseconds around its 17 arcseconds disk.
Jupiter reaches conjunction on the Sun’s far side on the 26th while Venus sweeps around the Sun’s near side on the 15th and reappears before dawn a few days later. Brilliant at magnitude -4.2, its height above Edinburgh’s eastern at sunrise doubles from 6° on the 25th to 12° by the 31st.
Also emerging in our morning twilight is the much dimmer planet Mars, magnitude 1.8. On the 20th and 21st it rises in the north-east two hours before the Sun and lies against the Praesepe or Beehive star cluster in Cancer. Before dawn on the 31st, Mars stands 9° above-left of Venus.
This is a slightly-revised version of Alan’s article published in The Scotsman on July 31st 2015, with thanks to the newspaper for permission to republish here.
New Horizons to be first at dwarf planet Pluto
Since our nights are still awash with summer twilight, we may be excused if our attention this month turns to Pluto as it is visited by a spacecraft for the first time.
Pluto was still regarded as a the solar system’s ninth planet when NASA’s New Horizons mission launched in 2006, but it was officially reclassified as a dwarf planet later that year. We now recognise it as one of several icy worlds, and not even the largest, in the Kuiper Belt of such objects beyond the orbit of Neptune.
Pluto is 2,368 km wide and has a system of five moons, two of them only discovered while New Horizons has been en route. The largest moon, Charon, is 1,207 km across and, like Pluto itself, will block the probe’s signal briefly as New Horizons zooms through the system at a relative speed of almost 14 km per second on the 14th. The closest approach to Pluto is due at 12:50 BST at a range of some 12,500 km from Pluto and 4,772 million km from the Earth. It will not hang around, though, since this is a flyby mission and the probe will speed onwards, perhaps to encounter another still-to-be-identified Kuiper Belt world before the end of this decade.
A conjunction of an altogether different type is gracing our western evening sky as July begins. The two most conspicuous planets have been converging over recent weeks and stand at their closest on the 1st when the brilliant Venus passes within 21 arcminutes, or two-thirds of a Moon’s breadth, of Jupiter.
On that evening, Venus is just below and left of Jupiter and sinks from 14° high in the west at sunset to set in the west-north-west about 100 minutes later. Shining at magnitude -4.4 from a distance of 76 million km, Venus appears 33 arcseconds in diameter and 33% illuminated, its dazzling crescent visible through a small telescope or even binoculars. Jupiter, 911 million km away on that evening, is 32 arcseconds wide but only one eleventh as bright at magnitude -1.8.
Over the coming days, Venus slips to the left with respect to Jupiter as both planets drop lower into the twilight. By July 15, Venus is only 7° high at sunset and sets within the hour, while Jupiter is 5° to its right and slightly higher, but unlikely to be seen without binoculars and a clear horizon. By then, too, Venus has closed to 61 million km and its crescent is taller but narrower, 41 arcseconds and 22% sunlit.
It is perhaps surprising that the Earth reaches aphelion, the farthest point from the Sun in its annual orbit, on the 6th. We are then 152,093,481 km from the Sun, 4,997,277 km further away than we were at perihelion on January 4.
Sunrise/sunset times for Edinburgh change from 04:31/22:01 BST on the 1st to 05:14/21:23 on the 31st. The Sun tracks 5° southwards during July to bring the return of nautical darkness for Edinburgh from the night July 11/12. By the last night of the month this official measure of darkness lasts for almost four hours.
The Moon is full on the 2nd, at last quarter on the 8th, new on the 16th, at first quarter on the 24th and full again on the 31st – there is a notion, sadly mistaken, that a second full moon in a month should be termed a “blue moon”.
The white star Vega climbs from high in the east at nightfall to dominate our high southern sky at the star map times. It stands at a distance of 25 light years, being the third brightest star ever seen in Scotland’s night sky after Sirius, which is currently out of sight, and Arcturus in Bootes which stands low in the west by the map times.
Vega is twice as massive as our Sun and 40 times more luminous but only one tenth as old. It has an extensive disk of dusty material, although observations hinting that this contained a planet appear not to be supported my more recent studies.
Vega is the leader of the small box-shaped constellation of Lyra the Lyre, representing a small harp from classical times. It is also the brightest star in the Summer Triangle that includes Deneb in Cygnus, high in the east at the map times, and Altair in Aquila, in the middle of our south-east. Far to the south of Vega is the so-called Teapot in Sagittarius which seems to be pouring to the right as it sits on Scotland’s southern horizon. We have much clearer views of this region of sky, rich in stars and star clusters, if we view them higher above the horizon under darker skies further south.
The red supergiant Antares in Scorpius glowers to the right of the Teapot and lies 13° below-left of Saturn which is twice as bright at magnitude 0.3 to 0.4. Indeed, after the Moon, it is the brightest object low down in the south at nightfall, moving to the south-west by our map times and setting less than two hours later. Currently creeping westwards in eastern Libra, it shows an 18 arcseconds disk through a telescope, set within glorious rings that stretch across 41 arcseconds and have their north face inclined towards us at 24°. Catch the Moon to the right of Saturn on the 25th and to its left a day later.
Of the other planets, Mars has yet to emerge from the Sun’s glare while Mercury hides low in our bright morning twilight as it moves towards superior conjunction on the Sun’s far side on the 23rd. | 0.905528 | 3.662871 |
Ceres is the largest object in the asteroid belt, a world more than 900 kilometers in diameter. It’s so big that planetary scientists tend to refer to it as a protoplanet rather than an asteroid. The latter group consists of pulverized rubble left over from the planetary formation process billions of years ago, but Ceres is different. It got big enough that it was well on its way to being a planet before it ran out of material to build with.
When we look at objects in the asteroid belt (and many moons of large planets), we see them covered in craters. Saturated, actually, with so many craters that a new impactor is likely to erase a few older ones when it hits.
The smaller the crater, the more of them there are. This makes sense; there are only a few objects big enough to create really big craters, but gazillions of smaller ones that can make smaller craters.
Still, pretty much every object we look at has a handful of really monster impact craters, some approaching the diameter of the object itself—remember, a crater will follow the curvature of the surface; Vesta, smaller than Ceres at 525 km across, has a crater 500 km across on it. That crater stretches over about a third (well, about 1/pi) of the surface.
So we expect to see a few very large craters on every object we study.
… except with Ceres we don’t. For some reason, Ceres has a definite paucity of really big craters.
The Dawn mission has been orbiting Ceres since March 2015, taking high-resolution images of the surface (as well as lots of other data). Using these images, scientists basically counted up the craters above a certain size. The biggest craters, named Keran and Yalode, are 280 and 270 km in size. That’s big, but Ceres is 940 km across. Where are the big craters?
And it’s not just the very biggest; the numbers start to drop off at craters wider than about 100 km in diameter. It’s weird, and that’s not just intuition. The numbers and sizes of craters can be predicted using impact models based on the numbers and sizes of asteroids in the main belt. They find that there should be six or so craters bigger than 280 km, but none is found. The chance of that happening is less than one percent! They also expect roughly 40 craters bigger than 100 km, but only 16 are seen. The odds of that occurring are essentially zero.
So what’s going on?
Most likely, Ceres did have huge craters long ago, but something happened to erase them. Either lots of subsequent impacts erased the evidence, or Ceres itself did. By that I mean perhaps the composition of Ceres itself makes it such that huge craters fill in, the material surrounding the crater flowing back into it ad “patching” it.
Under the huge pressure of impact rock can flow pretty well, and Ceres also has a lot of water ice under the surface, so this idea has merit. In fact, the authors of the research indicate this is the most likely solution; the process happens to big craters but not smaller ones, so it seems to be connected to Ceres itself, and not subsequent impacts.
I’ll note that there are three very large (>800 km wide) basins, or depressions, on the surface of Ceres. Those might be impact-related, but it’s difficult to be certain. The authors discuss those, and the idea that they’re so difficult to identify lends credence to the idea that something happened to resculpt them.
As I’ve written about before, looking at craters is a great way to understand what big bodies in the solar system have gone through over the eons. It helps establish a timeline of events across the solar system, and can be used to see how objects compare with one another. We already know Ceres is a bit weird—it has a mantle of briny water ice under the surface that oozes up, sublimates, and leaves behind brighter salty deposits, as one example of its odd behavior—so it’s likely that if we see other unusual things going on, they’re tied together. In this case, it’s due to the internal structure of Ceres.
Ceres is a midway point between the stuff used to make planets and the planets themselves. It’s a frozen remnant straddling that line from 4.5 billion years ago, and studying it tells us more about how our own planet came to be. | 0.871049 | 3.977644 |
Astronomers in the US have discovered a ‘bow shock’ around a red supergiant
star near the heart of our Galaxy. A bow shock arises when material streaming
through space meets an obstruction and is forced to flow around it. For
example, material streaming away from the Sun – the solar wind – hits the
Earth’s magnetic field, forming a bow shock.
Farhad Yusef-Zadeh of Northwestern University in Illinois and Fulvio
Melia of the University of Arizona have made a detailed map at radio wavelengths
of the red supergiant, known as IRS 7. The shape and orientation of the
bow shock reveal that it is created by a powerful wind from a star cluster
near the Galactic centre. The shock shows where the cluster’s wind smashes
into the weaker wind of material streaming away from the red supergiant.
The red supergiant is only about 1 light year from the Galactic centre,
which is about 27 000 light years from the Sun. The star cannot be seen
in visible light because dust blocks our view. However, it is bright at
radio wavelengths and in the infrared, which is why it bears the name IRS
7, short for Infrared Source 7. These longer wavelengths are able to penetrate
In 1990, Yusef-Zadeh and Mark Morris of the University of California
at Los Angeles made radio observations of IRS 7. They discovered that the
star has a long tail of ionised gas, and that this tail points away from
the Galactic centre (Astrophysical Journal Letters, vol 371, p L59). The
tail resembles that of a comet and stretches at least half a light year
from the star. Another team of astronomers, led by Eugene Serabyn of the
California Institute of Technology, independently discovered the tail when
they observed IRS 7 at infrared wavelengths (Astrophysical Journal, vol
378, p 557).
Since the preliminary observations astronomers have sought to find the
origin of the tail. In common with other red supergiants, IRS 7 loses material
in a stellar wind, which streams away from the star in all directions. However,
the existence of the tail indicates that something is pushing the material
away from the Galactic centre.
Now Yusef-Zadeh and Melia have observed the star with the Very Large
Array in New Mexico. The new observations reveal that the side of the star
facing the Galactic centre has a bow shock, so that whatever is generating
the tail lies in that direction.
One theory was that the tail arose because IRS 7 was ploughing through
a hot interstellar medium as it orbited the centre of the Galaxy. In this
scenario, the star resembles an iceberg cutting a swathe through a warm
sea, and leaving a trail of ice fragments.
Yusef-Zadeh and Melia say this idea is wong, because the shape of the
bow shock is different from that predicted. They say the cause of the bow
shock and tail is a wind streaming out of the Galactic centre.
Two objects lie near the Galactic centre. One is a peculiar radio source
named Sagittarius A* (pronounced ‘ay star’), which is probably at the very
centre of the Galaxy. Many astronomers believe that Sagittarius A* harbours
a black hole, and some had suspected that Sagittarius A* produces the wind
that hits IRS 7.
But Yusef-Zadeh and Melia say that Sagittarius A* is not the source
of the wind. Instead, the apex of IRS 7’s bow shock points towards another
culprit: a star cluster lying close to Sagittarius A*.
The star cluster, named IRS 16, contains several hot blue stars. These
stars are ejecting nearly 4 times the mass of the Earth every day in a powerful
stellar wind moving at between 500 and 700 kilometres per second. In contrast,
the wind created by IRS 7 travels at less than 30 kilometres per second.
Yusef-Zadeh and Melia believe that when the powerful wind from the IRS
16 star cluster hits the weaker wind emanating from IRS 7, it creates a
bow shock on the side of the supergiant facing the cluster and pushes the
red supergiant’s own wind back on the side facing away, creating IRS 7’s
Yusef-Zadeh and Melia will announce their results in a future issue
of Astrophysical Journal Letters. | 0.838562 | 4.026596 |
7. Olympus Mons
Olympus Mons is a massive shield volcano located on the planet Mars. Since it is the largest volcano in the Solar System to be discovered till now, it deserves to be one of the 7 Wonders of the Solar System. Olympus Mons is two and a half times as tall as the Earth’s highest feature, Mount Everest.
6. The Rings of Saturn
Another of the 7 Wonders of the Solar System, the rings of Saturn is the Solar System’s most extensive planetary ring system. The ring system comprises of small particles of water, ice or rocky material, ranging in size from a few micrometers to several meters. These particles orbit around the Saturn planet and reflect light that makes the Saturn appear bright.
5. The Oceans of Earth
Included among the 7 Wonders of the Solar System are the oceans of our planet Earth. The oceans cover about 71% of the Earth’s surface. Nowhere else in the Solar System, such vast stretches of water have been discovered. The oceans are not only a wonder because of their water content but also these saline water bodies are home to a great diversity of marine life.
4. The surface of the Sun
The sun is the center of the Solar System around which all the celestial bodies in the Solar System revolve. The sun is almost a perfect sphere of hot plasma and is the main source of energy that sustains all life on Earth. The surface of the sun is completely unapproachable due to the extremely high, scorching temperatures of about 6,000 K that would burn to ashes anything that comes in the vicinity of the surface. Hydrogen (~73%), helium (~25%), and smaller quantities of other gasses make up the sun. For these reasons, the surface of the sun is regarded as a Wonder of the Solar System.
3. The Asteroid belt
Located roughly between the orbits of the two planets of Jupiter and Mass, is a circumstellar disc of the asteroid belt. This belt includes a large number of asteroids including the largest ones: Ceres, Vesta, Pallas, and Hygiea. The smallest bodies of the Asteroid Belt as tiny as a dust particle. These asteroids also revolve around the earth in their own orbits.
2. The Great red spot -
The Great Red Spot, an anticyclonic storm, has persisted for at least 186 years (and as per other estimates over 300 years) on Jupiter, 22° south of the equator of the planet. The storm is believed to have a diameter greater than 40,000 km in diameter. Interestingly, the Great Red Spot is large enough to envelop an area two to three times the size of Earth. For all these reasons, it is regarded as one of the Solar System’s wonders.
Enceladus is Saturn’s sixth-largest moon. The most interesting fact about Enceladus is that it is largely covered by clean, fresh ice reflecting all the light of the sun that strikes its surface. It also has a highly varied terrain ranging from young, tectonically deformed landscapes to heavily cratered regions. The Enceladus is also enlisted as one of the 7 Wonders of the Solar System.
About the Author
Oishimaya is an Indian native, currently residing in Kolkata. She has earned her Ph.D. degree and is presently engaged in full-time freelance writing and editing. She is an avid reader and travel enthusiast and is sensitively aware of her surroundings, both locally and globally. She loves mingling with people of eclectic cultures and also participates in activities concerning wildlife conservation.
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