text
stringlengths 286
572k
| score
float64 0.8
0.98
| model_output
float64 3
4.39
|
|---|---|---|
Saturn’s largest moon, Titan, is a giant nightmare beach. While its electrically charged sand wouldn’t make for a relaxing holiday, new research suggests the planet might not be as hostile to robotic visitors as we think. Although its lakes are full of ultra-cold liquid methane and ethane, they could be placid enough for future space probe to land on. Still not great for swimming, though.
Image: Earth and Planetary Science Letters
In a new study, published on June 29th in Earth and Planetary Science Letters, researchers used radar data from NASA’s Cassini spacecraft to measure the roughness of three lakes located in near Saturnian moon’s north pole—Kraken Mare, Ligeia Mare and Punga Mare. Ligeia Mare, the second biggest of the bunch, is larger than Lake Superior and could hold more than 50 times Earth’s oil reserves, according to Science News.
By using a technique called radar statistical reconnaissance, the team was able to ascertain the size of Titan’s puny waves—apparently, at the time of measurement they only reached about 1 centimetre high and 20 centimetres long. Radar data has been used to study Titan’s waves before, and has yielded interesting results: in a study conducted in 2014, researchers asserted that a “Magic Island”on Ligeia Mare—which keeps appearing and disappearing—is actually just the result of wave action in the hydrocarbon sea.
The new measurements suggest Titan’s waves aren’t great for surfing. But then again, neither is methane.
Saturn and Titan. (Image: NASA Jet Propulsion Laboratory/Cassini Orbiter)
The data analysed in this particular study was all collected by Cassini during the early summer season, and it’s unclear how much the waves fluctuate over time. That said, the research is useful for future missions to the Saturnian system once Cassini’s gone. Whenever NASA (or other space agencies) decide to land on Titan, the new research suggests they may have smooth sailing. Concept missions specifically designed for the Titan seas are already bubbling up, like the Titan Mare Explorer (TiME). Though NASA ultimately passed on the project, a mockup of the lander was successfully tested in a Chilean mountain lake. The TiME team’s research could lay the groundwork for further missions.
Hopefully, Titan landers will steer clear of swimming, or at least get some cool X-Men powers out of it. [Earth and Planetary Science Letters] | 0.825703 | 3.25805 |
Can you imagine a world in which not need extra energy sources? A world where you will not need to think about how to save energy. It will be, if not free, then very cheap. Now imagine the Sunthat every second produces as much energy as humanity has spent in its entire history and not spend a long time. How can we realize the energy of the Sun on our planet? It turns out that for over 60 years, there are technologies that can provide us with almost limitless energy sources for minimum money and with the use of almost free fuel. A reasonable question: why aren’t we using this opportunity?
What is the tokamak
The word ”tokamak” means nothing — it’s just a reduction, which then became a full-fledged word. It is used not only in Russia but also abroad, because in our country this thing came up and that we are a long time actively developed.
Tokamak - therodalina kameasure mAgnatname toTuscany. And that's all.
The essence of the tokamak is to create a magnetic field that will flow fusion reaction. As the temperature of this reaction is not just high, but literally prohibitive (several million degrees Celsius), it can not be carried out inside just a camera — it will melt well before reaching operating temperature.
This temperature is achieved due to the fact that the inside of the tokamak the substance is in the fourth state of aggregation, which is achieved at these high temperatures. This state is called plasma.
Who invented the tokamak
The first who proposed the use of thermonuclear synthesis for industrial purposes, was a Soviet physicist O. A. Lavrent’ev. He did this in his work in 1950. His work began the study of ways to use fusion.
A year later, other physicists Sakharov and Tamm — developed the idea and said that the fusion reaction should be maintained within the closed compartment of the toroidal shape.
Torus (toroid) is a three-dimensional shape resulting from the rotation of the ring around the center of rotation. Rough examples of the Torah can serve as a donut, bagel or Cycling chamber is removed from the wheel.
The term for the designation of the tokamak was proposed by a student of academician Kurchatov, I. N. Golovin. However, in his version it was supposed to be ”Tokamak” (toroidal chamber magnetic), but later they began to use a more euphonious word ”tokamak”.
The first operating tokamak was built in 1954, but prior to 1968, they existed only in the Soviet Union, because very few people believed in the existence within the chamber of such high temperature. Only once in the tokamak T-3 in the Institute of atomic energy I. V. Kurchatov visited British scientists and their equipment confirmed the existence of temperature 11.6 million degrees Celsius, this has led to the explosive growth in popularity and research in this direction in the world.
The tokamak and is now considered the most promising method of producing energy of nuclear fusion and the study of plasma as the state of aggregation of matter.
On Earth plasma is in a natural environment found only in lightning and the Northern lights, in the space of it consists of just all - stars, nebula, interstellar space.
How does the tokamak
To create the inside of the tokamak magnetic field, it is made up of sections, within which are wound coils. As they go throughout the length of the camera, and create something like a closed tunnel, the resulting magnetic field is called toroidal. This is the working area of the installation.
Before operating from the chamber of the tokamak evacuated, and instead fill it with a mixture of deuterium and tritium. They are the basis of nuclear fusion.
Deuterium - an isotope of hydrogen, nucleus of which consists of one proton and one neutron. Tritium - an isotope of hydrogen, nucleus of which consists of a proton and two neutrons.
The advantage of using these two elements is that they are very cheap. Deuterium is very easily obtained from the water on our planet is more than enough, and the tritium is synthesized though slightly more complicated way, but it’s not a big problem.
When the chamber is filled, it creates a vortex electric field, which support the plasma inside the chamber, and simultaneously warms it, leading to the same temperature of several million degrees.
As field and heat generated by increasing current in the inductor, and it can not increase indefinitely the lifetime of the plasma in a stable condition does not exceed a few seconds. This is the main reason that we can’t use the tokamaks as a source of industrial energy. There are ways to solve this problem, including using a microwave radiation, but while the work in this direction is still in progress.
Contact the walls of the tokamak with no plasma, and therefore, they do not melt, but they still feel tough. Because of this, walls are made of beryllium and cut into small square plates. So it is easier to remove the heat.
However, microwave radiation and so are applied inside of the tokamak, as only the electromagnetic field is not enough to heat the plasma to the temperature necessary for the implementation of thermonuclear reactions.
The usual particle physics clearly tells us that nuclei with the same charge repel each other. But when it reaches ultra-high temperatures, they begin to behave differently, forming a helium nucleus plus one free neutron. It was at this point and releases a tremendous amount of energy. In normal conditions it is spent on the interactions of atoms among themselves.
The largest fusion reactor
Of course, we can say that the biggest fusion reactor is the Sun, but all this is conditional, there are stars and more. The biggest fusion reactor on Earth is ”the international thermonuclear experimental reactor” (ITER or ITER). It is based in the South of France since 2007 and, like the large hadron Collider is an international project.
First plasma was scheduled for 2020, and the first electricity network in 2027, but the deadline is not met due to the fact that a project has many participants (each in its own way hinders the project) and due to the fact that this has never been done.
In order to describe its features, suffice it to say that it will be achieved at a temperature of 150 million degrees Celsius. It’s 10 times more than within the solar core. To imagine such values impossible.
When ITER will be constructed (as we will describe in our news Telegram-channel), it will be the main study of thermonuclear fusion for future study the reaction of atoms, as a potential energy source of the future.
One of the interesting figures of ITER can be noted the size of the tokamak, which is 28 meters in diameter and 28 meters in height. The design capacity is 0.5 GW (2.5 more than the most powerful of what are now). The magnetic field is 10 Tesla (Earth’s magnetic field is of 0.00005 Tesla).
The project cost is just $ 15 billion. For comparison, the ISS has spent over 28 years $ 53 billion, and in preparation for the world Cup in Qatar in 2022 - about $ 130 billion.
Is it safe fusion reaction
The main advantage of fusion reaction taking place inside the tokamak, is its safety. You wonder how this is possible with the achievement of such high temperatures, but it’s true.
All due to the fact that the density of plasma a million times less than the density of the atmosphere. Due to such characteristics, explosion due to internal pressure simply is impossible. Yes, and if the temperature starts to fall, the plasma just as the physicists say, ”to crumble”. Plus, the fuel is fed during the whole reaction and to stop it simply to stop its flow. For example, a nuclear power plant just can not be shut down and I’ve already told you why.
The only danger is that the isotope tritium has a low radioactivity. However, it is not so high to worry about. It is significantly lower than that of the fuel for a nuclear power plant. For example, the half-life of uranium is almost 5 billion years (i.e. almost never), but tritium is only 12 years old. Yes and used it a minimal amount.
Only 80 grams of a mixture of deuterium and tritium in the tokamak give as much energy as 1000 tonnes of coal during combustion. So consider.
You can also add that the technology of nuclear fusion can not be applied for military purposes. The creation of the plasma outside of the tokamak is not yet possible, and use him as a weapon is poorly achievable due to the fact that it doesn’t explode.
Why not get energy from fusion
Despite all the promise of technology and what we are talking about it for more than 70 years ago, while it is impossible to achieve industrial operation of such devices. Still they have something to work on. For example, the possibility of continuous operation and further increase of plasma temperature.
When this problem will be solved, we will get on Earth a small piece of the Sun, and then we can say that we have reached perfection in energy production. Of course, you can invent other even more efficient methods of producing energy, but fusion can now change a lot. Most importantly, we will not only get the ability to turn off the light for the sake of economy.
And the release of energy webwait this: the Earth's Oceans heat up like every second is falling five atomic bombs | 0.812459 | 3.024066 |
The Hubble Space Telescope provides a detailed look at the planets, moons, rings, asteroids and comets in our celestial backyard. These investigations have helped answer age-old questions about how the solar system began, how planets formed and how Earth evolved. Hubble also explores the uncharted reaches of our solar system, revealing new moons and objects beyond Pluto.
In the last two decades, NASA has been at the forefront of discovering planets beyond our solar system. Hubble explores the nature of these worlds, from orbits to atmospheres, and helps answer fundamental questions about how extrasolar planetary systems compare to ours.
Many of Hubble's most iconic images reveal majestic nebulae in the nearby universe. These observations advance our understanding of how gas and dust come together to form nebulae, and how these nebulae become the sites for newborn star and planetary systems. Hubble's investigations provide important views of how stars form, live out their lives and die — eventually expelling enriched gas and dust back into the cosmos.
The keen eye of Hubble has revealed intricate details of the shapes, structures and histories of galaxies — whether alone, as part of small groups or within vast clusters. From supermassive black holes at galactic centers to giant bursts of star formation to titanic collisions between galaxies, these discoveries allow astronomers to probe the current properties of galaxies as well as examine how they formed and developed.
Through an ongoing series of ground-breaking observations, Hubble has pushed toward the farthest reaches of the universe. Observing the cosmic frontier, Hubble reveals some of the universe's earliest galaxies, explores the nature of the enigmatic dark matter and builds upon its discovery of the yet-unexplained phenomenon called dark energy. | 0.87787 | 3.805659 |
When it comes to fundamental physics, things can get spooky. At least that’s what Albert Einstein said when describing the phenomenon of quantum entanglement—the linkage of particles in such a way that measurements performed on one particle seem to affect the other, even when separated by great distances. “Spooky action at a distance” is how Einstein described what he couldn’t explain.
While quantum mechanics includes many mysterious phenomena like entanglement, it remains the best fundamental physical theory describing how matter and light behave at the smallest scales. Quantum theory has survived numerous experimental tests in the past century while enabling many advanced technologies: modern computers, digital cameras and the displays of TVs, laptops and smartphones. Quantum entanglement itself is also the key to several next-generation technologies in computing, encryption and telecommunications. Yet, there is no clear consensus on how to interpret what quantum theory says about the true nature of reality at the subatomic level, or to definitively explain how entanglement actually works.
According to Andrew Friedman, a research scientist at the University of California San Diego Center for Astrophysics and Space Sciences (CASS), “the race is on” around the globe to identify and experimentally close potential loopholes that could still allow alternative theories, distinct from quantum theory, to explain perplexing phenomena like quantum entanglement. Such loopholes could potentially allow future quantum encryption schemes to be hacked. So, Friedman and his fellow researchers conducted a “Cosmic Bell” test with polarization-entangled photons designed to further close the “freedom-of-choice” or “free will” loophole in tests of Bell’s inequality, a famous theoretical result derived by physicist John S. Bell in the 1960s. Published in the Aug. 20 issue of Physical Review Letters, their findings are consistent with quantum theory and push back to at least 7.8 billion years ago the most recent time by which any causal influences from alternative, non-quantum mechanisms could have exploited the freedom-of-choice loophole.
“Our findings imply that any such mechanism is excluded from explaining the results from within a whopping 96% of the space-time volume in the causal past of our experiment, stretching all the way from the Big Bang until today,” said Friedman. “While these alternatives to quantum theory have not been completely ruled out, we are pushing them into a progressively smaller corner of space and time.”
In their experiment, the researchers outsourced the choice of entangled photon measurements to the universe. They did this by using the color of light that has been traveling to Earth for billions of years from distant galaxies—quasars—as a “cosmic random number generator.”
“This is a rare experiment that comes along only very seldomly in a scientist’s career: a pioneering experiment that sets the bar so high few, if any, competitors can ever match it,” noted UC San Diego astrophysicist Brian Keating. “I’m so proud that my graduate student David Leon had the chance to make a significant contribution to this fascinating research, co-led by CASS research scientist, Dr. Andrew Friedman.”
Besides UC San Diego’s Friedman and Leon, the full research team included lead author and Ph.D. student Dominik Rauch, along with Anton Zeilinger and his experimental quantum optics group from the University of Vienna; theoretical physicists David Kaiser and Alan Guth at MIT; Jason Gallicchio and his experimental physics group at Harvey Mudd College, and others. Expanding upon their previous quantum entanglement experiments, Friedman and colleagues went to great effort to choose entangled particle measurements using 3.6 and 4.2 meter telescopes in the Canary Islands, allowing them to collect sufficient light from the much fainter, distant quasars.
To conduct their test, they shined laser light into a special crystal that generated pairs of entangled photons, which the scientists repeatedly sent through the open air toward both telescopes. From the quasar light collected, the scientists could choose polarization measurement settings while each entangled photon was in mid-flight. The group was allotted three nights and a few hours at the Roque de los Muchachos Observatory in La Palma, amidst operationally challenging conditions including freezing rain, high winds, and uncertainty about whether they would have enough time to complete the experiment. Additionally, Friedman and colleagues had to write software that could choose the best quasars to observe on-the-fly—from a database of more than 1.5 million—and predict the observation time needed to obtain a statistically significant result.
“We pushed to the limit what could be done within the time constraints,” said Friedman. “The experiment would not have been possible without an amazing international collaboration. It was a roller coaster experience to see it actually work.”
The research was funded by the Austrian Academy of Sciences; The Austrian Science Fund with SFB F40 (FOQUS) and project COQuS (W1210-N16); the Austrian Federal Ministry of Education, Science and Research; the University of Vienna (via the project QUESS); the National Science Foundation INSPIRE Grant (PHY-1541160); the U.S. Department of Energy (DE-SC0012567); the U.S. Department of Defense, through the National Defense Science & Engineering Graduate Fellowship Program, and UC San Diego’s Ax Center for Experimental Cosmology.
UC San Diego, prefers the path less traveled. And it has led to remarkable new ways of seeing and making a difference in the world. The university was recently ranked #2 for quality education at an affordable price by Money magazine. Additionally, the Academic Ranking of World Universities lists UC San Diego #15 in the world and #13 nationally. | 0.853604 | 3.739753 |
Eta Aquariid meteor shower to pass through Arizona skies in May
As the month of May opens up, get set for one of the best meteor showers of the entire year!
This meteor shower is known as the Eta Aquariid shower — and the peak of this great event is just days away.
Meteors are the debris that is left in the orbits of comets and they orbit around the Sun with a specific period. The Eta Aquariid meteor shower is the leftover debris from Halley’s Comet, one of the most famous of all comets.
The orbit of Halley’s Comet is some 76 years in length, giving the comet the title of “Mankind’s Comet,” making it visible at least once in the average lifetime of a human on Earth.
Astronomer Edmund Halley did not discover the comet that is named in his honor, but rather the fact that he predicted its orbit and the return of the comets orbit in a period of 76 years.
The last time that many remember the return of Halley’s Comet was back in the years 1910 and 1986!
Did you get to see Halley’s Comet in 1986?
If you did, remember that it will not return until July 28, 2061, when the comet will once again be closest to the Sun at perihelion.
But don’t let that stop you from viewing the debris from this most famous of all comets!
Plan on locating the darkest location you can find to set up camp and begin your observations on the evening of May 4. The moon will be at or near its new phase and will not pose a threat to observing the faintest of meteors.
You will need a clear view of the eastern sky as the radiant of the shower will not rise until 3 a.m. on the 5th.
For those of you that require additional specifics, please not that nautical twilight will begin to show early signs of light by around 4:37 a.m. and civil twilight will begin to wipe out the faintest meteors and stars by 5:10 a.m. on the morning of the 5th.
If all goes well, you may get to see upwards of 20 meteors per hour!
Your chance to get to see actual debris from the most famous of all comets.
The debris, the size of beach sand and pebbles, is entering the atmosphere at speeds of 150,000 mph!
Here is a basic finder chart for one of the best meteor showers in some time.
Good luck in viewing the meteor shower!
To print your own monthly star chart, click here.
To view satellites/dates/times of passage, click here.
Listen to the Dr. Sky Show on KTAR News 92.3 FM every Saturday morning at 3 a.m.
- Gilbert Regional Park continues progress on additional facilities
- AZDES receives additional coronavirus funds to help low-income individuals
- More than 200 arrested in downtown Phoenix for rioting, other charges
- Tempe continues to reopen amenities following COVID-19 closure
- Advocates question investigations used to target wolves in Arizona | 0.830355 | 3.353368 |
Quasar kicked out of its own galaxy in enormous event
THIS monster has been booted out of its home. So what does it take to get a supermassive black hole to run at 8 million kilometres an hour? Something even scarier?
Black holes are the top-feeding predators of the universe.
Giant black holes dominate entire galaxies.
They live in their hearts. Their immense gravity keeps every star in its place.
So when Hubble spotted one on the run in a galaxy called 3C 186, something big - very big - must have happened.
You don't simply push supermassive black holes about.
It's liable to tear you apart.
But a research paper about to be published in the journal Astronomy & Astrophysics has a good idea why.
Every galaxy has one: a supermassive black hole.
It's their anchor. Their engine. A source of destruction, and renewal.
These monsters represent the collapsed weight of more than a billion suns, producing cores so dense that their gravity governs the entire galaxy of stars orbiting them.
They're also easy for astronomers to spot: intense swirls of radiation glow around the invisible event horizon.
At this scale, these galactic overlords are called quasars.
This one has been dethroned.
Researchers pouring over Hubble photographs spotted something odd about the blurry blotch that was galaxy 3C 186.
It had the expected intense bright flare of an active quasar.
It's just that it was in the wrong spot.
The galaxy is spinning merrily along its way.
But the quasar is 35,000 light years outside its core.
"I thought we were seeing something very peculiar," study author Marco Chiaberge said in a release.
So the John Hopkins University researchers sought out as much data as they could find about the odd behaviour of 3C 186.
FINGERPRINTS OF THE GODS
The Chandra space observatory and Sloan Digital Sky Survey were co-opted to verify Hubble's strange sighting.
They peered beyond Hubble's gaze, into X-rays and the galaxy's red-shift (rate of movement away from Earth).
Like Hubble, they could not see the black hole itself. But they could also measure the size, speed and location of its superheated gas shroud.
It was real.
The clue as to why was written in the stars.
Galaxy 3C 186 bore faint scars of a colossal impact.
It's stars were bundled into vague arcs.
These are tidal-tales. Gravitational wave tsunamis imprinted upon the galaxy itself.
So what could cause this?
CLASH OF TITANS
Chiaberge's paper suggests we're observing an unusual aftermath of a clash of two galaxies.
Two intense quasars must have collided with the force of 100 million supernovas.
The quasar at the heart of Galaxy 3C 186 appears to have 'won' the duel, but at great cost.
A drawn-out interstellar wrestling match had the quasars circling each other, locked in a death struggle. The gravitational fallout of their fight lashed out among the stars around them.
3C 186 appears to have swallowed its opposing quasar, but the gravitational wrestling match unseated the victor
The paper argues that if one supermassive black hole was smaller than the other, their one-sided wrestling mach may have spun weaker gravitational waves out in one direction than the other.
Once the weakest was swallowed, the survivor would have suffered a 'recoil'.
The intergalactic judo-move toppled the victorious quasar in the opposite direction.
"This asymmetry depends on properties such as the mass and the relative orientation of the back holes' rotation axes before the merger," co-author Colin Norman writes. "That's why these objects are so rare."
Ultimately, the 3C 186 quasar's victory will be a hollow one.
It has been propelled beyond escape velocity.
In 20 million years it will pass beyond the outer rim of its family of stars, doomed to wander the universe alone.
Unless it finds another galaxy to muscle-in on. | 0.887449 | 3.767471 |
LY Aurigae is a multiple star system in the constellation Auriga. It is an eclipsing binary variable star, dropping in brightness by 0.7 magnitudes every 4 days. The system is around a thousand light years away in the Auriga OB1 stellar association.
LY Aur A is a double-lined spectroscopic binary with an O9 bright giant and an O9 giant star in contact and eclipsing each other as they orbit every 4 days. It is classified as a Beta Lyr eclipsing variable system. The primary eclipse is 0.69 magnitudes deep and the secondary eclipse is 0.60 magnitudes. Because of the contact nature of the system and the deformed shapes of the stars, the magnitude varies constantly throughout the orbital cycle. The orbital period is slowly changing due to mass exchange between the stars. Each star is over a hundred thousand times the luminosity of the sun.
LY Aur B is a single-lined spectroscopic binary with an orbital period of 20.5 days. It is probably an early B main sequence star and the companion is undetectable. The two stars combined are 47,000 times the luminosity of the sun.
- Paunzen, E. (2015). "A new catalogue of Strömgren-Crawford uvbyβ photometry". Astronomy & Astrophysics 580: A23. doi:10.1051/0004-6361/201526413. Bibcode: 2015A&A...580A..23P.
- Fabricius, C.; Høg, E.; Makarov, V. V.; Mason, B. D.; Wycoff, G. L.; Urban, S. E. (2002). "The Tycho double star catalogue". Astronomy and Astrophysics 384: 180–189. doi:10.1051/0004-6361:20011822. Bibcode: 2002A&A...384..180F.
- Malkov, O. Yu.; Oblak, E.; Snegireva, E. A.; Torra, J. (2006). "A catalogue of eclipsing variables". Astronomy and Astrophysics 446 (2): 785. doi:10.1051/0004-6361:20053137. Bibcode: 2006A&A...446..785M.
- Mayer, A.; Jorissen, A.; Paladini, C.; Kerschbaum, F.; Pourbaix, D.; Siopis, C.; Ottensamer, R.; Mečina, M. et al. (2014). "Large-scale environments of binary AGB stars probed by Herschel. II. Two companions interacting with the wind of π1 Gruis". Astronomy & Astrophysics 570 (113): A113. doi:10.1051/0004-6361/201424465. Bibcode: 2014A&A...570A.113M.
<ref>tag with name "van Leeuwen2007" defined in
<references>is not used in prior text.
https://en.wikipedia.org/wiki/LY Aurigae was the original source. Read more. | 0.826533 | 3.51192 |
The search for evidence of the universe's ancient faster-than-light expansion is heating up, just after a much-ballyhooed recent detection was deemed a false alarm.
In March 2014, a team of scientists using the BICEP2 telescope at the South Pole announced that they had spotted an apparent signal of primordial gravitational waves in the cosmic microwave background (CMB), the light that began saturating the universe about 380,000 years after the Big Bang.
The announcement made a big splash, and for good reason. For starters, it suggested that gravitational waves — hypothesized ripples in the fabric of space-time — do indeed exist. But more important, the finding seemed to confirm the basics of cosmic inflation theory, which posits that the universe expanded dramatically in the first tiny fractions of a second after the Big Bang (and produced primordial gravitational waves in the process). [Cosmic Inflation and the Big Bang Explained (Infographic)]
Just last month, however, the purported discovery vanished in a cloud of dust: Data from BICEP2, the Keck Array (also at the South Pole) and Europe's Planck spacecraft showed that much of the supposed gravitational-wave signal — curly patterns in CMB polarization known as "B-modes" — was actually caused by interstellar dust.
This news is reshaping and refining, rather than scuttling, the hunt for primordial gravitational waves, as researchers figure out how best to hunt for CMB B-modes in a dustier-than-expected sky.
"We're in a very good place right now to make good progress on this question," said John Kovac, of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, leader of the team that announced the discovery last March.
"We don't know what the answer is going to converge to, but we do know that progress is going to be very rapid," Kovac told Space.com. "It's going to be an exciting ride, and we can expect multiple rounds coming up in the next year or so."
Expanding the search
The supposed B-mode detection was based primarily on BICEP2 measurements of CMB polarization in one small patch of sky at a single frequency (150 gigahertz). Models available at the time suggested that galactic dust emission, which can produce B-mode signals, in that part of the sky is quite low, discovery team members said.
But Planck's observations showed that those models — and the CMB B-mode search strategy — needed to be revised. Data from the spacecraft, which studied the cosmic microwave background in nine different frequencies from 2009 to 2013, revealed that foreground dust emission is relatively high over the entire sky.
"Now, people really understand that observing at more than one frequency is completely mandatory," said Brendan Crill, of NASA's Jet Propulsion Laboratory in Pasadena, California, a member of both the BICEP2 and Planck teams. (The two groups worked together to produce the new study, which has been submitted to the journal Physical Review Letters. BICEP, incidentally, is short for "Background Imaging of Cosmic Extragalactic Polarization.")
"You really have to field instruments that are able to look at CMB and also dust, and distinguish the two," Crill told Space.com. [The Search for Gravitational Waves (Gallery)]
And that's just what Kovac and his colleagues are now doing. For the past 13 months, they've been using the Keck Array to measure CMB polarization at a second frequency, 95 gigahertz. Dust emission is expected to be five times weaker at this new frequency, Kovac said.
"Any signal that is in common between 95 gigahertz and 150 gigahertz — those two frequencies — is likely to be mostly CMB B-modes," he said. "So, looking for that cross correlation is going to be a really powerful next analysis."
That analysis is already underway, and is pretty far along, Kovac added.
"We don't know the final answer yet, but hopefully, within just a couple of months — we certainly expect it this spring," he said. "So it's not going to take very long to make the next big jump in this question."
There's no guarantee that the "big jump" will be a detection of B-modes from inflation, Kovac stressed. Rather, the constraints will simply tighten, in one direction or another. And they should continue to tighten over time; two newly installed Keck receivers are now studying the CMB sky at 220 gigahertz as well.
"So we have three colors now that are operating at very high sensitivity," Kovac said. "We can expect ultrasensitive maps over the next year's worth of data to come out in three frequencies now, and that should continue to increase the confidence of whatever interpretation is favored by the data."
And Kovac and his group aren't alone in the B-mode hunt. Other teams — including those affiliated with the Spider balloon experiment, the South Pole Telescope and the ACT and POLARBEAR projects, which both study the sky using telescopes in Chile — are gathering supersensitive CMB data as well.
The way forward
"The current generation [of instruments], I think, should be able to get a factor of five to 10 better constraints on the amplitude of [primordial] gravitational waves in the next three to five years," Crill said. "As to whether or not we'll see anything, that's really hard to say — the theoretical predictions are kind of all over the place."
Therefore, the failure of these ongoing searches to find B-modes in the CMB wouldn't necessarily be a knife through the heart of cosmic inflation theory; primordial gravitational waves may simply be very difficult to detect. (Their amplitude depends on the energy scale of inflation, which is unknown.)
If that's the case, a comprehensive ground-based survey, featuring sensitive new detectors and new telescopes at various spots around the world, may be required to confirm the existence of B-modes in the CMB, Kovac said. Such a survey could probably be performed for $100 million or less, he added.
Kovac and Crill would also love to see a new CMB-mapping space mission sometime down the road. (There have been three such missions to date: NASA's Cosmic Background Explorer and Wilkinson Microwave Anisotropy Probe, and Planck.)
"If evidence for inflationary gravitational waves starts to look quite firm, at whatever level the data prefers, the comprehensive mission that will map that signal out in detail probably should be from space, ultimately," Kovac said. "That'll get all the information." | 0.863338 | 4.090115 |
The team proposes two main scientific goals for JWST when it comes to observing these moons. The first task would be completing the infrared survey of major satellites. The second goal is geology-related and described as “monitoring surface changes of active satellites.” The researchers presented their proposal in a paper published on the arXiv.”The James Webb Space Telescope will allow observations with a unique combination of spectral, spatial, and temporal resolution for the study of outer planet satellites within our solar system. We highlight the infrared spectroscopy of icy moons and temporal changes on geologically active satellites as two particularly valuable avenues of scientific inquiry,” the scientists wrote in the paper.JWST will be equipped in four scientific instruments: the Near InfraRed Camera (NIRCam), the Near InfraRed Spectrograph (NIRSpec), the Mid-Infrared Instrument (MIRI) and the Fine Guidance Sensor/Near Infrared Imager and Slitless Spectrograph (FGS/NIRISS).These instruments provide a unique opportunity to obtain high spectral resolution infrared spectra from planetary satellites in wavelength regions that cannot be observed from Earth. JWST’s results could complement observations of outer solar system moons conducted by Voyager and Cassini missions.The scientists hope that the telescope’s key scientific contribution could be determining the compositions of giant gas planets’ irregular satellites. They note that even at very low spatial resolution, near-infrared spectroscopy is sensitive to H2O and other ices, as well as silicates and spectral slopes characteristic of complex organic “tholins” (heteropolymer molecules formed by solar ultraviolet irradiation of simple organic compounds such as methane or ethane).”JWST has the sensitivity to provide unique compositional data on irregular satellites. For example, in the one to 2.5 micron region of the near-infrared, amorphous vs. crystalline surface composition of icy bodies could be surveyed extensively using JWST NIRSpec,” the paper reads.Irregular satellites are important sources of dust in the giant planet systems. Dust orbits evolve under effects of radiation pressure and solar tides. By linking the sizes, densities, and albedos of dust particles to the source satellite surface compositions, JWST could offer new insights into the role of these satellites in the production of dust particles. More information: Observing Outer Planet Satellites (except Titan) with JWST: Science Justification and Observational Requirements, arXiv:1511.03735 [astro-ph.EP] arxiv.org/abs/1511.03735AbstractThe James Webb Space Telescope (JWST) will allow observations with a unique combination of spectral, spatial, and temporal resolution for the study of outer planet satellites within our Solar System. We highlight the infrared spectroscopy of icy moons and temporal changes on geologically active satellites as two particularly valuable avenues of scientific inquiry. While some care must be taken to avoid saturation issues, JWST has observation modes that should provide excellent infrared data for such studies. Explore further © 2015 Phys.org How Hubble’s successor will give us a glimpse into the very first galaxies Citation: Scientists plan to observe outer solar system moons using JWST (2015, November 30) retrieved 18 August 2019 from https://phys.org/news/2015-11-scientists-outer-solar-moons-jwst.html The rendering of the James Webb Space Telescope in space. Image credit: Northrop Grumman. Journal information: arXiv The observations of geologic activity of the outer solar system moons, described by Kestay and his colleagues as the second main goal for JWST could also bring remarkable scientific results. The telescope will be able to detect changes on the surface that are indicative of temporal variations in composition and temperature.Many of the outer planet satellites are remarkably active. For instance, Jupiter’s moon Io, Neptune’s largest moon Triton, and Enceladus, Saturn’s icy satellite, have active eruptions. The recent suggestion of active plumes above Europa, orbiting Jupiter, is especially exciting because it may provide samples from a habitable environment that is otherwise extremely challenging to access.The scientists believe that the best moon for these observations would be Io. They note that JWST could observe significant surface changes on this satellite where volcanic activity is very high.”The observations every six months that JWST can make of the Jovian system is very well suited for monitoring the creation and fading of colorful plume deposits on Io which typically happen on a timescales of several months and have diameters of many hundreds of kilometers,” the researchers wrote.They are convinced that JWST observations could also resolve other scientific problems related to Io, such as the eruption temperature of its lavas and the uncertainty about the composition and state of its mantle. This could be crucial to our understanding of how tidal heating works in the Jovian system.The researchers conclude that these two types of JWST observations will enable compelling science of outer solar system moons. They present the telescope as an important tool for studying planetary satellites, underlining that the road to understanding the origins of the universe leads through the observations of our outer solar system. Finally, they encourage the scientific community to use their paper to formulate more specific observation plans. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. NASA’s James Webb Space Telescope (JWST), often touted as Hubble’s successor, is slated to be launched in 2018 to study every phase of cosmic history, mainly by observing the most distant objects in the universe. The telescope will also be useful for investigating extrasolar planetary systems as well as planets within our solar system. Now, a team of researchers led by Laszlo Kestay, the director of the U.S. Geological Survey’s Astrogeology Science Center, has laid out its plan to use the telescope’s capabilities to better understand our planetary neighborhood by putting emphasis on outer solar system moons and their geology. | 0.886925 | 3.847169 |
The Hutton-Westfold Observatory at Monash University's Clayton campus means that Monash students are able to observe stars and distant galaxies that are ten thousand times fainter than what can be seen with the unaided eye. This allows students to discern much about these celestial objects and the Universe in which we reside. The facility has been developed jointly by the School of Physics and the School of Mathematics, and is named in honour of the late Don Hutton and the late Kevin Westfold, who made significant contributions to astronomy and student learning at Monash University over the course of several decades.
Third year students in ASP3231 (Observational Astronomy) use the observatory use to learn how to collect astronomical images, then process and calibrate these to produce data which can be used for scientific research. They do this in groups of 2-3 students, each group observing a different object. They spend half of the semester processing their images using the same software used by "real" astronomers, then in the second half of semester they use the data to carry out a scientific analysis of their astronomical object and produce a detailed report.
The main objects studied are:
- Exoplanets - students observe a star as one of its planet passes in front of it. As the planet moves in front of the star there is a drop in intensity of the light collected from it, because some is blocked by the planet. From this they can estimate the radius of the planet and with some extra information they can estimate its mass.
- Star clusters - produce a Hertzsprung-Russell (HR) diagram and use this to find the distance to the cluster, its age and mass function.
- Galaxies - estimate the age of stellar populations in the bulge and disk of the galaxy, produce a density profile and estimate the galaxy mass. | 0.851827 | 3.330959 |
Astronomers have spotted, for the first time, a dense galactic core blazing with the light of millions of newborn stars in the early universe.
The finding sheds light on how elliptical galaxies, the large, gas-poor gatherings of older stars, may have first formed in the early universe. It’s a question that has eluded astronomers for decades.
The research team first uncovered the compact galactic core, dubbed GOODS-N-774, in images from the Hubble Space Telescope. Later observations from the Spitzer Space Telescope, the Herschel Space Observatory, and the W.M. Keck Observatory helped make this a true scientific finding.
The core formed 11 billion years ago, when the universe was less than 3 billion years old. Although only a fraction of the size of the Milky Way, at that time it already contained above twice as many stars as our own galaxy.
Theoretical simulations suggest that giant elliptical galaxies form from the inside out, with a large core marking the very first stages of formation. But most searches for these forming cores have come up empty handed, making this a first observation and a phenomenal find.
“We really hadn’t seen a formation process that could create things that are this dense,” explained lead author Erica Nelson from Yale University in a press release. “We suspect that this core-formation process is a phenomenon unique to the early universe because the early universe, as a whole, was more compact. Today, the universe is so diffuse that it cannot create such objects anymore.”
Alongside determining the galaxy’s size from the Hubble images, the team dug into archived far-infrared images from Spitzer and Herschel to calculate how fast the compact galaxy is creating stars. It seems to be producing 300 stars per year, a rate 30 times greater than the Milky Way.
The frenzied star formation likely occurs because the galactic core is forming deep inside a gravitational well of dark matter. Its unusually high mass constantly pulls gas in, compressing it and sparking star formation.
But these bursts of star formation create dust, which blocks the visible light. This helps explain why astronomers haven’t seen such a distant core before, as they may have been easily missed in previous surveys.
The team thinks that shortly after the early time period we can see, the core stopped forming stars. It likely then merged with other smaller galaxies, until it transformed into a much greater galaxy, similar to the more massive and sedate elliptical galaxies we see today.
“I think our discovery settles the question of whether this mode of building galaxies actually happened or not,” said coauthor Pieter van Dokkum from Yale University. “The question now is, how often did this occur?”
The team suspects that other galactic cores are abundant, but hidden behind their own dust. Future infrared telescopes, such as the James Webb Space Telescope, should be able to find more of these early objects.
The paper was published Aug. 27 in Nature and is available online. | 0.874975 | 4.154713 |
March 31 (UPI) -- In the early 7th century Japan, a fan of bright red feathers flamed across the night sky. Onlookers likened the cosmic phenomenon to the tail of a pheasant.
In written accounts, witnesses speculated about the cosmic origins of the "red sign," but until now, the phenomenon's true identity was a mystery.
In a new study, published this week in journal Sokendai Review of Culture and Social Studies, astronomers claim a powerful aurora best explains the red light that flashed above Japan in 620 A.D.
"It is the oldest Japanese astronomical record of a 'red sign,'" Ryuho Kataoka, an expert on space weather and an associate professor at Japan's National Institute of Polar Research, said in a news release. "It could be a red aurora produced during magnetic storms. However, convincing reasons have not been provided, although the description has been very famous among Japanese people for a long time."
Scientists have previously speculated that the red sign was produced by an aurora, or magnetic storm. However, auroras don't typically look like pheasant tails. The usually appear in wave-like patterns.
Other researchers have suggested the red sign was caused by a comet skimming across Earth's atmosphere, but comets are rarely red in color.
Researchers determined that Japan's skies would have been more likely to host an aurora some 1,500 years ago. The island nation's magnetic latitude would have been 33 degrees in 620 A.D. Today, Japan's magnetic latitude is 25 degrees.
Modern studies have shown that especially powerful magnetic storms can produce auroras featuring shapes other than ribbons and waves.
"Recent findings have shown that auroras can be 'pheasant tail' shaped specifically during great magnetic storms," Kataoka said. "This means that the 620 A.D. phenomenon was likely an aurora."
The mystery of the red sign would have been much harder to solve were it not for the imagination and specificity of the written accounts.
"This is an interesting and successful example that modern science can benefit from the ancient Japanese emotion evoked when the surprising appearance of heaven reminded them of a familiar bird," Kataoka said. | 0.831192 | 3.379676 |
Absolute proper motions for ∼7:7 million objects were derived based on data from the South Galactic Cap u-band Sky Survey (SCUSS) and astrometric data derived from uncompressed Digitized Sky Surveys that the Space Telescope Science Institute (STScI) created from the Palomar and UK Schmidt survey plates. We put a great deal of effort into correcting the position-, magnitude-, and color-dependent systematic errors in the derived absolute proper motions. The spectroscopically confirmed quasars were used to test the internal systematic and random error of the proper motions. The systematic errors of the overall proper motions in the SCUSS catalog are estimated as _0:08 and _0:06 mas=yr for μα cos δ and μδ, respectively. The random errors of the proper motions in the SCUSS catalog are estimated independently as 4.2 and 4:4 mas=yr for μα cos δ and μδ. There are no obvious position-, magnitude-, and color-dependent systematic errors of the SCUSS proper motions. The random error of the proper motions goes up with the magnitude from about 3 mas=yr at u ¼ 18:0 mag to about 7 mas=yr at u ¼ 22:0 mag. The proper motions of stars in SCUSS catalog are compared with those in the SDSS catalog, and they are highly consistent.
|Original language||English (US)|
|Number of pages||8|
|Journal||Publications of the Astronomical Society of the Pacific|
|State||Published - Jul 6 2015|
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science | 0.864745 | 3.398397 |
I’m the Curator of the historic Ladd Observatory. The Observatory opened in 1891 and is part of the Department of Physics at Brown University. Today it is operated as a working museum where visitors can experience astronomy as it was practiced a century ago. I spend most of my time presenting science outreach and public education programs, demonstrations, and exhibits. I’m also responsible for the historic scientific instrument collection. My primary research interest is late 19th and early 20th century astronomy with a focus on precision timekeeping using mechanical clocks and transit telescopes. Other research includes the early history of wireless and the industrialization of Providence.
In a previous post I described an idea on how to triangulate on the orientation of the Brown Space Engineering (BSE) satellite EQUiSat using simultaneous observations from multiple SatNOGS ground stations. We’re running simulation software to model how the antenna beam might be changing orientation as the spacecraft spins. The gyroscope is reporting about 7 degrees per second around one axis. This seems very fast and we’re not sure if the readings are accurate. This initial modeling assumes they are correct.
In the figures below the antenna beam is shown by a torus surrounding the satellite. The pattern is projected to the ground as rainbow colored lines. The red lines are the center of the beam. This does not show how signal strength varies on the surface. We’ll get to that later. It is merely projecting the geometry of a dipole antenna to illustrate where the center of the beam could be and how it might be rotating as the spacecraft spins.
We scheduled observations of EQUiSat on multiple ground stations in the eastern United States during a pass a little after 1 AM local time on November 8th. The goal is to try to understand the orientation of the antenna (and also the entire spacecraft) by comparing signal strength when two or more stations hear the same packet. The simple 70 cm dipole antenna on the spacecraft is directional. The maximum signal strength is perpendicular to the wire. We might be able to infer how the antenna was oriented at that moment by looking at which stations missed hearing the packet or received a weak signal.
We noticed a signal in a recording of transmissions from EQUiSat that had a very odd Doppler shift. It turned out that there was a second satellite above the horizon at the same time and it was transmitting on a similar frequency. SiriusSat-1 uses 435.57 MHz and EQUiSat uses 435.55 MHz. If the first satellite is Doppler shifted by -10 kHz and the second is +10 kHz the signals will overlap. To understand the potential for interference I examined the orbits of the two.
Both satellites were deployed from the International Space Station (ISS) during the summer. EQUiSat in mid July then SiriusSat-1 and SiriusSat-2 in mid August. Because of the similar deployment the two satellites are in nearly identical orbits. The inclination of the two orbital planes is within a few ten thousandths of a degree.
The activity of the Sun increases and decreases in a cycle that lasts approximately 11 years. When the cycle reaches a maximum there are a larger number of sunspots and an increase in solar radiation and charged particles reaching our planet. This can cause the atmosphere of the Earth to expand slightly. A satellite in low Earth orbit experiences a small amount of atmospheric drag despite the low density of air. The exact amount depends on how active the Sun is. Each cycle varies somewhat in duration. A cycle can be as short as 9 years or as long as 14. The average is about 10.7 years. These variations complicate the process of making predictions of future activity which are important for estimating the orbital decay of a satellite.
The magnitude and shape of the peaks in activity is also variable. The maximums in the early 1800s were very small, a time period known as the Dalton minimum. The next figure is a closer look at the Sun’s activity during the space age. The maximum in the late 1950s when Sputnik launched was the largest ever observed. During the Apollo missions the maximum was lower than other recent peaks but greater than the most recent maximum.
During the early years of the space age techniques were developed to track objects in orbit and predict their future position. The mathematical technique for calculating an orbit is called a Simplified General Perturbations (SGP) model. These models were first used in the 1960s and were refined during the 1970s. This work was done by NORAD – the North American Aerospace Defense Command.
The computations were performed on large mainframe computer systems that cost several million dollars each. One of these computers was used for ballistic missile warning. A second was dedicated to space surveillance and tracking satellites. A third was available on standby as a backup system in case one of the primary computers failed. The various objects being tracked in air and space were displayed on consoles such as the one shown above. | 0.821521 | 3.012179 |
Jupiter is the fifth planet from the Sun and the largest planet of the Solar System. It is the oldest planet of the Solar System thus it was the first to take shape out of the remains of the solar nebula.
Key Facts & Summary
- Since it is the fourth brightest object in the sky, Jupiter was observed since ancient times and thus no one can be credited for its discovery. However, the first telescopic observations were conducted by Galileo Galilei in 1609 and in 1610 Galileo also discovered the major moons of Jupiter, but of course not the smaller ones.
- Since many cultures observed Jupiter, they all gave it different names but the Roman name remained used in the majority of cultures. Jupiter is named after the principal Roman god, the equivalent of the Greek god Zeus.
- Jupiter is one of the five visible planets (Mercury, Venus, Mars, Saturn), being the fifth most distant from the Sun at an average distance of 5.2 AU, its closest approach is at 4.9 AU and at its farthest 5.4 AU. Its exact position can be checked online since the planet is constantly tracked.
- It is the biggest planet of the Solar System, with a mean radius of 43.440 miles / 69.911 km, a diameter at the equator of about 88.846 mi / 142.984 km, and at the poles, the diameter is only 83.082 mi / 133.708 km.
- Jupiter is also twice as massive as all the other planets combined, having 318 times the mass of Earth.
- The gas giant has a gravity of 24.79 m/s², a little more than twice of Earth. Its powerful gravity has been used to hurl spacecraft into the farthest regions of the solar system.
- Jupiter rotates once every 10 hours – A Jovian day – thus it has the shortest day of all the planets in the solar system.
- A Jovian year is about 12 Earth years, quite long in comparison to its short days.
- Since Jupiter has a small axial tilt of only 3.13 degrees, it has little seasonal variations.
- Jupiter does not have a solid surface being comprised mostly out of swirling gases and liquids such as 90% hydrogen, 10% helium – very similar to the sun.
- A very small fraction of the atmosphere is made up of compounds such as ammonia, sulfur, methane, and water vapor. Jupiter’s atmosphere is the largest planetary atmosphere in the solar system. It makes up almost the entire planet.
- It holds a unique place in the history of space exploration since after it was observed through the telescope, some of its moons were also discovered and because of this, their movements were observed thus ending the belief that everything orbited the Earth.
- Though it remains the biggest planet, Jupiter has been dethroned as the moon king by Saturn, which now has 82 moons. Jupiter currently has only 79 known satellites.
- Among these satellites, four of them are quite famous: Io – for its volcanic activity, Ganymede – for its size, being the largest known moon of any planet, Europa – for hosting favorable conditions to find present-day environments suitable for some form of life beyond Earth, and Callisto – that may also host a subsurface ocean. They are known as the Galilean moons.
- Jupiter has 3 ring systems though they are fainter and smaller than Saturn’s. They are mostly made up of dust and small rocky pieces.
- It has a very strong magnetosphere, almost 20 times stronger than Earth’s magnetic field and 20.000 times larger.
- As a result, the aurora of Jupiter is stronger as well. It produces almost a million Megawatts – Earth’s aurora produces about 1.000 Megawatts.
- A distinct feature of Jupiter is its Great Red Spot – a persistent high-pressure region in the atmosphere that produces an anticyclonic storm, the largest in the solar system. It has been observed since 1830, and it is active for hundreds of years. It is also shrinking.
- Jupiter is surrounded by a plasma torus, produced by its strong magnetic field. It is a field of extremely charged particles making it difficult for a spacecraft to approach the planet, yet some zones are a bit safer. The charged particles also come from Io’s volcanic activity.
- The combination of the powerful magnetic field and the charged particles in the plasma torus creates the brightest auroras in the solar system. Sadly, they can only be seen through ultraviolet.
- It is now known if Jupiter has a core and recent analysis suggests that the atmosphere extends up to 3.000 km / 1.864 mi down, and beneath this is an ocean of metallic hydrogen going all the way down to the center. About 80-90% of its radius is now believed to be a liquid or technically, an electrically conducting plasma, maybe similar to liquid mercury.
Jupiter is the fourth brightest object in the sky, visible to the naked eye. It shines so brightly that even Venus dims in comparison. Because of this, it has been observed since ancient times by many different cultures. The discovery of Jupiter cannot be attributed to someone.
However, Galileo Galilei is the first astronomer to have observed Jupiter through his telescope. He began extensive observations of the planet in 1609. During this time and until 1610, Galileo discovered the four largest moons that orbit Jupiter: Io, Europa, Ganymede, and Callisto. They are called the Galilean moons in his honor.
He first thought of them as “fixed stars” but over time he witnessed that the objects changed positions, and he even almost correctly deduced their periods. This discovery was revolutionary since, at the time, most of Europe still endorsed the theory that all the planets orbited Earth.
Galileo’s discovery paved the way for the heliocentric model of the solar system, in which the planets orbit the Sun. Jupiter was known to the Babylonians as Marduk, the patron deity of the city of Babylon. The Romans called it “the star of Jupiter” – as they believed it to be sacred to the principal god of Roman mythology, whose name comes from the Proto-Indo-European vocative compound *Dyēu-pəter.
Jupiter is the counterpart to the mythical Greek king of the gods, Zeus, this name is retained even now in the modern Greek language. The ancient Greeks used to call Jupiter, Phaethon, which means “blazing star.” As supreme god of the Roman pantheon, Jupiter was the god of thunder, lightning, and storms, and appropriately called the god of light and sky.
Throughout the universe, there are many planetary systems similar to ours. Most of them contain terrestrial planets like our own and gas giants like Jupiter. However, they also contain super-Earths – planets that are several times more massive than Earth.
This indicates that our own Solar System should also have these types of planets and it is hypothesized that we did have them but they collided with Jupiter in the early formation of the Solar System. This resulted in Jupiter’s migration from the inner solar system to the outer solar system and thus allowed the inner solar planets to form. This theory is called the Grand Tack Hypothesis.
There are theories that hypothesize the fact that Jupiter may have formed before the Sun while others state that Jupiter formed after the sun about 4.5 billion years ago. Gravity pulled swirling gas and dust and resulted in the creation of Jupiter. Sometime around 4 billion years ago Jupiter settled in its current position in the outer solar system.
Distance, Size and Mass
It is the fifth most distant from the Sun with an average distance of about 5.2 AU. The closest approach is at 4.9 AU and at its farthest 5.4 AU. Its exact position can be checked online since the planet is constantly tracked.
It is the biggest planet of the Solar System, with a mean radius of 43.440 miles / 69.911 km. Almost 11 times bigger than Earth. Jupiter’s radius is about 1/10 the radius of the Sun, and its mass is 0.001 times the mass of the Sun, so the densities of the two bodies are similar.
The diameter at the equator of about 88.846 mi / 142.984 km, and at the poles, the diameter is only 83.082 mi / 133.708 km. The average density of Jupiter is about 1.326 g/cm3, much smaller than all the terrestrial planets.
Jupiter is also 2.5 times more massive than all the other planets combined, having 318 times the mass of Earth. It has a volume of about 1,321 Earths.
Orbit and Rotation
Jupiter rotates once every 10 hours – A Jovian day – thus it has the shortest day of all the planets in the solar system. A Jovian year, on the other hand, is about 12 Earth years, quite long in comparison to its short days. The orbital period is about two-fifths that of Saturn. The orbit of Jupiter is elliptical, inclined about 1.31 degrees when compared to Earth.
The eccentricity of the orbit is about 0.048. This results in its distance from the Sun varying from its perihelion to aphelion by about 75 million km / 46 mi. Jupiter’s upper atmosphere undergoes differential rotation since it’s made out of gases.
Since Jupiter has a small axial tilt of only 3.13 degrees, it has little seasonal variations Because of this low tilt the poles constantly receive less solar radiation than at the planet’s equatorial region.
Jupiter does not have a solid surface being comprised mostly out of swirling gases and liquids such as 90% hydrogen, 10% helium – very similar to the sun.
It is now known if Jupiter has a core and recent analysis suggests that the atmosphere extends up to 3.000 km / 1.864 mi down, and beneath this is an ocean of metallic hydrogen going all the way down to the center. About 80-90% of its radius is now believed to be liquid or technically – electrically conducting plasma – it may be similar to liquid mercury. The Juno mission will reveal more about Jupiter’s inner structure and if indeed it has a core.
The atmosphere of Jupiter is the largest planetary atmosphere in the Solar System, spanning over 5.000 km / 3.000 mi in altitude. It is perpetually covered with clouds composed of ammonia crystals and possibly ammonium hydrosulfide.
The clouds are located in the tropopause and are arranged into bands of different latitudes, known as tropical regions sub-divided into lighter-hued zones and darker belts. Because of their interactions, having conflicting circulation patterns, storms and turbulences are created.
Wind speeds of 100 m/s – 360 km/h are common in the zonal jets. The cloud layer is only about 50 km / 31 mi deep, consisting of at least 2 decks of clouds – a thin clearer region and a lower thick one.
The upper atmosphere is calculated to be comprised of about 88-92% hydrogen and 8-12% helium. Since helium atoms have more mass than hydrogen atoms, the composition changes. The atmosphere is thus estimated to be approximately 75% hydrogen and 24% helium with the remaining 1% of the mass consisting of other elements such as methane, water vapor, ammonia, silicon-based compounds, carbon, ethane, oxygen and more.
The outermost layer of the atmosphere contains crystals of frozen ammonia. The interior denser materials by mass are roughly 71% hydrogen, 24% helium and 5% other elements. These atmospheric proportions of hydrogen and helium are close to the theoretical composition of the primordial solar nebula.
The magnetic field of Jupiter is fourteen times stronger than that of Earth. It ranges from 4.2 gauss / 0.42 mT at the equator to 10-14 gauss / 1.0 – 1.4 mT at the poles.
This makes Jupiter’s magnetic field the strongest in the Solar System, with the exception of some phenomenon named “sunspots”, that occur on the Sun that are even stronger.
It is believed that the liquid metallic hydrogen present in Jupiter is responsible for this along with the volcanic activity present on Jupiter’s moon Io that emits large amounts of sulfur dioxide forming a gas torus along the moon’s orbit. This gas is ionized in the magnetosphere and through different influences creates a plasma sheet in Jupiter’s equatorial plane. This causes the deformation of the dipole magnetic field into that of a magnetodisk.
As a result, the aurora of Jupiter is stronger as well. It produces almost a million Megawatts – Earth’s aurora, in comparison, produces about 1.000 Megawatts. The combination of the powerful magnetic field and the charged particles from Io in the plasma torus creates the brightest auroras in the solar system. Sadly, most of them can only be seen through ultraviolet.
Because Jupiter is surrounded by this plasma torus, produced by its strong magnetic field, it makes it very difficult for a spacecraft to approach the planet, yet some zones are not so dangerous but the radiation is still present.
Data suggests that the temperature on Jupiter varies from -145 degrees Celsius / -234 degrees Fahrenheit in the clouds too much higher temperatures near the planet’s center. Some estimates concluded that it would get even hotter than the surface of the Sun.
One of the key features of Jupiter is its Great Red Spot. A storm that’s existed since 1831, and possibly since 1665. This oval-shaped object is greater in size than Earth and rotates counterclockwise within a period of six days. Its maximum altitude is about 8 km / 5 mi above the surrounding cloud tops. Since its discovery, it has decreased in size and recent observations state that it decreases in length by about 930 km / 580 mi per year. Storms are common on Jupiter, some are small and last hours while others are huge and last for centuries. Wind speeds of 100 m/s – 360 km/h are common on certain parts of the planet.
Jupiter was the king of the moons since recently, having a total of 79 known satellites. Recently, Saturn dethroned Jupiter having a total of 82 known satellites. These rankings can change as observations continue.
Out of the 79 satellites, 63 are less than 10 km / 6.2 mi in diameter, and have only been observed since 1975. The Galilean moons, Io, Europa, Ganymede, and Callisto are large enough to be seen from Earth with binoculars. They are among the largest satellites discovered in the Solar System with Ganymede being the largest out of all the satellites in our solar system.
Jupiter has both regular moons and irregular moons with further sub-divisions.
The regular moons of Jupiter consists of the Galilean moons and an inner group of 4 small moons with diameters less than 200 km / 124 mi, and orbits with radii less than 200.000 km / 124.274 mi. They all have orbital inclinations of less than half a degree. The Galilean moons orbit between 400.000 and 2.000.000 km – 248.548 mi and 1.242.742 mi. These moons are believed to have been formed together with Jupiter since they have nearly circular orbits near the plane of Jupiter’s equator.
Despite being the largest known satellite in the solar system, it lacks a substantial atmosphere. It is the 9th largest object in the solar system with a diameter of 5.268 km / 3.273 mi and is 8% larger than the planet Mercury, although only 45% as massive.
It was named after the mythological cupbearer of the Greek gods, who was kidnapped by Zeus for this purpose. It is the only moon known to have a magnetic field and though it posseses a metallic core, it has the lowest moment of inertia factor of any solid body in the Solar System.
Outward from Jupiter, it is the seventh satellite completing an orbit around Jupiter in about 7 Earth days. It is in a 1:2:4 orbital resonance with the moons Europa and Io. It is comprised mostly of equal amounts of silicate rock and water ice, having an iron-rich, liquid core, and an internal ocean that may contain more water than all of Earth’s oceans combined.
A third of its surface is covered by dark regions covered in impact craters and a light region, crosscut by extensive grooves and ridges possibly due to tectonic activity due to tidal heating. It has a thin atmosphere comprised of oxygen, ozone and other elements. There is some speculation on the potential habitability of Ganymede’s ocean.
The innermost and third-largest of the four Galilean moons of Jupiter, Io is the fourth-largest moon the solar system with the highest density and the least amount of water molecules of any known astronomical object in the Solar System.
Named after the mythological character Io, a priestess of Hera who became one of Zeus’ lovers, Io is the most geological active object in the Solar system having over 400 active volcanoes.
This extreme geological activity is due to tidal heating caused from friction generated within Io’s interior as it is pulled between Jupiter and the other Galilean moons.
It takes Io 1.77 Earth-days to orbit Jupiter. It is tidally locked to Jupiter, showing only one side to its parent planet, and has a mean radius of 1.131 miles / 1.821 km, slightly larger than Earth’s moon.
Many of Io’s volcanoes produce plumes of 500 km / 300 mi above the surface. More than 100 mountains are uplifted by extensive compression at the base of Io’s silicate crust. Some of these peaks are taller than Mount Everest, the highest point on Earth’s surface.
Io is composed primarily of silicate rock that surrounds a molten iron core. The plains of Io are coated with sulfur and sulfur-dioxide frost. The materials produced by Io’s volcanism make up its thin atmosphere, and result in the large plasma torus around Jupiter.
Europa is the smallest of the four Galilean moons and the sixth largest of all the moons in the Solar System. It was named after the Phoenician mother of King Minos of Crete and lover of Zeus.
It is slightly smaller than Earth’s moon having a diameter of 3.100 km / 1.900 mi. It is primarily made of silicate rock and has a water-ice crust, and a probably iron-nickel core.
Its atmosphere is thin, composed primarily of oxygen. The surface is very smooth. In fact it is the smoothest of any known solid object in the Solar System. The apparent youth of the smoothness of the surface led to the hypothesis that a water ocean exists beneath it, which could conceivably harbor extraterrestrial life.
Currently, Europa probably has the highest of either having or developing life, and thus it is one of the most closely studied objects in the solar system.
Callisto is the second-largest moon of Jupiter and the third-largest moon in the Solar System after Ganymede and Saturn’s moon Titan. It has a diameter of about 4.821 km / 2.995 mi, having about 99% the diameter of the planet Mercury but only a third of its mass.
Named after a nymph of Greek mythology, also another one of Zeus’s lovers, Callisto is the farthest Galilean moon orbiting Saturn at a distance of 1.8 million km. It is not in a orbital resonance like the other three Galilean moons and thus it is not appreciably tidally heated like the others. It is tidally locked with Jupiter and it is less affected by Jupiter’s magnetosphere than the other inner satellites because of its remote orbit.
It is composed primarily out of equal amounts of rock and ices, with a density of about 1.83 g/cm3, the lowest of Jupiter’s satellites. Investigations by the Galileo spacecraft suggest that Callisto has a silicate core and possibly a subsurface ocean of liquid water at depths of 100 km.
Interestingly, the surface of Callisto is the oldest and most heavily cratered in the Solar System. It has an extremely thin atmosphere composed of carbon dioxide and probably molecular oxygen.
The presence of an ocean within Callisto opens the possibility that it could harbor life but conditions are thought to be less favorable than on Europa. Regardless, it is considered the most suitable planet for a human base for future exploration of the Jovian system due to low radiation levels.
The irregular moons are small and have elliptical and inclined orbits. They are thought to be captured asteroids or fragments of captured asteroids. Their exact number is unknown but they are further divided into sub-divisions – groups, in which they share similar orbital elements and thus may have a common origin.
There are 4 groups:
- The Himalia group – a clustered group of moons with orbits around 11 million to 12 million km / 6 to 7 million mi from Jupiter.
- The Ananke group – a group with a retrograde orbit with rather indistinct borders, averaging from 21 million km / 13 million mi from Jupiter with an average inclination of 149 degrees.
- The Carme group – they are a group with a fairly distinct retrograde orbit that averages from 23 million km / 14 million mi from Jupiter with an average inclination of 165 degrees.
- The Pasiphae group – a very dispersed and only vaguely distinct retrograde group that covers all the outermost moons.
- There are three irregular moons that stand out from these groups:
- Themisto – it orbits halfway between the Galilean moons and the Himalia group.
- Carpo – it is at the inner edge of the Ananke group and orbits Jupiter in prograde direction.
- Valetudo – this moon has a prograde orbit but overlaps the retrograde groups and may result in future collisions with those groups.
Jupiter has a faint planetary ring system composed of three main segments: an inner torus of particles known as the halo, a relatively bright main ring, and an outer gossamer ring.
They appear to be made out of dust rather than ice as with Saturn’s rings. It is believed that the main ring is made of material ejected from the satellites Adrastea and Metis.
In a similar manor, the moons Thebe and Amalthea probably produce the two distinct components of the dusty gossamer ring.
Since it doesn’t have a true surface but rather swirling fluids it is not conducive to life as we know it. Ganymede, Callisto, and Europa on the other hand, have higher chances of sustaining life.
Future plans for Jupiter
Juno is a spacecraft that was launched in 2011 and even now it is still analyzing Jupiter and sending data. Future missions are already set in motion for Ganymede, Europa, Callisto and Io. They are set to be launched on 2020 and 2026. The high probability of life, the powerful volcanic activity and the overall missing details of Jupiter are strong factors in driving these missions.
Did you know?
- When Jupiter was formed it had twice its current diameter.
- Jupiter shrinks 2 cm every year because it radiates too much heath.
- Jupiter is so massive that its barycenter with the Sun lies above the Sun’s surface at 1.068 solar radii from the Sun’s center. It is the only planet whose barycenter with the Sun lies outside the volume of the Sun.
- If Jupiter would be 75 times more massive, it would probably become a star.
- If a person who weighs 100 pounds on Earth would somehow stand on the surface of Jupiter, that person would weigh about 240 pounds due to Jupiter’s gravitational force.
- Although Simon Marius, a German astronomer, is not credited with the sole discovery of the Galilean satellites, his names for the moons were adopted.
- Jupiter experiences almost 200 times more asteroid and comet impacts than Earth
- Jupiter has been called the Solar System’s vacuum cleaner, because of its immense gravity well. It receives the most frequent comet impacts of the Solar System’s planets.
- It was thought that the planet served to partially shield the inner system from cometary bombardment. However, recent computer simulations suggest that Jupiter does not cause a net decrease in the number of comets that pass through the inner Solar System, as its gravity perturbs their orbits inward roughly as often as it accretes or ejects them. This topic remains controversial.
- Jupiter may have been responsible for the Late Heavy Bombardment of the inner Solar System’s history. | 0.853881 | 3.553265 |
New observations by three of the world's largest radio telescopes have revealed that an asteroid discovered last year is actually two objects, each about 3,000 feet (900 meters) in size, orbiting each other.
Three of the world's largest radio telescopes team up to show a rare double asteroid. 2017 YE5 is only the fourth binary near-Earth asteroid ever observed in which the two bodies are roughly the same size, and not touching. This video shows radar images of the pair gathered by Goldstone Solar System Radar, Arecibo Observatory and Green Bank Observatory.
Near-Earth asteroid 2017 YE5 was discovered with observations provided by the Cadi Ayyad University Morocco Oukaimeden Sky Survey on Dec. 21, 2017, but no details about the asteroid's physical properties were known until the end of June. This is only the fourth "equal mass" binary near-Earth asteroid ever detected, consisting of two objects nearly identical in size, orbiting each other. The new observations provide the most detailed images ever obtained of this type of binary asteroid.
On June 21, the asteroid 2017 YE5 made its closest approach to Earth for at least the next 170 years, coming to within 3.7 million miles (6 million kilometers) of Earth, or about 16 times the distance between Earth and the Moon. On June 21 and 22, observations by NASA's Goldstone Solar System Radar (GSSR) in California showed the first signs that 2017 YE5 could be a binary system. The observations revealed two distinct lobes, but the asteroid's orientation was such that scientists could not see if the two bodies were separate or joined. Eventually, the two objects rotated to expose a distinct gap between them.
Bi-static radar images of the binary asteroid 2017 YE5 from the Arecibo Observatory and the Green Bank Observatory on June 25. The observations show that the asteroid consists of two separate objects in orbit around each other. Credit: Arecibo/GBO/NSF/NASA/JPL-Caltech
Full image and caption
Scientists at the Arecibo Observatory in Puerto Rico had already planned to observe 2017 YE5, and they were alerted by their colleagues at Goldstone of the asteroid's unique properties. On June 24, the scientists teamed up with researchers at the Green Bank Observatory (GBO) in West Virginia and used the two observatories together in a bi-static radar configuration (in which Arecibo transmits the radar signal and Green Bank receives the return signal). Together, they were able to confirm that 2017 YE5 consists of two separated objects. By June 26, both Goldstone and Arecibo had independently confirmed the asteroid's binary nature.
The new observations obtained between June 21 and 26 indicate that the two objects revolve around each other once every 20 to 24 hours. This was confirmed with visible-light observations of brightness variations by Brian Warner at the Center for Solar System Studies in Rancho Cucamonga, California.
Radar imaging shows that the two objects are larger than their combined optical brightness originally suggested, indicating that the two rocks do not reflect as much sunlight as a typical rocky asteroid. 2017 YE5 is likely as dark as charcoal. The Goldstone images taken on June 21 also show a striking difference in the radar reflectivity of the two objects, a phenomenon not seen previously among more than 50 other binary asteroid systems studied by radar since 2000. (However, the majority of those binary asteroids consist of one large object and a much smaller satellite.) The reflectivity differences also appear in the Arecibo images and hint that the two objects may have different densities, compositions near their surfaces, or different surface roughnesses.
Scientists estimate that among near-Earth asteroids larger than 650 feet (200 meters) in size, about 15 percent are binaries with one larger object and a much smaller satellite. Equal-mass binaries like 2017 YE5 are much rarer. Contact binaries, in which two similarly sized objects are in contact, are thought to make up another 15 percent of near-Earth asteroids larger than 650 feet (200 meters) in size.
Radar images of the binary asteroid 2017 YE5 from NASA's Goldstone Solar System Radar (GSSR). The observations, conducted on June 23, 2018, show two lobes, but do not yet show two separate objects. Credit: GSSR/NASA/JPL-Caltech
Full image and caption
The discovery of the binary nature of 2017 YE5 provides scientists with an important opportunity to improve understanding of different types of binaries and to study the formation mechanisms between binaries and contact binaries, which may be related. Analysis of the combined radar and optical observations may allow scientists to estimate the densities of the 2017 YE5 objects, which will improve understanding of their composition and internal structure, and of how they formed.
The Goldstone observations were led by Marina Brozovic, a radar scientist at NASA's Jet Propulsion Laboratory in Pasadena, California.
Anne Virkki, Flaviane Venditti and Sean Marshall of the Arecibo Observatory and the University of Central Florida led the observations using the Arecibo Observatory.
Patrick Taylor of the Universities Space Research Association (USRA), scientist at the Lunar and Planetary Institute, led the bi-static radar observations with GBO, home of the Green Bank Telescope (GBT), the world's largest fully steerable radio telescope.
The Arecibo, Goldstone and USRA planetary radar projects are funded through NASA's Near-Earth Object Observations Program within the Planetary Defense Coordination Office (PDCO), which manages the Agency's Planetary Defense Program. The Arecibo Observatory is a facility of the National Science Foundation operated under cooperative agreement by the University of Central Florida, Yang Enterprises, and Universidad Metropolitana. GBO is a facility of the National Science Foundation, operated under a cooperative agreement by Associated Universities, Inc.
In addition to the resources NASA puts into understanding asteroids, the PDCO also partners with other U.S. government agencies, university-based astronomers, and space science institutes across the country, often with grants, interagency transfers and other contracts from NASA. They also collaborate with international space agencies and institutions that are working to track and better understand these smaller objects of the Solar System. In addition, NASA values the work of numerous highly skilled amateur astronomers, whose accurate observational data helps improve asteroid orbits after discovery.
More information about asteroids and near-Earth objects is at these sites:
News Media ContactCalla Cofield
Jet Propulsion Laboratory, Pasadena, Calif.
NASA Headquarters, Washington | 0.852663 | 3.745701 |
After nearly a decade of development, construction, and testing, the world’s most advanced instrument for directly imaging planets around other stars is pointing skyward and producing its first images of planets outside our solar system.
(The image at right shows the planet Beta Pictoris b, orbiting the star Beta Pictoris. The star is hidden behind a mask in the center of the image. The near-infrared image (1.5-1.8 microns) shows the planet glowing brightly from infrared light released during its formation.)
The Gemini Planet Imager (GPI), was designed, built, and optimized for imaging faint planets next to bright stars and analyzing their atmospheres. It is attached to one of the world’s biggest telescopes – the 8-meter Gemini South telescope in Chile. An extraordinarily complex astronomical instrument the size of a small car, the GPI carried out its first observations last November.
“Even these early first-light images are almost a factor of 10 better than the previous generation of instruments. In one minute, we are seeing planets that used to take us an hour to detect,” says Bruce Macintosh of the Lawrence Livermore National Laboratory who led the team that built the instrument.
“Seeing a planet close to a star after just one minute, was a thrill, and we saw this on only the first week after the instrument was put on the telescope!” added Gemini team member Fredrik Rantakyro. “Imagine what it will be able to do once we tweak and completely tune its performance.”
For GPI’s first observations, the team targeted previously known planetary systems, including the well-known Beta Pictoris system and the very young planet Beta Pictoris b. The researchers also used the instrument’s polarization mode – which can detect starlight scattered by tiny particles – to study a faint ring of dust orbiting the very young star HR4796A (pictured below). With previous instruments, only the edges of this dust ring (which may be the debris remaining from planet formation) could be seen, but with GPI, astronomers can observe the entire circumference of the ring.
“Some day, there will be an instrument that will look a lot like GPI, on a telescope in space,” Macintosh predicts. “And the images and spectra that will come out of that instrument will show a little blue dot that is another Earth.”
Discuss this article in our forum
Innovative fiber optic imager may soon photograph exoplanets
Hubble spots water on distant exoplanets
Habitable Earth-like planets? New analysis suggests there are billions
Europa report: moon’s ocean currents make life possible | 0.839464 | 3.808514 |
After almost a year of searching, NASA's Curiosity rover has turned up no traces of the four-pronged hydrocarbon known as methane. This special molecule is regarded by many as a chemical signature of past or present life on the red planet. That means there's no life on Mars, right? Wrong.
First and foremeost: this is not the first time NASA has reported an absence of methane on Mars. The Agency made almost the exact same announcement last November, when Curiosity's initial scans of the planet's atmosphere failed to turn up any sign of the organic molecule in the Martian firmament. The newly published findings – which appear in the latest issue of Science – are essentially a confirmation of those early observations. Curiosity has had a few more months to scan for CH4 with its arsenal of highly sensitive scientific equipment (the big gun in the rover's hunt for methane being its Tunable Laser Spectrometer) and has come up empty handed.
More specifically, lead scientist Chris Webster and crew have reported that if there is methane on Mars, it exists in quantities smaller than 1.3 parts per billion by volume (ppbv). That's the lowest quantity the Tunable Laser Spectrometer can accurately detect. It's also roughly six times lower than other recent estimates.
But what does this mean for the search for life on Mars? In the words of Webster and his colleagues, the finding "greatly reduces" the probability that there are methane-producing microorganisms currently living on Mars. Important finding? Obviously. A conclusive ruling in the debate over past and present life on Mars? No. No on several fronts.
As we've explained before, methane is not the end-all-be-all of evidence for or against life on Mars. An absence of methane ≠ an absence of life, the same way that a positive trace of methane would not be conclusive evidence for Martian microbes. To quote Michael Meyer, NASA's lead scientist for Mars exploration, Webster's findings address "only one type of microbial metabolism [and] there are many types of terrestrial microbes that don't generate methane." Similarly, there are non-biological processes capable of producing and consuming methane. I could go on, but suffice to say that methane is not a robust metric for the presence (or absence) of life.
And so what's really interesting about these results is that they appear to conflict with lot of other recently collected data on the composition of Mars's atmosphere. In 2009, researchers led by planetary scientist Michael Mumma concluded that big – albeit highly localized – plumes of methane are released sporadically from beneath the planet's surface. Since then, additional observations made from Earth and Mars orbit have supported the existence of localized methane concentrations of up to 45 parts per billion in the Martian atmosphere.
What Curiosity provides that these previous investigations don't is, quite literally, an on-the-ground assessment of Mars's atmospheric makeup. On one hand, this is great. Curiosity can stick its scientifically sophisticated nose in the air and sniff out the chemical makeup of its surroundings – not from Earth, not from orbit, but from right there in Gale Crater! This in situ approach offers researchers a degree of specificity that is unmatched by observations made with ground-based telescopes, or satellites in Mars orbit.
But then, do Curiosity's findings really contradict those made in other studies? Remember: previous observations have pointed to the existence of highly localized patches of methane that are eliminated very quickly from large, vertical columns of the atmosphere. Who's to say that Gale Crater isn't just a methanic dead-zone? If it is, can Curiosity (which samples from the first meter of air above the floor of Gale Crater – what Webster's team admits is "the very lowest part of the Mars atmosphere") really speak to the composition of the planet's atmosphere as a whole?
Webster and his team say it can. Their line of reasoning is as follows: it takes several hundred years for methane to disappear via photochemical processes, but only a few months to circulate throughout the Martian atmosphere and mix evenly with any pockets of air lacking in methane. This, write the researchers, suggests that the measured upper limit of 1.3 ppbv "is representative of the global mean background level." More than that – to quote study co-athor Sushil Atreya of the University of Michigan, Ann Arbor – it suggests that "there cannot be much methane being put into the atmosphere by any mechanism, whether [biological], [geological], or by ultraviolet degradation of organics delivered by the fall of meteorites or interplanetary dust particles."
Emphasis added, because, Michael Mumma (who, you'll recall, led the 2009 study on Martian methane plumes) takes a decidedly different stance.
"These findings are actually consistent with our results," Mumma said of Webster's team's findings, in an interview with National Geographic. "We reported that the methane releases are likely to be sporadic and that the methane is quickly eliminated in the atmosphere."
Emphasis added again, because, as Mumma notes, his team's findings hinge largely on the rapid elimination of methane from the atmosphere. Which brings us to the contentious mystery at the center of this whole story.
In Mumma's paper, his team proposes a very short lifetime for methane in the Martian atmosphere – between 0.4 and 4 years. This lifetime, Webster's team criticizes, would require "powerful destruction mechanisms that have not been identified to date." And while several models for such mechanisms have been proposed, Webster and crew claim there remains no evidence for their existence at Mars, nor for their ability to reduce the lifetime of methane by the factor of 100 or more compared to its photochemical lifetime:
With an expected photochemical lifetime of methane in the Martian atmosphere of hundreds of years, there currently remains no accepted explanation for the existence and distribution of the reported plumes, nor of the apparent disappearance of methane over the last few years.
In case you somehow missed it: them's fightin' words! The true nature of Martian methane is a planetary mystery with what now appear to be at least two surprisingly divergent explanations. Determining which is closest to reality will require years of further investigation, conducted from the surface of Mars, from the planet's orbit, and even from right here on Earth. Regardless of whether Mars is – or ever was – home to microbial life, the truth of the matter is that there's some weird-ass chemistry happening on the Red Planet that we're just beginning to understand! And that's pretty damn amazing as it is.
The researchers' findings are published in the latest issue of Science. | 0.828152 | 3.797546 |
NASA’s discovered its tiniest solar system yet, which includes the three smallest exoplanets ever found.
Data from NASA’s Kepler mission has revealed planets that are 0.78, 0.73 and 0.57 times the radius of Earth, orbiting a single star called KOI-961. The smallest is about the size of Mars.
All three are thought to be rocky like Earth, but orbit close to their star, making them too hot for liquid water to exist.
Of the more than 700 exoplanets thus far discovered, only a handful are known to be rocky.
“Astronomers are just beginning to confirm thousands of planet candidates uncovered by Kepler so far,” says Doug Hudgins, Kepler program scientist.
“Finding one as small as Mars is amazing, and hints that there may be a bounty of rocky planets all around us.”
The three planets are very close to their star, taking less than two days to orbit around it. KOI-961 star is a red dwarf with a diameter one-sixth that of our sun, making it just 70 percent bigger than Jupiter.
“This is the tiniest solar system found so far,” says John Johnson, the principal investigator of the research from NASA’s Exoplanet Science Institute.
“It’s actually more similar to Jupiter and its moons in scale than any other planetary system. The discovery is further proof of the diversity of planetary systems in our galaxy.”
And with red dwarfs the most common kind of star in our Milky Way galaxy, the discovery suggests that the galaxy could be teeming with similar rocky planets.
“These types of systems could be ubiquitous in the universe,” says Caltech’s Phil Muirhead. “This is a really exciting time for planet hunters.” | 0.919472 | 3.359046 |
Fire in the air
During the 18th century, scientists understood fire and combustion to be the result of a mysterious substance called phlogiston. Although this theory had great explanatory power and was widely accepted among scientists for approximately 100 years, it nevertheless fell eventually (and its fall, once it occurred, happened very quickly). Phlogiston teaches us that just because a theory is widely accepted among scientists, is believed to explain all the evidence, and reigns supreme for a long time, does not mean that it is true. Indeed, phlogiston was in many ways a stronger theory than is evolution today; however, since evolution allows mankind to shake his fist at his Creator, it is not subjected to the same standard of proof as other, more empirical theories such as phlogiston.
What is fire? What happens when something burns? The search for the answers to these questions lasted for centuries, involved many people, and also has much to teach us today as Christians.
Robert Boyle (1627–1691), a devout Christian who is often called ‘the father of chemistry’,1 was very much interested in combustion and made many contributions in this area. Many of his experiments used an air pump invented around 1658 by his assistant Robert Hooke. Boyle had heard of the air pump invented by Guericke2 in 1647, and instructed Hooke to construct a similar device: one that would allow Boyle to evacuate air from a large glass vessel, accessible through a hole in the top. Although crude by today’s standards, this apparatus allowed Boyle to perform and observe experiments in a near vacuum.
Boyle discovered that candles, glowing coals, and sulfur would not burn without air. He also found that flies, bees, butterflies, mice, and birds would ‘swoon’ and then die in a vacuum. Obviously there was some similarity between respiration and combustion. Also, before dying, the mice and birds would first produce vapors—‘steams’3 —that would condense inside the glass first. Boyle surmised that they died because they were poisoning their own air. (He wrote about ‘recrementitious steams that are separated from the mass of blood in its passage through the lungs’3 —he understood that some sort of waste was removed during respiration, but didn’t understand as well that air supplied anything necessary for life.)
Stahl and phlogiston
Subsequently, German chemist Georg Ernst Stahl (1659–1734) popularized4 an idea called phlogiston. Like most scientists of his time, Stahl was heavily influenced by Greek philosophy and the idea that there were certain ‘essences’ which made up all physical matter. The phlogiston theory was that all material was made up of three basic components: the pure form of the material, the essence of fire (called phlogiston, after the Greek word phlogistos, meaning ‘burning’), and finally any impurities that also happened to be present. Combustion was merely a process by which the inherent phlogiston of a material, its essential fire, was released into the air. As the phlogiston escaped, it produced a whirling motion in the air—the flame.
Stahl’s theory made sense. After all, when a piece of wood burns, the ash that’s left over was obviously much less substantial than the wood itself had been. Something must have left, and that something was phlogiston. The leftover ash was therefore the essence of the wood (plus any contaminants). Different materials varied in their amount of phlogiston. Rock had almost none—thus it wouldn’t burn. Conversely, lampblack was perhaps pure phlogiston, since it burned readily and left very little residue.
The new theory explained past observations very well. For example, it had been known for centuries that the heating of most metals in open air resulted in the formation of a powder. This powder was called a calx (and the process calcination). Now it was understood that the calx was the pure essence of the metal after the phlogiston was removed. The transformation was quite often reversible—many calces could be smelted with charcoal (a source of phlogiston) and be transformed into the metal again.
The phlogiston theory required that air be present during combustion to absorb the phlogiston. Of course, the experiments of Boyle and others had already shown that combustion couldn’t occur in a vacuum. Neither could respiration, which was consistent since respiration was thought to be a form of combustion. However, scientists also realized that a given amount of air can only absorb so much phlogiston. Creatures or flames placed into airtight spaces lived for a while, then died. Obviously, the air would only accept phlogiston until it was saturated, then combustion would cease. Air that was saturated with phlogiston became known as ‘phlogisticated air’.
British chemist Joseph Priestley (1733–1804) even discovered5 that he could manipulate the amount of phlogiston in the air. He heated mercury in air, which turned it into a reddish substance that he called the precipitate per se. Then, when the precipitate per se was heated again to a different temperature, it not only turned back into mercury but also produced a new kind of air. This new air allowed mice to live longer, and wood burned more brightly in it. Obviously this new kind of air could accept more phlogiston than normal air—that must mean it started out with less phlogiston in the first place. Therefore, Priestley named it ‘dephlogisticated air’.
The phlogiston idea was applied to a wide variety of phenomena. Left to its own devices, iron will slowly produce its calx (rust). Therefore, the rusting process was also a (slow) form of combustion. Fermentation, the interactions of acids and alkalis, and the formation of salts, were all explained using phlogiston. Some investigators even suspected that phlogiston itself could be isolated. English scientist Henry Cavendish (1731–1810) dissolved metals in acids and produced ‘inflammable air’, so named because it burned so easily. Cavendish thought it to be pure phlogiston.6
Phlogiston was widely accepted, but it did have some problems. For example, wood ash obviously weighed much less than the wood itself had weighed, and so the phlogiston that had been released must have accounted for at least some of that weight that was lost. However, it had been known for some time that metals gained weight when they were calcified. For example, Boyle had heated tin in a sealed flask. When he opened the flask and weighed the tin afterwards, he found that it had gained weight. (He attributed this to ‘particles of fire’ being absorbed by the metal.) Others had examined this question as well. Louis Bernard Guyton de Morveau (1737–1816) published his Dissertation sur le phlogistique in 1772. He had investigated all of the calcinable metals, and ‘had confirmed in experiments of exceptional precision and care that metals increased in weight when they were roasted in air’ (emphasis in original).7 He proposed that in this case phlogiston had a ‘levity’; thus, when the metals gave up their phlogiston, they became heavier.
French scientist Antoine-Laurent Lavoisier (1743–1794) became skeptical of phlogiston, at least partly because of dissatisfaction with Guyton de Morveau’s ‘absurd’8 explanations. He reperformed many of the classic experiments himself, although being more precise in his measurements and more exact in his overall approach than the original experimenters had been. In 1775 he read the first9 of a series of papers before the French Academy of Sciences, developing a new hypothesis: ‘dephlogisticated air’ was itself responsible for combustion, and there was no such thing as phlogiston. He was very clear that his theory was revolutionary; it was ‘directly contrary to the theory of Stahl’10 and ‘the system of Stahl will be found to be shaken to its foundations’.10
Today we know ‘dephlogisticated air’ as oxygen, and of course we accept his idea as true. Oxygen is of course required for both combustion and respiration, and heated metals absorb it (Priestley’s precipitate per se is today known as mercuric oxide). Rust, also known as iron oxide, is similarly understood today as being the result of the iron being ‘oxidized’ (combined with oxygen). ‘Inflammable air’ is now known as hydrogen. Today we understand combustion in general to be a process whereby oxygen combines with other elements in the material, sometimes producing various gases and other times solids, several forms of energy.
Lavoisier did not stop until he had completely overturned the foundations of chemistry in his day. Among other things, his Traîte elementaire de chimie, published in 1789, replaced the four ancient ‘elements’ with 33.11 Also, ‘The language of chemistry’, Lavoisier now felt, had to be transformed to go with his new theory, and he undertook a revolution in nomenclature, too, replacing the old, picturesque but uninformative terms—like butter of antimony, jovial bezoar, blue vitriol, sugar of lead, fuming liquor of Libavius, flowers of zinc—with precise, analytic, self-explanatory ones. If an element was compounded with nitrogen, phosphorus, or sulfur, it became a nitride, a phosphide, a sulfide. If acids were formed, through the addition of oxygen, one might speak of nitric acid, phosphoric acid, sulfuric acid; and of the salts of these as nitrates, phosphates, and sulfates. If smaller amounts of oxygen were present, one might speak of nitrites or phosphites instead of nitrates and phosphates, and so on. Every substance, elementary or compound, would have its true name, denoting its composition and chemical character, and such names, manipulated as in an algebra, would instantly indicate how they might interact or behave in different circumstances’.12 Laviosier’s insights were so powerful that the old paradigm of phlogiston was completely swept away.
Lavoisier’s new hypothesis was not immediately embraced by all of his peers. The phlogiston theory had been the dominant paradigm for almost 100 years, and it was based on philosophical views that had been in place for over a millenium. But his challenges to the phlogiston theory were substantial, and he pointed out that the advocates of the phlogiston theory (known as ‘Phlogistians’) had many inconsistencies in their explanations: for example, how could wood lose weight when phlogiston was lost, but metal gain weight when phlogiston was lost? In his Mémoires de Chimiel (believed to have been written in 1792 and published posthumously in 1805) he complained:
‘ … chemists have turned phlogiston into a vague principle, … which consequently adapts itself to all the explanations for which it may be required. Sometimes this principle has weight, and sometimes it has not; sometimes it is free fire and sometimes it is fire combined with the earthy element; sometimes it passes through the pores of vessels; sometimes these are impervious to it; it explains both causticity and non-causticity, transparency and opacity, colours and their absence, it is a veritable Proteus changing in form at every instant.’13
Lavoisier had much better explanations. For example, he had reperformed Boyle’s tin heating experiment, but unlike Boyle, he weighed the tin and the flask together, before and after the heating. He observed that, even after the heating, the combined weight had not changed. Once he opened the flask, air rushed in, and then the tin gained weight. Therefore, he concluded, the tin was absorbing oxygen from the air, and this accounted for the weight gain. Many of Lavoisier’s contributions to science were due to his insistence on precise quantitative measurements—this emphasis was unusual until that time, and lent great empirical weight to his arguments.
The Phlogistians did not give up easily to the Antiphlogistians, and they pointed out problems with Lavoisier’s ideas as well. However, Lavoisier refined and corrected his hypothesis over time, and the Antiphlogistian case became stronger. As the debate progressed, more and more Phlogistians became Antiphlogistians. Eventually, the Antiphlogistians won, with Priestley (a Phlogistian to the end) mourning in 1796:14
“The old system is entirely exploded … I hardly know of any person, except my friends of the Lunar Society at Birmingham, who adhere to the doctrine of phlogiston; and what may now be the case with them, in this age of revolutions, philosophical as well as civil, I will not at this distance answer for.”
Comparing phlogiston to evolution
So how is this relevant to us today? The phlogiston theory lasted for over 100 years. For most of that time, all the prominent scientists believed it. It seemed to explain so much. But it was wrong. Although many today would laugh at the phlogiston theory as being hopelessly naive, nevertheless it is in many ways better than the ruling paradigm of our time: evolution. Let’s compare the two:
- Phlogiston accumulated a large body of evidence over time. When this evidence was re-examined, much of it was shown not to support the idea after all, causing scientists to abandon the theory. Not so with evolution—as earlier ‘evidence’ for evolution has been subsequently disproved, this has not seemed to affect anybody’s faith in the idea. For example, most of the ‘evidence’ for evolution that was presented in the 1925 Scopes trial has since been thrown away (e.g. Piltdown Man,15 horse evolution,16 embryonic recapitulation,17 etc.). It doesn’t seem to matter that the ‘evidence’ is always changing.
- Phlogiston was discarded by many scientists because they saw that many of its predictions were not upheld by new experiments and data. Not so with evolution—for example, Darwin acknowledged that the fossil evidence for his theory was lacking, and admitted that it was ‘the most obvious and serious objection which can be urged against the theory’.18 He placed his faith in the ‘extreme imperfection of the geologic record’,18 expressing confidence that the evidence would be found later. Today, after more than a century of tireless digging, the evidence still hasn’t been found—but rather than acknowledging the tremendous problem this poses, some evolutionary paleontologists claim that this lack of fossil evidence for evolution is, instead, evidence for a certain version of evolution.19,20 Similarly, in astronomy we see that the measured Cosmic Microwave Background is only about 10% of that required by the big bang inflation model— nevertheless, this is claimed to support the model!21
- Phlogiston was also discarded by many scientists because they grew uncomfortable with the increasingly ad hoc explanations that were necessary in order to preserve the theory against the growing body of evidence. Not so with evolution—we often see situations where it is preferable to make up implausible stories than to question evolution. For example, we see stars whose orbits are unstable (over billions of years anyway) within their parent galaxies. Rather than accepting the possibility that the galaxies are young, evolutionists would rather invent ‘dark matter’ instead (an invisible, undetectable material that’s surrounding each galaxy and galaxy cluster).22,23 There’s also ‘dark energy’: a mysterious unknown force operating on the entire universe, which is necessary to keep the big bang model viable.24 Other serious problems with the big bang have had to be repaired with the ‘inflation’ hypothesis25—the idea that soon after the big bang, the Universe suddenly increased its rate of expansion to more than the speed of light, then a little while later suddenly slowed down again. How solid is this idea? Even its proponents admit: ‘What drove inflation? Nobody knows’.26 We see that phlogiston was rightly thrown out when it became necessary to spin tales to explain away the evidence, yet sadly we see this same sort of story-telling appear perfectly respectable today in evolutionary thought.
Phlogiston, although obsolete as a scientific idea, nevertheless has much to teach us today. We see that just because an idea seems to explain a lot of things, and is believed by all the prominent scientists of the day, who all proclaim it to be the ultimate explanation of how things work, does not necessarily mean that this idea won’t be thrown onto the garbage heap later.
There’s no reason why this shouldn’t be as true of today’s evolutionary theories as it was of phlogiston. As creationists, we are often mocked because ‘the majority of scientists believe in evolution.’ Even if that is true, it’s irrelevant. As a paradigm, phlogiston was perceived to be just as powerful then as evolution is today, yet it was completely uprooted and destroyed in a few short years.
(We even see that evolution is actually on shakier ground than phlogiston was. Why then has it not been overthrown yet? Because, unlike phlogiston, the creation/evolution issue is a spiritual battle as well as a scientific one. A godless society will fight tooth and nail to reject any possibility of responsibility towards a creator. If alternative explanations don’t match the evidence, then so be it—anything is preferable to the truth.)
Phlogiston teaches us to resist trusting the majority’s opinions, just because they are held by the majority. We see that those opinions can change in an instant. On the other hand, the Bible is the Word of the Creator of Heaven and Earth. It has been the same from the beginning, and its truth remains … today and forever.
References and notes
- E.g. the title of Ref. 3. A brief biography, The man who turned chemistry into a science, was published in Creation 12(1):22–23, December 1989. Return to text.
- Gillispie, C.C. (Ed.), Dictionary of Scientific Biography, Charles Scribner’s Sons, New York, Vol. V, pp. 574–575, 1975. Return to text.
- As quoted in Sootin, H., Robert Boyle: Founder of Modern Chemistry, Franklin Watts, USA, p. 91, 1962. Return to text.
- Stahl, G.E., Zymotechnia Fundamentalis, Halle, 1697. Return to text.
- As published in the second volume of his Experiments and Observationson Different Kinds of Air, J, Johnson, London, 1775. Gillispie, Ref. 2, Vol. VIII, p. 75. Return to text.
- Gillispie, Ref. 2, Vol. III, p. 156. Return to text.
- Sacks, O., Uncle Tungsten, Memories of a Chemical Boyhood, Alfred A. Knopf, New York, p. 108, 2001. Return to text.
- Sacks, Ref. 7, p. 109. Return to text.
- Lavoisier, A-L., Mémoire sur la nature du principe qui se combine avecles metaux pendant leur calcination, et qui en augmente le poids (Memoir on the nature of the principle which combines with metals during their calcination and which increases their weight); read before the Academy, 26 April 1775; a revised version was published in the Academy’s Memoires in 1778. Return to text.
- Lavoisier, A-L., Mémoire sur la combustion en général (Memoir on Combustion in General); presented to the Academy in 1777. Return to text.
- More precisely, the 33 elements corrected the 55 that Lavoisier had earlier proposed in his Méthode de nomenclature chimique (1787). Gillispie, Ref. 2, Vol. VIII, p. 80. Return to text.
- Sacks, Ref. 7, p. 112. Return to text.
- Encyclopaedia Britannica, 11th Edition, 4:35, 1911. Return to text.
- Priestley, J., Considerations On The Doctrine Of Phlogiston And The Decomposition Of Water, 1796. Return to text.
- Now acknowledged to be a deliberate fake—a human skull with an orangutan jaw, stained to look old. Return to text.
- Sarfarti, J., The non-evolution of the horse, Creation 21(3):28–31, 1999. Return to text.
- Grigg, R., Fraud rediscovered, Creation 20(2):49–51, 1998. Return to text.
- Darwin, C., The Origin of Species By Means Of Natural Selection Or The Preservation Of Favored Races In The Struggle For Life, Random House, Inc., New York, p. 406, 1993. Return to text.
- Batten, D., Did creationists ‘hijack’ Gould’s idea?, J. Creation 16(2):22–24, 2002. Return to text.
- Batten, D., Punctuated equilibrium: come of age?, J. Creation 8(2):131–137, 1994. Return to text.
- Hartnett, J., Cosmologists can’t agree and are still in doubt!, J. Creation 16(3):21–26, 2002. Return to text.
- DeYoung, D.B., Dark matter, CRSQ 36(4):177–182, 2000; creationresearch.org. Return to text.
- Oard, M. and Sarfati, J., No dark matter found in the Milky Way galaxy, J. Creation 13(1):3–4, 1999. Return to text.
- The biggest problem with this idea is that no one has any idea what dark energy is. “So far, all we’ve been able to do is name it,” says Turner. “It could be the energy associated with nothing, or the influence of hidden spatial dimensions.” Sincell, S., The 8 greatest mysteries of cosmology, Astronomy, June 2001, p. 46. Return to text.
- There are actually a number of inflation models today. Physicists have suggested different models to describe the inflating universe, but all the solutions are mathematical conveniences with no particular physical basis. “All the theories of inflation amount to proof that we don’t have one good theory yet,” says Fermi National Accelerator Laboratory astrophysicist Edward W. “Rocky” Kolb. Sincell, Ref. 24, p. 49, emphasis added. Return to text.
- Sincell, Ref. 24, p. 49. Even Alan Guth, the inventor of inflation, has admitted, “Although the basic idea still looks very attractive [because the big bang is invalid otherwise], we don’t know the real details of inflation or the mechanism that drives it." Nadis, S., Cosmic inflation comes of age, Astronomy, April 2002, p. 30, material in brackets added. Return to text. | 0.861702 | 3.196983 |
A visible light image of the Andromeda Galaxy.
|Observation data (J2000 epoch)|
|Right ascension||00h 42m 44.3s|
|Declination||+41° 16′ 9″|
|Redshift||−301 ± 1 km/s|
|Distance||2.54 ± 0.06 Mly|
(778 ± 17 kpc)a
|Apparent dimensions (V)||190′ × 60′|
|Apparent magnitude (V)||4.4|
|M31, NGC 224, UGC 454, PGC 2557, 2C 56 (Core), LEDA 2557|
The Andromeda Galaxy (also known as Messier 31, M31, or NGC 224; often referred to as the Great Andromeda Nebula in older texts) is a spiral galaxy approximately 2.5 million light-years away in the constellation Andromeda. It is the nearest spiral galaxy to our own, the Milky Way. As it is visible as a faint smudge on a moonless night, it is one of the farthest objects visible to the naked eye, and can be seen even from urban areas with binoculars. It is named after the princess Andromeda (Greek: Ανδρομέδη - Andromédē) in Greek mythology. Andromeda is the largest galaxy of the w:Local Group, which consists of the Andromeda Galaxy, the Milky Way Galaxy, the Triangulum Galaxy, and about 30 other smaller galaxies. Although the largest, it may not be the most massive, as recent findings suggest that the Milky Way contains more dark matter and may be the most massive in the grouping. The 2006 observations by the Spitzer Space Telescope revealed that M31 contains one trillion (1012) stars, greatly exceeding the number of stars in our own galaxy. While the 2006 estimates put the mass of the Milky Way to be ~80% of the mass of Andromeda, which is estimated to be 7.1×1011 [solar masses, a 2009 study concluded that Andromeda and the Milky Way are about equal in mass.
At an apparent magnitude of 4.4, the Andromeda Galaxy is notable for being one of the brightest Messier objects, making it easily visible to the naked eye even when viewed from areas with moderate light pollution. Although it appears more than six times as wide as the full moon when photographed through a larger telescope, only the brighter central region is visible with the naked eye.
The earliest recorded observation of the Andromeda Galaxy was in 964 CE by the Persian astronomer, Abd al-Rahman al-Sufi (Azophi), who described it as a "small cloud" in his Book of Fixed Stars. Other star charts of that period have it labeled as the Little Cloud. The first description of the object based on telescopic observation was given by Simon Marius in 1612. Charles Messier catalogued it as object M31 in 1764 and incorrectly credited Marius as the discoverer, unaware of Al Sufi's earlier work. In 1785, the astronomer William Herschel noted a faint reddish hue in the core region of the M31. He believed it to be the nearest of all the "great nebulae" and, based on the color and magnitude of the nebula, he incorrectly estimated that it was no more than 2,000 times the distance of w:Sirius.
w:William Huggins in 1864 observed the w:spectrum of M31 and noted that it differed from a gaseous nebula. The spectra of M31 displayed a w:continuum of frequencies, superimposed with dark absorption lines that help identify the chemical composition of an object. The Andromeda nebula was very similar to the spectra of individual stars, and from this it was deduced that M31 had a stellar nature. In 1885, a supernova (known as "S Andromedae") was seen in M31, the first and so far only one observed in that galaxy. At the time M31 was considered to be a nearby object, so the cause was thought to be a much less luminous and unrelated event called a nova, and was named accordingly "Nova 1885".
The first photographs of M31 were taken in 1887 by w:Isaac Roberts from his private observatory in w:Sussex, England. The long-duration exposure allowed the spiral structure of the galaxy to be seen for the first time. However, at the time this object was commonly believed to be a nebula within our galaxy, and Roberts mistakenly believed that M31 and similar spiral nebulae were actually solar systems being formed, with the satellites nascent planets. The w:radial velocity of this object with respect to our w:solar system was measured in 1912 by w:Vesto Slipher at the w:Lowell Observatory, using w:spectroscopy. The result was the largest velocity recorded at that time, at 300 kilometres per second (186 miles/s.), moving in the direction of the Sun.
In 1917, w:Heber Curtis observed a nova within M31. Searching the photographic record, 11 more novae were discovered. Curtis noticed that these novae were, on average, 10 magnitudes fainter than those that occurred within our Galaxy. As a result he was able to come up with a distance estimate of 500,000 light-years. He became a proponent of the so-called "island universes" hypothesis, which held that spiral nebulae were actually independent galaxies.
In 1920 the w:Great Debate between w:Harlow Shapley and w:Heber Curtis took place, concerning the nature of the w:Milky Way, spiral nebulae, and the dimensions of the w:universe. To support his claim that Great Andromeda Nebula (M31) was an external galaxy, Curtis also noted the appearance of dark lanes resembling the dust clouds in our own Galaxy, as well as the significant w:Doppler shift. In 1922 w:Ernst Öpik presented a very elegant and simple astrophysical method to estimate the distance of M31, his result (450 kpc) put Andromeda Nebula far outside our Galaxy. w:Edwin Hubble settled the debate in 1925 when he identified extragalactic w:Cepheid variable stars for the first time on astronomical photos of M31. These were made using the 2.5 metre (100 in) w:Hooker telescope, and they enabled the distance of Great Andromeda Nebula to be determined. His measurement demonstrated conclusively that this feature was not a cluster of stars and gas within our Galaxy, but an entirely separate galaxy located a significant distance from our own.
This galaxy plays an important role in galactic studies, since it is the nearest giant spiral (although not the nearest galaxy). In 1943, w:Walter Baade was the first person to resolve stars in the central region of the Andromeda Galaxy. Based on his observations of this galaxy, he was able to discern two distinct populations of stars based on their w:metallicity, naming the young, high velocity stars in the disk Type I and the older, red stars in the bulge Type II. This nomenclature was subsequently adopted for stars within the Milky Way, and elsewhere. (The existence of two distinct populations had been noted earlier by w:Jan Oort.) Dr. Baade also discovered that there were two types of Cepheid variables, which resulted in a doubling of the distance estimate to M31, as well as the remainder of the Universe.
Radio emission from the Andromeda Galaxy was first detected by w:Grote Reber in 1940. The first radio maps of the galaxy were made in the 1950s by John Baldwin and collaborators at the Cambridge Radio Astronomy Group. The core of the Andromeda Galaxy is called 2C 56 in the 2C radio astronomy catalogue. In 2009, the first planet may have been discovered in the Andromeda Galaxy. This candidate was detected using a technique called w:microlensing, which is caused by the deflection of light by a massive object.
The Andromeda Galaxy is approaching the w:Sun at about 300 kilometers per second (186 miles/s.), so it is one of the few w:blue shifted galaxies. The Andromeda Galaxy and the Milky Way are approaching one another at a speed of 100 to 140 kilometers per second (62–87 miles/s.; 223,200–313,200mph). The collision is predicted to occur in about 2.5 billion years. In that case the two galaxies will likely merge to form a giant w:elliptical galaxy. However, Andromeda's tangential velocity with respect to the Milky Way is only known to within about a factor of two, which creates uncertainty about the details of the collision. Such events are frequent among the galaxies in w:galaxy groups. The fate of the w:Earth and the w:Solar System in the event of a collision are presently unknown, but there is a small chance that the Solar System could be ejected from the Milky Way or join Andromeda.
The measured distance to the Andromeda Galaxy was doubled in 1953 when it was discovered that there is another, dimmer type of w:Cepheid. In the 1990s, measurements of both standard w:red giants as well as w:red clump stars from the w:Hipparcos satellite measurements were used to calibrate the Cepheid distances.
Recent distance estimates
At least four distinct techniques have been used to measure distances to the Andromeda Galaxy.
In 2003, using the infrared w:surface brightness fluctuations (I-SBF) and adjusting for the new period-luminosity value of Freedman et al. 2001 and using a metallicity correction of -0.2 mag dex−1 in (O/H), an estimate of 2.57 ± 0.06 Mly (787 ± 18 kpc) was derived.
In 2005, a group of astronomers consisting of w:Ignasi Ribas (CSIC, IEEC) and his colleagues announced the discovery of an eclipsing binary star in the Andromeda Galaxy. The binary star, designated M31VJ00443799+4129236,c has two luminous and hot blue stars of types O and B. By studying the eclipses of the stars, which occur every 3.54969 days, the astronomers were able to measure their sizes. Knowing the sizes and temperatures of the stars they were able to measure the w:absolute magnitude of the stars. When the visual and absolute magnitudes are known, the distance to the star can be measured. The stars lie at the distance of 2.52 ± 0.14 Mly (770 ± 40 kpc) and the whole Andromeda Galaxy at about 2.5 Mly. This new value is in excellent agreement with the previous, independent Cepheid-based distance value.
Andromeda is close enough that the w:Tip of the Red Giant Branch (TRGB) method may also be used to estimate its distance. The estimated distance to M31 using this technique in 2005 yielded 2.56 ± 0.08 Mly (785 ± 25 kpc).
Averaged together, all these distance measurements give a combined distance estimate of 2.54 ± 0.06 Mly (778 ± 17 kpc).a Based upon the above distance, the diameter of M31 at the widest point is estimated to be 141 ± 3 kly.d
Mass and luminosity estimates
Mass estimates for the Andromeda halo (including w:dark matter) give a value of approximately 1.23×1012 M☉ (or 1.2 million million w:solar masses) compared to 1.9×1012 M☉ for the Milky Way. Thus M31 may be less massive than our own galaxy, although the error range is still too large to say for certain. Even so, the masses of the Milky Way and M31 are comparable, and M31's spheroid actually has a higher stellar density than that of the Milky Way.
In particular, M31 appears to have significantly more common stars than the Milky Way, and the estimated w:luminosity of M31, ~2.6×1010 L☉, is about 25% higher than that of our own galaxy. However the rate of star formation in the Milky Way is much higher, with M31 only producing about one solar mass per year compared to 3–5 solar masses for the Milky Way. The rate of w:supernovae in the Milky Way is also double that of M31. This suggests that M31 has experienced a great star formation phase in its past, but is now relatively w:quiescent, whereas the Milky Way is experiencing more active star formation. Should this continue, the luminosity in the Milky Way may overtake that of M31 in the future.
Based on its appearance in visible light, the Andromeda galaxy is classified as an SA(s)b galaxy in the de Vaucouleurs-Sandage extended classification system of spiral galaxies. However, data from the w:2MASS survey showed that the bulge of M31 has a box-like appearance, which implies that the galaxy is actually a barred galaxy with the bar viewed almost directly along its long axis.
In 2005, astronomers used the w:Keck telescopes to show that the tenuous sprinkle of stars extending outward from the galaxy is actually part of the main disk itself. This means that the spiral disk of stars in Andromeda is three times larger in diameter than previously estimated. This constitutes evidence that there is a vast, extended stellar disk that makes the galaxy more than 220,000 light-years in diameter. Previously, estimates of Andromeda's size ranged from 70,000 to 120,000 light-years across.
The galaxy is inclined an estimated 77° relative to the Earth (where an angle of 90° would be viewed directly from the side). Analysis of the cross-sectional shape of the galaxy appears to demonstrate a pronounced, S-shaped warp, rather than just a flat disk. A possible cause of such a warp could be gravitational interaction with the satellite galaxies near M31. The galaxy M33 could be responsible for some warp in M31's arms, though more precise distances and radial velocities are required.
Spectroscopic studies have provided detailed measurements of the rotational velocity of M31 at various radii from the core. In the vicinity of the core, the rotational velocity climbs to a peak of 225 kilometres per second (140 miles/s.) at a radius of 1,300 w:light-years, then descends to a minimum at 7,000 light-years where the rotation velocity may be as low as 50 kilometres per second (31 miles/s.). Thereafter the velocity steadily climbs again out to a radius of 33,000 light-years, where it reaches a peak of 250 kilometres per second (155 miles/s.). The velocities slowly decline beyond that distance, dropping to around 200 kilometres per second (124 miles/s.) at 80,000 light-years. These velocity measurements imply a concentrated mass of about 6×109 M☉ in the nucleus. The total mass of the galaxy increases w:linearly out to 45,000 light-years, then more slowly beyond that radius.
The w:spiral arms of Andromeda are outlined by a series of w:H II regions that Baade described as resembling "beads on a string". They appear to be tightly wound, although they are more widely spaced than in our galaxy. Rectified images of the galaxy show a fairly normal spiral galaxy with the arms wound up in a clockwise direction. There are two continuous trailing arms that are separated from each other by a minimum of about 13,000 light-years. These can be followed outward from a distance of roughly 1,600 light-years from the core. The most likely cause of the spiral pattern is thought to be interaction with M32. This can be seen by the displacement of the neutral hydrogen clouds from the stars.
In 1998, images from the w:European Space Agency's w:Infrared Space Observatory demonstrated that the overall form of the Andromeda galaxy may be transitioning into a w:ring galaxy. The gas and dust within Andromeda is generally formed into several overlapping rings, with a particularly prominent ring formed at a radius of 32,000 light-years from the core. This ring is hidden from visible light images of the galaxy because it is composed primarily of cold dust.
Close examination of the inner region of Andromeda showed a smaller dust ring that is believed to have been caused by the interaction with M32 more than 200 million years ago. Simulations show that the smaller galaxy passed through the disk of Andromeda along the latter's polar axis. This collision stripped more than half the mass from the smaller M32 and created the ring structures in Andromeda.
Studies of the extended halo of M31 show that it is roughly comparable to that of the Milky Way, with stars in the halo being generally "metal-poor", and increasingly so with greater distance. This evidence indicates that the two galaxies have followed similar evolutionary paths. They are likely to have accreted and assimilated about 1–200 low-mass galaxies during the past 12 billion years. The stars in the extended halos of M31 and the Milky Way may extend nearly one-third the distance separating the two galaxies.
M31 is known to harbor a dense and compact star cluster at its very center. In a large telescope it creates a visual impression of a star embedded in the more diffuse surrounding bulge. The luminosity of the nucleus is in excess of the most luminous globular clusters.
In 1991 w:Tod R. Lauer used WFPC, then on board the w:Hubble Space Telescope, to image Andromeda's inner nucleus. The nucleus consists of two concentrations separated by 1.5 w:parsecs. The brighter concentration, designated as P1, is offset from the center of the galaxy. The dimmer concentration, P2, falls at the true center of the galaxy and contains a 108 M☉ w:black hole.
w:Scott Tremaine has proposed that the observed double nucleus could be explained if P1 is the projection of a disk of stars in an eccentric orbit around the central black hole. The eccentricity is such that stars linger at the orbital apocenter, creating a concentration of stars. P2 also contains a compact disk of hot, spectral class A stars. The A stars are not evident in redder filters, but in blue and ultraviolet light they dominate the nucleus, causing P2 to appear more prominent than P1.
While at the initial time of its discovery it was hypothesized that the brighter portion of the double nucleus was the remnant of a small galaxy "cannibalized" by Andromeda, this is no longer considered to be a viable explanation. The primary reason is that such a nucleus would have an exceedingly short lifetime due to tidal disruption by the central black hole. While this could be partially resolved if P1 had its own black hole to stabilize it, the distribution of stars in P1 does not suggest that there is a black hole at its center.
Multiple X-ray sources have been detected in the Andromeda Galaxy, using observations from the ESA's w:XMM-Newton orbiting observatory. w:Robin Barnard et al. hypothesized that these are candidate black holes or w:neutron stars, which are heating incoming gas to millions of kelvins and emitting X-rays. The spectrum of the neutron stars is the same as the hypothesized black holes, but can be distinguished by their masses.
There are approximately 460 w:globular clusters associated with the Andromeda galaxy. The most massive of these clusters, identified as w:Mayall II, nicknamed Globular One, has a greater luminosity than any other known globular cluster in the w:local group of galaxies. It contains several million stars, and is about twice as luminous as w:Omega Centauri, the brightest known globular cluster in the w:Milky Way. Globular One (or G1) has several stellar populations and a structure too massive for an ordinary globular. As a result, some consider G1 to be the remnant core of a w:dwarf galaxy that was consumed by M31 in the distant past. The globular with the greatest apparent brightness is w:G76 which is located in the south-west arm's eastern half.
In 2005, astronomers discovered a completely new type of star cluster in M31. The new-found clusters contain hundreds of thousands of stars, a similar number of stars that can be found in globular clusters. What distinguishes them from the globular clusters is that they are much larger – several hundred light-years across – and hundreds of times less dense. The distances between the stars are, therefore, much greater within the newly discovered extended clusters.
Like the Milky Way, Andromeda Galaxy has satellite galaxies, consisting of 14 known dwarf galaxies. The best known and most readily observed satellite galaxies are M32 and M110. Based on current evidence, it appears that M32 underwent a close encounter with M31 (Andromeda) in the past. M32 may once have been a larger galaxy that had its stellar disk removed by M31, and underwent a sharp increase of w:star formation in the core region, which lasted until the relatively recent past.
M110 also appears to be interacting with M31, and astronomers have found a stream of metal-rich stars in the halo of M31 that appears to have been stripped from these satellite galaxies. M110 does contain a dusty lane, which may indicate recent or ongoing star formation.
In 2006 it was discovered that nine of these galaxies lay along a plane that intersects the core of the Andromeda Galaxy, rather than being randomly arranged as would be expected from independent interactions. This may indicate a common tidal origin for the satellites.
- ^a average(787 ± 18, 770 ± 40, 772 ± 44, 783 ± 25) = ((787 + 770 + 772 + 783) / 4) ± ((182 + 402 + 442 + 252)0.5 / 4) = 778 ± 17
- ^b Apparent Magnitude of 4.36 - w:distance modulus of 24.4 = −20.0
- ^c J00443799+4129236 is at celestial coordinates R.A. 00h 44m 37.99s, Dec. +41° 29′ 23.6″.
- ^d distance × tan( diameter_angle = 190′ ) = 141 ± 3 kly diameter
- "NASA/IPAC Extragalactic Database". Results for Messier 31. http://nedwww.ipac.caltech.edu/. Retrieved 2006-11-01.
- Karachentsev, I. D.; Kashibadze, O. G. (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". Astrophysics 49 (1): 3–18. doi:10.1007/s10511-006-0002-6. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2006Ap.....49....3K.
- I. D. Karachentsev, V. E. Karachentseva, W. K. Hutchmeier, D. I. Makarov (2004). "A Catalog of Neighboring Galaxies". Astronomical Journal 127: 2031–2068. doi:10.1086/382905. http://adsabs.harvard.edu/abs/2004AJ....127.2031K.
- I. Ribas, C. Jordi, F. Vilardell, E.L. Fitzpatrick, R.W. Hilditch, F. Edward (2005). "First Determination of the Distance and Fundamental Properties of an Eclipsing Binary in the Andromeda Galaxy". Astrophysical Journal 635: L37–L40. doi:10.1086/499161. http://adsabs.harvard.edu/abs/2005ApJ...635L..37R.
- McConnachie, A. W.; Irwin, M. J.; Ferguson, A. M. N.; Ibata, R. A.; Lewis, G. F.; Tanvir, N. (2005). "Distances and metallicities for 17 Local Group galaxies". Monthly Notices of the Royal Astronomical Society 356 (4): 979–997. doi:10.1111/j.1365-2966.2004.08514.x. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005MNRAS.356..979M.
- Jensen, Joseph B.; Tonry, John L.; Barris, Brian J.; Thompson, Rodger I.; Liu, Michael C.; Rieke, Marcia J.; Ajhar, Edward A.; Blakeslee, John P. (February 2003). "Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuations". Astrophysical Journal 583 (2): 712–726. doi:10.1086/345430. http://adsabs.harvard.edu/abs/2003ApJ...583..712J.
- "Dark matter comes out of the cold". BBC News. February 5, 2006. http://news.bbc.co.uk/2/hi/science/nature/4679220.stm. Retrieved 2006-05-24.
- Young, Kelly (2006-06-06). "Andromeda galaxy hosts a trillion stars". NewScientist. http://www.newscientist.com/article/dn9282-andromeda-galaxy-hosts-a-trillion-stars.html. Retrieved 2006-06-08.
- , CfA Press Release No.: 2009-03 For Release: Monday, January 05, 2009 01:00:00 PM EST.
- Frommert, H.; Kronberg, C. (August 22, 2007). "Messier Object Data, sorted by Apparent Visual Magnitude". SEDS. Archived from the original on 2007-07-12. http://web.archive.org/web/20070712184703/http://seds.lpl.arizona.edu/messier/dataMag.html. Retrieved 2007-08-27.
- Kepple, George Robert; Glen W. Sanner (1998). The Night Sky Observer's Guide, Volume 1. Willmann-Bell, Inc.. pp. 18. ISBN 0-943396-58-1.
- W. Herschel (1785). "On the Construction of the Heavens". Philosophical Transactions of the Royal Society of London 75: 213–266. doi:10.1098/rstl.1785.0012.
- William Huggins (1864). "On the Spectra of Some of the Nebulae". Philosophical Transactions of the Royal Society of London 154: 437–444. doi:10.1098/rstl.1864.0013.
- Backhouse, T. W. (1888). "nebula in Andromeda and Nova, 1885". Monthly Notices of the Royal Astronomical Society 48: 108. Bibcode: 1888MNRAS..48..108B. http://adsabs.harvard.edu//abs/1888MNRAS..48..108B. Retrieved 2009-07-27.
- Roberts, Isaac (1899). A Selection of Photographs of Stars, Star-clusters and Nebulae, Vol. II. London: The Universal Press.
- V.M. Slipher (1913). "The Radial Velocity of the Andromeda Nebula". Lowell Observatory Bulletin 1: 2.56–2.57. http://adsabs.harvard.edu/abs/1913LowOB...1b..56S.
- Heber D. Curtis (January 1988). "Novae in Spiral Nebulae and the Island Universe Theory". Publications of the Astronomical Society of the Pacific 100: 6. doi:10.1086/132128.
- Öpik, Ernst (1922). "An estimate of the distance of the Andromeda Nebula". Astrophysical Journal 55: 406–410. doi:10.1086/142680. http://adsabs.harvard.edu/abs/1922ApJ....55..406O.
- E. P. Hubble (1929). "A spiral nebula as a stellar system, Messier 31". Astrophysical JournalEngl 69: 103–158. doi:10.1086/143167. http://adsabs.harvard.edu/cgi-bin/bib_query?1929ApJ....69..103H.
- W. Baade (1944). "The Resolution of Messier 32, NGC 205, and the Central Region of the Andromeda Nebula". Astrophysical Journal 100: 137. doi:10.1086/144650. http://adsabs.harvard.edu/abs/1944ApJ...100..137B.
- Gribbin, John R. (2001). The Birth of Time: How Astronomers Measure the Age of the Universe. Yale University Press. p. 151. ISBN 0300089147.
- van der Kruit, P. C.; Allen, R. J. (1976). "The Radio Continuum Morphology of Spiral Galaxies". Annual Review of Astronomy and Astrophysics 14: 417-445. doi:10.1146/annurev.aa.14.090176.002221.
- Ingrosso, G.; Calchi Novati, S.; De Paolis, F.; Jetzer, Ph.; Nucita, A. A.; Zakharov, A. F.. "Pixel-lensing as a way to detect extrasolar planets in M31". arXiv. http://arxiv.org/abs/0906.1050. Retrieved 2009-07-10.
- Malik, Tariq (2002-05-07). "Crash Course: Simulating the Fate of Our Milky Way". SPACE.com. Archived from the original on 2002-06-06. http://web.archive.org/web/20020606060654/http://www.space.com/scienceastronomy/astronomy/galaxy_collides_020507-1.html. Retrieved 2006-09-18.
- Cox, T.J., Loeb, A. (2008). "The collision between the Milky Way and Andromeda". Monthly Notices of the Royal Astronomical Society 386 (1): 461–474. doi:10.1111/j.1365-2966.2008.13048.x. http://adsabs.harvard.edu/abs/2008MNRAS.tmp..333C.
- "The Grand Collision". The Sky At Night. November 5, 2007.
- Cain, Fraser (2007). "When Our Galaxy Smashes Into Andromeda, What Happens to the Sun?". Universe Today. http://www.universetoday.com/2007/05/10/when-our-galaxy-smashes-into-andromeda-what-happens-to-the-sun/. Retrieved 2007-05-16.
- Holland, Stephen (1998). "The Distance to the M31 Globular Cluster System". The Astronomical Journal 115 (5): 1916–1920. doi:10.1086/300348. http://adsabs.harvard.edu/abs/1998astro.ph..2088H.
- Stanek, K.Z., Garnavich, P.M. (1998). "Distance to M31 With the HST and Hipparcos Red Clump Stars". Astrophysical Journal Letters 503: 131–141. http://arxiv.org/abs/astro-ph/?9802121.
- N. W. Evans & M. I. Wilkinson (2000). "The mass of the Andromeda galaxy". Monthly Notices of the Royal Astronomical Society 316 (4): 929–942. doi:10.1046/j.1365-8711.2000.03645.x. http://adsabs.harvard.edu/cgi-bin/bib_query?2000MNRAS.316..929E.
- Kalirai, J.S. et al. (2006). "The Metal-Poor Halo of the Andromeda Spiral Galaxy (M31)". Astrophysical Journal 648: 389–404. doi:10.1086/505697.
- van den Bergh, Sidney (1999). "The local group of galaxies". The Astronomy and Astrophysics Review 9 (3–4): 273–318. doi:10.1007/s001590050019.
- W. Liller, B. Mayer (July 1987). "The Rate of Nova Production in the Galaxy". Publications Astronomical Society of the Pacific 99: 606–609. doi:10.1086/132021. http://adsabs.harvard.edu/abs/1987PASP...99..606L.
- R.L. Beaton, E. Athanassoula, S.R. Majewski, P. Guhathakurta, M.F. Skrutskie, R.J. Patterson, M. Bureau (2006). "Unveiling the Boxy Bulge and Bar of the Andromeda Spiral Galaxy". Astrophysical Journal Letters 658: L91. doi:10.1086/514333. http://adsabs.harvard.edu/abs/2006astro.ph..5239B.
- S. C. Chapman, R. Ibata, G. F. Lewis, A. M. N. Ferguson, M. Irwin, A. McConnachie, N. Tanvir (2006). "A kinematically selected, metal-poor spheroid in the outskirts of M31". Astrophysical Journal 653: 255. doi:10.1086/508599. http://adsabs.harvard.edu/cgi-bin/bib_query?astro-ph/0602604. Also see the press release, CalTech Media Relations (February 27, 2006). "Andromeda's Stellar Halo Shows Galaxy's Origin to Be Similar to That of Milky Way". Press release. http://pr.caltech.edu/media/Press_Releases/PR12801.html. Retrieved 2006-05-24.
- UC Santa Cruz (January 9, 2001). "Astronomers Find Evidence of an Extreme Warp in the Stellar Disk of the Andromeda Galaxy". Press release. http://www.ucsc.edu/news_events/press_releases/archive/00-01/01-01/andromeda.html. Retrieved 2006-05-24.
- V. C. Rubin, W. K. J. Ford (1970). "Rotation of the Andromeda Nebula from a Spectroscopic Survey of Emission". Astrophysical Journal 159: 379. doi:10.1086/150317. http://adsabs.harvard.edu/abs/1970ApJ...159..379R.
- H. Arp (1964). "Andromeda Nebula from a Spectroscopic Survey of Emission". Astrophysical Journal 139: 1045. doi:10.1086/147844. http://adsabs.harvard.edu/abs/1964ApJ...139.1045A.
- R. Braun (1991). "The distribution and kinematics of neutral gas, w:HI region in M31". Astrophysical Journal 372, part 1: 54–66. doi:10.1086/169954. http://adsabs.harvard.edu/abs/1991ApJ...372...54B.
- Esa Science News (October 14, 1998). "ISO unveils the hidden rings of Andromeda". Press release. http://www.iso.vilspa.esa.es/outreach/esa_pr/andromed.htm. Retrieved 2006-05-24.
- "Busted! Astronomers Nab Culprit in Galactic Hit-and-Run". Harvard-Smithsonian Center for Astrophysics. October 18, 2006. http://www.cfa.harvard.edu/press/pr0628.html. Retrieved 2006-10-18.
- J. S. Kalirai, K. M. Gilbert, P. Guhathakurta, S. R. Majewski, J. C. Ostheimer, R. M. Rich, M. C. Cooper, D. B. Reitzel, R. J. Patterson (2006). "The Metal-Poor Halo of the Andromeda Spiral Galaxy (M31)". Astrophysical Journal 648: 389. doi:10.1086/505697. http://adsabs.harvard.edu/abs/2006astro.ph..5170K.
- J.S. Bullock and K.V. Johnston (2005). "Tracing Galaxy Formation with Stellar Halos I: Methods". Astrophysical Journal 635 (2): 931–949. doi:10.1086/497422. http://adsabs.harvard.edu/abs/2005ApJ...635..931B.
- Lauer, T. R. et al. (1993). "Planetary camera observations of the double nucleus of M31". Astronomical Journal 106 (4): 1436–1447, 1710–1712. doi:10.1086/116737.
- Tremaine, Scott (1995). "An Eccentric-Disk Model for the Nucleus of M31". Astronomical Journal 110: 628–633. doi:10.1086/117548. http://adsabs.harvard.edu/abs/1995AJ....110..628T.
- Hubble news desk STScI-1993-18 (July 20, 1993). "Hubble Space Telescope Finds a Double Nucleus in the Andromeda Galaxy". Press release. http://hubblesite.org/newscenter/newsdesk/archive/releases/1993/18/text/. Retrieved 2006-05-26.
- Schewe, Phillip F.; Stein, Ben. "The Andromeda Galaxy has a Double Nucleus". Physics News Update (American Institute of Physics). http://www.aip.org/pnu/1993/split/pnu138-2.htm. Retrieved 2009-07-10.
- R., Barnard; U. Kolb; J.P. Osborne (August 2005). "Timing the bright X-ray population of the core of M31 with XMM-Newton". A&A. http://adsabs.harvard.edu/abs/2005astro.ph..8284B.
- P. Barmby, J.P. Huchra (2001). "M31 Globular Clusters in the Hubble Space Telescope Archive. I. Cluster Detection and Completeness". Astronomical Journal 122: 2458–2468. doi:10.1086/323457. http://www.iop.org/EJ/article/1538-3881/122/5/2458/201285.html.
- Hubble news desk STSci-1996-11 (April 24, 1996). "Hubble Spies Globular Cluster in Neighboring Galaxy". Press release. http://hubblesite.org/newscenter/newsdesk/archive/releases/1996/11/. Retrieved 2006-05-26.
- G. Meylan, A. Sarajedini, P. Jablonka, S.G. Djorgovski, T. Bridges, R.M. Rich (2001). "G1 in M31 - Giant Globular Cluster or Core of a Dwarf Elliptical Galaxy?". Astronomical Journal 122: 830–841. doi:10.1086/321166. http://www.iop.org/EJ/article/1538-3881/122/2/830/201075.html.
- A.P. Huxor, N.R. Tanvir, M.J. Irwin, R. Ibata (2005). "A new population of extended, luminous, star clusters in the halo of M31". Monthly Notices of the Royal Astronomical Society 360: 993–1006. doi:10.1111/j.1365-2966.2005.09086.x. http://arxiv.org/abs/astro-ph/0412223.
- K. Bekki, W.J. Couch, M.J. Drinkwater, M.D. Gregg (2001). "A New Formation Model for M32: A Threshed Early-type Spiral?". Astrophysical Journal 557 (1): L39–L42. doi:10.1086/323075. http://adsabs.harvard.edu/abs/2001ApJ...557L..39B.
- R. Ibata, M. Irwin, G. Lewis, A.M. Ferguson, N. Tanvir (July 5, 2001). "A giant stream of metal-rich stars in the halo of the galaxy M31". Nature 412 (6842): 49–52. doi:10.1038/35083506.
- Young, L. M. (November 2000). "Properties of the Molecular Clouds in NGC 205". The Astronomical Journal (5): 2460–2470. doi:10.1086/316806.
- A. Koch and E.K. Grebel (2006). "The Anisotropic Distribution of M 31 Satellite Galaxies: A Polar Great Plane of Early-Type Companions". Astronomical Journal 131 (3): 1405–1415. doi:10.1086/499534. http://adsabs.harvard.edu/abs/2005astro.ph..9258K.
- Simbad data on M31
- Messier 31, SEDS Messier pages
- Astronomy Picture of the Day: July 18, 2004 • October 17, 1998 • December 22, 2005
- Globular Clusters in M31 at The Curdridge Observatory
- First direct distance to Andromeda − Astronomy magazine article
- Andromeda galaxy at SolStation.com
- Andromeda Galaxy at The Encyclopedia of Astrobiology, Astronomy, & Spaceflight
- M31, the Andromeda Galaxy at NightSkyInfo.com
- Ker Than (January 23, 2006). "Strange Setup: Andromeda's Satellite Galaxies All Lined Up". SPACE.com. http://space.com/scienceastronomy/060123_andromeda_plane.html. | 0.845237 | 3.996239 |
Mergers of Compact Objects are a core activity. The detection of gravitational waves from merging black holes by LIGO, and the multi-messenger observation of a binary neutron star merger are expected to be only the first events in a long-anticipated sequence of discoveries. Several research groups in Astrophysics and Physics are actively engaged in modeling the gravitational wave emission from mergers, and predicting the light curves expected from events involving neutron stars. Precise calculations are essential, because the gravitational wave forms of such mergers detected by LIGO encode information about the properties (e.g. radius) of the progenitors, and this in turn can provide important constraints on new physics, such as the equation of state for the dense nuclear matter in a neutron star.
The spatial structure and time variability of the image from the Event Horizon Telescope (EHT) will teach us much about the properties of the black holes in these systems, as well as the kinetic plasma physics in the extreme strong gravity regime near the event horizon. A variety of research groups in Astrophysics have been studying this regime of black hole accretion flows, as well as more luminous systems where radiation pressure effects become important. In the latter case, feedback from black hole accretion on the properties of the surrounding galaxies can be measured using astronomical observations and used to constrain black hole properties.
Time-domain astronomy, as represented by HATPI, LSST, and targeting neutron-star neutron-star mergers, offer a novel observational window which should significantly constrain the physics of mergers of compact objects. The light curves of candidate merger events will be detected over a broad spectrum of wavelengths, and to properly understand the results we will have to make detailed calculations involving strong gravity, fluid dynamics, and radiation.
The detection or non-detection of primordial gravitational waves via polarization measurements on the cosmic microwave background will have important implications for current models of the early universe and the (still hypothetical) initial singularity or epoch that preceded the Big Bang. The presence and strength of primordial gravitational waves is one of the biggest questions in cosmology, so there is much insight to be gained from continuing to refine theoretical models in anticipation of data from the next generation of observatories. Similarly important is to improve our theoretical understanding of the expansion history and growth of structure in the universe so as to capitalize on data from HSC, PFS, Euclid, and WFIRST. | 0.841474 | 4.10422 |
On Monday, I wrote that there were only two possibilities for why Venus’ surface temperature is so hot – either something internal to the planet’s crust and core was keeping Venus hot, or something about the atmosphere was. Tuesday I showed that it wasn’t internal heating. Wednesday I disproved the “Venus formed recently” hypothesis. And yesterday I ruled out a celestial collision that might have melted Venus’ crust, effectively absolving Venus’ core of any responsiblity for Venus’ surface temperature. Given the planet itself can’t be the source of the heat,the atmosphere has to be keeping the surface hot somehow.
There are two ways that Venus’ atmosphere could be responsible for keeping the surface hot, either individually or in combination. First, Venus’ atmosphere is very dense, and there is a physical relationship known as the ideal gas law that indicates that gases under pressure tend to be hotter. Second, robotic probes have measured Venus’ atmosphere to be about 97% CO2, and we can see from the image above (click for a larger version) that the absorption spectrum for CO2 (at Earth temperature and pressure – Venusian temperature and pressure increases the width of the absorption bands, making CO2 a stronger absorber in Venus’ atmosphere than in Earth’s) strongly overlaps the peak emission spectrum of Venus’ surface. The overlap in the spectra suggests that the greenhouse effect of so much CO2 is the cause Let’s investigate the ideal gas law first.
The ideal gas law states
where P is the pressure of the gas (in N·m2), V is the volume of the gas (in m3), n is the amount of the gas (in mols), R is the gas constant, and T is the temperature (in K).
This equation is a useful tool in many applications, but doesn’t apply universally. In fact, it only applies when the following conditions are met:
- the particles of gas are perfectly elastic (they bounce when they hit each other and don’t lose energy in the collision);
- the particles of gas have no size;
- if the gas is contained, the walls of the container are also perfectly elastic AND perfectly insulate the interior volume from the exterior.
Every atom or molecule of a gas has some volume, so we know right there that the ideal gas law is only a convenient approximation. Furthermore, gases like the Earth’s atmosphere are not composed of single molecules or single atoms, two conditions that tend to make a real gas closer to ideal. Instead, an atmosphere tends to be a mix of multiple different gases (nitrogen, CO2, oxygen, etc.), each of which behaves differently. Venus’ atmosphere is about 97% CO2, so it’s closer to ideal in this sense than the Earth’s atmosphere. But as we’ll see, that’s not enough.
The “perfectly insulating container” restriction is one of major problems with applying the ideal gas law to Venus’ atmosphere. An ideal gas is assumed to not lose energy that is added to the system. Increase the temperature of an ideal gas and the pressure and/or volume increases (assuming a constant amount of gas). But in a real gas, that added energy will leak out somewhere. As an example, imagine a balloon that floats into a sunbeam in a home. When the balloon is in the sun, the additional solar energy causes the volume to increase until the pressure inside the balloon equals the air pressure on the outside of the balloon. But if you take the balloon out of the sun, the volume doesn’t stay the same – the extra energy bleeds away as the air temperature inside the balloon drops to room temperature again (and the volume of the balloon drops as a result). Thermodynamics breaks the ideal-ness of the gas in the balloon.
The same thing happens with Venus’ atmosphere. The sun heats up Venus’ surface and then that surface heat flows into the atmosphere. But that heat doesn’t stay in one place. Some of the hot gas rises in the atmosphere until the heat can be radiated into space, some of the heat is re-radiated back to the ground where it’s reabsorbed, and some of it is radiated into the atmosphere where it is reabsorbed and re-radiated. All of this thermal interaction makes the atmosphere of any planet non-ideal.
Furthermore, convection creates other effects like the temperature lapse rate (the average change in temperature of the atmosphere as you change altitude in the troposphere) and state changes (such as the condensation of gases in to liquid clouds) are further reasons why we can’t view a planetary atmosphere as an ideal gas.
Finally, a planet’s atmosphere isn’t like a balloon or Druidia’s air shield, where some barrier prevents the atmosphere from being further out from the surface than that barrier. Instead, a planetary atmosphere is extends out to the point where the inherent energy of the gas molecules is more than the escape velocity of the planet’s gravity well, or until the solar wind strips the atoms away from the planet’s gravity. In either case, however, the volume of the atmosphere is highly variable and, in most respects, undefined.Given that the ideal gas law can’t be used to define the temperature of Venus’ surface, we need to identify what does define the surface temperature. On Monday I identified two possibilities – something inherent in the planet itself, and something inherent in the planet’s atmosphere. The figure at right shows what the energy fluxes would be for a surface temperature generated by Venus’ core.
Note that this graphic shows that, in this case, conservation of energy would not be maintained – Venus’ core itself would be generating most of the energy in the system. But the problem is that I’ve proven that energy flow up from Venus’ core can’t be the source of the surface temperature, so we know that the dashed red line up to the surface is wrong. Furthermore, scientists don’t observe anything even close to 735 K as Venus’ effective temperature, so we know that the dashed red line showing nearly 19 kW·m2 exiting the atmosphere is also wrong. Without the massive flow of energy from Venus’ core, we need a system where conservation of energy is largely maintained, which means that this diagram does not correctly represent energy in Venus’ climate.What we do see is closer to this diagram. Conservation of energy is still broken due to the small amount of energy flow from Venus’ core to the surface (0.17 W·m2), but because the effect is several orders of magnitude less than the other energies flowing in the diagram, we can essentially ignore it. When we do that, however, we are forced to apply conservation of energy to any interface – top of the atmosphere (TOA), surface, clouds, even the planet as a whole.
This diagram shows that, once the hot surface temperature was established who knows how long ago, it reached an thermal equilibrium state with a large amount of energy transfer between the surface and the lower levels of the atmosphere, and the planet as a whole reached an equilibrium state with the Sun. At this point, imagine Venus’ atmosphere as a space blanket that lets just enough heat through the atmosphere to keep the insides extra toasty.
Sherlock Holmes once said “when you’ve eliminated the impossible, whatever remains, however improbable, must be the truth.” We’ve eliminated all the other possibilities, reasonable and otherwise – the only one remaining hypothesis is that Venus’ surface temperature is due to the greenhouse effect as produced by an atmosphere that is 97% CO2.
It’s possible that there are other possibilities that I haven’t considered. I’m not worried about those hypotheses, because there is so much conservatism built into the calculations (especially those on Tuesday) that something could be wrong by a factor of 10 and my results wouldn’t be seriously affected in most cases. In addition, there is so much independent corroborating evidence that CO2 behaves exactly as climate scientists think it does that Venus’ climate is ultimately an interesting sideshow. There is a lot of technology today that relies directly or indirectly on CO2‘s infrared properties, and none of them would work correctly (or at all, in some cases) if CO2‘s infrared properties weren’t well known. Some examples include CO2 lasers used for metal cutting and welding, heat seeking missiles, IR imagers, and orbital CO2 imagers.
I’ll leave you with a demonstration of the thermal absorption properties of CO2 that makes the case for 2 being a strong IR absorber (and thus a greenhouse gas) stronger than all the physics I did this past week.
Special thanks to Arthur Smith, Michael Tobis, John Cook, Ray Weymann, Robert Rhode, Kevin Trenberth, and the many other scientists and experts who helped me refine this series through their unending patience with my odd and/or ignorant questions.
- Speed of light in a vacuum: c = 299792458 m·s-1 (exact)
- Plank’s Constant: h = 6.62606896 × 10−34 J·s
- Boltzman’s Constant: k = 1.3806504 × 10−23 J·K-1
- Stefan-Boltzman constant: σ =
6.669 x 10-8W·m-2·K-4)
- Universal Gravitation constant: G = 6.674 x 10-11 N·m2·kg-2
- Avagadro’s number: NA = 6.023 x 1023 items·mol-1
- Gas constant: R = 8.314 J·mol-1·K-1
- Mean radius of the Sun: rSun = 6.955 x 108 m
- Mean radius of Venus: rVenus = 6.052 x 106 m
- Mean orbital distance from Venus to the Sun: rVorbit = 1.0821 x 1011 m
- Mass of Venus: mVenus = 4.87 x 1024 kg
- Mass of the Sun: mSun = 1.99 x 1030 kg
- Approximate thickness of Venus’ crust: lcrust = 50 km
- Average surface temperature of the Sun: TSun = 5778 K
- Average surface temperature of Venus: TVenus = 735 K
- Estimated temperature of Venus’ core: TVcore = 7000 K
- Specific heat capacity of silica (SiO2): κsilica = 703 J·kg-1·K-1
- Thermal conductivity of silica: ksilica = 1.38 W·m-1·K-1
- Approximate density of silica: Dsilica = 2203 kg·m-3
- Molar mass of silica: Msilica = 2.81 x 10-2 kg·mol-1
- Heat of fusion of silicon: Hfuse-Si = 5.021 x 104 J·mol-1 | 0.82495 | 3.975636 |
This beauty image is one of sixteen sunsets seen by the astronauts aboard the International Space Station during one orbit of Earth. It was taken over the Indian Ocean on May 25 and shows several layers of our atmosphere. The limb is the profile or edge of the Earth. Credit: NASA
You get into bed and pull the covers up to stay warm. The atmosphere’s like that. Blankets of air wrap the Earth and keeps us warm. Imagine what life would be like without an atmosphere. On the upside, every night (and day) would be clear so you could go out skywatching any time you’d like. Unfortunately the negatives would outweigh the pluses. After the oceans boiled away for lack of atmospheric pressure, surface temperatures would drop rapidly after every sunset to something close to 300 below zero Fahrenheit, similar to what the moon experiences.
In the moon’s equatorial and mid-latitude regions, daytime temperatures push the mercury up to around 224 degrees, hotter than boiling water. North of 70 degrees latitude in the polar regions, daytime highs aren’t as extreme because the sun is low in the sky there just as it near Earth’s poles. Lunar nighttime lows are around -298 and drop sharply north of 80 degrees latitude. Losing the atmosphere, we’d also lose the ozone layer and have no protection against powerful ultraviolet radiation from the sun. We’d have to go back to living in caves … deep caves.
The atmosphere is divided into five different layers, the most familiar of which is the one closest to the ground called the troposphere. This is the domain of the clouds and where almost all our weather occurs. Its thickness depends upon your latitude. At the equator the troposphere extends to 56,000 feet or just over 10 miles, while at the poles it’s 23,000. Transcontinental planes try to get above the troposphere and into the next layer called the stratosphere if they can. Air resistance is less there plus the ride isn’t nearly as bumpy. In the troposphere air up and down as well as sideways, but in the stratosphere it flows evenly parallel to the Earth’s surface.
This cutaway shows the four main layers of Earth’s atmosphere. Most of the action happens in the troposphere, but some of our favorite sights like aurora and meteors happen at the top of mesophere and lower thermosphere. Credit: NASA
Near the top of the stratosphere lies the ozone layer, which we respect and appreciate even if we can’t see it, because it protects us against otherwise massive doses of harmful ultraviolet light coming from the sun. The stratosphere tops out around 32 miles before giving way to the mesophere. Extending up to about 53 miles, the mesophere is where lots of meteors burn up as well as being host to those eerie night-shining or noctilucent clouds. You’ll find temperatures there over 125 below, the coldest average temperatures on Earth.
Beyond the mesophere, temperatures rise again as we enter the thermosphere which extends from 53 to 480 miles high and is home to the space station and northern lights. The ‘thermo’ part of thermosphere comes from the layer’s extremely high temperature of over 2000 degrees. Don’t worry about the space station burning up — that thermometer reading is mostly a measure of how fast the atoms are moving up there, and since there are so few of them, it doesn’t really feel hot in the sense we know heat.
Some descriptions of the atmosphere include one additional layer, the exosphere. This is the very limit of Earth’s air; beyond it is true outer space. The exosphere is populated by hydrogen and helium atoms many miles apart and all moving quickly on their way into interplanetary space.
Next time you pull the covers over, think about the layers overhead that keep life on this planet humming. Compared to the enormity of the globe, our atmosphere is a thin film, a membrane of sorts, that protects us every day from the brutal reality of outer space.
Tonight and tomorrow night, watch for the game-loving moon to play tag with Mars and Regulus in the western sky starting at the end of evening twilight. There are some nice gatherings in the offing. Wishing you clear skies! Created with Stellarium | 0.810757 | 3.682864 |
Back in the late 1960s Wernher von Braun developed an architecture for colonising the Red Planet and the Moon, as a by-product, using Apollo-style boosters and NERVA-style nuclear rockets. Basically the Interplanetary vehicles were composed of three independent components – the Primary Propulsion Modules, the Planetary Mission Modules and the Mars Excursion Modules/Vehicles. A single Interplanetary Vehicle was composed, usually, of 3 PPMs, 1 PMM and 1 MEM, but an extra-PPM would be needed for some mission configurations. This was quite different to an earlier mission architecture which favoured using 4 PPMs, minimum, and an EEV (Earth Entry Vehicle) for direct returns, Apollo-style, to Earth. Von Braun believed that an Orbital Receiving Laboratory, at a 50 person Orbital Operations Centre (“Space Base”), was needed to isolate possible biological samples from Mars – von Braun had discussed the possibility of intelligent Martian life in his literature on Mars from the early 1960s, so he was being consistent.
The heaviest components were the PPMs, as fully fuelled they massed nearly 246 tons each. Each PPM was shrouded in a heavy meteoroid shield and staging components until they fired. They would be launched into orbit via a modified Saturn V, the Saturn V-25 (S)U Earth Launch Vehicle, designed to lift a maximum of 249 tons when the basic core was wrapped in 4 large Solid Rocket Boosters.
Stephen Baxter’s fictional account of a 1986 Mars Expedition, “Voyage”, explodes one such booster configuration in a launch accident in 1981 – due to a flaw in the SRBs, just like the real “Challenger” disaster of 1986. In “Voyage” that launch disaster and a core explosion in the Apollo-N nuclear test causes NASA to adopt chemical propulsion. While that was an option for a single-shot mission, von Braun’s long-term plan was to colonise Mars. Each vehicle was to carry 6 personnel, and two vehicles would carry 12 people to Mars. In one option two MEMs would depart for the surface and place 6 people on the surface, but another option was for a single lander and orbital operations amongst the Martian moons using a Space-Tug, itself capable of missions to both moons.
But eventually more people would need to be based on Mars and to do so specially designed freighters were required. These would carry Base Modules – the surface equivalent of a PMM – and Descent Modules, essentially the lander-half of an MEM. A single freighter could carry four of either at a time, and they would be combined in Mars orbit for delivery to the surface. A single Base Module could accommodate 12 personnel, just like the PMM and the core Space Station module that the PMM was to have evolved from.
On that issue, the Space Station, the original was to have launched in c.1975, to carry the “Skylab” experiment even further, and provide training in long-duration in-space activities for 12 astronauts, male and female. “Apollo” itself was to have finished with Apollo XX in 1975, to be succeeded by the much more powerful Space-Tug. The Space-Tug was to have been launched via a single Saturn-V for 14-day missions to the Lunar Surface with a crew of 3. Eventually a Space Station module was to have been landed using a Space-Tug Propulsion Module and to form the nucleus of a Moon Base. To sustainably operate a Base the Nuclear Shuttle was to have been introduced in 1978 to service the Base, carrying multiple loads of Base Modules, Propulsion Stages and freight modules. Eventually the Base was to be powered via nuclear reactors and/or solar power, depending on the applications.
You can see how the Moon Base was to be a practice run for Mars – power reactors, Nuclear Shuttles and PMM/Base Modules. A very crowded schedule with a first Mars Mission launching in 1981… | 0.86332 | 3.163593 |
We always have some weird thoughts in our minds regarding space and the universe. This topic is so much vast that it cannot be explained in one article, but many of us always have this question in mind: “What Happens If Pluto replaces Earth’s Moon?”
Of course, in reality, the movement of such massive celestial bodies is beyond our capabilities. However, if you imagine that in some hypothetical way the Moon will disappear, and instead Pluto will appear in the same place, moving at the same speed as the Moon is moving now, then several interesting and not quite obvious consequences will arise.
In the beginning, Pluto will revolve around the Earth in the same way that the Moon rotated.
Pluto is brighter than the Moon. Its albedo is about 50% and its diameter is 2370 km, while the moon’s albedo is only 12% and its diameter is 3474 km. This will cause Pluto in the night sky to be approximately two times brighter than the Moon now. But at the same time a little less.
Being so close to Earth, Pluto will receive more sunlight and heat. The surface of Pluto is almost completely covered with frozen nitrogen, hydrocarbons, water, etc. The surface of Pluto, heated by the sun’s rays, will begin to boil and evaporate!
Evaporating gases form a coma around Pluto thus it will become a giant comet, surrounding itself with a giant coma. The coma will consist of gases – mainly nitrogen and a small amount of dust.
Coma of Pluto will reflect a large amount of sunlight, which on average will make nights on Earth a little brighter, and days a little less sunny.
Nitrogen has an average thermal velocity of 470 m/s at a temperature of 293K (average temperature on Earth). This is not so far from Pluto’s second cosmic velocity – 1200 m/s, so that under the influence of the solar wind a coma of Pluto will lose gas molecules and a tail will form in Pluto, like in a comet!
As Pluto moves around the Earth, the tail will constantly collide with the Earth. This will not significantly affect the Earth’s atmosphere, and it is mainly composed of nitrogen, but it will create beautiful meteor showers when dust particles from the tail of Pluto burn out in the atmosphere.
Due to the active degassing of Pluto caused by heating, it will also lose rather large rock fragments over time, which will likely lead to the fall on Earth of a large number of meteorites over the entire surface of the planet.
Also, the degassing of Pluto over time will lead to difficultly predictable perturbations of its orbit. Most likely, sooner or later Pluto will approach the Earth to the distance of the Roche limit and will be torn apart by tidal forces.
After that, all frozen gases and ice in the bowels of Pluto will begin to heat up by the Sun and evaporate. This will lead to the fact that the Earth will be surrounded by a huge cloud of gas. Over time, this gas will partially fall to the Earth and replenish the Earth’s atmosphere (including greenhouse gases such as methane or carbon dioxide), partially will be carried away into space by the solar wind.
The stony remains of Pluto in this scenario form a system of rings around the Earth, something similar to the system of rings of Saturn. However, the rings, especially the inner ones, will gradually fall to the Earth due to the resistance of the upper layers of the Earth’s atmosphere.
Needless to say, humanity is very likely not to survive such a development of events, especially in the last stages. | 0.918269 | 3.522951 |
The Lunar Reconnaissance Orbiter fired its braking thrusters for 40 minutes early today, successfully inserting the spacecraft into orbit around the Moon. Over the next several days, LRO’s instruments will be turned on and its orbit will be fine-tuned. Then LRO will begin its primary mission of mapping the lunar surface to find future landing sites and searching for resources that would make possible a permanent human presence on the moon. Also, early Tuesday, the companion mission Lunar Crater Observation and Sensing Satellite (LCROSS) sent back live video as it flew 9,000 km above the Moon, as it enters its elongated Earth orbit, which will bring it on course to impact the Moon’s south pole in October.
The two spacecraft reached the Moon four-and-a-half days after launch. LRO’s rocket firing began around 9:20 GMT (5:47 a.m. EDT) and ended at 10:27 GME (6:27 a.m. EDT), putting the spacecraft into an orbit tilted 30 degrees from the moon’s poles with a low point of 218 km (136 miles) and a high point of 3,000 km (1,926 miles). Over the next five days, additional rocket firings will put the spacecraft into the correct orbit for making its observations for the prime mission, which lasts a year — a polar orbit of about 31 miles, or 50 kilometers, the closest any spacecraft has orbited the moon.
Meanwhile, at 12:20 GMT (8:20 EDT) on Tuesday, LCROSS made a relatively close flyby of the Moon, sending back live streaming video. Watch the replay here.
LCROSS is now in its “cruise phase” and will be monitored by the mission operations team. During the flyby, the science team was able to obtain the data needed to focus and adjust the cameras and spectrometers correctly for impact.
LCROSS will never actually be lunar orbit, but is working its way to an elongated Earth orbit which will eventually bring it to the correct orientation for meeting up with the south pole of the Moon later this year. LCROSS will search for water ice on the moon by sending the spent upper-stage Centaur rocket to impact part of a polar crater in permanent shadows. The LCROSS spacecraft will fly into the plume of dust left by the impact and measure the properties before also colliding with the lunar surface. | 0.800975 | 3.026484 |
exomoons may give us first glimpse of habitable worlds
Once taken, these images will provide unprecedented clues about the moon\'s ability to sustain life by providing chemical features carried in the light.
\"If we can go straight
\"Imagine them, we can shoot their spectrum, which means we can determine the molecular types in their atmosphere,\" said Mary Anne Peters of Princeton University . \".
So far, more than 800 planets outside the solar system have been discovered by indirect methods, for example, when a planet passes through its front, it absorbs the dim light of the star.
However, it is difficult to collect the spectra of rocky planets similar in size to Earth by these methods.
The album of planets is thinner & colon;
Only four systems were imaged.
One challenge is that the stars are bright and the planets are dim, so a planet must be far enough away from its stars to avoid being overtaken.
This means that the world that has been imaging orbits outside the habitable zone, the area around the star is warm enough to hold liquid water.
In addition, planets that are bright enough to appear in the photo must glow from the heat formed and therefore too young to hold life.
But if a Moon runs around a giant gas planet similar to Jupiter\'s mature gas, then the planet\'s gravity may continuously squeeze and stretch the moon to keep its interior molten.
As we all know, this process is called tidal heating, which fuels the melting pot of Jupiter moon Io, the most volcanic celestial body in our solar system.
With the heat of the tide, there should be a superenergy phenomenon in the picture.
\"In a sense, what we\'re talking about is that there\'s a way to keep warm in addition to the Starlight,\" said Edwin Turner of Princeton University . \".
\"Even if we can\'t see the planets, it will make us imagine the satellites in the planetary system directly.
To validate the idea, Turner and Peters calculate the temperature at which the current telescope sees the moon.
They found that most of today\'s observatory, such as the Keke telescope in Hawaii or the space telescope,
Telescopes based on the Hubble and Spitzer telescopes should be able to take pictures of the moon, but only if the satellite is around scorching °c.
Future telescopes will be sensitive to carrying satellites in more lives.
For example, the James Webb Space Telescope should be able to see high-temperature external spin tubes at a comfortable 27 °c, as long as their main star is similar to the distance between Saturn or Uranus and the sun.
However, René Heller of the Institute of astrophysical studies in lebuitz, Potsdam, Germany, warned that tidal heating may be detrimental to life.
The same squeezing of heat can also produce adverse seismic activities, such as volcanoes that constantly emit lava and sulfur gas on Io.
\"This may mean that tidal heating does not extend your habitable zone, because once you have enough tidal heating to keep the surface temperature above 0 °c because of these\" hell \"phenomena, you have destroyed any life on the surface, \"said Hile.
Nevertheless, even the moon that is not suitable for life will be a major discovery.
\"We don\'t know that there is a moon outside the solar system,\" Turner said . \".
\"We don\'t know if satellites in the solar system are unusual or unusual.
This is exploration-just find out what\'s out there.
\"This new study does come up with the tempting possibility that we already have a photo of exomoon.
One of the planets directly imaged, Fomalhaut B, is at the center of the controversy about whether it is really a planet, in part because it has an unusual orbit.
Turner believes that this world of weird behavior may be the first Earth to be directly imaged, and its orbit may be due to the path of the moon around an invisible world.
Magazine reference and colon; arxiv. org/abs/1209. | 0.879522 | 3.811161 |
Add Enceladus, a small moon orbiting the giant ringed planet Saturn, to the growing list of places beyond Earth that have oceans - and prospects for hosting life, a study released on Thursday shows.
Situated some 850 million miles (1.3 billion km) away in the outer solar system, icy Enceladus seems an unlikely place for liquid water.
But gravity measurements taken by NASA's Saturn-orbiting Cassini spacecraft indicate the moon contains an underground ocean in its southern hemisphere. The ocean is believed to be at least as big as Lake Superior, according to research published this week in the journal Science.
Computer models indicate the ocean is likely sandwiched between the moon's rocky core and its ice-covered surface, said planetary scientist David Stevenson, with the California Institute of Technology.
It likely formed and is sustained by tidal heat from gravitational tugging by Saturn and sister moons on Enceladus.
Cassini previously discovered water plumes jetting out from hot spots in Enceladus' south pole. Analysis showed the plumes contain salts and organic molecules.
An underground ocean "provides one possible story to explain why water is gushing out of these fractures," Stevenson said in a statement.
The prospect of liquid water, particularly water that comes close enough to rock to leach out minerals, raises the likelihood that Enceladus has chemistry suitable for life, planetary scientist Jonathan Lunine with Cornell University told reporters on a conference call on Wednesday.
"The interior of Enceladus is a very attractive potential place to look for life," Lunine said.
Enceladus, which is only about 300 miles (500 km) in diameter, joins Saturn's large moon Titan and Jupiter's Europa and Ganymede as places beyond Earth that are likely to contain oceans.
Only Enceladus and Europa, however, show evidence that their oceans are in contact with rock.
To get Enceladus' gravity maps, scientists had to tease out signals in Cassini's radio transmissions that changed by just a fraction of a millimeter per second.
The measurements were made as Cassini flew close by Enceladus three times from 2010 to 2012. The flybys showed Enceladus had a different gravitational grip on Cassini depending on whether the spacecraft passed over the moon's northern or southern hemisphere.
Taking into account what materials are available in the outer solar system - namely rock and ice - the scientists then set about running computer models to assess the most likely cause of Enceladus' asymmetrical gravity.
Their answer: a large ocean about 6 miles (10 kilometers) deep that is covered by 19 to 25 miles (30 to 40 km) of ice.
Cassini, which has been studying the Saturn system for a decade, has three more passes by Enceladus before its mission ends in September 2017. No more gravity measurements are slated during those flybys, however.
Scientists are working on follow-on missions proposed for both Enceladus and Europa.
"I don't know which of the two is going to be more likely to have life. It might be both. It could be neither. I think what this discovery tells us is that we just need to be more aggressive in getting the next generation of spacecraft both to Europa and to the Saturn system once the Cassini mission is over," Lunine said. | 0.858996 | 3.725473 |
Saturn's "Death Star" moon Mimas
Much has been learned about Saturn's system of moons in recent decades, thanks to the Voyager missions and the more recent surveys conducted by the Cassini spaceprobe. Between its estimated 150 moons and moonlets (only 53 of which have been identified and named) there is no shortage of scientific curiosities, and enough mysteries to keep astronomers here on Earth busy for decades.
Consider Mimas, which is often referred to as Saturn's "Death Star Moon" on a count of its unusual appearance. Much like Saturn's moons Tethys and Rhea, Mimas' peculiar characteristics represents something of a mystery. Not only is it almost entirely composed ice, it's coloration and surface features reveal a great deal about the history of the Saturnian (aka. Cronian) system. On top of that, it may even house an interior, liquid-water ocean.
Discovery and Naming:
Saturn's moon Mimas was discovered by William Herschel in 1789, more than 100 years after Saturn's larger moons were discovered by Christian Huygens and Giovanni Cassini. As with all the seven then-known satellites of Saturn, Mimas' name was suggested by William Herschel's son John in his 1847 publication Results of Astronomical Observations made at the Cape of Good Hope.
Mimas takes its name from one of the Titans of Greek mythology, who were the sons and daughters of Cronus (the Greek equivalent to Jupiter). Mimas was an offspring of Gaia, born from the blood of the castrated Uranus, who eventually died during the struggle with the Olympian Gods for control of the universe.
Size, Mass and Orbit:
With a mean radius of 198.2 ± 0.4 km and a mass of about 3.75 ×1019 kg, Mimas is equivalent in size to 0.0311 Earths and 0.0000063 times as massive. Orbiting Saturn at an average distance (semi-major axis) of 185,539 km, it is the innermost of Saturn's larger moons, and the 8th moon orbiting Saturn. It's orbit also has a minor eccentricity of 0.0196, ranging from 181,902 km at periapsis and 189,176 km at apoapsis.
With an estimated orbital velocity of 14.28 km/s, Mimas takes 0.942 days to complete a single orbit of Saturn. Like many of Saturn's moons. Mimas rotation period is synchronous to its orbital period, which means it keeps one face constantly pointing towards the planet. Mimas is also in a 2:1 mean-motion resonance with the larger moon Tethys, and in a 2:3 resonance with the outer F Ring shepherd moonlet, Pandora.
Composition and Surface Features:
Mimas' mean density of 1.1479 ± 0.007 g/cm3 is just slightly higher than that of water (1 g/cm³), which means that Mimas is mostly composed of water ice, with just a small amount of silicate rock. In this respect, Mimas is much like Tethys, Rhea, and Dione – moon's of Saturn that are primarily composed of water ice.
Due to the tidal forces acting on it, Mimas is noticeably prolate – i.e. its longest axis is about 10% longer than the shortest, giving it its egg-shaped appearance. In fact, with a diameter of 396 km (246 mi), Mimas is just barely large and massive enough to achieve hydrostatic equilibrium (i.e. to become rounded in shape under the force of its own gravitation). Mimas is the smallest known astronomical body to have achieved this.
Three types of geological features are officially recognized on Mimas: craters, chasmata (chasms) and catenae (crater chains). Of these, craters are the most common, and it is believed that many of them have existed since the beginning of the Solar System. Mimas surface is saturated with craters, with every part of the surface showing visible depressions, and newer impacts overwriting older ones.
Mimas' most distinctive feature is the giant impact crater Herschel, named in honor of William Herschel (the discoverer of Uranus, its moons Oberon, and Titania, and the Cronian moons Enceladus and Mimas). This large crater gives Mimas the appearance of the "Death Star" from Star Wars. At 130 km (81 mi) in diameter, Herschel's is almost a third of Mimas' own diameter.
Its walls are approximately 5 km (3.1 mi) high, parts of its floor measure 10 km (6.2 mi) deep, and its central peak rises 6 km (3.7 mi) above the crater floor. If there were a crater of an equivalent scale on Earth, it would be over 4,000 km (2,500 mi) in diameter, which would make it wider than the continent of Australia.
The impact that made this crater must have nearly shattered Mimas, and is believed to have created the fractures on the opposite side of the moon by sending shock waves through Mimas's body. In this respect, Mimas' surface closely resembles that of Tethys, with its massive Odysseus crater on its western hemisphere and the concentric Ithaca chasma, which is believed to have formed as a result of the impact that created Odysseus.
Mimas' surface is also saturated with smaller impact craters, but no others are anywhere near the size of Herschel. The cratering is also not uniform, with most of the surface being covered with craters larger than 40 km (25 mi) in diameter. However, in the south polar region, there are generally no craters larger than 20 km (12 mi) in diameter.
Data obtained in 2014 from the Cassini spacecraft has also led to speculation about a possible interior ocean. Due to the planet's libration (oscillation in its orbit), scientists believe that the planet's interior is not uniform, which could be the result of a rocky interior or an interior ocean at the core-mantle boundary. This ocean would likely be maintained thanks to tidal flexing caused by Mimas' orbital resonances with Tethys and Pandora.
A number of features in Saturn's rings are also related to resonances with Mimas. Mimas is responsible for clearing the material from the Cassini Division, which is the gap between Saturn's two widest rings – the A Ring and B Ring. The repeated pulls by Mimas on the Cassini Division particles, always in the same direction, forces them into new orbits outside the gap.
Particles in the Huygens Gap at the inner edge of the Cassini division are in a 2:1 resonance with Mimas. In other words, they orbit Saturn twice for each orbit competed by Mimas. The boundary between the C and B ring is meanwhile in a 3:1 resonance with Mimas; and recently, the G Ring was found to be in a 7:6 co-rotation eccentricity resonance with Mimas.
The first mission to study Mimas up close was Pioneer 11, which flew by Saturn in 1979 and made its closest approach on Sept. 1st, 1979, at a distance of 104,263 km. The Voyager 1 and 2 missions both flew by Mimas in 1980 and 1981, respectively, and snapped pictures of Saturn's atmosphere, its rings, its system of moons. Images taken by Voyager 1 probe were the first ever of the Herschel crater.
Mimas has been imaged several times by the Cassini orbiter, which entered into orbit around Saturn in 2004. A close flyby occurred on February 13, 2010, when Cassini passed Mimas at a distance of 9,500 km (5,900 mi). In addition to providing multiple images of Mimas' cratered surface, it also took measurements of Mimas' orbit, which led to speculation about a possible interior ocean.
The Saturn system is truly a wonder. So many moons, so many mysteries, and so many chances to learn about the formation of the Solar System and how it came to be. One can only hope that future missions are able to probe some of the deeper ones, like what might be lurking beneath Mimas' icy, imposing "Death Star" surface! | 0.83371 | 3.862841 |
Comfortable August nights seem to be tailor-made for backyard astronomers. Warm August evenings are great opportunities to get the whole family outside for stargazing fun exploring the heavens with your telescope or astronomy binoculars.
- Here are some of our top suggestions for August stargazing:
- Moon occults Saturn - Get outside during the evening of August 4th with a pair of 10x50 or larger binoculars to see ringed planet Saturn appear to "hide" behind the Moon during an occultation. You can also take a closer look at this celestial disappearing act in a telescope as the Moon passes between Earth and Saturn.
- Supermoon - The closest and largest Full Moon of 2014 will brighten up the night sky of August 10th. The Moon will not come as close to Earth again until September of 2015. This so-called "Supermoon" is also called a perigee Full Moon, since "perigee" is defined as the point in space where an Earth-orbiting object is closest to our planet. Even though the Moon will be much closer to Earth than normal, it is rather difficult to visually notice the difference in size, but it should still be a spectacular sight.
- The Perseid Meteor Shower - One of the most popular meteor showers of the year, the Perseids, peaks between August 10 and August 13. A waning Gibbous Moon in the sky may make it difficult to spot as many meteors as in past years, but we think it's worth getting outside for a chance to see these fleeting fireballs. Get some lawn chairs, a clear view of the sky and gather your friends & family for a night of stargazing punctuated by beautiful meteors!
- Venus and Jupiter Conjunction - The two planets will come within just ¼ degree of each other in the pre-dawn sky of August 18th. As an added bonus, M44 the Beehive Cluster will only be a degree away as well. This will be a spectacular conjunction to observe a few mornings in a row as the planets move closer to each other.
- The Summer Milky Way - As soon as it gets dark on the evening of August 25th, when the Moon isn't visible during the New Moon phase, you can see the grandest unaided-eye sight in the night sky from a dark sky location - our home galaxy, the Milky Way. Use binoculars and telescopes to scan and tease out dozens of star clusters, nebulas and planetary nebulas. From a dark sky location, away from city lights, the Milky Way is easy to see and majestic in scale, but you can't see it near heavily populated areas due to light pollution; so plan a summer adventure to a national park or your favorite dark sky site to experience this "must-see" astronomical sight.
- Venus in the Morning Sky - Shining with astounding brightness throughout August is Venus, our next-door neighbor planet. To find Venus, get a clear view to the east in the predawn sky. it will be the brightest thing in the sky, except for the Moon! For an interesting sight, take a look at Venus through a telescope to see its partially illuminated "phase".
- Say "See You Later" to Saturn - August will be the last month this year to get a good view of Saturn through a telescope. At the beginning of August, Saturn will still be well above the horizon as the sky gets dark, so the "seeing" should be acceptable for good telescopic views. By the end of the month, it will be only about 10 degrees above the horizon at twilight's end. As an added bonus, Saturn will appear very close to the Moon - just 21 arc minutes away - on August 31st in a very close conjunction. Grab a powerful pair of binoculars or a telescope to see this nice pairing in the sky.
- Grand Summer Nebulas - Hercules Galaxy Cluster: These excellent examples of gaseous nebulas are well placed for viewing in August - See the star chart in Orion's online Community section to find out where you can track them down. The brightest are M16 the Star Queen Nebula, M17 the Swan Nebula, M20 the Trifid Nebula and the very bright M8, the Lagoon Nebula. All are visible in binoculars from dark locations with good seeing. Use a small to moderate aperture telescope with the aid of an Oxygen-III eyepiece filter or SkyGlow filter to see them from more suburban locations.
- Summertime Star Clusters - Hercules Galaxy Cluster: Even from the city, you can track down some of the brightest star clusters of the summer sky in August. The brightest and best include M13, M93, M11, M6 and M7. You can see these under good skies with a humble 60mm scope, but it will take something larger like a StarBlast 4.5 or a 6" to 8" Dobsonian reflectorto reveal their true beauty.
- August's Challenge Object - This month, our challenge is actually a very easy object to see with a telescope, but not so easy with binoculars! Well suited for observing this month is M27, the Dumbbell Nebula in the constellation of Vulpecula, just south of Cygnus, the Swan or Northern Cross. M27 is one of the nearest and therefore one of the brightest and largest planetary nebulas visible from Earth. It's so big that it can be spotted in 7x50 binoculars! Try to track M27 down this August with your binoculars, it will be a small dot, slightly larger than the surrounding stars, but definitely visible through binoculars. What's the smallest binocular you can see it with?
All objects described above can easily be seen with the suggested equipment from a dark sky site, a viewing location some distance away from city lights where light pollution and when bright moonlight does not overpower the stars. All objects have been verified by actual observations by Orion Telescopes & Binoculars Staff at Fremont Peak State Park, and/or Deep Sky Ranch, 60 miles and 90 miles respectively from San Jose International Airport, San Jose, CA. | 0.911243 | 3.087207 |
In this VIS image, taken by the NASA - Mars Odyssey Orbiter on January, 7th, 2015, and during its 57.962nd orbit around the Red Planet, we can see a nice example of an Unnamed Crater with a perfectly defined Central Peak; this still Unnamed Crater is located on the Floor of the very large Newton Crater (approx. 300 Km - such as about 186,3 miles - in diameter) in the Martian Region known as Terra Sirenum.
The remnants of (what could have been, in a far, distant past) a Pedestal, are still very well visible, on its South-Western Outer Rim (lower and lower-left - Sx - side of the frame); furthermore, a large portion of the Inner Rim, as far as we can see here (since only a little more of one half of the Crater has been photographed by the NASA - Mars Odyssey Orbiter), appears to be characterized by the presence of extremely fresh (---> sharp and deep) Gullies. Last, but not least, faint traces of an ancient Landslide can be seen at about 9 o'clock of the Crater, and the Central Peak itself shows two small Depressions - on its Western (and shadowed) Side, which could be the evidence of two small Impact Events.
Latitude (centered): 42,1211° South
Longitude (centered): 201,8140° East
This image (which is an Original Mars Odyssey Orbiter b/w and Map-Projected frame published on the NASA - Planetary Photojournal with the ID n. PIA 19200) has been additionally processed, magnified to aid the visibility of the details, contrast enhanced and sharpened, Gamma corrected and then colorized in Absolute Natural Colors (such as the colors that a normal human eye would actually perceive if someone were onboard the NASA - Mars Odyssey Orbiter and then looked down, towards the Surface of Mars), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team. | 0.851421 | 3.600133 |
Scotland’s Sky in November, 2017
Astronomers spot a mystery interstellar visitor
Comets have always been of particular interest. Appearing without warning, and sometimes with impressive tails, it was not surprising that they were regarded as portents of battles to be won or lost and of the passing of kings.
It was in 1705 that Edmond Halley first published the orbit of the comet that now bears his name. This, and the more than 5,000 comets that have been studied since, have all proved to be members of our solar system.
Some, like Halley, follow closed elongated orbits, returning to perihelion in the Sun’s vicinity every few years. Many more, though, trace almost parabolic paths as they dive towards the Sun from the Oort cloud, a spherical reservoir of icy worlds at the edge of the Sun’s influence – if they ever return to perihelion it may not be for millions of years. A handful, though, receive a sufficient gravitational boost as they pass a planet that they are flung beyond the Oort cloud into interstellar space, never to return.
Now astronomers have sighted a faint object which appears to have originated far beyond the Oort cloud, perhaps as an escapee from another star. Discovered by the Pan-STARRS 1 telescope in Hawaii on 18 October, it had already reached its perihelion within 38 million km of the Sun nine days before and passed 24 million km from the Earth on the 14th. Dubbed at first Comet/2017 U1 (PanSTARRS) because of its highly eccentric comet-like orbit, its name was changed to A/2017 U1 on 25 October when observers failed to detect any trace of a tail or hazy coma surrounding its small nucleus, probably less than 200 metres wide. So, for the moment, it is classed as an asteroid.
Its path though is certainly hyperbolic, having entered the solar system at a relative speed of 26 km per second from a direction close to the bright star Vega in the constellation Lyra. This is also close to the direction that our solar system is moving at 20 km per second with regard to the stars around us, so it may be expected that interstellar intruders, be they comets or asteroids, are most likely to appear from this region. As our first known visitor from interstellar space, frantic efforts are underway to investigate its spectrum and nature before it recedes forever from view in the direction of the Square of Pegasus.
Vega, itself, is the brightest object very high in the south-west at nightfall, falling into the west by our star chart times as Pegasus and Andromeda occupy our high meridian. Orion is rising in the east below Taurus whose brightest star, Aldebaran, is occulted by the bright Moon on the morning of the 6th. Use a telescope to watch it slip behind the Moon’s lower-left limb between 02:27 and 03:26 as seen from Edinburgh
Our sole bright evening planet, Saturn at magnitude 0.5, is easy to miss as it hangs low in the south-west at nightfall, sinking to Edinburgh’s horizon at 18:40 on the 1st and by 16:58 on the 30th. We may need binoculars to spy it in the twilight 5° left of the young earthlit Moon on the 20th and 8° below-right of the Moon a day later. Mercury stands 22° east of the Sun on the 24th but is unlikely to be visible from our latitudes.
The other naked-eye planets are all in our predawn sky. Mars rises in the east just before 04:00 throughout November, climbing to stand 15° to 20° high in the south-east before its magnitude 1.8 pinprick is swallowed by the twilight. This month, it tracks 19° east-south-eastwards in Virgo to pass 3° north of Virgo’s leading star Spica on the 28th. Mars stands to the right of the waning Moon on the 15th when a telescope show it as only 4 arcseconds wide – too small to see any detail.
Venus continues as a brilliant morning star of magnitude -3.9, but it stands lower each morning as it approaches the Sun’s far side. Currently above and left of Spica but speeding east-south-eastwards into Libra, it rises a little more than two hours before the Sun on the 1st and one hour before sunrise by the 30th.
Jupiter, about to emerge from the Sun’s glare below-left of Venus, climbs to pass a mere 16 arcminutes, or half the Moon’s diameter, below-right of Venus on the 13th. Conspicuous at magnitude -1.7, the Jovian disk appears 31 arcseconds wide as compared with only 10 arcseconds for Venus. On the 17th, the incredibly slim earthlit Moon lies above-left of Venus and to the left of Jupiter while the later stands 18° above-right of Venus by the 30th.
Sunrise/sunset times for Edinburgh change from 07:20/16:32 on the 1st to 08:18/15:45 on the 30th. The Moon is full on the 4th, at last quarter on the 10th, new on the 18th and at first quarter on the 26.
The annual Leonids meteor shower lasts from the 15th to the 20th and peaks on the night of the 17th-18th. Its meteors, all of them very fast and many leaving glowing trains in their wake, emanate from the Sickle, the reversed question-mark of stars above Regulus in Leo. This rises in the north-east at 22:00, with most Leonids visible during the predawn hours as it climbs through our eastern sky. The shower has given some spectacular meteor storms in the past, notably in 1966 and 1999, but the parent comet, Comet Tempel-Tuttle, is now near the farthest point of its orbit and rates may be around a dozen meteors per hour. For once, though, moonlight is no hindrance.
This is a slightly revised version of Alan’s article published in The Scotsman on October 31st 2017, with thanks to the newspaper for permission to republish here.
Posted on 31/10/2017, in Uncategorized and tagged A/2017 U1, Alan Pickup, Aldebaran, ASE, asteroid, Astronomical Society of Edinburgh, Comet, Comet Halley, Comet Tempel-Tuttle, Comet/2017 U1 (PanSTARRS), Edmund Halley, Jupiter, Leo, Leonids, Mars, Mercury, meteor shower, moon, Neptune, Night Sky, Oort cloud, orion, Orionids, Pan-STARRS, Regulus, Saturn, Scotland, Spica, The Scotsman, Uranus, Vega, Venus. Bookmark the permalink. Leave a comment. | 0.925782 | 3.808658 |
Titan is the only satellite in our Solar System with a dense atmosphere. The surface pressure is 1.5 bar (ref. 1) and, similar to the Earth, N 2 is the main component of the atmosphere. Methane is the second most important component, but it is photodissociated on a timescale of 10 years (ref. 3). This short timescale has led to the suggestion that Titan may possess a surface or subsurface reservoir of hydrocarbons to replenish the atmosphere. Here we report near-infrared images of Titan obtained on 26 October 2004 by the Cassini spacecraft. The images show that a widespread methane ocean does not exist; subtle albedo variations instead suggest topographical variations, as would be expected for a more solid (perhaps icy) surface. We also find a circular structure ∼30 km in diameter that does not resemble any features seen on other icy satellites. We propose that the structure is a dome formed by upwelling icy plumes that release methane into Titan's atmosphere.
ASJC Scopus subject areas | 0.820507 | 3.641349 |
Since the times of the Manhattan Project one cannot expect transparency in applied areas such as particle physics. Such concepts as the point particle, special relativity, or the segregation of thermodynamic problems, not to mention quantum mechanics itself, render a great service as a smokescreen for the real physical processes. This veil was found convenient and has been maintained so far in the technology sectors of strategic value. We’ll give here both a historical perspective and future prospects.
The electron theory, already since the works of Lorentz of 1895, seems to close definitively the problems of Maxwell classic electrodynamics and lead directly to the problems of Relativity; on the other hand this particle is the very workshop in which quantum mechanics is developed. Thus, the entire foundations of twentieth-century physics, at the micro and macroscopic levels, find here a common Gordian knot. Later, the relativistic extension of classical mechanics and quantum mechanics acquired such an unfolding that the open questions of electromagnetism seemed too distant, if not irrelevant. That this was not so, and still is not so, is conclusively demonstrated by the fact that the main numbers of quantum electrodynamics, such as the mass, the electron charge or the fine structure constant, are still put by hand and are not derived from anything, which leaves this whole outstanding construction hanging in the air.
That enormous unknown that we call “electron”, the faithful and common servant of all our technology, so apparently ordinary that it leaves no room in us for suspicion, so rubbed, used and abused even in our most trivial devices, is a genie unlike any other: the only genie, perhaps, that would allow us to realize certain desires not by taking it out, but by taking it back to the lamp.
The basic problem of self-interaction in current models is that of radiative reaction: an accelerated charge radiates electromagnetic energy and moment and therefore there must be a reaction on the particle, or from its electromagnetic field on itself. The causes of radiation do not necessarily have to be external, they can also be due to interaction with other particles.
For some of the authors of QED, Feynman for example, the idea of self-interaction is just silly, and the only sensible thing to do is to get rid of it and ignore the whole problem simply stating that an accelerated electron does not radiate at all. The issue has always been highly controversial and here we would not like to take side on any particular stance, but it seems to us that the position above mentioned is first and foremost a matter of convenience, and that there is no clear admission of the reasons for this convenience.
It is not said, for example, that Special Relativity, in reality the general case, is only a local framework for punctual events, in which extended particles don’t make any sense —in the same way that in General Relativity, in reality a particular case for gravity, it doesn’t make sense to speak of point masses.
Maxwell’s equations have general covariance but this does not lead to the Lorentz transformation that gives rise to Special Relativity. The original Maxwell equations have integral form and contain more information than their later differential version, but even in this last one they do not yet consider discrete charges which is the case that Lorentz introduces. However, Maxwell’s equations, in their most universal form and free of the metric expressly introduced for the electromagnetic force have natural invariance as Cartan, Kottler and van Dantzig recognized in their time.
Maxwell’s theory, limited as it is, does not cease to be a theory of the physical (not geometric) Continuum, but in Special Relativity this is the first victim, no matter how much one speaks of a space-time Continuum. Its operationalist character entails just that: the discretional cutting of that continuum with the introduction of arbitrary postulates incompatible with the continuum such as the invariance of the speed of light. This creates an additional contradiction with the principle of global synchronization that is not stated here but that since Newton always has been assumed.
If in Newton this principle is just a metaphysical statement, in STR, since it is a local framework of punctual events, only local conservation laws can be considered. In fact, if even today a extended particle model does not seem viable, it is because the special relativity already excludes it right from the start. Such basic phenomena as inductance and self-inductance, that obviously require circuits with a defined extension, don’t have a place in this theory. Then we find ourselves in the strange situation that a global synchronization is assumed that is excluded by the theory itself and that this very theory makes impossible to implement. Minkowski invariance is incompatible with any classical equation of motion, and, moreover, it does not seem that Special Relativity can give an appropriate transformation for accelerated frames of reference, and therefore, for radiation.
The question here is not to make a diatribe against Special Relativity, but to see that this is incompatible with the idea of an extended particle and with other basic features of the classical field theory such as acceleration and radiation. From the very beginning, STR is highly abstract and divorced from physical context, a sort of Solomonic judgement to move beyond the impasse of the frames of reference problem, later generalized without the slightest restraint to other cases with a rich material context. In all this, Special Relativity catches no mice, and a high price is paid by sacrificing everything to its formalisms. But this is not admitted, and attention is drawn to subordinate and secondary matters.
We don’t really know whether an extended particle model or a point particle one would be preferable, whether to contemplate the problems of radiation or to forget about them; but in any case to decide it we would have to start from a sufficiently impartial frame. Special Relativity is not impartial, neither Maxwell or Maxwell-Lorentz’s electrodynamics. In the classical electromagnetic field there is no place for point particles, and on the other hand, if Bohr was still proposing circular orbits in 1913, it was because Maxwell equations don’t tell under which precise conditions radiation is or is not emitted.
There is a gap in the balance of forces in Maxwell equations if they radiate whenever accelerated, and the radiated energy is the compensation of the work done by the auto-force (although in Maxwell’s original theory is not explicitly a force law). It is obvious that if we don’t know yet when there is radiation or not, auto-force and auto-energy constitute possible adjustment terms for the big numbers whose origin still remains unclear, besides enabling a reopening and a redefinition of the thermodynamics and irreversibility topics which were “outsourced” from fundamental physics. Both things seem to be as inconvenient for the QED version that pretend to be the last word on the issue, as they are promising for other approaches free of such commitments.
On the other hand, the opposition between point particle and extended particle is surely not as sharp as we sometimes want to put it, because there has never been anything like a “point particle” to begin with, but a particle-in-the-field whose center admits a point on which a force can be applied. Hertz had already seen the need to distinguish between material particle and material point: the first is an indestructible point of application of forces, the second is an extended variable set internally connected. These are different meanings and application domains, in a sense very similar to the one later raised by de Broglie.
What is an electron supposed to be made of? Of electromagnetic fields, of what else. This is why the particle cannot be out of the continuum, and this is also a good reason for self-interaction to raise. And as electromagnetic fields, electrons are not point particles; the vast majority of their energy lies within a radius of 2.8×10-11 meters, which for long distances gives a good approximation as a point particle that cannot be maintained for distances short enough. The wave of an electron in a superconductor can occupy meters and even kilometers, showing to what extent a particle is what its environment allows it. In any case the density of its field decreases as 1/r2, and if the magnetic field around a current is appreciable at meters, the same goes with each electron. In the limit this field extends to infinity to the greatest size and minimum structure; and it is in the opposite direction, with confinement, that the details are to be find —details that to some extent mirror of the confinement itself.
So there is no point particle without field. It is assumed that quantum electrodynamics was just about that, but then came the Aharonov-Bohm effect and the confusion among the champions of local action was more eloquent than millions of words; and it is even more eloquent if we consider that the effect can be derived entirely from the classical Hamilton-Jacobi equation and that Berry and others even found its exact analogous on the surface of the water, with illustrations so reminiscent of those of Bjerkness at the Paris International Exposition of 1881. In spite of everything, and who knows why, it is still common to hear that the well-known effect is a clear exponent of the unique character of quantum potentials.
We are told once and again that quantum mechanics is the fundamental level and classical electromagnetism necessarily follows from it, as it should be, but in practice without a classical view quantum mechanics is basically blind, a standard calculation formalism to which one has to tell how to operate with, and furthermore the transition zone between both is extremely diffuse and lacks a general criterion. Quantum mechanics is not a vision, but a recipe.
Self-interaction without radiation: Weber’s electrodynamics and retarded potentials
Weber’s electrodynamics, which precedes Maxwell’s by quite a number of years, is a theory of direct action with many similarities with the direct electrodynamics arising after Special Relativity but without any of its contraindications, which still makes its revision so recommendable today. Maxwell himself finally recognized in his Treatise the basic equivalence between field theories and the then called action at a distance theories such as Weber’s one.
Wilhelm Weber developed in passing an elliptical atom model fifty or sixty years before Bohr drew his circular orbit model and without the benefit of any of the data known to the Danish. Moreover, the nucleus remained stable without need of nuclear forces.
Weber’s law is the first case in which central forces are defined not only by distances but also by relative radial accelerations; beyond a critical distance, which converges with the classical electron radius, the inertial mass of the charge change sign from positive to negative.
A decisive point is that Weber’s electrodynamics, although largely equivalent to Maxwell’s, allows us to see another side of self-interaction that does not necessarily pass through radiation. Rather, it is a self-interaction of the whole system under consideration, a global feedback of the circuit, rather than self-interaction as a local reaction. In Maxwell’s original conception everything should be global and circuital as well, but you can’t work with point charges. Weber’s formulation allow both point and extended particles.
As Assis likes to remember, Weber’s electric force law of 1846 is the first equation of motion completely homogeneous and relational, that is, expressed in known quantities of the same type. The generalized use of heterogeneous quantities already tells us how far we are from transparency, just as the use of dimensional or “universal” constants shouts from the rooftops just that a theory is not universal. Weber’s force law of 1846 is fully relativistic 59 years before the not-so-relativistic Special Theory of Relativity, without any postulate or rupture with the continuum.
It is also the first law in dynamics that is a natural extension, rather than an amendment, of Newton’s central forces law. As usual, Newton’s followers were more newtonian than Newton himself, but the first definition in the Principia don’t ask that the magnitude of central forces should depend only on the distance between points, as with a string attached, so to speak. This they took from a mere metaphor like that of the slingshot, but not from definitions.
The extension of the law of central forces, apparently suggested by Gauss in 1835 and later reformulated by Weber, is in fact the most natural form of evolution of Newtonian mechanics: it involved only the static case (gravitostatic), and thus introduces the dynamic case in which force is not invariable but depends on relative velocities and accelerations. This combination of dynamic and static factors, represented by kinetic and potential energy, will also be key in Maxwell’s later formulation.
However, by the time physicists had come to grips with the idea of central forces, they also had needlessly overdetermined it. Weber’s law was criticized by Helmholtz and Maxwell for not complying with energy conservation since the delay of the potential grows with the increase in the relative velocity of bodies, and more potential energy seems to be lost than is kinetically recovered. In 1871 Weber succeeded in demonstrating the conservation of energy in cyclic operations, but various events, such as Hertz’s experimental findings, finally tipped the scales in favor of Maxwell’s view.
The same type of force law and retarded potential was applied by Gerber to gravity in 1898 to explain the anomaly of Mercury’s precession; to claim, as so many historians have done, that this was an empirical correction without theoretical basis is, unless one understands by theoretical grounds the introduction of arbitrary postulates, truth upside down.
It has been said that the greatest limitation of Weber’s model is that it does not include electromagnetic radiation, but the truth is that if it does not predict it, it does not exclude it in any way. In fact it is with Weber’s formulas that the term for the speed of light is introduced for the first time, something Maxwell knew perfectly. The dynamic extension of Weber’s force has a discrepancy with respect to the static case of the same order as the Lorentz factor, which is why results similar to those of Special and General Relativity can be obtained in a much more natural way.
Weber’s mechanics is not free of problems and ambiguities either. The most obvious, already noted by Poincaré, is that if we are obliged to multiply the velocity squared we no longer have a way of distinguishing between kinetic and potential energies, and even these cease to be independent of the internal energy of the bodies under consideration. On the other hand, if we are obliged to work with point particles we can hardly consider internal energies or forces. If Relativity predicts an increase in mass with velocity, Weber’s law, the purely relational one, predicts a decrease in force and an increase in internal energy, which we can perhaps attribute to frequency. Without this ambiguity there would be no non-trivial feedback cycle, no possibility of real self-interaction.
Of course, the increase in frequency is not Weber’s prediction, but that of nuclear engineer Nikolay Noskov, who took up the track of retarded potentials in various articles since 1991 and gave it a universal range of validity. Since Weber’s law gives correct predictions, and energy is after all preserved, Noskov assumes that the non-uniform character of the retarded potential causes longitudinal vibrations in moving bodies, which are a normal occurrence at the most diverse levels: “This is the basis of the structure and stability of nuclei, atoms, and planetary and stellar systems. It is the main reason for the occurrence of sound (and the voices of people, animals and birds, as well as the sound of wind instruments), electromagnetic oscillations and light, tornadoes, hydrodynamic pulsations and wind blows. It finally explains the orbital motion, in which the central body is in one of the focuses rather than in the center of the ellipse. Moreover, the ellipse cannot be arbitrary since the lengths of the cyclic and longitudinal oscillations have different values with a resonance v1 = v2. This circumstance determines the ellipticity in each concrete case.”
Remarkably, Noskov, who doesn’t restrain himself of making generalizations either, dares mention the case of the elliptical orbits of celestial mechanics, an inconvenient subject by nearly all standards. It has been repeated so many times by history and publicity that Newton definitively explained the shape of the ellipses, that saying otherwise must be met with disbelief. But it is evident that Newton did not explain the case, which in turn gives rise to a very pertinent comment.
Whoever has become accustomed to the Newtonian description of orbits, assumes that (for the two-body problem) ballistics and a force dependent only on distance are enough to grant them stability. But the truth is that in Newton the innate motion of the body —unlike orbital velocity – is by his very definition invariable, which only allows two options. The first one is that the planet increases and decreases its velocity like a rocket with an autonomous impulse, which I don’t think anyone is willing to admit. This option also has a comic reverse: let us accept, instead of self-propulsion, that centripetal vectors can stretch and shrink under a certain quantitative easing. The second option is that which Newton himself proposes with his sleight of hand, and which everyone has accepted, combining in a single variable orbital velocity and innate motion.
What is not noticed in this second circumstance is that if the centripetal force counteracts the orbital velocity, and this orbital velocity is variable even though the innate motion does not change, the orbital velocity is in fact already a result of the interaction between the centripetal and the innate force, so that then the centripetal force is also acting on itself. We do not see how self-interaction can be avoided. According to modern relativistic field equations, gravity must be non-linear and able to couple with its own energy; however, all this is already present at the most elementary level in the old original problem of the ellipse, which General Relativity has never dared to touch.
So even Newton’s equations would be hiding a self-interaction and, whether we think in terms of action at a distance, or in terms of fields, what would distinguish the fundamental forces of Nature from those we humans apply by external contact in the Three Principles of Mechanics is precisely this self-interaction of the system as a whole. Hertz, the creator of contact physics, already noticed that precisely in celestial mechanics there is no way to verify the Third Principle.
Then, rather than disputing over which theory best “predicts” the tiny anomaly in the precession of Mercury, which after all is subjected to many other incidences, we could take the larger case of the planetary ellipse and its elementary asymmetry. For our so-called fundamental laws have still been unable to account for this the most fundamental asymmetries of nature in terms of contemporary forces instead of initial conditions which beyond the innate force and its vector here are completely irrelevant.
The Lagrangian of an orbital system, the difference between kinetic and potential energy, is a positive value, and not zero as one would expect. The Lagrangian is the quantity conserved, but nobody explains us why the heck there is more motion than its corresponding potential energy. According to the logic of the Principia, kinetic and potential energy, directly derived from appreciable motion and position, should be as equal as action and reaction. Is the retarded potential of any use to explain the difference?
It serves to save the time lapse of the forces in terms of energy, as the Lagrangian but in a more explicit way. With retarded potentials it is the energy what is not present at a given moment, which is another way of demanding an action principle. So this seems to be the limit of application for contemporary forces themselves.
It is said of Newtonian gravity that it is the first fundamental law expressed as a differential equation, but in the specific case of the orbit it is the differential or contemporary description what fails notoriously. According to the vectors of an invariable force, the orbit should open and the planet move away; there is no way to grant stability. The Lagrangian version in terms of energy arises to obviate this difficulty, not because it is more convenient for complex systems. So in the strict sense there is no local conservation of forces here, what there is is the discretional derivatives based on the integral action followed from calculus; and this is the criterion for a theory to be considered as “local”.
The “unreasonable effectiveness of mathematics in the natural sciences”,as Wigner put it, is only unreasonable if we forget what the procedure was.The fundamental forces of nature, independent of human mechanics, and which we try to restrict within the three principles of mechanics, do not satisfy these but indirectly —Newton’s gravity and Maxwell’s electromagnetism are theories with an indisputably integral origin and an interpretation as differential as their application. Nature does not obey our equations, our equations are instead the inverse engineering of nature, and it’s only normal that our engineering, like our knowledge, always falls short.
Noskov’s longitudinal oscillations depend on three variables: distance, force of interaction and phase velocity. Its length is directly proportional to the phase velocity and inversely proportional to the distance between the bodies and the force of interaction. Two cardinal formulas can be derived naturally from this: the Planck radiation law and the de Broglie correlation, which should include a phase velocity. This phase factor could also be applied to the so-called mass defects of nuclear physics.
We know that the de Broglie correlation applies without discussion to diffraction experiments showing waves in matter from electrons to macromolecules. Schrödinger’s equation itself is a hybrid of oscillations in a medium and in the moving body, which led Born, famous for his statistical interpretation, to consider it in terms of longitudinal waves too; Planck’s constant is reduced to a local constant relevant only for the electromagnetic force and masses of the order of an electron. Another proof that Weber’s force has something to say about the electron at the atomic level is the straight derivation that as early as 1926 Vannevar Bush made of the fine structure of the hydrogen atom levels using Weber’s equations without the assumption of mass change with velocity. Broadly speaking at least, is not that hard to reconcile quantum mechanics and classical relational mechanics.
This way Weber’s force and its retarded potential is in the best position possible at the crossroads of Maxwell’s field or classical continuum theory, Special and General Relativity, and Quantum Mechanics —being earlier and immensely simpler than all of them. And although it will surely be said that the aforementioned connection with quantum mechanics is too generic, the mere fact that it occurs without forcing things and without a chain of ad hoc postulates is already something.
There are, of course, many ways to rewrite quantum hieroglyphics and send them back to a classical conception; but few, if any, as direct as the royal road opened by Weber, which has historical and logical precedence over the others. One has complete freedom to tread other paths, but it is always advisable to contrast them with the original one.
Weber’s law can easily be transformed into a field theory integrating over a fixed volume as shown by J. P. Wesley, and then it is revealed that Maxwell’s equations are simply a particular case of the former. In this way and with retarded potentials high speed variations and cases with radiation are fully workable. Wesley also proposed other modifications of Weber’s law that we will not touch here.
Noskov’s connection with Planck’s radiation formula is unavoidable since the retarded potential demands by itself an action principle. On the other hand, if the case of the ellipse in the Newtonian terms of an invariable force and an invariable innate motion leads to a gradually open orbit, what would be hopelessly lost here is the closed and reversible system, as if we had a dissipation rate. A virtual dissipation rate, it is understood, because that the orbit is conserved is something we already know. Since we have ellipses both in the micro and macrocosm, this is, therefore, the most obvious form of connection between the reversibility of mechanics and thermodynamic irreversibility. Thus, we can situate relational mechanics at the junction of classical mechanics, quantum mechanics and thermodynamics.
One might fear, as Robert Wald says, that an extended particle irreducible to the point particle case will be lost in details and unable to yield a universal equation; but in Weber’s electrodynamics, unlike Maxwell’s, one can work with extended particles knowing that one can always get back to point particles with solutions that make sense. Such neutrality is absolutely desirable in any possible respect.
Quantum thermodynamics and open meta-stable systems
Physicists and mathematicians nearly in equal shares try to get away from thermodynamics as much as they can, and if they have to deal with it, at least it is expected to be the most habitual equilibrium thermodynamics, not that of open systems far from equilibrium and in exchange with the environment. This last case is supposed to be that of living beings, characterized by levels of complexity far away from anything germane to fundamental physics.
Distrust could be justified if what is at risk is the closed and strictly reversible character of the so-called fundamental laws —the most precious treasure of science. But on the other hand, there is no loss that cannot be turned into a gain; and in this case, the prize would be nothing less than the return of physics to the general current of fire and life.
Macroscopic irreversibility in no way can be derived from microscopic reversibility. Boltzmann and many after him have assumed a highly refined statistical argument, but there are also topological arguments, free of statistics, that show irreversible aspects in electromagnetism independently of scale or metric. Beyond any sophistication, statistical or not, we never see the emitted light rays returning to their source, which already tells us that theoretical physics has a very peculiar criterion about what is irreversible and what is fundamental.
Finally the experimental evidence has begun to arrive and could multiply in the next few years if interest really exists —and interest exists for obvious technological reasons. Needless to say, the experimental and technological environment in microscopic physics has changed beyond recognition. New disciplines such as continuous quantum measurement, quantum feedback and quantum thermodynamics are flourishing, enabling an increasing filtering of noise and an always better distinction between quantum and thermal fluctuations.
The print of atomic irreversibility has to be proportionally small and only become macroscopically relevant with the usual large numbers, but there are and there will be more and more ways to measure and detect it. The subject is closely related to that of the point electron —one more idealization- which is an excellent approximation for long distances but which in close enough distances is bound to failure. Macroscopic irreversibility should be only “the global superposition of the microscopic irreversibility due to the large number of atoms and molecules in matter“.
Following the logic of miniaturization, that of nanomachines or quantum information, there is much more interest in taking into account dissipation than in ignoring it, since it sets the very limits of operation for this devices. A different story, though, is that of reporting data transparently. Once again, applied physics will find new problems for theoretical physics, but we can predict that people will keep saying everything are fantastic new confirmations of the incredible quantum mechanics.
It seems then that it is the same interaction between photons and matter particles, what else, what affects in an irreversible way the electron and the center of mass of the atom; some already have advanced an estimate of the order of 10-13 joules. On the other hand, if we can only imagine electrons being made of electromagnetic fields —or by the constitutive tensions and deformations that translate it into its most material limit-, sooner or later it’s inevitable to think, as it has done so often, that particles of matter are only trapped light transforming linear into angular momentum. At least laboratories has been trying to create electrons and positrons from photons for years and the prospect of doing so seems reasonable.
The idea that reversible mechanisms depend on irreversible dynamics, that closed systems are drawn on an open background, or that irreducible and ideal particles are not such, sounds to the ears of the theoretical physicist as a loss of status, a fall from the mathematical firmament of pure ideas. But it is the only outcome to expect if things are taken far enough, even respecting the margin of validity of closed and reversible systems or point particles. Real things use to have structure.
This does not mean that an electron should decay, photons apart, into other material particles. It is enough that its limiting surface and its spin have a differential structure, not necessarily geometric, that can account for its continuous evolution and its always ephemeral configurations. That is, the structure describes the momentary relationship with the environment, not an internal composition in terms of other equally abstract particles. Models for this have already been suggested. Once we have a limiting surface for a volume, we also have a framework for its changes, the structure of its spin, density, statistics, etcetera, etcetera. I don’t know why we should give all this up in the name of a mere principle divorced from physical reality.
As for the magical ring of reversibility, as long as physicist believes is their own right they will never be able to receive it as a gift. Since the only thing that makes it valuable is the background from which it is conditionally, precariously constituted.
V. E Zhvirblis studied the osmotic and electrical rings in perpetual operation and came to the conclusion that systems where there are stationary forces cannot be isolated. Quantum mechanics, which pretend to do that, is, from a thermodynamical point of view, illegitimate. It is curious that this is considered completely normal at the quantum level but is banished from the macroscopic level in cases as clear as Lazarev’s koltsar when the only thing we have to accept is that isolated systems are simply not possible.
The problem is that in these cases the quantities, although measurable, are not controllable, and physics is based first and foremost on controllable quantities such as forces. The only way to solve the paradox, as Zhvirblis observes, is if the interaction forces in thermodynamic systems are described only in terms of thermodynamics itself.
Thus all systems, from particles and atoms to living beings and stars, could be seen as metastable systems, islands temporarily far from equilibrium supported by their own internal equilibrium laws.
Current physics constantly speaks of energy conservation but atoms theirselves seem unverifiable perpetual motion machines, not to mention the same energy and matter, which are conserved but have emerged from nowhere in a remote past. It would have to be more interesting to see what a system is capable of doing in the present than twelve billion years ago, to try to guess why a real entity such as a particle is not a point, than to imagine how the whole universe comes out from a point without extension. Both things are more closely related than we think, but some lead to answers here and now, while the others just take us as far away as possible.
It is not so difficult to find the thermodynamic print and the origin in continuum of particles: it’s enough to look for it with a zeal similar to the one that has been put in ignoring both -in separating them from what is really fundamental.
Relational Clock, Piston Engine, Whirlwind Computer
For the ancients, to ask why the world existed was like imagining how fire came out of water; and to ask about life was like figuring out how water incorporated fire again without extinguishing it. Two apparent impossibilities that nevertheless balanced each other and acquired the intangible consistency of facts. In physics, the only way to create a similar relationship would be to try to see how the reversible comes out from the irreversible, and how a closed mechanism makes the omnipresent trace of heat disappear for a while. Surely we will never be able to explain one or the other, but perhaps their perspicuous balance would free us from the compulsive need for explanations.
Nothing can replace rectitude in reasoning, but in modern physics it is impossible to go very far without the use of a certain statistical apparatus that is, we might say, the inseparable companion of calculus. Not only quantum mechanics, even something as basic as the classical electromagnetic field has undeniable and basic statistical aspects. And above all, we would like to find a different general position for thermodynamics.
The reasons for creating a competent statistical-relational apparatus are multiple and range from the most obvious to the deepest.
The pure relational, in its very emptiness, reminds us reversibility itself; on the contrary, of heat we are left only with its statistical fingerprint. To see how they interpenetrate we need first to make a broad detour. In physics we will never have too much perspective since perspective itself is already the best part of knowledge.
Relational statistics can be seen, in its simplest version, as a modality of dimensional analysis, which tries to bring the equations, constants and units of the formulas of the current theories as close as possible to Fourier’s Principle of Homogeneity, generalized in more recent times by Assis as Principle of Physical Proportions: the desideratum that all the laws of physics must depend only on the ratio between known quantities of the same type, and therefore cannot depend on dimensional constants. Such were, for example, Archimedes’ laws of statics, Hook’s original constitutive law, or, shifting towards dynamics, Weber’s force law of electrodynamics.
It can be said that this principle of homogeneity is an ideal, not only of Greek science, but of science in general; it’s a universal zenith or pole. Needless to say, nearly all the laws of modern physics violate this requirement, so the issue is not to discard them, which is out of the question, but to bear this factor in mind for what might allow us to see one day.
It is not necessary to expand on the more standard modalities of dimensional analysis, already well known, and which over time have extended to other fundamental combinatory branches such as group theory. On the other hand it is not superfluous to bear in mind that when we say “relational statistics” we are uniting in a single concept ideas that in physics are rather antagonistic: the purely relational is the most transparent, the purely statistical is the most opaque at the physical level.
In any case, it is always useful to start with the dimensional analysis before proceeding with the major complexities of statistical analysis. Even today the interaction between these two branches of the analysis is scarce, due in part to the fame of superficial that it has among the highly creative theoretical physicists, more concerned also about the predictive capacity of their equations than about their cleanliness or legitimacy. In addition, an elementary dimensional analysis often calls into question the basis of many of their assumptions, such as the uncertainty principle.
An example of relational statistical analysis is that proposed by V. V. Aristov. Aristov introduces a constructive and discrete model of time as motion using the idea of synchronization and physical clocks that Poincaré introduced precisely for the electron problem. Here every moment of time is a purely spatial picture. But it is not only a question of converting time into space, but also of understanding the origin of the mathematical form of the laws of physics: “The ordinary physical equations are the consequences of the mathematical axioms, which are “projected” onto physical reality by means of the fundamental instruments. One may assume that it is possible to construct different clocks with different structure, and in this case we would have different equations for the description of motion.”
With a model of rigid rules for geometry and clocks for time, a space-time model of dimensionless
variables is created. In the exposition of his idea Aristov deals basically with the Lorentz transformations, the axiomatic construction of a geometry and the most basic relation of the quantum uncertainty principle; and if this is mandatory on one side of the map, on the other side we can put Weber’s own relational mechanics with its derivations, just as we can place as a clock at the center an extensive model of the electron, using its vectors for many other correlations.
A chronometric approach to relational statistics is opportune because of the many discrete aspects that will never cease to exist in physics and that are independent of quantum mechanics: real particles, diverse aspects of the waves, collisions, acts of measurement and time measurements in particular, or cuts imposed at the axiomatic level are discrete.
The performance of a relational network is cumulative. Its advantages, such as those of the physics that bears that name —and information networks in general- are not noticeable at first glance but increase with the number of connections. The best way to prove this is to extend the network of relational connections. All this is about collective work and intelligence. With arbitrary cuts to relational homogeneity, destructive interference and irrelevant redundancy increases; on the contrary, the greater the relational density, the greater the constructive interference. I don’t think this requires demonstration: Totally homogeneous relationships allow higher order degrees of inclusion without obstruction, just as equations made of heterogeneous elements can include equations within equations as opaque elements or unravelled knots.
From continuity and homogeneity comes the unwritten legitimacy of laws, just as from primordial waters came the sovereignty of ancient kings and emperors.
In his sketch of relational statistics Aristov has no considerations for thermodynamics, but it is precisely this that would have to give a special relevance to statistics. Instead of a Poincaré-style clock, we could have introduced, for example, a “piston engine” like the one exemplified by Zhvirblis in order to generate forces without leaving the thermodynamic realm.
Let us return to our peculiar perspective exercise. Physics would have a “relational” north pole from which it aspires to explain everything as mere relations of homogeneous motion, and a “substantial” south pole from which it could give an authentic mechanical explanation of phenomena, generally with a kind of medium that provides continuity for the transmission of forces between separate parts of matter.
Trying to satisfy both extremes, the commitments of the history of physics left us in the middle, with Newton’s physics of absolute magnitudes, or with modern field theories, which attempt to maintain continuity but make use of the wrongly termed universal constants, in fact absolute magnitudes as in Newton.
This apparently philosophical disquisition contains the issue of the universal synchronizer. Between fire and water one would not put a cylinder and a piston, but perhaps a whirlwind, as in the famous Newton’s own bucket experiment, distant heir to a more daring one already conceived by the father of the theory of the four elements. Empedocles noticed that turning a bucket of water vertically prevented it from falling, counteracting, in other words, gravity.
The Newtonian bucket experiment and its centrifugal force obliges us to take a stance. What is the reason for the curvature of water? Newton says that absolute space; Leibniz, Mach and relational physics, that the relationship with the rest of the objects, including distant stars. For Newton, even if we could eliminate all the surrounding matter, the same phenomenon would occur; for the relational physics such a thing is impossible. And what would be the substantialist position? This one would say that an absolute medium of reference is required, and that it is that medium in any case the only that can transmit the influence of bodies from the environment, whether distant or not.
There do not seem to be more conceivable positions than these. And yet none of the three seems satisfactory to us. The assertion that there are absolute magnitudes independent of the environment, though preserved in all modern physics, is metaphysical in nature. On the other hand, pure kinematic relationships will never be able to explain physical reality, however desirable the principle of homogeneity may be. Finally, the determination of a framework independent of measuring devices seems to violate the relational principle —and the relativist one that came later; apart from the fact that the non-uniqueness of the action principles precludes the identification of unique causes.
But a fourth position, such as that of Mario Pinheiro, can be held; you can affirm that there is no kinematics without irreversibility. Pinheiro observes that what is important here is the transport of angular momentum holding the balance between centrifugal force and pressure.
I believe that this answer reveals at least both the part of truth that can be found in any of the three postures and its manifest insufficiency. Pinheiro advocates the use of a new variational principle for out-of-equilibrium rotating systems and a mechanical-thermodynamic time in a set of two first-order differential equations. There is a balance between the minimum variation of energy and the maximum production of entropy that fits in the simple classical examples such as free fall and that would have to be relevant in dynamics in general and electrodynamics in particular, because the conversion of angular and linear momentum should be central to it, no matter if this is not how is told.
As a sign of the times, the efforts to integrate dynamics with the the entropy/information concept are increasing dramatically. The reasons for this are diverse but convergent: the ever-increasing tendency to consider matter as mere support for information, the exhaustion of viable dynamic models, the gradual introduction of statistical factors and physical magnitudes of higher level. These trends are not going to subside. However, so far the use of entropy helps little or nothing to understand where the dynamical regularities we observe arises from.
It is also said that gravity takes entropy to its limit by area -in singularities-, though our ordinary experience says quite the opposite, that it is the only force that seems to compensate and revert it. In this case entropy reaches its extreme because the theory of gravity as an absolute force inescapably have to dispose of everything else; in a relational theory there is no place for gravitational singularities, because the force decreases with the increase of velocity. On the other hand it is curious that in Newtonian physics the forces that produce deformation, which is the only thing to expect, are considered pseudo-forces, while the fundamental force does not cause deformation of bodies when in motion, but only through potential energy in the static case.
Surely it is impossible to understand the relationship between the reversible and the irreversible, great key to nature, while subordinating nature exclusively to prediction. It is clear that what is predictable is regular and that this tend to confer to a certain extent the rank of law. But to what extent? Without due contrast, we will never know. We pride ourselves on the predictive power of our theories, but prediction alone needs not to be knowledge, and can rather be blindness.
Yes, power of prediction is also power of obfuscation. There is nothing more practical than a good theory, and a good theory is the least artificial and most respectful with the case presented. Our knowledge is always very limited, even regardless of our degree of information, and the respect for the little we know, being aware that it is intrinsically incomplete, is also respect for everything we do not know. It is clear that the ad hoc postulates, the teleology of our principles of action, or the inverse mathematical engineering, drastically reduce the quality of our generalizations no matter what degree of universally we attribute to them. It is not a matter of detracting from its merits any human achievement, but of being aware of its limitations.
R. M. Kiehn already spoke in 1976 of “retrodictive determinism”: “It seems that a system described by a tensor field can be statistically predictive, but retrodictively deterministic.” It is conceivable, for instance, that we can deduce initial conditions from the final global deformation of a solid, while conversely we can only calculate probabilities from the initial condition and the applied force.
The irreversible, dissipative part of electromagnetism seems to be included within the intrinsic covariance that Maxwell’s (and Weber’s) equations show in the language of outer differential forms. There has to be another way of reading “the book of nature” and this form cannot be simply an inversion —it cannot be merely symmetrical or dual with respect to predictive evolution. Ultimately it is neither a matter of going forwards nor backwards, of future or past, but of what can be revealed between both.
The whole quantum electrodynamics can be retrospectively derived from the classical Huygens principle, which is a principle of homogeneity, just as the conservation of momentum derives directly from the homogeneity of space. However, everything suggests that gravity exists due to the heterogeneous character of time and space. This brings us back to our previous considerations in terms of extremes.
The enigma of the relationship between dissipation and usable mechanical work, externally seen as a problem of natural laws, is only one with that of the relationship between effort —which is not the same as work-, work and reversible transactions in the logic of capital. It is not surprising that thermodynamics developed in the very years of the vindication of work as an autonomous category, and that that happened between both considerations of physiology, blood and heat (Mayer) and those of metal and machines (Joule) in the 1840s. There is still an unexpected circle to be closed here, and the more we manage to go full circle, the greater will be the repercussions on our vision of “external” nature (exploitable resources) and “internal” nature (society). And perhaps then we will begin to fully understand to what extent exploiting nature is the same as exploiting ourselves.
The double-speak of modern physics
It is well known that since the 17th century scientists have been pleased in encrypt their communications in order to be able to claim priority while at the same time avoiding giving an advantage to their competitors. Moreover, even in the time of Galileo or Newton there was a great awareness of the strategic, commercial and military value entailed even in a knowledge as apparently detached from the ground as astronomy or the maritime calculation of length.
Thus, for centuries science developed in the West in a delicate balance between its eagerness to expand and communicate, and the convenience of masking to a greater or lesser extent its procedures. If this happened even in the most pure and abstract disciplines, such as number theory, we can imagine a little of what happened with applied sciences.
When in the first decades of the twentieth century quantum mechanics and the theory of relativity developed, although certainly a reinvention of the public image of science was already underway, it can still be assumed that physicists communicated their theories with some spontaneity and that the rush to advance rapidly and at any cost created a kind of “natural selection” in the supply of methods, hypotheses, and interpretations. But then the Second World War came, with things like the Manhattan Project —Big Science in short- and scientists, as Oppenheimer admitted, lost whatever little amount of innocence they had left.
It is to be assumed that it was more or less around that time or shortly thereafter that it was fully understood that the two great new theories served as much to conceal as to communicate, which for such compromised areas as particle physics was specially convenient.
Why someone as practical and well-informed as Bush was wasting his precious time with the forgotten Weber theory in 1926, just when quantum mechanics was in full swing? The same inevitable Feynman, spokesman for the new algorithmic style in physics and man of the Manhattan Project, once admitted that the law of retarded potentials covered all cases of electrodynamics including relativistic corrections. Even Schwinger worked for the government in radar development. It is no exaggeration to say that the gestation years of QED make up the epoch when the dividing line between theoretical and applied physics, with all that implies for both, fades away forever.
Simply put, it’s too hard to believe that armies of talented physicists have not dared to leave the superfluous relativistic framework in particle physics when any amateur who considers it can see that it is a full-fledged embargo to any steady progress in the field. That this is not said is even more significant. Of course, in order to convince us otherwise, an unprecedented new specimen of physicist came out from nowhere, extrovert, casual, persuasive, fantastically gifted for communication and public relations. The spitting image of superficiality —and with a remarkable resemblance to Cornel Wilde. Each shall judge for himself.
We will ignore the things that have been said about the atomic bomb and the theory of relativity, because the atrocities of the advertising industry could still embarrass physicists. We can always blame it on the journalists. It is obvious that relativity has practically nothing to do with the development of nuclear physics, and just as obvious should be how little quantum electrodynamics had to do with the myriad of applied achievements of all these last decades.
The famous “shut up and calculate” of the aforementioned physicist and spokesman conveys wonderfully what is expected of the new researcher. The calculation would have to be only a third of the work in physics, theoretical or not. If we divide the sequence of any human activity into principles, means and ends, in physics calculation or prediction would be only the means between the intelligent use of principles (which are present at all times), and interpretations, which, far from being a subjective or philosophical luxury, are inexcusable when it comes to making sense of the mass of empirical data, continuing research and motivating the synthesis of applications. Ends as purposes are both interpretations and applications.
So you don’t see why in physics interpretation should be of less practical interest than calculation, and I think these arguments are so basic that anyone can understand them. Those only concerned with the means will also be used only as a means. Besides that, quantum mechanics and relativity, rather than facilitate calculations, often make them unusually difficult. Compare, for example, the calculations required for the simplest problem in General Relativity with those of a Weber law for gravity; not to mention the somewhat more complicated cases where it becomes completely unmanageable. The prescription of the relativistic particle has a very clear meaning and it is to make impossible any calculation with physical meaning. It goes without saying that experimental and applied achievements have been obtained in spite of this stumbling block, ignoring it rather than observing its prescriptions.
“Shut up and calculate” simply means “calculate what I tell you and don’t even think of anything else”. Curious slogan coming from someone who has been glorified as an incarnation of unrestricted originality and of the genius on his own. He could also have said, “Keep it superficial and forget about getting to the bottom of the matter forever.” Calculation is completely blind if it is not properly coordinated with principles and interpretations; you can even make sure that this coordination is more important than everything else. But we should not see in this nothing inconsistent, but on the contrary a faithful translation of Big Science double-speak and its defined priorities behind the ever-present screen of public relations.
Known is how in 1956 Bohr and von Neumann came to Columbia to tell Charles Townes that the idea of the laser, which required the perfect phase alignment of a large number of light waves, was impossible because it violated the inviolable Heisenberg’s Uncertainty Principle. The rest is history. Now of course what is said is that the laser is just one more triumph of quantum mechanics, from which is a trivial particular case.
The above case has not been the exception but the general trend. We are told that quantum mechanics is something very serious because its mass of experimental evidence surpasses that of any theory, but for me it seems more serious the work of engineers and experimenters trying very hard to figure out causal relationships and applications without the support and even with the obstruction of an interpretation that prohibits physical interpretation and that seems expressly conceived to sabotage any attempted concrete application.
And as for the incomparable predictive power of quantum mechanics and QED, which cannot even imagine the collapse of the wave function it postulates, we must understand, what else, a power of a posteriori prediction. Today they also predict the Berry phase, that even appears in the soup, although with the opportune extensions of that which is not even “a theory”, but hard facts only. It is clear that procedures that subtract infinite from infinite in a recurrent and interminable way, can be bent to obtain practically any result; but in spite of all this we are still told that it is a very restrictive theory. Perhaps it is, in the light of some abstract principle of symmetry among other principles still more abstract. It will be, no doubt, after you have adjusted all the nuts and bolts imaginable to the case in hand. Who said self-interaction? This is already a self-adjusting theory. And the best of all, you can make say anything to an incoherent theory.
Nothing could be more castrating for the physicist than to ask him exclusive fidelity to the calculations. All the more so if these calculations are so unscrupulous that they are used in an openly teleological way to replicate certain results —pure reverse engineering, hacking of nature to which one wants to give the category of Law.
If what is hacked from nature soon becomes Law, then it is not surprising that it is used as Law lest others hack into it.. And that is why today the Great Theories are used as the more effective blockade to technology transfer.
Nothing is more practical than a good theory. But those who are only interested in governing nature are not worthy of illuminating it, let alone understanding it. So surely we have the level of understanding that our social structure can tolerate, and this is the natural thing, first because scientific knowledge is a pure social construction, and second because all social construction is second nature trying to isolate itself from a supposed first nature.
Today, transformation optics and the anisotropy of metamaterials are used to “illustrate” black holes or to “exemplify” and “design” —it is said – different space-times. And yet they are only manipulating the macroscopic properties of the old Maxwell’s equations. Can distortion and distraction be taken further? And the fact is that all this could serve to investigate the uncontrollable aspects of the electromagnetic continuum that are but the classical form of the famous non-local aspects of quantum mechanics. Haven’t we seen that if Schrödinger’s wave function describes vibrations in a moving body and in the medium, classical electromagnetic waves are also a statistical average of both things?
In something as apparently well-trodden as the electron we can find not only the key to particle physics, but also the limits of application of nanotechnologies, quantum computing, and a legion of emerging new technologies. But if all these are matters of power and interest, we can already forget the truth.
That you can’t serve simultaneously both truth and power is something known to all. That scientific publicity develops its stories and narratives as if this conflict did not exist is the only thing you would expect. If the current accounts delay scientific development a little or a lot, it is not something we should regret either, since more technological advances, in the absence of other things, can only mean more disorder.
Fortunately, those who in one way or another obstruct knowledge are not capable of developing second-order knowledge free from their own distortions either; the complexity of their compromises strictly limits them. All the cunning of the world, all the experimental-statistical-mathematical-computational arsenal, cannot replace the sense of rectitude, the only one capable of delving into the unlimited promise of simplicity.
N.K. Noskov, The theory of retarded potentials versus the theory of Relativity
N.K. Noskov, The phenomenon of the retarded potentials
J. P. Wesley, Weber electrodynamics
Assis, A. K. T, Relational Mechanics -An implementation of Mach’s Principle with Weber’s Gravitational force, Apeiron, Montreal, 2014
T. B. Batalhao, A. M. Souza, R. S. Sarthour, I. S. Oliveira, M. Paternostro, E. Lutz, R. M. Serra
Irreversibility and the arrow of time in a quenched quantum system
Lucia, U, Macroscopic irreversibility and microscopic paradox: A Constructal law analysis of atoms as open systems
V. E. Zhvirblis, V. E, Stars and Koltsars, 1996
N. Mazilu, M. Agop,* Role of surface gauging in extended particle interactions: The case for spin*
N, Mazilu, Mechanical problem of Ether Apeiron, Vol. 15, No. 1, January 2008
V.V. Aristov, On the relational statistical space-time concept
R. M Kiehn, Retrodictive Determinism
M.J. Pinheiro, A reformulation of mechanics and electrodynamics | 0.80932 | 3.027964 |
An axion is a theoretical particle named after a laundry detergent. As particles go, it is a strange one. Its mass is tiny—somewhere between one trillionth the mass of the proton and one billion-trillion-trillionth. It is so lightweight, in fact, that it doesn’t even behave as a particle, but as a wave that could straddle a galaxy. It is also feeble—its influence extends over an almost absurdly short distance, a millionth of what the Large Hadron Collider is able to discern. These short distances stem from the possible relation between axions and very high energy physics, possibly even quantum gravity.
When I first heard of the axion, I had no idea it would become my life’s work. I was a new grad student looking for a starter project, and I came across a paper with such a peculiar title that I couldn’t help but read it: “String Axiverse.” It was written by a group of people including John March-Russell, a theoretical physicist in my department at Oxford. Speaking to John and cosmologist Pedro Ferreira (who both later became my Ph.D. advisors), I realized that the axion was just what I wanted to work on: a fascinating theoretical construct, but with direct connection to the exciting modern progress in cosmology.
An unknown particle that may exist in profusion: the axion is an ideal candidate for dark matter. But it is a very different beast than we’re used to thinking about, requiring us to go about the search for dark matter in a different way.
The Nobelist Frank Wilczek gave the axion its name because it cleaned up a problem in the Standard Model of particle physics. In the 1970s, he and others puzzled over a mismatch between the two forces that govern atomic nuclei: the strong and weak nuclear forces. The strong force has a symmetry in its workings that the weak lacks, even though, a priori, there is no reason it should. Helen Quinn and Robert Peccei proposed that the force is not innately symmetrical, but develops this symmetry under the action of a new field akin to the Higgs field. The axion particle is a remnant of this field.
To play its role, the axion must be extremely lightweight. For our current theories, that is awkward, because it creates an enormous gulf between this particle and all the others. But the low mass is entirely natural in string theory, our leading candidate for a unified theory of nature. String theory predicts there is not just one type of axion, but there are typically 30 or more different kinds, and it predicts that their masses are spread out over a wide range. Some therefore must be lightweight. String theory is often criticized for not making testable predictions, but that’s not quite right, because the theory does predict axions. Although I wouldn’t claim that discovering lots of axions would be evidence for string theory, I think it is fairly safe to say that, according to almost any theory other than string theory, it would be surprising if we discovered large numbers of them.
If axion dark matter exists, it is completely invisible to a conventional experiment.
Axions are like other candidates for dark matter in that they are dark—they have no electric charge and therefore do not emit or absorb light—and interact very weakly with ordinary matter. But there the resemblance stops. Compare it to the most commonly discussed type of dark matter, the WIMP, or weakly interacting massive particle. It is a so-called thermal relic, which, according to theory, is produced the same way as protons, neutrons, and atomic nuclei: from the collisions between particles in the hot, dense, early universe. Given the amount of missing mass that astronomers infer, this production mechanism for WIMPs sets their mass and interaction strength: 100 times the mass of the proton (hence “massive”) with an interaction strength roughly equal to the weak nuclear force (hence “weakly interacting”). These would be lumbering particles, and that is just what astronomers need to explain the distribution of galaxies. If they exist, we should be able to detect them in particle detectors similar to those we use to detect neutrinos, and we should even be able to produce them ourselves by mimicking those hot, dense conditions in the Large Hadron Collider.
Axions, in contrast, have a different origin story. Their production is determined not by the temperature of the plasma in the early universe, but gravitationally, by the expansion of space in the big bang. This production mechanism sets their mass and interaction strength, which are vastly different from those of WIMPs.
Axions would interact with ordinary matter to a limited degree, but only by a unique set of interactions. For this reason, if axion dark matter exists, it is completely invisible to a conventional experiment such a WIMP detector or even the Large Hadron Collider.
The poster-child axion direct-detection experiment is ADMX, which operates at the University of Washington and relies on a concept invented by Pierre Sikivie in 1983. Though “dark”, axions do interact with electromagnetism in other ways and, in the presence of a magnetic field, can metamorphose into photons or vice versa. ADMX attempts to perform the metamorphosis inside a microwave radio-frequency cavity like those used in radar equipment and microwave relay stations. So far ADMX have observed nothing, but it is sensitive only to axions whose wavelengths are comparable to the size of the cavity, and it has still not completed its full search program. Proposed experiments such as MADMAX and CASPEr would probe a much wider range of wavelengths.
In principle, axions might have shown up in experiments intended for other purposes. With colleagues at the University of Sussex, the Swiss Federal Institute of Technology, and the University of New South Wales, as well as two talented grad students, Nicholas Ayres and Michał Rawlik, I have been digging through the archives of the nEDM experiment, which ran for a number of years at the Institut Laue-Langevin in France and is now at the Paul Scherrer Institute in Switzerland. It has been measuring neutrons, which would oscillate in a particular way if a galactic axion wave happened to pass through it, and we are reanalyzing the data to look for this signal.
In this field, there’s room for young theorists such as me to make headway.
If axions exist, stars would produce them naturally. Some of the photons produced during nuclear fusion in the core could metamorphose into axions, and they would escape the star more readily than photons do. This would drain the star of energy and cause it to age faster. Astronomers have been combing through star clusters for stars that look older than they actually are, and they have found no evidence of extra cooling. This null result sets limits on how strongly axions can interact with the constituents of stars.
With my colleagues Dan Grin and Renée Hložek, I have also been searching for axions in cosmological data. Their wavelike properties might give them away. Over distances smaller than the axion wavelength, multiple axion waves would overlap and interfere with one another, causing them to exert an outward pressure and puff up galaxies. And indeed astronomers do find that galaxies are less clumpy than WIMPs should cause them to be (although there are many possible explanations for this, not just axions). My colleagues and I have been exploring this idea further by combining galaxy data with cosmic microwave background radiation measurements, as well as conducting simulations of galaxy formation with axion dark matter.
Finally, axions would alter what happened during cosmic inflation, the primeval period when the universe was expanding at a breakneck rate. Cosmologists generally think the inflationary process created a torrent of gravitational waves, but if dark matter is made of axions, it would have generated very few. So, the discovery of primordial gravitational waves could be taken as falsification of the axion idea, at least in a wide range of models. (If we ever detected both axion dark matter and these gravitational waves, then something would be wrong with standard inflationary theory.)
Only a small band of devotees have given much thought to axions. That makes it a fun field to be working in. There’s room for young theorists such as me to make headway and feel like we’re adding to the understanding of the community, which is much harder to do in a more mature field such studying WIMPs.
It should be said that there is room in the universe for both axions and WIMPs. Both have a firm grounding in fundamental physics and in cosmology, and both may exist out there. For me, one of the benefits of thinking about axions is that they force to think beyond WIMPs. If all we ever do is study and simulate WIMPs because it is relatively easy, as a community we run the risk of confirmation bias, where WIMPs always come up trumps because they are all we know. Thankfully, that doesn’t seem to be how the field of dark-matter research is going. People are exploring a huge range. Dark matter is out there and discovering it is just a matter of time. When we do discover it, whatever it is, it will revolutionize our ideas of particle physics and cosmology.
Lead image: Microwave cavity in the ADMX axion detection experiment at the University of Washington. Credit: ADMX. | 0.842343 | 3.886241 |
Astronomers have spotted an enormous planet orbiting a tiny star about 31 light years away. It is so big that it can’t have formed in the way that we think most planets do.
Juan Carlos Morales at the Autonomous University of Barcelona in Spain and his colleagues spotted the planet, called GJ 3512 b, using a technique called the radial velocity method. This takes advantage of the fact that as a planet orbits its star, the star moves slightly in a way that allows astronomers to determine the planet’s mass and orbit.
Using more than two years of observations with the CARMENES exoplanet survey in Spain, the researchers found that GJ 3512 b is at least 46 per cent as massive as Jupiter and orbits its star once every 204 days. The star itself is only 12 per cent as massive as our sun – or about 126 times the mass of Jupiter.
“With the first observations, it looked like two stars orbiting each other,” says Morales. More observations clarified that it was a planet, but it was unexpectedly large.
“Giant planets are fairly rare in general, but as you go to lower and lower mass stars, they become even rarer,” says Greg Laughlin at Yale University. “The processes that lead to the formation of these planets is not well understood.”
The usual method of planet formation is called core accretion. In this process, a planet slowly forms as dust and pebbles clump together in the disk of debris surrounding a star, growing its core until it is big enough to hold on to a gas atmosphere by virtue of its own gravity. But when Morales and his colleagues ran simulations of GJ 3512 b, they found it couldn’t have been formed in that way.
Instead, they say it was probably formed in a process called gravitational instability, where a disk of gas spontaneously collapses to form the core of a planet all at once. “This is the first time that we have a clear detection of a planet where the only possible way to explain it is gravitational instability,” says Morales. That may mean that the process of planet formation is more diverse than we thought, and it is possible that there are more giant planets like this than we previously envisaged, he says.
Journal reference: Science, DOI: 10.1126/science.aax3198
More on these topics: | 0.84861 | 3.837133 |
A bright spot that appeared on Uranus has caused a flurry of excitement among amateur astronomers, but what has happened to it is a puzzle.
The spot, assumed to be a storm in the ice giant’s clouds, was revealed in images taken with a 60-inch telescope at the historic observatory at Mount Wilson, California, on October 22nd.
Photographer Blake Estes posted on Instagram to show the spot he had imaged with Richard Bell on the southern edge of the planet’s bright polar region. It was said to have been detected with amateur telescopes too.
Appeals for further observations were made, including by Mike Foulkes, Director of the Saturn, Uranus and Neptune Section of the British Astronomical Association.
Mike wanted to know whether the feature was still visible or had been short-lived. He told me that similar bright features had imaged in 2016 by larger amateur instruments, generally using infrared (IR) filters.
One potential problem is that imaging the planet is very challenging for amateurs, and over-processing with software afterwards can introduce artefacts.
Mike said that the few recent images he had seen showed the bright region in the northern hemisphere plus a darker band to the south. Of the spot itself, observations of November 9th and November 18th possibly showed something, but nothing appeared on others taken on October 20th and November 15th. Mike was planning to examine the images more closely.
When I received the BAA alert, I recalled having seen a tweet from a Hubble Space Telescope account at the weekend, reporting that the orbiting observatory was observing Uranus with its Wide Field Camera 3 for Dr Amy Simon, who is Senior Scientist for Planetary Atmospheres Research at NASA’s Goddard Space Flight Center. So I emailed her to ask what Hubble might have seen.
Dr Simon said that the Space Telescope team want to produce a press release of their own in due course, so are not making the latest images of Uranus available to the public at the moment.
However, she told me that they had imaged Uranus with Hubble through two full rotations, adding: “I can say that we do see storms, though nothing as big as the initial report.” (Uranus rotates once every 17h 14m).
So whatever the bright spot was on Uranus on October 22nd, it sounds like it had diminished substantially by the time Hubble came to observe the planet a month later.
Uranus is an unusual planet in that its axis is tilted so much that it virtually rolls around the Sun on its side. For half its 84-year orbit, the northern hemisphere is directed towards the Sun before the southern hemisphere is turned towards the sunlight. But at two points in its orbit, known as the equinoxes, the Sun shines equally on both hemispheres. Uranus, which is known to be a windy planet, was last at an equinox in 2017.
At these equinoxes, storms appear to become more frequent in Uranus’s disturbed atmosphere, in contrast to the calm conditions and bland cloud tops observed by NASA’s Voyager 2 space probe when it flew past the ice giant in January 1986.
Stormy weather has been observed a number of times in recent years, however, with a notably bright one appearing in 2014, seven years after the last equinox.
Dr Simon told me: “We’ve seen some sustained storm activity well past equinox,” adding “in a sense that was no surprise, because on any planet, we often see storms well after equinox, and there can be a lag between when an area heats up and when you see storms.”
★ Keep up with space news and observing tips. Click here to sign up for alerts to our latest reports. No spam ever - we promise! | 0.837292 | 3.34493 |
When the New Horizons spacecraft made its flyby of Pluto on July 14, 2015, there was worldwide celebration that we’d finally gotten our first detailed look at this completely new type of planet in the outer reaches of our solar system.
But for those of us on the New Horizons science team, that day and those first images were only the beginning. Since then, I’ve been watching with amazement as the New Horizons spacecraft has transmitted spectacular images back that reveal surprises all over the place. We’ve been making discovery after discovery about the dwarf ice planet Pluto and its moon Charon, and this is likely to continue as we get more data back from the spacecraft. Here’s a summary of just a few of our scientific results to date.
What do we see on Pluto’s surface?
Perhaps one of the biggest surprises that was obvious from the very first images was that Pluto has a surface that is incredibly diverse.
Some surface areas, such as those that are heavily cratered from asteroid impacts, seem to date back to just after Pluto formed, about 4.5 billion years ago. Other regions show evidence of geological activity that may have lasted throughout Pluto’s billions of years of history. Enormous ice volcanoes (cryovolcanoes) must have taken a large fraction of Pluto’s history to form. These volcanoes are driven by warm underground liquids, such as, perhaps, water and ammonia, instead of liquid rock-magma that we have on Earth, and their rough, crusty surface is made of stuff that has erupted from deep within Pluto’s interior.
Other areas, such as the informally named Sputnik Planum – the heart-shaped, Texas-sized nitrogen ice glacier – show no evidence of asteroid impacts at all, suggesting continual surface activity, such as convection of ices from underground. This surface can’t be more than 10 million years old – a blink of the eye on a geological time scale!
Pluto is geologically active! I doubt there’s a single person on Earth who would have expected to see that!
What’s Pluto made of?
The diverse chemical compositions we’ve seen on Pluto are giving us some important clues to understanding Pluto’s geological history and climate.
The high-resolution images from the New Horizons cameras show diverse ice reservoirs across Pluto’s surface. By studying the reflected spectra from the surface, we’ve identified several different types of ices: in particular, nitrogen, methane and carbon monoxide. The locations and characteristics of these ice reservoirs mean that there have been long epochs of ice transport across the dwarf planet’s surface.
A darker veneer on top of the ices is probably tholin material – organic compounds processed by solar radiation. These are produced slowly in Pluto’s atmosphere and gently rain down, even now, onto the surface. An enormous darker region, informally named Cthulhu Regio, has a meters-thick layer of this organic tholin material that has built up over billions of years. Frozen water is one of the strongest solids at the low temperatures we see on Pluto. We believe that the ice mountains that extend several miles above the surface are made of water ice – the biggest ice cubes in the solar system.
Charon, too, had some major surprises in store for us. Pluto’s largest moon has an extended equatorial region of smooth plains that may also be due to material that erupted from Charon’s interior via ice volcanoes that then flowed over its surface about four billion years ago. We suspect that was when Charon’s subsurface water ocean froze, causing global fractures as the moon expanded in size (water expands when it freezes).
Charon has dark poles that may be related to volatile gases that escaped from Pluto’s atmosphere only to be captured by the moon’s cold poles. These gases trigger chemical reactions on the surface that, we believe, produce the darker color of the poles.
How does Pluto’s atmosphere work?
The spacecraft’s Alice instrument made observations of sunlight passing through Pluto’s atmosphere. We see absorption features that indicate an atmosphere made up of nitrogen (like Earth’s) with methane, acetylene and ethylene as minor constituents.
Pluto’s small size and low gravity cause it to hold onto its atmosphere much more weakly than larger planets like the Earth (which has 16 times stronger gravity than Pluto). Prior to the New Horizons’ encounter, we expected this would produce an atmosphere that was greatly extended and rapidly escaping to space. But it turned out the upper atmosphere is much colder than we thought it would be and so more compact – the atmosphere does not extend nearly as far into space as we expected and the escape rate of atmospheric gases is extremely slow. But why the atmosphere is so cold is still a complete mystery.
As an atmospheric scientist, I found the most amazing discovery to be the brilliant, light blue, globally extensive haze that we can see because large numbers of small atmospheric particles scatter sunlight. This haze extends hundreds of kilometers into space, and embedded within it are over 20 very thin, but far brighter, layers. We suspect the thin layers are produced by some type of atmospheric wave that causes localized regions of condensation of some as-yet-unknown gas. The largest moon of Saturn, Titan, shows similar layering of haze in its upper atmosphere. So there may be some interesting comparative planetary studies that come out of the analysis of the Pluto data.
Where did Pluto’s moons come from?
The origin of Pluto’s five moons has been a long-standing question. But the flyby observations have given us some critical data that we needed in order to develop convincing explanations.
We believe that Charon is just about as old as Pluto, having formed when Pluto was very young. An impact between Pluto and another large Kuiper Belt object early in their history ejected an enormous amount of debris into orbit around Pluto. As time went on, this orbital debris coalesced into Charon.
Previous speculation was that the four smaller moons are actually asteroids captured by Pluto’s gravity as they passed too near the dwarf planet. But the New Horizons observations showed that these four moons have an unusually high reflectivity – much different than the extremely dark materials that we see on asteroids in the outer solar system. This has led to a compelling argument that the smaller moons are also made of debris from the same impact that formed Charon.
How does Pluto interact with its space environment?
As the New Horizons spacecraft approached Pluto, there was some concern that a small amount of debris might still remain in orbit around the dwarf planet. A collision between New Horizons and even one particle of debris the size of a grain of sand could cause considerable damage to, or possibly destroy, the spacecraft.
But the student-built Dust Counter, which measures small micrometer size dust particles in space, detected only a single particle during the flyby – and it was much too small to cause spacecraft damage. This means Pluto’s environment is now largely devoid of debris – all of it likely swept up by the moons early in the system’s history.
The New Horizons spacecraft also carried instruments to study what happens to the solar wind when it encounters Pluto’s atmosphere. The detailed way in which solar wind particles from the sun interact with a planet’s atmosphere provides important clues about the nature of that atmosphere, particularly how far it extends into space and the escape rate of atmospheric gases. The interaction region between Pluto and the solar wind was observed to be much smaller than expected, only about 12 Pluto diameters across. This means that the atmosphere is smaller than expected, and so these results confirm the Alice observations that the upper atmosphere is much colder than expected.
So much more yet to come
These are just a few of the many exciting, and unexpected, results from the New Horizons flyby of Pluto and Charon. The discoveries we’ve already made will mean that textbooks on planetary science must be rewritten. And yet this sampling of the New Horizons results is just from the tip of an ice mountain of data that we’ll be analyzing and writing papers about for many years, perhaps decades. The data are so rich in things we’ve never seen before that I’m sure there are many more surprises yet to come. | 0.875223 | 3.868061 |
One aspect of general relativity that always amazes me is the level of precision needed to distinguish it from Newtonian gravity. Take, for example, the advance of Mercury’s perihelion. When you count in the gravitational tugs from the sun and all the planets, Newton predicts Mercury’s perihelion will advance about 531.65 arcseconds per century. When we measure the orbit of Mercury, we find its perihelion actually advances 574.10 arcseconds per century. This means Newton’s prediction is off by about 42.45 arcseconds per century. I say “about” because there is an uncertainty in our observations of about 0.65. General relativity predicts an “extra” perihelion advance of 42.98, which agrees exactly with experimental observation.
The difference between Newton’s model and Einstein’s amounts to 28 millionths of a degree each orbital revolution. Put another way, Mercury makes one orbit every 87.969 days, but it reaches its perihelion about a half second later than Newton says it should. The difference between Newton and Einstein is less than a human heartbeat in time.
The most amazing thing about all this? This deviation from Newton was first accurately measured by Urbain Le Verrier in 1859. | 0.824791 | 3.184404 |
Yesterday I mentioned that hypernovae (super-supernovae) are the result of the explosion of a star that’s about as massive as a star can be (about 150-200 solar masses). But how exactly do we know that this is an upper limit?
The first clue comes from a derivation by Arthur Eddington. In 1916, Eddington demonstrated that there was a limit to how bright a stable star could be. The basic idea is that the atmosphere of a star is being gravitationally attracted by the mass of the star (giving it weight), and this weight is balanced by the pressure of the deeper layer of the star. For a star to be stable, the weight and pressure must be equal, so the star doesn’t collapse inward or push the atmosphere outward.
We typically think of pressure as being due to gas and such, but light can also exert pressure on a material. We don’t notice light pressure in our daily lives because it is so small. Even in our Sun, the pressure on the atmosphere is relatively small, so the weight of our Sun’s atmosphere is mostly balanced by the pressure of the plasma in the layer underneath it. But if the Sun were brighter, the light it emits would push harder against the particles of the atmosphere. What Eddington showed is that there is a limit where the pressure of a star’s light on the atmosphere is large enough to balance the gravitational weight of the stellar atmosphere entirely, known as the Eddington luminosity limit. If the star were any brighter, the light of the star would push away the outer layers of the atmosphere, thus causing the star to lose mass.
When Eddington first derived this limit, he found that the maximum luminosity (brightness) of a star was proportional to the mass of a star. This meant that more massive stars could be brighter than less massive stars, but it didn’t say anything about an upper limit on mass. Then in 1924, Eddington discovered a relationship between the mass of a star and its luminosity, specifically that the brightness of a star is roughly proportional to the mass cubed.
This meant the brightness of a star increased with mass faster than the luminosity limit, so there must be an upper limit on a star’s mass. Stars with larger masses would be so bright that they would burn away their outer layers. With Eddington’s calculation, this limit is around 65 solar masses. Later, more detailed calculations put this limit at around 150 solar masses, which is generally considered an upper limit for stable stars.
In 2007, a research team made a study of the Aches cluster,1 which is the densest known star cluster in our galaxy. Looking at the brightest stars in this cluster, they found no stars greater than about 120 solar masses. Using their observations to make a statistical extrapolation, they found that the upper limit for stars is likely 150 solar masses.
But recently new evidence has questioned that limit. Theoretical work has shown that it is possible to have stable stars with a brightness greater than the Eddington luminosity limit. Effects such as turbulence within the atmosphere and photon bubbles, where light could pass through the stellar atmosphere more easily would allow super-luminous stars to remain stable. Then there are calculations from hypernova explosions that estimate the progenitor (the star that exploded) had a mass of about 200 solar masses. Finally, there is a star known as R136a1. Discovered in 2010 which is currently the most luminous known star,2 and has an estimated mass of about 265 solar masses.
So while 150 solar masses is generally considered an upper limit, that limit seems to be more of a guideline.
Martins, F., et al. “The most massive stars in the Arches cluster.” Astronomy & Astrophysics 478.1 (2008): 219-233. ↩︎
Crowther, Paul A., et al. “The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 M⊙ stellar mass limit.” Monthly Notices of the Royal Astronomical Society 408.2 (2010): 731-751. ↩︎ | 0.824213 | 4.212703 |
While the search for unknown life forms most often takes place in the vast reaches of space, there remain many undiscovered living things on Earth hiding in deep, dark places far beyond the reaches of humankind. While there has long been speculation that there could be underground races of aliens or mutated men living within the Earth, no evidence has ever been found to confirm such theories, However, a recent study by researchers from the University of Alberta has revealed that ancient underground water samples might contain unknown organisms unlike any other known living things on Earth.
According to their research published in Nature Communications, the geochemical and thermal conditions of these waters imply that any microbes found within might be biologically similar to the lifeforms we might find within, say, Martian soil, which has a similar composition:
The discovery of hydrogen-rich waters preserved below the Earth’s surface in Precambrian rocks worldwide expands our understanding of the habitability of the terrestrial subsurface. [These] findings have implications for planetary habitability and the exploration for evidence of life on Mars.
These water samples have been sealed off from the surface of our planet for over 2.7 billion years. The microbes found in these ancient water samples are believed to survive off of hydrogen and sulfates found in the subterranean water and surrounding rocks.
According to lead researcher Long Li, this same combination of elements and molecules is believed to be under the surface of Mars, implying that similar microbes might be found on the red planet:
Because this is a fairly common geological setting on modern Mars, we think that as long as the right minerals and liquid water are present, maybe kilometers below the Martian surface, they may interact and produce energy for life, if there is any.
I know what you’re thinking. You were hoping for green-skinned, bug-eyed aliens walking around zapping things with ray guns and what not. Still, microbes are cool, right? Any life we might find on Mars, however small, will open the possibility for more advanced lifeforms and show us that we’re not alone in this mysterious universe. | 0.804685 | 3.022554 |
UNTIL the 1990s there was no evidence for the existence of planets beyond our solar system. But in recent years techniques for detecting planets orbiting stars many light years away have been discovered, While the light from 'extra solar planets' is drowned out by their parent stars there are two methods of detecting them indirectly, and pupils at a Widnes school have just become the first to try their hand with one of the techniques. ADRIAN SHORT reports.
ONE of the most fascinating topics in astronomy came under the spotlight when a professional scientist delivered a workshop on planets which exist elsewhere in the galaxy.
Dr Chris Leigh, an astronomer at Liverpool John Moores University, was joined by physics teacher Andrea Fesmer, of Saints Peter and Paul City Learning Centre (CLC), in leading a workshop which involved pupils looking at real information from space to find out more about the planets which orbit stars other than our own star, the Sun.
The pupils heard that planets out-side of our Sun and its planets (like the Earth and Mars) are called exoplanets.
Exoplanets were unknown until about 15 years ago and, as of July 2005, 161 planets have now been discovered revolving around stars many light years away from the Sun.
The pupils were shown an artist's impression of what an exoplanet may look like and saw real images from the Hubble
Space Telescope of stars surrounded by disks of materials believed to be a collection of dust, chemicals and boulders - from which planets could form in the future.
Dr Leigh said that our own solar system would have looked like that in the distant past.
The pupils learned that the first exo-planet was discovered in 1995 around a star called 51 Pegasi.
Astronomers noticed that 51 Pegasi was wobbling every three-and-a-half days.
Dr Leigh explained that when two objects are stuck together, or are relatively close together, they move around a common centre of mass which causes a wobble in the bigger object's path.
This can be compared to the wobble of a hammer thrower as he swings the hammer around him in athletics.
They realised that the planet must be very close to its parent star if it was able to orbit in three days - unlike the earth which takes 365 days to orbit the Sun. Even the closest planet to the Sun, Mercury, takes 88 days to orbit.
Dr Leigh said the object was so incredibly close to 51 Pegasi that it would have a surface temperature of 1,200ºC, far too hot for life, as we know it, to exist there.
He said that astronomers cannot detect exoplanets visually, as no planet produces any light of its own and, as they are such a long way away, they become lost against the blinding glare of the star they orbit.
Typically an exoplanet would be 20,000 times fainter than the star it orbits, as it merely reflects a small part of the light from that star.
Another way of detecting an exo-planet, apart from looking at its star's wobble, is to look at how much light it blocks off from its star as it passes in front of it. If there is a planet there, then observers can detect a periodic reduction in the brightness of a star.
The pupils at Sts Peter and Paul CLC used computer programs to analyse images taken with the Liverpool Telescope in the Canary Islands of a possible exoplanet star.
The star they looked at was TrES-1-b which is thought to be orbited by a gas giant planet similar to Jupiter - our Sun's largest planet.
Six out of the 161 known exoplanets have been discovered by measuring the fall in light caused as by the exoplanet passes in front of its Sun.
The rest were detected by wobble - even Jupiter causes our own Sun to wobble by a velocity up to 12.5 metres per second in its year (which takes 12 Earth years).
Nine pictures of the TrES-1 star were taken at 10-15 minute intervals, before being looked at by the pupils.
The pupils then used a computer program, which calculated the changes in brightness of the star.
The time taken for known exoplanets to travel once around their stars has been found to range from an incredibly quick year of 2.5 days to a year of more than 5,000 days.
Hopefully, one day, scientists will be able to capture light directly from a distant exoplanet which would let them pinpoint which chemicals are present, and then we'll know exactly what the exoplanets are made of. | 0.899132 | 3.727457 |
Jupiter and Orion rule our New Year nights
The annual Quadrantids meteor shower hits its intense peak even before Jupiter comes to opposition on the 5th. The giant planet shines brightly throughout our January nights and Orion, too, is ideally placed in a sky awash with bright stars.
What is missing, though, is any sign of Comet ISON. Any hopes that the comet might blossom into a spectacular sight during December were shattered when its icy nucleus failed to survive its brush with the Sun on 28 November. A so-called ghost of ISON did emerge from its perihelion, but this must have been a dispersing cloud of dust which soon disappeared. Searches since then, including by Hubble, have failed to spot anything at all. So much for the Comet Of The Century.
Our charts show the Pleiades in Taurus glimmering high in the south at our map times as Orion strides towards the meridian. Trailing Orion are his two dogs, Canis Major and Canis Minor, with their bright stars Sirius and Procyon. Together with Betelgeuse at Orion’s shoulder, these form the Winter Triangle. Orion’s immediate foe, of course, is Taurus the Bull whose main star Aldebaran lies against a more remote V-shaped star cluster, the Hyades. The tips of the bull’s long jutting horns are marked by the stars Elnath and Zeta Tauri and it is just 1.1° north-west of Zeta that we find the famous Crab Nebula. The debris from a supernova explosion recorded by Chinese astronomers in 1054, it lies about 6,500 light years away and appears as an oval eighth magnitude smudge through a telescope.
January sees the Sun climb 6° northwards as sunrise/sunset times for Edinburgh change from 08:43/15:49 on the 1st to 08:09/16:44 on the 31st. The Moon is new on the 1st, at first quarter on the 8th, full on the 16th, at last quarter on the 24th and new again on the 30th.
With no moonlight, and if the weather permits, this could be good year for Quadrantid meteors. The shower lasts from the 1st to the 6th but has an unusually brief peak when the meteor rate could reach 80 or so per hour for an observer under ideal conditions. That peak is expected at about 19:00 GMT on the 3rd when the radiant, the point in the sky from which the meteors diverge, lies rather low in the north so that only a fraction of the ideal number of meteors may be seen. Even so, I’d expect to see several long-trailed meteors speeding overhead from north to south. Later in the night, the radiant follows the Plough as it climbs through the eastern sky.
The brightest object on our charts, Jupiter, shines at magnitude -2.7, three times brighter than Sirius, when it stands opposite the Sun on the 5th. It then rises in the north-east at sunset, crosses our high meridian at midnight and sinks to set in the north-west at dawn. The arrow on our chart shows it tracking westwards against the stars of central Gemini, some 10° below and right of Castor and Pollux. As such, it is unmistakable above and to the left of Orion later in the night. Look for it to the left of the almost-full Moon on the evening of the 14th. Jupiter is 630 million km distant at opposition, its slightly rotation-flattened disk measuring 47 arcseconds in diameter.
Appearing even larger than Jupiter is the dazzling magnitude -4.3 evening star Venus which sinks from 10° above Edinburgh’s south-western horizon at sunset on the 1st to set itself 100 minutes later. A full arcminute in diameter but only 4% illuminated, its slender crescent is obvious through binoculars. Weather and horizon permitting, the view may be more stunning on the 2nd when Venus lies 2.7° below-right of the narrow arc of the 2% illuminated Moon.
Venus soon disappears from our evening sky as it sweeps through inferior conjunction on the Sun’s near side on the 11th. Within another four or five days, though, Venus reappears as a morning star in the south-east and by the 31st it rises two hours before the Sun, shines at magnitude -4.6 and is a 12% sunlit crescent 52 arcseconds across.
Mercury emerges as an evening star later in the month as it moves to lie 18° east of the Sun on the 31st. Between the 19th and 31st, its altitude in the south-west forty minutes after sunset doubles from 4° to 8° as it dims only slightly from magnitude -0.9 to -0.5. Use binoculars to spy it in the twilight if you have a favourable horizon.
Mars rises in the east in the middle of the night and is tracking eastwards against the stars of Virgo to pass 5° north of Spica on the 28th. Its pink-red glow brightens from magnitude 0.8 to 0.3 and its disk swells to 9 arcseconds by the month’s end, large enough for some surface detail to be visible telescopically. It is best to observe it when it is highest as it crosses the meridian at an latitude of almost 30° shortly before dawn. The Moon lies alongside Spica and below Mars on the 23rd.
Saturn, another morning object, is creeping eastwards in Libra, about 6° to the east (left) of the wide double star Zubenelgenubi. It rises in the east-south-east at about 04:20 on the 1st, two hours earlier by the 31st, and at mag 0.6 to 0.5 is the brightest object low down in the south before dawn. When it lies alongside the Moon on the 25th, its disk appears 16 arcseconds wide while its glorious rings are 37 arcseconds across and have their north face tipped 22° towards us.
This is a slightly-revised version of Alan’s article published in The Scotsman on January 1st 2014, with thanks to the newspaper for permission to republish here.
Comet ISON – probably not the Comet Of The Century
Comet ISON swept through its perihelion within 1,165,000 km of the Sun’s surface at about 18:38 GMT on 28 November, but did it even make it that far in one piece? There have been signs that its brightening was halting again and perhaps that its icy nucleus might be breaking up even before it encountered the extreme heat and tidal forces of perihelion. In my view, sensationalist claims that ISON would be the Comet Of The Century, visible in broad daylight and an unmistakable spectacle in our night sky, are about to be proved wrong. While I am duty-bound to speculate on its appearance as it emerges from the Sun’s glare, no-one knows exactly what if anything we will see.
After a disappointing few months, a sudden surge in ISON’s activity and brightness began on 13 November. I glimpsed it through binoculars three days later and it continued to brighten as it dived lower in our south-eastern pre-dawn sky, first passing the star Spica in Virgo and then Mercury, by which time it was near the fourth magnitude and disappearing into the twilight. Since then we have relied mainly on observations from spacecraft. Claims that it may have stopped brightening as the production of gas and dust from its nucleus fell dramatically, and even that the nucleus was already disintegrating, painted a pessimistic picture. However, the mood changed when ISON appeared to be remarkably healthy and intact in the final hours before perihelion.
Even if the nucleus does shatter, it may not spell the end of ISON as an interesting object. Its gas and dust has to go somewhere, and that may lead to the comet’s tail remaining visible, and possibly brightly so. Don’t miss any opportunity to look for it stretching almost vertically above our east-south-eastern horizon before dawn over the coming few days, perhaps beginning as early as 1 December. It may also be glimpsed reaching up and to the right from our western horizon after sunset.
The comet’s head and nucleus, assuming it survives, tracks almost due northwards in the sky, climbing steeply in the east before dawn and heading to a position halfway between the bright stars Vega and Arcturus on the 21st. Our “Looking North” chart picks up ISON at this point and depicts its progress onwards and upwards into Draco by the year’s end. It is closest to the Earth, 64 million km, on the 26th but will it still be visible at Christmas?
Even if ISON fails miserably, our December nights are a treat to behold. They begin with Venus blazing low down between the south and south-west as it sinks from about 10° high at sunset. The planet is at its brilliant best, magnitude -4.7, as it stands 7° below-left of the young Moon on the 5th and 12° below-right of the Moon on the 6th. By Hogmanay it sets 105 minutes after the Sun as seen from Edinburgh and is 59 arcseconds in diameter, near enough (42 million km) and large enough for its slender 4% illuminated crescent to be recognised easily through binoculars, and perhaps by the keenest naked eyes.
Our second prominent planet, Jupiter, rises at Edinburgh’s north-eastern horizon at 18:21 GMT on the 1st and only 16 minutes after sunset by the 31st. Conspicuous in the east at our map times, it passes high in the south six hours later and is sinking in the west before dawn. Jupiter lies some 9° below and right of Castor and Pollux in Gemini and is slowly retrograding (tracking westwards) to pass only 0.25° north of the third magnitude star Wasat or Delta Geminorum on the 10th. Telescopically, the Jovian globe swells from 45 to 47 arcseconds as the planet approaches opposition in early January.
Orion, stands to the south of east at our map times, and is impressive as it climbs to cross the meridian during the midnight hours. A line upwards along Orion’s Belt extends to Aldebaran and the Pleiades in Taurus. Look for the Moon close to Aldebaran on the night of the 15th and near Jupiter on the 18th.
Mars rises in the east at 01:00 on the 1st and 30 minutes earlier on the 31st. Tracking eastwards against the stars of Virgo, it improves from magnitude 1.2 to 0.8 this month as its disk swells from 5.6 to 6.8 arcseconds in diameter – still too small for surface detail to be seen easily through a telescope. Look for Mars above the Moon on Boxing Day morning. Our second morning planet, Saturn, lies in Libra and rises in the east-south-east at about 06:00 at present. By year’s end, though, it rises at 04:20 and shines at magnitude 0.6, making it the brightest object low in the south-east to south before dawn. Catch it above-right of the waning Moon on the 29th.
Only a few days before the end of its best apparition of 2013, Mercury shines brightly at magnitude -0.7 and stands almost 5° high in the south-east forty minutes before sunrise tomorrow.
The annual Geminids meteor shower is active from the 8th to the 17th and is expected to peak in the predawn hours on the 14th. The bright moonlight for most of the night may still allow several slow bright Geminids meteors to be seen as they stream away from a radiant point close to Castor, roughly where the M of GEMINI lies on our north star map.
The Sun reaches its most southerly point in our sky at 17:11 GMT on the 31st, marking the winter solstice. Sunrise/sunset times for Edinburgh vary from 08:19/15:44 on the 1st to 08:42/15:40 on the 21st and 08:44/15:48 on the 31st. Nautical twilight persists for about 95 minutes at dawn and dusk. The Moon is new on the 3rd, at first quarter on the 9th, full on the 17th and last quarter on the 25th.
This is a slightly-revised version of Alan’s article published in The Scotsman on November 29th 2013, with thanks to the newspaper for permission to republish here.
Comet ISON sweeps close to the Sun on the 28th
A brace of comets and the year’s best apparition by Mercury might be enough to tempt us outside during the chill predawn hours this month.
Let us start with the evening, though, where Venus remains poorly placed for our northern latitudes. Although it blazes brilliantly at magnitude -4.4, it stands less than 6° above Edinburgh’s south-south-western horizon at sunset on the 1st and sinks to set in the south-west only 91 minutes later. It is also at its greatest angle of 47° to the east of the Sun. On the 6th, it is 8° below and left of the young Moon and at a more southerly declination (celestial latitude) than at any time since 1930. Turning northwards again, it is 9° high in the south at sunset on the 30th, when it remains visible for 157 minutes and is brighter still at magnitude -4.6.
Our charts show the stars of the Summer Triangle, Vega, Altair and Deneb, tumbling into the west as the Square of Pegasus crosses the meridian. To the south of Pegasus are Pisces and Aquarius where the two most distant planets, Uranus and Neptune, shine dimly as binocular objects of magnitude 5.7 and 7.9 respectively.
The winter constellations are beginning to climb in the east, with their centrepiece, Orion, just rising below Taurus and the Pleiades. Jupiter, magnitude -2.4 and brighter than any star, rises 35 minutes before our map times and climbs to pass 56° high in the S before dawn. By the month’s end it has improved to magnitude -2.6 but has hardly shifted in position in Gemini, below and to the right of Castor and Pollux. The Moon is nearby on the night of the 21st/22nd when Jupiter’s cloud-banded disk appears 44 arcseconds wide if viewed telescopically.
Mars rises in the east at 01:17 on the 2nd and shines at magnitude 1.5 well up in the south-east, 10° below and left of Regulus in Leo, before dawn. Speeding eastwards into Virgo, it brightens to magnitude 1.3 by the 30th when it rises only 16 minutes later. Catch it below the Moon on the 27th.
Comet ISON is on track to graze within 1,100,000 km of the Sun’s surface when it reaches perihelion at 18:35 GMT on the 28th. However, whether it will survive the encounter is anyone’s guess. Sadly, hopes that it would blossom into the Comet of the Century have been dimming by the day as its performance has fallen further and further below what most comet experts were predicting after its discovery more than a year ago. Even this summer, the expectations were that it would be an easy binocular object by now and that it would surpass Venus at perihelion. As it is, it has still not been sighted through binoculars and it is even being suggested that it may never be visible to the unaided eye.
Claims earlier in October that the comet was already on the brink of disintegrating were soon countered by Hubble telescope observations showing it still to be intact. Images show a greenish head or coma surrounding ISON’s nucleus, with a tail pointing away from the Sun and narrowing along its length. It is brightening, but only by as much as can be explained by the intensifying sunlight and there are few signs that it is actually growing larger and more active.
Plunging sunwards, Comet ISON crosses the Earth’s orbital distance today and may be a telescopic object near magnitude 8.5 some 8° below-left of Mars in the south-east before dawn on the 2nd. It may be as much as a magnitude brighter and Moon’s breadth right of the star Beta Virginis before dawn on the 7th and perhaps near the sixth magnitude, and visible through binoculars, when it lies 0.7° below-left of Virgo’s brightest star, Spica, on the 18th.
Mercury, meantime, is emerging from the Sun’s glare to become conspicuous low down in the morning twilight in the south-east. Between the 10th and 29th, it rises more than 100 minutes before the Sun, climbs to stand between 8° and 11° high 30 minutes before sunrise, and brightens from magnitude 0.6 to -0.7. It is joined before dawn by Saturn (magnitude 0.6) which stands just 0.5° above Mercury on the 26th.
We can use Mercury to locate ISON later in the period. The comet may yet become a naked-eye object with its tail slanting back towards Spica as it sinks from 7° to the right of Mercury on the 21st to lie 5° below-right of Mercury three days later. That may be our final view of it until after perihelion. Comet Encke, a much more predictable and reliable binocular fuzz-ball at about the fifth magnitude, sinks from 6° above-right of Mercury on the 13th to pass 1.5° right of Mercury on the 18th before we lose it in the twilight.
With Comet ISON no longer expected to excel at perihelion, and because of the serious danger to our eyesight, do not attempt to observe it close to the Sun. If its tail does unfurl spectacularly, though, it may climb steeply from our south-eastern horizon before dawn on the 29th and 30th.
As the Sun tracks southwards, sunrise/sunset times for Edinburgh change from 07:20/16:32 on the 1st to 08:18/15:45 on the 30th. New moon on the 3rd is followed by first quarter on the 10th, full on the 17th and last quarter on the 25th. The new moon brings a solar eclipse on the 3rd which begins as an annular or ring eclipse over the western Atlantic but soon evolves to a total eclipse whose narrow path tracks eastwards to cross equatorial Africa from Gabon to Somalia. Surrounding areas, but not Britain, see a partial eclipse.
This is a slightly-revised version of Alan’s article published in The Scotsman on November 1st 2013, with thanks to the newspaper for permission to republish here.
Mars meets Regulus as Jupiter dominates before dawn
Our main interests this month lie in our predawn sky where Jupiter shines brighter than any star and where Mars is in conjunction with the star Regulus in Leo. Sweeping close to Mars is Comet ISON which remains dim at present but may yet brighten to become an impressive sight later in the year.The Summer Triangle of Vega, Altair and Deneb still looms high on the meridian at dusk but has tumbled westwards by our star map times. Trailing behind it is Delphinus where a nova flared in August. That stellar outburst was still just visible through binoculars in late September but was perhaps on the verge of plunging much fainter as is becomes shrouded in dust forming in the wake of the explosion.
Our charts show the Square of Pegasus approaching the meridian as the Plough rotates counterclockwise below Polaris in the north and the “W” of Cassiopeia nears the zenith. Taurus and the Pleiades are climbing in the east while Gemini is rising in the north-east with the Twins, Castor and Pollux, one above the other.
Jupiter stands 8° below and to the right of Pollux and rises less than 30 minutes after our map times, climbing to prominence high in the south-south-east to south before dawn. The planet creeps 2° eastwards during October, passes only 7 arcminutes north of the magnitude 3.5 star Delta Geminorum on the 4th and is above the Moon on the 26th. Jupiter improves from magnitude -2.2 to -2.4 this month and swells from 38 to 41 arcseconds wide if viewed telescopically.
Our other pre-dawn planet, Mars, stands above-left of the Moon on the 1st and again on the 30th. Rising for Edinburgh in the east-north-east at 02:27 BST on the 1st and by 01:18 GMT on the 31st, it is climbing well up into the south-east before dawn. From 9° above-right of Leo’s leading star Regulus as the month begins, it speeds eastwards to pass 1.0° north of Regulus late on the 14th and lie 9° below-left of the star at month’s end. It improves slightly from magnitude 1.6 to 1.5 but remains just fainter than the magnitude 1.4 of Regulus. Note, though, the contrast in appearance with Mars being steady and reddish while Regulus is bluish-white and twinkling. Through a telescope, the planet’s tiny ochre disk is 4 to 5 arcseconds wide.
Comet ISON remains something of an enigma. Discovered just over a year ago when it lay beyond the orbit of Jupiter, it has been diving towards the Sun on a path that carries it 1,100,000 km above the Sun’s surface on 28 November. Some predictions have it as bright as the full moon at that point, albeit swamped in the Sun’s glare. In fact, its brightening has been slower than most were expecting and it was still a dim 12th magnitude object in late September. Hopes remain that it will be a naked-eye object in mid-November and again during December when it may well sport an impressive tail.
Its orbit takes it within 10.5 million km of Mars on the 1st and it is already being observed by spacecraft at the planet. It stands 2.0° above-left of Mars in our morning sky on the 2nd, moving to lie within 0.9° of Mars on the 18th and 6° below-left of the planet by the 31st. We can only hope that it might be visible through binoculars by the month’s end.
An unfortunate fact concerning our autumn sky is that planets that lie to the east of the Sun are hugging our horizon at sunset. Take Venus, for example. As seen from Edinburgh at sunset on the 1st, the brilliant magnitude -4.2 evening star stands 135 million km away and 45° away from the Sun but is only 5° high in the south-west. It sets 53 minutes later and should be obvious as the twilight fades, but only if our horizon is clear. Contrast this with Australia where Venus is a stunning object 43° high in the W at sunset and remains visible for almost four hours.
The reason, of course, is that the planets never stray far from the ecliptic, the Sun’s apparent annual path against the stars. At present the ecliptic slants low across Scotland’s south-western sky at nightfall as it traces the Sun’s southerly motion until midwinter.
By the 31st, Venus stands 5° above Edinburgh’s south-south-western horizon at sunset, shines a little brighter at magnitude -4.4 and is 6° below-right of the Sun’s midwinter position against the stars. As Venus approaches to 101 million km this month, its telescopic diameter swells from 19 to 25 arcseconds while the dazzling sunlit part of its disk changes from 63% to 50%. Look for the planet 4° below the young crescent Moon on the 8th and 1.5° above the red supergiant Antares in Scorpius on the 16th.
We have no chance of seeing Saturn or Mercury which are both fainter and closer to the Sun in the evening sky than Venus.
This month the Sun tracks 11° southwards as sunrise/sunset times for Edinburgh change from 07:16/18:48 BST (06:16/17:48 GMT) on the 1st to 07:18/16:34 GMT on the 31st. Nautical twilight persists for about 82 minutes at dawn and dusk. The Moon is new on the 4th, at first quarter on the 12th, full on the 19th and at last quarter on the 27th.
The southern 76% of the Moon’s disk slips through the fringe of the Earth’s shadow on the night of the 18th/19th to cause a penumbral lunar eclipse. Although only a slight dimming may be noticed, at least the Moon is well placed being in Pisces in the middle of our southern sky. The eclipse lasts from 22:51 to 02:50 BST. | 0.876232 | 3.634903 |
A team of astronomers led by the UNIGE has discovered five new planets with periods of revolution between 15 and 40 years. It took 20 years of regular observations to achieve this result.
Over 4000 exoplanets have been discovered since the first one in 1995, but the vast majority of them orbit their stars with relatively short periods of revolution. Indeed, to confirm the presence of a planet, it is necessary to wait until it has made one or more revolutions around its star. This can take from a few days for the closest to the star to decades for the furthest away: Jupiter for example takes 11 years to go around the Sun. Only a telescope dedicated to the search for exoplanets can carry out such measurements over such long periods of time, which is the case of the EULER telescope of the Geneva University (UNIGE), Switzerland, located at the Silla Observatory in Chile. These planets with long periods of revolution are of particular interest to astronomers because they are part of a poorly known but unavoidable population to explain the formation and evolution of planets. An article published by the journal Astronomy & Astrophysics .
"It took 20 years and many more observers,» comments Emily Rickman, first author of the study and researcher in the Astronomy Department of the UNIGE Faculty of Science. "This result would have been impossible without the availability and reliability of the CORALIE spectrograph installed on the EULER telescope, a unique instrument in the world." Since 1995, when the first exoplanet was discovered, about 4000 planets have been found. The vast majority of them are massive planets close to their stars which are the easiest to detect relying on the current technology. However, planets with long periods of revolution are of great interest to astronomers. Being farther away from their stars, they can be observed using direct imaging techniques. Indeed, to date, almost all planets have been discovered using the two main indirect methods: radial velocities, which measure the gravitational influence of a planet on its star, and transits, which detect the mini eclipse caused by a planet passing in front of its star.
Planets directly observed
The EULER telescope is a telescope that depends only on the UNIGE Astronomy Department and is mainly dedicated to the study of exoplanets. Since its commissioning in 1998 it has been equipped with the CORALIE spectrograph which allows to measure radial velocities with an accuracy of a few meters per second, allowing for the detection of planets which mass is as small as Neptune’s. "As early as 1998, a planetary monitoring programme was set up and carried out scrupulously by the many UNIGE observers who took turn every two weeks in La Silla for 20 years", says Emily Rickman. The result is remarkable: five new planets have been discovered and the orbits of four others known have been precisely defined. All these planets have periods of revolution between 15.6 and 40.4 years, with masses ranging approximately from 3 to 27 times that of Jupiter. This study contributes to increasing the list of 26 planets with a rotation period greater than 15 years, "but above all, it provides us with new targets for direct imaging!", concludes the Geneva researcher.
April 17, 2019 | 0.878996 | 3.932687 |
In a post from 4 years ago I discussed “Dark Matter Powered Stars”.
The context here was neutralino dark matter, which is a possible explanation for very massive stars in the early universe. The idea is that the very first stars could be thousands of solar masses, much greater than is possible with ordinary matter dominated stars. They would be powered by dark matter annihilation in their cores during the early part of their life. They would eventually collapse to black holes and could be candidates to seed supermassive black holes found at the center of many galaxies.
Hubble Space Telescope image of Sirius A and Sirius B (lower left)
NASA, ESA, H. Bond (STScI), and M. Barstow (University of Leicester)
Another dark matter candidate apart from the neutralino is the axion. While the neutralino is expected to have masses in the several to tens of GeV (Giga-electron-Volts), the axion mass is a tiny fraction of an eV, at least a trillion times smaller than the expected neutralino mass. So there would be many more of them, of course, to explain the amount of dark matter we detect gravitationally.
Neither neutralinos nor axions have been discovered to date. The axion does not require supersymmetry beyond the Standard Model of particle physics, so in that sense it is a more conservative proposed candidate.
Currently we detect dark matter only through its gravitational effects – in galaxies, in clusters of galaxies, and at the very large scale by looking at thermal variations in the cosmic microwave background radiation.
In addition there are three main direct methods to try to ‘see’ these elusive particles. One is to directly detect dark matter (e.g. neutralinos) here on Earth when it collides with ordinary matter – or in the case of axions – generates photons in the presence of a magnetic field. Another is to attempt to create it at the Large Hadron Collider, and the third is to look in space for astrophysical signals resulting from dark matter. These could include gamma rays produced in the galactic center when dark matter mutually annihilates.
In a paper recently published in the journal Physical Review Letters and titled “Accretion of dark matter by stars”, Richard Brito, Vitor Cardoso and Hirotada Okawa discuss a different kind of dark star, one whose dark matter component is axions. The paper is available here.
There are two formation scenarios envisaged. The first is that dark matter (axion) stellar cores form and then these accrete additional dark matter and ordinary matter. In the second scenario, a star forms primarily from ordinary matter, but then accretes a significant amount of dark matter.
We are talking about dark matter fractions which may be say 5% or 20% of the total mass of the star.
The authors find that stable configurations seem to be possible and that the axion dark matter may lead to stellar oscillations in the microwave band. So looking for stellar oscillations in the Gigahertz range may be another astrophysical detection method for dark matter. They intend to explore the idea more deeply in future research. | 0.903308 | 4.083943 |
eso1423 — Science Release
ALMA Finds Double Star with Weird and Wild Planet-forming Discs
30 July 2014
Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found wildly misaligned planet-forming gas discs around the two young stars in the binary system HK Tauri. These new ALMA observations provide the clearest picture ever of protoplanetary discs in a double star. The new result also helps to explain why so many exoplanets — unlike the planets in the Solar System — came to have strange, eccentric or inclined orbits. The results will appear in the journal Nature on 31 July 2014.
Unlike our solitary Sun, most stars form in binary pairs — two stars that are in orbit around each other. Binary stars are very common, but they pose a number of questions, including how and where planets form in such complex environments.
“ALMA has now given us the best view yet of a binary star system sporting protoplanetary discs — and we find that the discs are mutually misaligned!” said Eric Jensen, an astronomer at Swarthmore College in Pennsylvania, USA.
The two stars in the HK Tauri system, which is located about 450 light-years from Earth in the constellation of Taurus (The Bull), are less than five million years old and separated by about 58 billion kilometres — this is 13 times the distance of Neptune from the Sun.
The fainter star, HK Tauri B, is surrounded by an edge-on protoplanetary disc that blocks the starlight. Because the glare of the star is suppressed, astronomers can easily get a good view of the disc by observing in visible light, or at near-infrared wavelengths.
The companion star, HK Tauri A, also has a disc, but in this case it does not block out the starlight. As a result the disc cannot be seen in visible light because its faint glow is swamped by the dazzling brightness of the star. But it does shine brightly in millimetre-wavelength light, which ALMA can readily detect.
Using ALMA, the team were not only able to see the disc around HK Tauri A, but they could also measure its rotation for the first time. This clearer picture enabled the astronomers to calculate that the two discs are out of alignment with each other by at least 60 degrees. So rather than being in the same plane as the orbits of the two stars at least one of the discs must be significantly misaligned.
“This clear misalignment has given us a remarkable look at a young binary star system,” said Rachel Akeson of the NASA Exoplanet Science Institute at the California Institute of Technology in the USA. “Although there have been earlier observations indicating that this type of misaligned system existed, the new ALMA observations of HK Tauri show much more clearly what is really going on in one of these systems.”
Stars and planets form out of vast clouds of dust and gas. As material in these clouds contracts under gravity, it begins to rotate until most of the dust and gas falls into a flattened protoplanetary disc swirling around a growing central protostar.
But in a binary system like HK Tauri things are much more complex. When the orbits of the stars and the protoplanetary discs are not roughly in the same plane any planets that may be forming can end up in highly eccentric and tilted orbits .
“Our results show that the necessary conditions exist to modify planetary orbits and that these conditions are present at the time of planet formation, apparently due to the formation process of a binary star system,” noted Jensen. “We can’t rule other theories out, but we can certainly rule in that a second star will do the job.”
Since ALMA can see the otherwise invisible dust and gas of protoplanetary discs, it allowed for never-before-seen views of this young binary system. “Because we’re seeing this in the early stages of formation with the protoplanetary discs still in place, we can see better how things are oriented,” explained Akeson.
Looking forward, the researchers want to determine if this type of system is typical or not. They note that this is a remarkable individual case, but additional surveys are needed to determine if this sort of arrangement is common throughout our home galaxy, the Milky Way.
Jensen concludes: “Although understanding this mechanism is a big step forward, it can’t explain all of the weird orbits of extrasolar planets — there just aren’t enough binary companions for this to be the whole answer. So that’s an interesting puzzle still to solve, too!”
If the two stars and their discs are not all in the same plane, the gravitational pull of one star will perturb the other disc, making it wobble or precess, and vice versa. A planet forming in one of these discs will also be perturbed by the other star, which will tilt and deform its orbit.
The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Southern Observatory (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.
This research was presented in a paper entitled “Misaligned Protoplanetary Disks in a Young Binary Star System”, by Eric Jensen and Rachel Akeson, to appear in the 31 July 2014 issue of the journal Nature.
The team is composed of Eric L. N. Jensen (Dept. of Physics & Astronomy, Swarthmore College, USA) and Rachel Akeson (NASA Exoplanet Science Institute, IPAC/Caltech, Pasadena, USA).
ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.
- Research paper
- NRAO press release about HK Tauri results
- Image of HK Tauri from the NASA/ESA Hubble Space Telescope
- More about ALMA
- Photos of ALMA
- Videos of ALMA
- ALMA brochure
- The movie ALMA — In Search of our Cosmic Origins
- The ALMA Photo Book In Search of our Cosmic Origins – The Construction of the Atacama Large Millimeter/submillimeter Array
- More press releases with ALMA
Eric L. N. Jensen
Lead Scientist, Swarthmore College
Tel: +1 610-328-8249
NASA Exoplanet Science Institute, IPAC/Caltech
Tel: +1 626-395-1812
Charles E. Blue
Public Information Officer, National Radio Astronomy Observatory
Tel: + 1 434 296 0314
Cell: +1 202 236 6324
Public Information Officer, ESO
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591 | 0.874566 | 3.767979 |
Type Ia supernovae, some of the most dazzling phenomena in the universe, are produced when small dense stars called white dwarfs explode with ferocious intensity. At their peak, these supernovae can outshine an entire galaxy. Although thousands of supernovae of this kind were found in the last decades, the process by which a white dwarf becomes one has been unclear.
That began to change on May 3, 2014, when a team of Caltech astronomers working on a robotic observing system known as the intermediate Palomar Transient Factory (iPTF)—a multi-institute collaboration led by Shrinivas Kulkarni, the John D. and Catherine T. MacArthur Professor of Astronomy and Planetary Science and director of the Caltech Optical Observatories—discovered a Type Ia supernova, designated iPTF14atg, in nearby galaxy IC831, located 300 million light-years away.
The data that were immediately collected by the iPTF team lend support to one of two competing theories about the origin of white dwarf supernovae, and also suggest the possibility that there are actually two distinct populations of this type of supernova.
The details are outlined in a paper with Caltech graduate student Yi Cao the lead author, appearing May 21 in the journal Nature.
Type Ia supernovae are known as "standardizable candles" because they allow astronomers to gauge cosmic distances by how dim they appear relative to how bright they actually are. It is like knowing that, from one mile away, a light bulb looks 100 times dimmer than another located only one-tenth of a mile away. This consistency is what made these stellar objects instrumental in measuring the accelerating expansion of the universe in the 1990s, earning three scientists the Nobel Prize in Physics in 2011.
There are two competing origin theories, both starting with the same general scenario: the white dwarf that eventually explodes is one of a pair of stars orbiting around a common center of mass. The interaction between these two stars, the theories say, is responsible for triggering supernova development. What is the nature of that interaction? At this point, the theories diverge.
According to one theory, the so-called double-degenerate model, the companion to the exploding white dwarf is also a white dwarf, and the supernova explosion initiates when the two similar objects merge.
However, in the second theory, called the single-degenerate model, the second star is instead a sunlike star—or even a red giant, a much larger type of star. In this model, the white dwarf's powerful gravity pulls, or accretes, material from the second star. This process, in turn, increases the temperature and pressure in the center of the white dwarf until a runaway nuclear reaction begins, ending in a dramatic explosion.
The difficulty in determining which model is correct stems from the facts that supernova events are very rare—occurring about once every few centuries in our galaxy—and that the stars involved are very dim before the explosions.
That is where the iPTF comes in. From atop Palomar Mountain in Southern California, where it is mounted on the 48-inch Samuel Oschin Telescope, the project's fully automated camera optically surveys roughly 1000 square degrees of sky per night (approximately 1/20th of the visible sky above the horizon), looking for transients—objects, including Type Ia supernovae, whose brightness changes over timescales that range from hours to days.
On May 3, the iPTF took images of IC831 and transmitted the data for analysis to computers at the National Energy Research Scientific Computing Center, where a machine-learning algorithm analyzed the images and prioritized real celestial objects over digital artifacts. Because this first-pass analysis occurred when it was nighttime in the United States but daytime in Europe, the iPTF's European and Israeli collaborators were the first to sift through the prioritized objects, looking for intriguing signals. After they spotted the possible supernova—a signal that had not been visible in the images taken just the night before—the European and Israeli team alerted their U.S. counterparts, including Caltech graduate student and iPTF team member Yi Cao.
Cao and his colleagues then mobilized both ground- and space-based telescopes, including NASA's Swift satellite, which observes ultraviolet (UV) light, to take a closer look at the young supernova.
"My colleagues and I spent many sleepless nights on designing our system to search for luminous ultraviolet emission from baby Type Ia supernovae," says Cao. "As you can imagine, I was fired up when I first saw a bright spot at the location of this supernova in the ultraviolet image. I knew this was likely what we had been hoping for."
UV radiation has higher energy than visible light, so it is particularly suited to observing very hot objects like supernovae (although such observations are possible only from space, because Earth's atmosphere and ozone later absorbs almost all of this incoming UV). Swift measured a pulse of UV radiation that declined initially but then rose as the supernova brightened. Because such a pulse is short-lived, it can be missed by surveys that scan the sky less frequently than does the iPTF.
This observed ultraviolet pulse is consistent with a formation scenario in which the material ejected from a supernova explosion slams into a companion star, generating a shock wave that ignites the surrounding material. In other words, the data are in agreement with the single-degenerate model.
Back in 2010, Daniel Kasen, an associate professor of astronomy and physics at UC Berkeley and Lawrence Berkeley National Laboratory, used theoretical calculations and supercomputer simulations to predict just such a pulse from supernova-companion collisions. "After I made that prediction, a lot of people tried to look for that signature," Kasen says. "This is the first time that anyone has seen it. It opens up an entirely new way to study the origins of exploding stars."
According to Kulkarni, the discovery "provides direct evidence for the existence of a companion star in a Type Ia supernova, and demonstrates that at least some Type Ia supernovae originate from the single-degenerate channel."
Although the data from supernova iPTF14atg support it being made by a single-degenerate system, other Type Ia supernovae may result from double-degenerate systems. In fact, observations in 2011 of SN2011fe, another Type Ia supernova discovered in the nearby galaxy Messier 101 by PTF (the precursor to the iPTF), appeared to rule out the single-degenerate model for that particular supernova. And that means that both theories actually may be valid, says Caltech professor of theoretical astrophysics Sterl Phinney, who was not involved in the research. "The news is that it seems that both sets of theoretical models are right, and there are two very different kinds of Type Ia supernovae."
"Both rapid discovery of supernovae in their infancy by iPTF, and rapid follow-up by the Swift satellite, were essential to unveil the companion to this exploding white dwarf. Now we have to do this again and again to determine the fractions of Type Ia supernovae akin to different origin theories," says iPTF team member Mansi Kasliwal, who will join the Caltech astronomy faculty as an assistant professor in September 2015.
The iPTF project is a scientific collaboration between Caltech; Los Alamos National Laboratory; the University of Wisconsin–Milwaukee; the Oskar Klein Centre in Sweden; the Weizmann Institute of Science in Israel; the TANGO Program of the University System of Taiwan; and the Kavli Institute for the Physics and Mathematics of the Universe in Japan. The Caltech team is funded in part by the National Science Foundation. | 0.869626 | 4.106576 |
While performing an extensive X-ray survey of our galaxy's central regions, NASA's Swift satellite has uncovered the previously unknown remains of a shattered star. Designated G306.3-0.9 after the coordinates of its sky position, the new object ranks among the youngest-known supernova remnants in our Milky Way galaxy.
Astronomers have previously cataloged more than 300 supernova remnants in the Galaxy. The new analysis indicates that G306.3-0.9 is likely less than 2,500 years old, making it one of the 20 youngest remnants identified.
This composite of supernova remnant G306.3-0.9 merges Chandra X-ray observations (blue), infrared data acquired by the Spitzer Space Telescope (red and cyan) and radio observations (purple) from the Australia Telescope Compact Array. The image is 20 arcminutes across, which corresponds to 150 light-years at the remnant's estimated distance.
Astronomers estimate that a supernova explosion occurs once or twice a century in the Milky Way. The expanding blast wave and hot stellar debris slowly dissipate over hundreds of thousands of years, eventually mixing with and becoming indistinguishable from interstellar gas.
Like fresh evidence at a crime scene, young supernova remnants give astronomers the best opportunity for understanding the nature of the original star and the details of its demise.
Supernova remnants emit energy across the electromagnetic spectrum, from radio to gamma rays, and important clues can be found in each energy band. X-ray observations figure prominently in revealing the motion of the expanding debris, its chemical content, and its interaction with the interstellar environment, but supernova remnants fade out in X-ray light after about 10,000 years. Indeed, only half of those known in the Milky Way galaxy have been detected in X-rays at all.
The Swift Galactic Plane Survey is a project to image a two-degree-wide strip along the Milky Way's central plane at X-ray and ultraviolet energies at the same time. Imaging began in 2011 and is expected to complete this summer.
The Swift survey leverages infrared imaging previously compiled by NASA's Spitzer Space Telescope and extends it into higher energies. The infrared and X-ray surveys complement each other because light at these energies penetrates dust clouds in the galactic plane, while the ultraviolet survey of the region is the first one ever done.
On Feb. 22, 2011, Swift imaged a survey field near the southern border of the constellation Centaurus. Although nothing unusual appeared in the ultraviolet exposure, the X-ray image revealed an extended, semi-circular source reminiscent of a supernova remnant. A search of archival data revealed counterparts in Spitzer infrared imagery and in radio data from the Molonglo Observatory Synthesis Telescope in Australia.
To further investigate the object, the team followed up with an 83-minute exposure using NASA's Chandra X-ray Observatory and additional radio observations from the Australia Telescope Compact Array.
Using an estimated distance of 26,000 light-years for G306.3-0.9, the scientists determined that the explosion's shock wave is racing through space at about 1.5 million mph (2.4 million km/h). The Chandra observations reveal the presence of iron, neon, silicon and sulfur at temperatures exceeding 50 million degrees F (28 million C), a reminder not only of the energies involved but of the role supernovas play in seeding the galaxy with heavy elements produced in the hearts of massive stars.
A paper describing the team's findings will appear in an upcoming edition of The Astrophysical Journal and was published online on Friday. | 0.89912 | 4.031827 |
A supernovaspotted earlier this year may actually represent a cosmic event closer toenergetic gamma ray bursts, rather than classic stellar explosions.
Europeanresearchers now suggest that the supernova known as SN 2008D resulted from amassive star collapsing into a black hole. That event produced a five-minutelong burst of X-rays, which NASA?s Swift telescope detected on January 9, 2008.
"Ourobservations and modeling show this to be a rather unusual event, to be betterunderstood in terms of an object lying at the boundary between normalsupernovae and gamma-ray bursts," said Paolo Mazzali, an Italianastrophysicist at the Padova Observatory and Max-Planck Institute forAstrophysics.
Stars thatwere about eight times more massive at birth than our sun end their relativelyshort life in a cataclysmic explosion and collapse into either neutron stars orblack holes. The massive exploding stars emit a shortcry of agony in the form of light, X- or gamma-rays, with gamma-rays beingthe most energetic.
Mazzali?steam found that the early behavior of the supernova indicated that it was ahighly energetic event for a supernova, although not quite as powerful as agamma-ray burst. Theoretical models show that the original star was at birth asmassive as 30 times the Sun, but had lost so much mass that at the time of theexplosion the star had a mass of only 8 to10 solar masses. The likely result ofthe collapse of such a massive star is a blackhole.
The originalstar also shed much of its hydrogen and helium-rich outer layers beforeexploding, characteristics normally associated with gamma-ray bursts. However,Mazzali?s team saw a helium signature still lingering in the explosion?saftermath, which suggests that the star did not quite reach the level of agamma-ray burst.
Thispresents an alternative explanation to one detailed earlier in the journal Natureby another group of astronomers. That team suggested that X-rays were detectedonly because stargazers caught the star in the act ofexploding, and that the event was a more typical supernova.
- Video: X-Ray-Emitting Black Holes
- Top 10 Star Mysteries
- The Strangest Things in Space | 0.851392 | 3.996847 |
For decades, NASA has released enormous scientific balloons into Earth’s atmosphere, miles above the altitude of commercial flights. The Balloon Program is currently preparing new missions bearing sensitive instruments, including one designed to investigate the birth of our universe and another with ballooning origins that will fly on the International Space Station.
NASA’s Primordial Inflation Polarization Explorer (PIPER), which will launch a series of test flights over the next few years, could confirm the theory that our nascent universe expanded by a trillion trillion (1024) times immediately following the big bang. This rapid inflation would have shaken the fabric of space-time, generating ripples called gravitational waves. These waves, in turn, should have produced detectable distortions in the cosmic microwave background (CMB), the earliest light in the universe lengthened into microwaves today by cosmic expansion. The patterns will appear in measurements of how the CMB light is organized, a property called polarization. Discovering twisting, pinwheel-like polarization patterns in the CMB will prove inflation occurred and take astrophysicists back to the brink of the big bang.
While Albert Einstein’s theories accurately describe gravity in today’s dilated cosmos, these large-scale physical laws did not apply when our universe was still the size of a hydrogen atom. To reconcile this disparity, PIPER will map the entire sky at four different frequencies, differentiating between twisting patterns in the CMB (indicating primordial gravitational waves) and different polarization signals due to interstellar dust. To maintain sensitivity, the telescope will fly immersed in a bucket of liquid helium the size of a hot tub but much cooler — nearly 457 degrees below zero Fahrenheit (minus 272 degrees Celsius) and close to absolute zero, the coldest temperature possible.
The PIPER mission was designed, built and tested at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, in collaboration with Johns Hopkins University in Baltimore, the University of British Columbia, Canada, the National Institute of Standards and Technology at Boulder, Colorado, and Cardiff University in Wales.
“We’re hoping to gain insight into our early universe as it expanded from subatomic size to larger than a planet in less than a second,” said Goddard's Al Kogut, PIPER's principal investigator. “Understanding inflation also augments our knowledge of high-energy particle physics, where the forces of nature act indistinguishably from one another.”
While PIPER prepares to observe roughly 20 miles above Earth, the latest iteration of the Cosmic Ray Energetics and Mass (CREAM) experiment is scheduled to launch to the International Space Station in August. Although CREAM was balloon-borne during its seven prior missions, the new payload will take the technology past Earth’s atmosphere and into space. Called ISS-CREAM, the experiment will directly sample fast-moving matter from outside the solar system, called cosmic rays, from its new vantage point on the Japanese Experiment Module Exposed Facility.
Cosmic rays are high-energy particles traveling at near the speed of light that constantly shower Earth. But precisely how they originate and accelerate through space requires more study, as does their abrupt decline at energies higher than 1,000 trillion electron volts. These particles have been boosted to more than 100 times the energy achievable by the world's most powerful particle accelerator, the Large Hadron Collider at CERN.
ISS-CREAM — about the size of a refrigerator — will carry refurbished versions of the silicon charge detectors and ionization calorimeter from the previous balloon missions over Antarctica. ISS-CREAM will contain two new instruments: the top/bottom counting detectors, contributed by Kyungpook National University in Daegu, South Korea, and a boronated scintillator detector to distinguish electrons from protons, constructed by a team from Goddard, Pennsylvania State University in University Park and Northern Kentucky University in Highland Heights.
The international collaboration, led by physicist Eun-Suk Seo at the University of Maryland, College Park, includes teams from numerous institutions in the United States as well as collaborating institutions in the Republic of Korea, Mexico and France. Overall management and integration of the experiment was led by NASA’s Wallops Flight Facility on Virginia’s Eastern Shore under the direction of Linda Thompson, the CREAM project manager.
According to co-investigator Jason Link, a University of Maryland, Baltimore County research scientist working at Goddard, the evolution of the CREAM project demonstrates the power of NASA’s Balloon Program as a developmental test bed for space instrumentation.
“A balloon mission can go from an idea in a scientist’s head to a flying payload in about five years,” Link said. “In fact, many scientists who design experiments for space missions get their start in ballooning. It’s a powerful training ground for researchers and engineers.”
As is true with any complex mission, things don’t always go as planned. Such was the case for the Balloon Experimental Twin Telescope for Infrared Interferometer (BETTII) experiment, intended to investigate cold objects emitting light in the far-infrared region of the electromagnetic spectrum.
BETTII launched on June 8 from NASA’s Columbia Scientific Balloon Facility in Palestine, Texas. Although nearly all the mission components functioned as they should, the payload detached from its parachute and fell 130,000 feet in 12 minutes as the flight ended the following day.
BETTII Principal Investigator Stephen Rinehart at Goddard estimates it will take several years to secure funding and rebuild the mission.
Designed, assembled and tested at Goddard in collaboration with the University of Maryland, Johns Hopkins University, Cardiff University, University College London and the Far-Infrared Interferometric Telescope Experiment team in Japan, BETTII is designed to examine lower infrared frequencies with unprecedented resolution. While optical telescopes like Hubble cannot see stars shrouded by thick dust clouds, far-infrared observations pierce the veil, revealing how these objects form and evolve.
“BETTII is one of the more complex balloon experiments ever flown,” Rinehart said. “As a research community, we understand that this risk is necessary for the scientific and technical progress we make with balloons.”
After all, just as risk and failure go hand in hand, so do risk and reward.
For more information about NASA’s Balloon Program, visit:
Banner image: This illustration shows the Balloon Experimental Twin Telescope for Infrared Interferometer (BETTII) ascending into the upper atmosphere. The experiment was severely damaged on June 9, when the payload detached from its parachute and fell. Credit: NASA's Goddard Space Flight Center Conceptual Image Lab/Michael Lentz | 0.883198 | 4.096415 |
Gaia launches on cosmic census mission
A cosmic census got under way this morning as ESA’s Gaia mission lifted off atop a Soyuz–Fregat from the European Spaceport in Kourou, French Guiana at 9:12:19 AM GMT (10:12:19 AM CET). The 2,030 kg (4,475 lb) unmanned probe is at the start of a five-year mission to carry out a survey of one percent of one percent of the 100 billion stars that make up our galaxy as part of a project to produce the most detailed three-dimensional galactic map ever attempted.
According to ESA, the liftoff went as scheduled and without a hitch. As the rocket rose, it carried out a series of automated sequences. About 118 seconds into the flight, the four side boosters on the Soyuz fell away, and at 220 seconds the protective fairing around the Gaia spacecraft was jettisoned. At 42 minutes, Gaia separated from the Fregat third stage and after entering orbit at 88 minutes, the spacecraft began deploying its 10.5 m- (34.4 ft-) wide parasol-like sunshield.
Gaia is now in the early orbit phase of its mission as it heads into a Lissajous-type orbit around Lagrange 2 point, where the gravitational fields of the Sun and the Earth balance out, allowing the probe to maintain a stable position trailing the Earth at a distance of 1.5 million km (930,000 miles). It will carry out a six-month commissioning phase, after which it will use its instruments to chart the positions and velocities of billions of stars, as well as their brightness, temperature, and composition.
In addition, ESA expects it to discover hundreds of thousands of asteroids and comets in the Solar System, extrasolar planets, tens of thousands of brown dwarfs, up to twenty thousand supernovae, and hundreds of thousands of quasars. It carries the largest digital camera ever to have been sent into space, with a resolution of one billion pixels, and can make 40 million observations in a single day of objects one million times fainter than can be seen with the naked eye. ESA estimates that by the end of the mission it will collect one petabyte of data – the equivalent of 200,000 DVDs.
Gaia was originally scheduled to launch on November 20, but a malfunction in its X-band transponders caused a delay. | 0.916318 | 3.136403 |
In 2005, NASA’s Cassini spacecraft gave us an incredible view of Enceladus chuffing out fountains of water vapor and ice. This action creates an enormous halo of gas, dust and ice that surrounds this Saturnian satellite and enables the planet’s E ring. Now Enceladus is once again in the spotlight as the only moon in the Solar System known to significantly contribute to its parent planet’s chemistry.
Earlier this year, ESA announced that its Herschel Space Observatory had observed a huge torus of water vapor around Saturn which apparently originated from Enceladus. It spans approximately 600,000 kilometers across and runs about 60,000 kilometers deep, but more so than its size is what it appears to be doing… adding water to Saturn’s upper atmosphere. Because the vapor isn’t detectable at visible wavelengths, this observation came as revelation for the Herschel scope.
“Herschel is providing dramatic new information about everything from planets in our own solar system to galaxies billions of light-years away,” said Paul Goldsmith, the NASA Herschel project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, California.
While the Herschel infrared observation is new, the indication of a vapor torus around Saturn isn’t. NASA’s Voyager and Hubble missions had given astronomers clues in the past. In 1997, the European Space Agency’s Infrared Space Observatory cited water in Saturn’s atmosphere and two years later NASA’s Submillimeter Wave Astronomy Satellite confirmed it again. But this confirmation only added up to a puzzle. Water found in Saturn’s lower cloud levels couldn’t rise past the colder, upper deck… So where was the water coming from? The answer came in the form of Herschel’s observations and some very astute computer modeling.
“What’s amazing is that the model, which is one iteration in a long line of cloud models, was built without knowledge of the observation.” says Tim Cassidy, a recent post-doctoral researcher at JPL who is now at the University of Colorado’s Laboratory for Atmospheric and Space Physics, Boulder. “Those of us in this small modeling community were using data from Cassini, Voyager and the Hubble telescope, along with established physics. We weren’t expecting such detailed ‘images’ of the torus, and the match between model and data was a wonderful surprise.”
Through these simulations, researchers hypothesized that much of the water in the torus was simply lost to space and some is pulled back by gravity to add material to Saturn’s rings. However, it’s the 3-5% that made it back to Saturn’s atmosphere that’s the most interesting. Just how much water vapor is out there? Thanks to combining information from both Herschel and the Ultraviolet Imaging Spectrograph (UVIS) instrument aboard the Cassini spacecraft, we’ve learned that about 12,000 kilograms is being ejected from Enceladus every minute. Can you image how much that would add up to in the period of a year… or more?!
“With the Herschel measurements of the torus from 2009 and 2010 and our cloud model, we were able to calculate a source rate for water vapor coming from Enceladus,” said Cassidy. “It agrees very closely with the UVIS finding, which used a completely different method.”
“We can see the water leaving Enceladus and we can detect the end product — atomic oxygen — in the Saturn system,” said Cassini UVIS science team member Candy Hansen, of the Planetary Science Institute, Tucson, Ariz. “It’s very nice with Herschel to track where it goes in the meantime.”
A tiny percentage adds up to some mighty big numbers, and the water molecules from the torus impact Saturn’s atmosphere to a great degree by contributing hydrogen and oxygen.
“When water hangs out in the torus, it is subject to the processes that dissociate water molecules,” said Hansen, “first to hydrogen and hydroxide, and then the hydroxide dissociates into hydrogen and atomic oxygen.” This oxygen is dispersed through the Saturn system. “Cassini discovered atomic oxygen on its approach to Saturn, before it went into orbit insertion. At the time, no one knew where it was coming from. Now we do.”
Very few days go by that we don’t learn something new about the Solar System and its inner workings. Thanks to observations like those done by the Herschel Space Observatory and missions like Cassini-Huygens, we’re able to further understand the dynamics behind the beauty… and how a tiny player can carry a major role.
“The profound effect this little moon Enceladus has on Saturn and its environment is astonishing,” said Hansen.
Original Story Source: JPL News Release. | 0.881552 | 3.944548 |
Some of the “mistakes” that have led to our current understanding of science
- That scientific endeavours often fail, and that’s OK
- Some of the biggest scientific failures in history
- That null results are important on the road to discovery
1. When the world conspires against you — Guillaume Le Gentil and the curse of Venus
Often, our endeavours rely on factors outside our control and, while some challenges can be overcome, sometimes you can be downright unlucky. That is how you might describe Guillaume Le Gentil, who set out in the eighteenth century to measure the transit of Venus in order to calculate the size of the Solar System. The phenomenon occurs in pairs — with Venus transiting twice in the astronomically short timeframe of eight years. As adjacent pairs happen less frequently than once every hundred years; this was Le Gentil’s only chance. He travelled to the other side of the world, where the transits would be visible, but an extraordinary series of misfortunes befell him; between wars and the weather, he was unable to measure the first transit, and unable to view the second one at all. After a difficult journey home, Le Gentil discovered that everyone back in France had assumed him dead, his belongings had been taken by relatives and his wife had remarried. Le Gentil became well-known for his memoirs and his other scientific studies, but this was probably little consolation as he watched his competitor Captain Cook revel in success.
2. When teamwork lets you down — John Couch Adams and the elusive eighth planet
In the early nineteenth century, Uranus was behaving strangely. The planet had been discovered forty years earlier, but its movements weren’t following the expected path, leading to speculation about an unseen planet beyond it, interfering with its orbit. The young astronomer John Couch Adams set out to discover this new eighth planet. He spent years making calculations of its location, some of them correct. But the observers just couldn’t find this planet, even though they saw it, and mistook it for a star! What we now know as Neptune was discovered soon afterwards by another team of astronomers. Disheartening as this must have been, Adams moved on, applying himself to other questions and making great discoveries, most notably that the spectacular Leonid meteor showers originate from the debris of comet Tempel-Tuttle.
3. When you’re right for the wrong reasons — Albert Einstein and the cosmological constant
Einstein’s name may be synonymous with genius, but even the great logician was not immune to error. When his equations of general relativity suggested the size of the Universe was changing, he added in a term, the cosmological constant, to make the equations compatible with the Universe being static, a widely-held assumption at the time. After Hubble discovered that the Universe was actually expanding, Einstein scrapped the constant, whose introduction became known as his biggest blunder. But it turned out that scrapping it was the real mistake. Decades later it transpired that, not only is the Universe expanding, but the expansion is accelerating. Describing this using the equations of general relativity again required the cosmological constant. So when Einstein made his great mistake, he unwittingly fixed his equations to fit a characteristic of the Universe that he would never know.
4. When you bury your head in the sand — Fred Hoyle and the big bang
One astrophysicist famously opposed the idea that the Universe had a beginning, and his reaction has become embedded in our language. Fred Hoyle was one of the authors of the steady state model, which says that the Universe is pretty much the same as it always has been. When the Universe was found to be expanding, physicists extrapolated backwards to conclude that it started as something much smaller and denser, threatening Hoyle’s steady state model. Devoted to his theory, Hoyle described the new proposal as a "Big Bang". As evidence mounted for the Universe’s beginning, Hoyle refused to accept it, instead contriving ways in which a steady state Universe could explain new observations. Despite his vehement opposition, he left the biggest imprint on the public perception of the idea — the "Big Bang" is quite a catchy name after all!
But failures still occur today in our quest to find out more about the Universe…
5. When there is much more at stake — NASA and the Apollo disasters
NASA’s famous Apollo missions led to what is arguably humanity’s most remarkable achievement: setting foot on the Moon. In attempting something that has never been done before, especially something so ambitious, mistakes are inevitable. However, as disheartening as failure normally is, it becomes infinitely more serious when people’s lives are in jeopardy. Tragically, failures in the Apollo 1 mission led to the fatalities of three crew members. In subsequent launches, it was absolutely vital to learn from those mistakes. Most of the later missions were successful, but spaceflight remained high-risk, as demonstrated by the Apollo 13 mission, when an oxygen tank exploded in space. After an unimaginably nail-biting period of trying to set the craft on a safe path to Earth, the crew made it back alive, partly thanks to safeguards built in after Apollo 1. While most missions have been successful, there have been spaceflight fatalities since, highlighting the paramount importance of vigilance when people’s lives depend on it, no matter how many successful missions have gone before.
6. When the devil is in the detail —NASA and the imperial disaster
Fortunately, the Mars Climate Orbiter was an unmanned spacecraft, allowing some humour to be found in the circumstances of its failure. Built by NASA to study the Martian atmosphere, it burned up and disintegrated after making it almost all the way to the red planet. The problem was in the communication of two pieces of code in the programming. One calculated the force, in imperial pounds, that the thrusters needed to exert, and another read these calculations — in metric Newtons! The spacecraft followed the wrong path at the wrong speed, and burned up in Mars’ atmosphere instead of going into orbit around the red planet. A unit conversion might have been the easiest part of programming the spacecraft, but its simplicity clearly didn’t negate its importance!
7. All’s well that ends well — Short-sighted Hubble
When the Hubble Space Telescope sent its first images home, they were blurry, not discerning in detail the celestial objects that it had been sent up to see. The problem was identified as an error in the primary mirror; a tiny error of just two microns in an instrument used in the mirror’s production had made the mirror too flat, rendering its images useless. Since bringing Hubble back was not an option, NASA and ESA decided to build an additional set of mirrors that could correct Hubble’s vision. The ‘spectacles’ were installed by astronauts on a special mission, and they worked, allowing Hubble to begin its distinguished career sending back sharp views of the distant Universe. This story tells us that failure doesn’t always mean the end. Often, with determination and creativity, mistakes are fixable.
What we can be sure of is that mistakes are absolutely essential to progress; an adage often attributed to Einstein states “a person who never made a mistake never tried anything new”, and science is all about trying new things and pushing boundaries. The scientific method by which our knowledge progresses is built on taking what we think we know and testing it to its limits, seeing if it holds up, and being ready to change our ideas if it turns out to be wrong. So, filling in the backdrop of all the attention-worthy illustrious scientific achievements, it is really the failures that make this millennia-long endeavour to understand the thing that we call science.
Biography Laura Hiscott
As a science communication intern, Laura assists ESO’s public outreach department with its communication of astronomy and all things ESO. Laura discovered at school that she very much enjoyed finding out how things work, which led her to study for a degree in Physics. During her time at university however, she found that what she enjoyed even more than getting to grips with a new concept, was then going and telling someone else about it. She explored this interest while writing about scientific phenomena and the relationship of science with society for her student science magazine, Broadsheet.
Biography Nicole Shearer
Among other roles, Nicole Shearer works as a Public Information Officer assistant at the European Southern Observatory. She studied Physics and Astronomy at Durham University, specialising in the public communication of astronomy. For ESO she develops various public engagement products, and helped with the preparation and testing of the education programme for the ESO Supernova Planetarium & Visitor Centre. Previously she worked in the Education department of the European Space Agency. | 0.893318 | 3.384226 |
Detecting and analyzing the information carried by gravitational waves is now allowing us to observe the Universe in a way never before possible. It has opened up a new window of study and has already given us a deeper understanding of cataclysmic events and ushered in exciting new research in physics, astronomy, and astrophysics. Historically, scientists have relied almost exclusively on electromagnetic EM radiation visible light, X-rays, radio waves, microwaves, etc.
Each of these sources of information provides scientists with a different but complementary view of the Universe. Gravitational waves, however, are completely unrelated to EM radiation. They are as distinct from EM radiation as hearing is to vision. Thus, they are unique messengers of information about cosmic events. Having this new 'sense' with which to observe the Universe is important because things like colliding black holes are utterly invisible to EM astronomers. To LIGO, however, such events are beacons in the vast cosmic sea. But that number will grow as. Ground telescopes like the Subaru are much more powerful light-gatherers than space telescopes like the Hubble , chiefly because nobody has yet figured out how to squeeze a foot mirror into a rocket and blast it into space.
But ground telescopes have a serious drawback: They sit under miles of our atmosphere. This is accomplished by directing the light from a star onto a shape-shifting mirror, smaller than a quarter, activated by 2, tiny motors.
- A Guide to the Best Astronomical Events in When, Where And How To Shoot Them | PhotoPills!
- Biotransformations in Organic Chemistry — A Textbook.
- An Earthling’s Guide to Black Holes.
- Where You Can See The Best Stars In 'Dark Skies' Around The World | Here & Now?
- Book Excerpt: "Dark Skies".
Next comes the squinting part. But the eventual result, once the next-gen telescopes are built, will be a visible dot of light that is actually a rocky planet. Shunt this image to a spectrometer, a device that can parse light into its wavelengths, and you can start dusting it for those fingerprints of life, called biosignatures.
We already have a planet to prove it. On Earth, plants and certain bacteria produce oxygen as a by-product of photosynthesis. So if we can find evidence of it accumulating in an atmosphere, it will raise some eyebrows. Even more telling would be a biosignature composed of oxygen and other compounds related to life on Earth. Most convincing of all would be to find oxygen along with methane, because those two gases from living organisms destroy each other.
Finding them both would mean there must be constant replenishment. It would be grossly geocentric, however, to limit the search for extraterrestrial life to oxygen and methane. Life could take forms other than photosynthesizing plants, and indeed even here on Earth, anaerobic life existed for billions of years before oxygen began to accumulate in the atmosphere.
Mysterious objects at the edge of the electromagnetic spectrum
As long as some basic requirements are met—energy, nutrients, and a liquid medium—life could evolve in ways that would produce any number of different gases. The key is finding gases in excess of what should be there. There are other sorts of biosignatures we can look for too. The chlorophyll in vegetation reflects near-infrared light—the so-called red edge, invisible to human eyes but easily observable with infrared telescopes.
But the vegetation on other planets might absorb different wavelengths of light—there could be planets with Black Forests that are truly black, or planets where roses are red, and so is everything else. And why stick to plants? Lisa Kaltenegger, who directs the Carl Sagan Institute at Cornell University , and her colleagues have published the spectral characteristics of microorganisms, including ones in extreme Earth environments that, on another planet, might be the norm. The light-gathering capacity of its meter feet mirror will exceed all existing Subaru-size telescopes combined.
Astronomy Without A Telescope - Mass Is Energy - Universe Today
They are smaller and dimmer than our sun, a yellow dwarf, so their habitable zones are closer to the star. The nearer a planet is to its star, the more light it reflects. Alas, the habitable zone of a red dwarf star is not the coziest place in the galaxy. This would render half the planet too hot for life, the other half too cold. The midline, though, might be temperate enough for life.
But he agrees with Seager that the best chance of finding life will be on an Earth-like planet orbiting a sunlike star.
Breakthrough Starshot is an ambitious plan in development to send tiny probes on a year journey to the exoplanet Proxima Centauri b. But even a featherweight spacecraft needs fuel. The farther it goes, the more it needs. The proposed solution? Forget fuel: Launch it from an orbiting satellite and propel it with Earth-based lasers.
Each probe has a quarter-inch chip weighing five grams or less that performs the roles of a camera, computers, and. Breakthrough Starshot is an ambitious plan in development to send tiny probes on a year. Forget fuel: Launch it from an.
- Choose country!
- Contraception and Abortion from the Ancient World to the Renaissance!
- Visible and Invisible - The Wonders of Light Phenomena | Olmes Bisi | Springer.
- Green star (astronomy) - Wikipedia.
- Astronomers witness birth of binary star system for the first time;
- How do we know dark matter exists if we can't see it?.
- Green Parties in Europe?
Situated in low Earth orbit, a satellite houses thousands of probes. When the individual probes are released, their sails automatically unfurl. On Earth, nearly a billion laser beams are directed at a probe to create a pulse with the power of gigawatts, lasting several minutes.
Proxima b after a voyage of more than 20 years. During its high-speed flyby, it takes images and records a range of data. The probe beams the information back using a laser embedded in its chip. Each transmission takes about four years to reach the Earth. Its design consists of 28 panels arranged around a center hub like a giant sunflower, more than feet across. The petals are precisely shaped and rippled to deflect the light from a star, leaving a super-dark shadow trailing behind. The two spacecraft will work together in a sort of celestial pas de deux: Starshade will amble into position to block the light from a star so WFIRST can detect any planets around it and potentially sample their spectra for signs of life.
Then, while WFIRST busies itself with other tasks, Starshade will fly off into position to block the light of the next star on its list of targets. Though the dancers will be tens of thousands of miles apart, they must be aligned to within a single meter for the choreography to work.go
Join Kobo & start eReading today
Seager, who hopes to lead the project, is confident. One can only hope. The ATA is the only facility on the planet built expressly for detecting signals from alien civilizations. Funded largely by the late Microsoft co-founder Paul Allen, it was envisioned as an assembly of radio telescopes, with dishes six meters 20 feet in diameter. But owing to funding difficulties—a regrettable leitmotif in SETI history—only 42 have been built. Smoke veils the view of the surrounding mountains, and in the haze the dishes seem primordially still, like Easter Island statues, each one staring implacably at the same spot in a featureless sky.
Richards takes me to one of the dishes, opening the bay doors beneath it to reveal its newly installed antenna feed: a crenellated taper of shiny copper housed in a thick glass cone. SETI scientists have focused in particular on a quiet zone in the radio spectrum, free of background noise from the galaxy.
It made sense to search in this relatively undisturbed range of frequencies, since that would be where sensible aliens would be most likely to transmit. Richards tells me that the ATA is working through a target list of 20, red dwarfs. In the evening, he makes sure everything is working properly, and while he sleeps, the dishes point, the antennas rouse, photons scuttle through fiber optic cables, and the radio music of the cosmos streams to enormous processors.
So far, however, all the signals of interest have been false alarms. Unfortunately, Congress long ago lost interest in dipping the cup, abruptly terminating support in The good news is that SETI the research endeavor, if not SETI the institute, has recently received a remarkable boost in funding, sending ripples of excitement through the field. Before that, he founded a highly successful internet company in Russia.
He tells me about his background—a degree in physics, a lifelong passion for astronomy, and parents who named him after the cosmonaut Yuri Gagarin, who became the first human in outer space seven months before Milner was born. That was in , which he points out is the same year SETI began. Appreciating the magnitude of this challenge requires some perspective. The first Voyager spacecraft, launched in , took 35 years to enter interstellar space. | 0.932833 | 4.022406 |
Dawn Journal: Faraway Viewing Through the Mind's Eye
Dear Auld Dawn Synes,
Dawn concludes 2012 almost 13,000 times farther from Vesta than it began the year. At that time, it was in its lowest orbit, circling the alien world at an average altitude of only 210 kilometers (130 miles), scrutinizing the mysterious protoplanet to tease out its secrets about the dawn of the solar system.
To conduct its richly detailed exploration, Dawn spent nearly 14 months in orbit around Vesta, bound by the behemoth's gravitational grip. In September they bid farewell, as the adventurer gently escaped from the long embrace and slipped back into orbit around the sun. The spaceship is on its own again in the main asteroid belt, its sights set on a 2015 rendezvous with dwarf planet Ceres. Its extensive ion thrusting is gradually enlarging its orbit and taking it ever farther from its erstwhile companion as their solar system paths diverge.
Meanwhile, on faraway Earth (and all the other locations throughout the cosmos where Dawnophiles reside), the trove of pictures and other precious measurements continue to be examined, analyzed, and admired by scientists and everyone else who yearns to glimpse distant celestial sights. And Earth itself, just as Vesta, Ceres, Dawn, and so many other members of the solar system family, continues to follow its own orbit around the sun.
Thanks to a coincidence of their independent trajectories, Earth and Dawn recently reached their smallest separation in well over a year, just as the tips of the hour hand and minute hand on a clock are relatively near every 65 minutes, 27 seconds. On Dec. 9, they were only 236 million kilometers (147 million miles) apart. Only? In human terms, this is not particularly close. Take a moment to let the immensity of their separation register. The International Space Station, for example, firmly in orbit around Earth, was 411 kilometers (255 miles) high that day, so our remote robotic explorer was 575 thousand times farther. If Earth were a soccer ball, the occupants of the orbiting outpost would have been a mere seven millimeters (less than a third of an inch) away. Our deep-space traveler would have been more than four kilometers (2.5 miles) from the ball. So although the planet and its extraterrestrial emissary were closer than usual, they were not in close proximity. Dawn remains extraordinarily far from all of its human friends and colleagues and the world they inhabit.
As the craft reshapes its solar orbit to match Ceres's, it will wind up farther from the sun than it was while at Vesta. (As a reminder, see the table here that illustrates Dawn's progress to each destination on its long interplanetary voyage.) We saw recently, however, that the route is complex, and the spacecraft is temporarily approaching the sun. Before the ship has had time to swing back out to a greater heliocentric range, Earth will have looped around again, and the two will briefly be even a little bit closer early in 2014. After that, however, they will never be so near each other again, as Dawn will climb higher and higher up the solar system hill, its quest for new and exciting knowledge of distant worlds taking it farther from the sun and hence from Earth.
NASA / ESA / J. Parker (SwRI) / L. McFadden (UM)
Ceres and Vesta compared
Although our cosmic ambassador is much, much too remote to be discerned with our humble eyes, our far more powerful minds' eyes can locate it. As a convenient guide to begin, you can use the moon on Jan. 21. The details of the geometry will be somewhat dependent on your terrestrial position, which determines when the moon is above your horizon and how it aligns with the more distant cosmic landscape. Nevertheless, if you look at the moon that day, Dawn will appear to be nearby in the sky (although more than 670 times farther away). For observers in the continental United States, as the sun sets, the probe will be about five degrees to the east (left) of the moon, or about the width of three fingers held at arm's length. (Your correspondent has found that the measurement works best if you use not only your own fingers, but also your own arm.) As the evening progresses, they will draw closer and closer together. By the time the moon sinks below the western horizon at around 3:30 a.m. on Jan. 22, they will be separated by less than two degrees for observers on the east coast, and those on the west coast will find Dawn less than one degree away.
After using the moon to guide your eyes to the general location of the intrepid ship in the sky, let your mind take over. Allow it to transport you far, far into space, beyond all the human-made satellites around Earth, beyond the moon, beyond the orbit of Mars, and continue out farther than the sun (although in a different direction). Deep in the main asteroid belt, where no other spacecraft has ever taken up permanent residence and farther than all but a handful of probes have ever ventured, you can espy Dawn. Its long solar array wings, spanning nearly 20 meters (almost 65 feet) are pointing at the sun, capturing its light. A lovely beam of xenon ions glows blue-green as it propels the craft toward Ceres. Almost like a living creature, it is intensely active within; computers and myriad electronic circuits, heaters, and other components are working together to keep the ship flying true. Out there, in that direction, alone, far away from any firm surface or familiar ground, this Brobdingnagian celestial dragonfly flies gracefully, silently, and patiently toward its next planetary perch.
Dawn is 2.7 million kilometers (1.7 million miles) from Vesta and 57 million kilometers (38 million miles) from Ceres. It is also 1.65 AU (247 million kilometers or 153 million miles) from Earth, or 625 times as far as the moon and 1.68 times as far as the sun today. Radio signals, traveling at the universal limit of the speed of light, take 27 minutes to make the round trip.
Dr. Marc D. Rayman 6:30 p.m. PST December 31, 2012 | 0.902204 | 3.435261 |
Crescent ♎ Libra
Moon phase on 8 November 2088 Monday is Waning Crescent, 24 days old Moon is in Virgo.Share this page: twitter facebook linkedin
Previous main lunar phase is the Last Quarter before 2 days on 5 November 2088 at 19:22.
Moon rises after midnight to early morning and sets in the afternoon. It is visible in the early morning low to the east.
Moon is passing about ∠21° of ♍ Virgo tropical zodiac sector.
Lunar disc appears visually 1.9% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1901" and ∠1937".
Next Full Moon is the Beaver Moon of November 2088 after 20 days on 28 November 2088 at 14:18.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 24 days old. Earth's natural satellite is moving from the second to the final part of current synodic month. This is lunation 1098 of Meeus index or 2051 from Brown series.
Length of current 1098 lunation is 29 days, 15 hours and 52 minutes. It is 2 hours and 28 minutes shorter than next lunation 1099 length.
Length of current synodic month is 3 hours and 8 minutes longer than the mean length of synodic month, but it is still 3 hours and 55 minutes shorter, compared to 21st century longest.
This New Moon true anomaly is ∠96.1°. At beginning of next synodic month true anomaly will be ∠131.6°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
6 days after point of perigee on 1 November 2088 at 14:54 in ♊ Gemini. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 9 days, until it get to the point of next apogee on 17 November 2088 at 14:57 in ♑ Capricorn.
Moon is 377 082 km (234 308 mi) away from Earth on this date. Moon moves farther next 9 days until apogee, when Earth-Moon distance will reach 405 757 km (252 126 mi).
10 days after its descending node on 29 October 2088 at 10:27 in ♈ Aries, the Moon is following the southern part of its orbit for the next 2 days, until it will cross the ecliptic from South to North in ascending node on 11 November 2088 at 08:03 in ♎ Libra.
24 days after beginning of current draconic month in ♏ Scorpio, the Moon is moving from the second to the final part of it.
6 days after previous North standstill on 2 November 2088 at 06:05 in ♊ Gemini, when Moon has reached northern declination of ∠18.864°. Next 7 days the lunar orbit moves southward to face South declination of ∠-18.899° in the next southern standstill on 15 November 2088 at 20:48 in ♐ Sagittarius.
After 4 days on 13 November 2088 at 06:32 in ♏ Scorpio, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.198984 |
Tuesday, December 21, 2010
New Theory Tackles Asteroids
The only catch is that the recent work on planets around other nearby stars is showing us something that is not nearly so neat. I find it much easier to blame Jupiter for all of it.
Jupiter acts as the sun’s binary and it happens to be spinning close to gravitational instability. That allows it to be a planet pump quite able to produce the inner planets while leaving debris in the asteroid belt.
In an earlier posting, I pointed out that Venus is best explained as a recent emergent that is has only begun to cool and that the red spot is the scar so caused. All others such events took place early in the solar system’s formation. This last event was likely triggered by a large planetoid impacting into Jupiter sending it over the limit of stability.
The rest of the solar system is a handful of gas giants that may be explained by this model. However, I expect to find it much more messy than all that.
Elegant New Theory Explains Origin Of Asteroid Belt
The Solar System consists of distant gas giants and inner rocky planets separated by an asteroid belt. Now an elegant new theory explains how this structure arises
When it comes to planet formation, the conventional thinking has been with us for over 40 years. It goes like this: bits of rock and dust clump together to form rocky planets which then attract the gases that form their atmospheres. The gas giants form when these rocky cores grow to at least ten times the size of Earth and so can attract huge gaseous envelopes.
There are numerous problems with this model, not least of which is explaining how metre-sized lumps of rock end up sticking together after smashing into each other at random. Then there is the problem of planetary rotation. If the planets form from the random aggregation of rock and dust, why do almost all of them rotate in the same direction? Surely, their rotations should be randomly distributed.
But in the last few months various astrophysicists have begun discussing another idea that solves these problems. Today, Sergei Nayakshin at the
of Leicester in the gives a neat
account of this new thinking. UK
The new approach turns the conventional model on its head. Planet formation begins at distances in excess of 50 AU from the mother star, when random variations in the density of the protoplanetary gas cloud begin to attract more gas and so grow under the force of gravity.
Inside these loose clumps, called giant planet embryos, any rocky material aggregates at the centre forming a rocky core. These cores all rotate in the same direction as the original gas cloud because they from by the gravitational collapse of the cloud rather than by random collisions.
As the cores are forming, the embryonic planets interact with the mother star's gas cloud causing them to spiral inwards. Astronomers have long known that huge gaseous atmospheres are unstable at distances closer than a critical radius because of various factors, such as tidal forces and irradiation from the Sun. So when the embryonic planets get closer than this critical radius, they loose their gas envelopes leaving behind terrestrial rocky planets like ours.
Incidentally, at the critical radius, the inspiralling planets discard not only gas but any solids still mixed up in their outer atmospheres. This radius corresponds to the asteroid belt in our system. This new thinking explains for the first time how the belt formed and why it separates the gas giants from the terrestrial planets.
The gas giants like Jupiter are planetary embryos that simply hadn't made it this far towards the Sun when the orbital dynamics settled into the relatively stable system we have now.
One impressive feature of this model is that it naturally accounts for the structure of the Solar System, with the distant gas giants separated from the inner rocky planets by an asteroid belt. No other model does this so elegantly. It is this elegance that has focused so much attention on it so quickly.
What's curious about this new thinking is that none of the mechanisms it relies on are new ideas. But in the past, each has been suggested and then discarded.
For example, the idea that terrestrial planets are gas giants that have lost their gas envelopes was first put forward over 30 years ago. Astronomers abandoned it after various calculations showed that gas giants couldn't form close to a star where we find rocky planets today.
And the idea that planets can migrate great distances in a planetary system has also been around for years.
What's new is the re-ordering of these processes so that the gas giants form first and then migrate, losing their atmospheres as they get closer to the mother star. All of a sudden, it looks obvious.
There's still work to be done, of course. Nayakshin points out that the new model doesn't yet account for structures such as the Kuiper Belt, the Oort Cloud not can it explain the composition of comets.
But there's a sense of excitement about this idea that is giving it considerable momentum in the community. You can be sure that astronomers will be poring over the details as I write. Expect to hear more about it in the coming months. | 0.895502 | 3.733881 |
In the movie Interstellar, they go to a planet where time flows by much slower for them while on it because of the increased gravity that planet is experiencing due to the nearby black hole. My question is whether or not something much smaller, like an asteroid or a dwarf planet even, could pass by Earth close enough to slow down time from our perspective? Is there something that could do the opposite and speed it up, and effectively slow everything else down?
Time wouldn't slow down from our perspective. The time dilation would be evident only if we were to check our clocks against a clock that's far enough from the celestial object (just as shown in interstellar) and/or after the celestial object is gone.
That being said, since it's a function of mass, a sufficiently massive asteroid could cause dilation significant enough to be observable from one side of the planet to the other. But if the asteroid is too massive (because a millionth of a second off here and there won't make an interesting plot point), there might be many other inconvenient (and potentially devastating) effects of such a massive object passing by. How a small asteroid/planet is able to be contain so much mass would probably require a super dense fictional substance. Alternatively, you could just speed up earth, but it'll mean that the time dilation is same everywhere on the planet (aside from other interesting/devastating consequences).
Speeding time up on earth in comparison to rest of the universe is much trickier but if we were to speed up the time on earth compared to another planet or a region of space then it's doable - Just put the massive celestial object close to the region of space and you could, in theory, say that the time on earth has sped up compared to that region of space. The region must be far enough from earth so that earth is only nominally affected by the massive object. | 0.859756 | 3.225403 |
A team of scientists led by University of Hawaiʻi at Mānoa School of Ocean and Earth Science and Technology (SOEST) researcher Hope Ishii has discovered that certain interplanetary dust particles (IDPs) contain dust leftover from the initial formation of the solar system, as reported by UH.
The initial solids from which the solar system formed consisted almost entirely of amorphous silicate, carbon and ices. This dust was mostly destroyed and reworked by processes that led to the formation of planets. Surviving samples of pre-solar dust are most likely to be preserved in comets—small, cold bodies that formed in the outer solar nebula.
In a relatively obscure class of IDPs believed to originate from comets, there are tiny glassy grains called GEMS, or glass embedded with metal and sulfides—typically only tens to hundreds of nanometers in diameter, less than 1/100th the thickness of human hair.
Building Blocks of Planets and Stars
Using transmission electron microscopy, Ishii and colleagues made maps of the element distributions and discovered that these glassy grains are made up of subgrains that aggregated together in a different environment and prior to the formation of the comet parent body. This aggregate is encapsulated by carbon of a different type than the carbon that forms a matrix gluing together GEMS and other components of cometary dust.
The types of carbon that rims the subgrains and that forms the matrix in these particles decomposes with even weak heating, suggesting that the GEMS could not have formed in the hot inner solar nebula, and instead formed in a cold, radiation-rich environment, such as the outer solar nebula or pre-solar molecular cloud.
“Our observations suggest that these exotic grains represent surviving pre-solar interstellar dust that formed the very building blocks of planets and stars,” said Ishii, who is based at the UH Mānoa HawaiʻiInstitute of Geophysics and Planetology. “If we have at our fingertips the starting materials of planet formation from 4.6 billion years ago, that is thrilling and makes possible a deeper understanding of the processes that formed and have since altered them.”
Excellence in Space Science at UH
UH has a strong footprint in space science and state-of-the-art instrumentation and is recognized as world-class in this field.
“This is an example of research that seeks to satisfy the human urge to understand our world’s origins and serves the people of Hawaiʻi by boosting our reputation for excellence in space science and as a training ground for our students to be engaged in exciting science,” said Ishii.
The team plans to search the interiors of additional comet dust particles, especially those that were well-protected during their passage through the Earth’s atmosphere, to increase understanding of the distribution of carbon within GEMS and the size distributions of GEMS subgrains.
Funding and Collaboration
This work was funded by NASA’s Cosmochemistry, Emerging Worlds and Laboratory Analysis of Returned Samples Programs and was enabled, in part, by the Advanced Electron Microscopy Center at UH. Portions of the work were also performed at national user facilities at the Molecular Foundry and the Advanced Light Sourceat Lawrence Berkeley National Laboratory, which are supported by the Office of Science, Basic Energy Sciences, U.S. Department of Energy. | 0.841621 | 3.965565 |
Hunting down clues to Earth's early molten days
Learning how liquid silicates behave at extreme temperatures and pressures has been a longstanding challenge in the geosciences.
Far below the Earth’s surface, about 1,800 miles deep, lies a roiling magmatic region sandwiched between the solid silicate-based mantle and molten iron-rich core: The core-mantle boundary. It’s a remnant of olden times, the primordial days about 4.5 billion years ago when the entire planet was molten, an endless sea of magma. Although the region’s extreme pressures and temperatures make it difficult to study, it contains clues about the mysterious origin story of the world as we know it.
“We’re still trying to piece together how the Earth actually started to form, how it transformed from a molten planet to one with living creatures walking around on its silicate mantle and crust,” says Arianna Gleason, a scientist at the Department of Energy’s SLAC National Accelerator Laboratory. “Learning about the strange ways materials behave under different pressures can give us some hints.”
Now, scientists have developed a way to study liquid silicates at the extreme conditions found in the core-mantle boundary. This could lead to a better understanding of the Earth’s early molten days, which could even extend to other rocky planets. The research was led by scientists Guillaume Morard and Alessandra Ravasio. The team, which included Gleason and other researchers from SLAC and Stanford University, published their findings this week in the Proceedings of the National Academy of Sciences.
“There are features of liquids and glasses, in particular silicate melts, that we don't understand,” says Morard, a scientist at the University of Grenoble and Sorbonne University in France. “The problem is that molten materials are intrinsically more challenging to study. Through our experiments we were able to probe geophysical materials at the extremely high temperatures and pressures of deep Earth to tackle their liquid structure and learn how they behave. In the future we will be able to use these types of experiments to recreate the first moments of Earth and understand the processes that shaped it.”
Hotter than the sun
At SLAC’s Linac Coherent Light Source (LCLS) X-ray free-electron laser, the researchers first sent a shockwave through a silicate sample with a carefully tuned optical laser. This allowed them to reach pressures that mimic those at the Earth’s mantle, 10 times higher than previously achieved with liquid silicates, and temperatures as high as 6,000 kelvins, slightly hotter than the surface of the sun.
Next, the researchers hit the sample with ultrafast X-ray laser pulses from LCLS at the precise moment the shockwave reached the desired pressure and temperature. Some of the X-rays then scattered into a detector and formed a diffraction pattern. Just like every person has their own set of fingerprints, the atomic structure of materials is often unique. Diffraction patterns reveal that material fingerprint, allowing the researchers to follow how the sample’s atoms rearranged in response to the increase of pressure and temperature during the shockwave. They compared their results to those of previous experiments and molecular simulations to reveal a common evolutionary timeline of glasses and liquid silicates at high pressure.
“It’s exciting to be able to gather all these different techniques and get similar results,” says SLAC scientist and co-author Hae Ja Lee. “This allows us to find a combined framework that makes sense and take a step forward. It's very comprehensive compared to other studies.”
Connecting the atomistic to the planetary
In the future, the LCLS-II upgrade, as well as upgrades to the Matter in Extreme Conditions (MEC) instrument where this research was performed, will allow scientists to recreate the extreme conditions found in the inner and outer core to learn about how iron behaves and the role it plays in generating and shaping Earth’s magnetic field.
To follow up on this study, the researchers plan to perform experiments at higher X-ray energies to make more precise measurements of the atomic arrangement of liquid silicates. They also hope to reach higher temperatures and pressures to gain insight into how these processes unfold in planets bigger than Earth, so-called super-Earths or exoplanets, and how the size and location of a planet influences its composition.
“This research allows us to connect the atomistic to the planetary,” Gleason says. “As of this month, more than 4,000 exoplanets have been discovered, about 55 of which are positioned in the habitable zone of their stars where it’s possible for liquid water to exist. Some of those have evolved to the point where we believe there's a metallic core that could generate magnetic fields, which shield planets from stellar winds and cosmic radiation. There are so many pieces that need to fall into place for life to form and be sustained. Making the important measurements to better understand the construction of these planets is crucial in this age of discovery.”
Ravasio is a scientist at Sorbonne University and Ecole Polytechnique in France. SLAC scientist and co-author Roberto Alonso-Mori also played a key role in this research. The team included researchers from Arizona State University; the University of Oslo, Norway; the National Museum of Natural History, Clermont Auvergne University, the French Alternative Energies and Atomic Energy Commission and the European Synchrotron Radiation Facility in France; and Helmholtz-Zentrum Dresden-Rossendor in Germany.
LCLS is a DOE Office of Science user facility. This research was supported in part by the Office of Science. | 0.828993 | 3.708323 |
Theories about an unknown planet hidden on the outskirts of the Solar System seem to be definitively disproved by NASA’s research. The case of the so-called “Planet X” dates back to the early 20th century, when the American astronomer Percival Lowell proposed the existence of such a body in order to explain some inexplicable features of the orbit of Uranus.
When Pluto was discovered in 1930, many astronomers rushed to celebrate the discovery of the infamous Planet X. But celebrations were premature, since it was finally found that Pluto was not big enough to explain the orbital anomalies of the outer planets. Today, most astronomers do not believe in the idea of an unknown planet in the Solar System, although the case of Lowell remains theoretically open.
The latest study, published in the journal «Astrophysical Journal», is based on data from the WISE infrared space telescope of NASA, which swept twice around the sky in 2010-2011 period, with an interval of six months between scans.
The researchers examined 750 million objects – stars, galaxies, asteroids, etc. – and looked for bodies that had been moved from the first scan to the second, indicating that they are relatively close to Earth.
The study concludes that there is no object of the size of Saturn or greater in distance up to 10,000 astronomical units. The researchers were able to further exclude a second, similar theory, according to which the Sun has a companion star which is located at a long distance and somehow remains unknown to this day.
The theory, which now has few supporters, was proposed to explain the supposed schedule of the asteroid attacks on Earth. The companion star is supposed to periodically approach the Sun and disturb the orbits of asteroids, sending some of them to the Earth.
Such a companion star or brown dwarf companion did not appear in the data provided by the WISE telescope. “The outer solar system does not seem to contain a small companion star or a gas giant planet,” is the conclusion of the study according to the author, Kevin Luhman of the Pennsylvania State University.
In a second study based on the data of WISE, a different research team announced the discovery of 3,525 stars and brown dwarfs located at a distance of up to 500 light years from Earth.
“Till now we did not know the neighborhood of the Sun as well as you would imagine,” says Ned Wright, principal investigator of the WISE mission.
- How to Deal with Failure When Everything Goes Wrong - May 10, 2020
- 9 Signs of Needy People & How They Manipulate You - May 7, 2020
- 6 Types of Toxic People Who Become Involuntary Manipulators - April 30, 2020
Copyright © 2012-2020 Learning Mind. All rights reserved. For permission to reprint, contact us. | 0.876332 | 3.469274 |
by Dr. E. Myles Standish, Jr., Jet Propulsion Laboratory
The residuals of Uranus and Neptune do not demand the existence of a tenth planet, for there are other explanations that are at least as plausible. It is easy to ignore the fact that the residuals themselves need reexamination.
Do the residuals represent true deviations in the motion of the planets? Or can the residuals be more simply explained as errors and inaccuracies in the procedures of working with the observational measurements?
There is a succession of steps involved in determining the residuals for a planet:
1. Begin with the raw measurements. Classical planetary position observations are made by measuring the altitudes of both the planets and the stars and timing their transits across the meridian (the north-south line in the sky). This step can never be repeated for a specific observation. One cannot go back and reobserve the position of Mars in 1850.
2. Derive the observed positions, 0. Using the raw measurements and the most accurate catalog of star positions available derive the observed positions of the planets. These derived "observables" have been published and, more recently, have been put into computer-readable form Many of the raw measurements have also been published, while others still exist only in the original observing notebooks These raw measurements have not, how ever, been put into computer-readable form—a task that would be colossal.
3. Calculate the computed positions, C. Use an existing orbit (ephemeris) to predict positions of the planet for comparison with the observed positions.
4. Form the residuals, O-C. The residuals are the differences between the observed or bital positions, O, and the computed orbital positions, C. In the ideal world, with
0f 0.02 seconds of arc—about 20 times better than standard posi-^ gl measurements by telescopic photography in the optical wavelengths.
pushing beyond that accuracy are teams of astronomers at the Cali-■ institute of Technology's Jet Propulsion Laboratory and NASA's rd Space Flight Center. They are using very widely separated radio
I scopes to determine the positions of quasars to an accuracy of 0.001 second. Quasars are the most distant objects in the universe and therefore are the closest thing the cosmos offers to a fixed background of objects that do not appear to move up, down, or sideways. By relating cecraft ancj planets to the reference background of quasars, navigation of space probes and the predicted positions of planets should be improved by a further factor of 20.
Thinking back over his discovery of Pluto and his 14 years of planet searching, Clyde Tombaugh offered Ten Special Commandments for a Wbuld-Be Planet Hunter. The Final commandment decrees: "Thou shalt not engage in any dissipation, that thy years may be many, for thou shalt need them to finish the job."19
perfect observations and with perfect ephemerides, the residuals would be zero.
5. Adjust the computed orbit of the planet, C, to fit the observed positions, O, as nearly as possible, so as to minimize the residuals. (This adjustment is usually accomplished using the mathematical method of least squares, developed by Gauss.)
6. Examine the final residuals. What keeps them from being zero? Perhaps the catalog of star positions still has distortions. Perhaps the computed orbit can be further improved. When no more improvements are possible, one goes on to step 7.
7. Other explanations of the residuals. What can cause nonzero residuals to a best-fit orbital calculation? A defect in the law of gravity? Planet X?
Star catalogs produced since 1910 have been shown to contain significant distortions. Certainly earlier and cruder catalogs must also contain distortions of similar, if not greater, magnitude. However, ■>o one has ever gone back to step 2, properly reprocessing the raw measurements of the planets using a modern star catalog.
For the post-1910 data, a lesser alternative has been used: updating the published positions using general differences found by comparing the original catalog with a modern one. For data previous to 1910, not even this lesser alternative has been applied. The original catalog distortions remain embedded in the residuals.
At best, a few tenth-planet seekers start at step 5, cranking out new orbits in an attempt to fit the observations. Far worse, most begin with step 7: "May 1 get a copy of your residuals?"
The complete job must start back at step 2—taking the original measurements of the planets and recalculating their positions using modern star catalogs. Such an analysis would bring no funding or headlines. It would be time-consuming anc tedious. But until the basic observations (from which come the residuals) are processed properly there is no necessity to invoke Planet X.
Was this article helpful? | 0.837217 | 3.998064 |
Scientists from NASA Goddard have discovered that not only are Saturn's rings younger than previously thought, but also that the rings are actually disappearing at a rapid pace through a process called "ring rain." Learn more about this phenomena in this animated video.
Video narrated by: Jerome Hruska
Music Provided by Killer Tracks: "The Butterfly Effect" - Gresby Race Nash
This video explores how Saturn is losing its rings at a rapid rate, and what that also reveals about the planet's history.
Infrared observations of Saturn were recorded using the 10-meter diameter Keck telescope in Hawaii. Through a careful analysis, Dr. James O'Donoghue and his team found a series of unusual bright and dark bands extending around the planet's upper atmosphere. It was found that these bands are linked to Saturn's rings by magnetic field lines, indicating that water ice from the rings is "raining" into the planet.
This mechanism is called "ring rain," and was discovered using Voyager spacecraft data in the 1980s by study co-author Dr. Jack Connerney. In this process, electrically charged icy dust in Saturn's rings is pulled into the planet along magnetic field lines by gravity. Modeling work by study co-author Dr. Luke Moore shows that if there is a small amount of rain, the ionosphere glows, while if there is a large amount of rain, it becomes dark.
In this new study, the rate of water flow into the planet is estimated to be one Olympic sized swimming pool every half an hour, meaning Saturn's rings will be gone in under 300 million years. This is short relative to the 4.5 billion-year age of the solar system. The findings suggest that giant planetary ring systems are not built to last forever. | 0.904856 | 3.673261 |
Stellar spectra near Lithium line (6707 A) for the HAT-P-4 A star (blue dotted line), which displays a higher Lithium abundance than the companion star (Black continuous line). Spectrum acquired using GRACES which uses fiber-fed light from the Gemini North telescope with the Canada-France-Hawaii Telescope’s ESPaDOnS Spectrograph.
Astronomers using the Gemini Observatory and the Canada-France-Hawaii Telescope have discovered remarkable differences in the abundance of heavier elements, and the Lithium content, in a binary star pair. The research team speculates that this difference is caused by the engulfment of rocky planets early in the system’s evolution which enriched one of the stars. The work also hints at a formation scenario resulting in gas giant planets forming relatively far from their host star.
A team of astronomers led by Carlos Saffe (Instituto de Ciencias Astronómicas, de la Tierra y el Espacio, Argentina) observed the peculiar binary system called HAT-P-4, which includes a confirmed exoplanet orbiting one of the stars in the pair. The team used the 8-meter Gemini North Telescope and the Gemini Remote Access to CFHT ESPaDOnS Spectrograph (GRACES) located at the Canada-France-Hawaii Telescope to perform high-resolution spectroscopy of the two stars. These spectra revealed that the star pair have markedly different quantities of heavy elements or what astronomers call “metallicity.”
“Both stars are believed to have formed together with the same chemical composition, which makes the difference in metallicity found in this binary system remarkable,” according to Saffe. In particular, says Saffe, the different refractory (rocky) content points toward a history of a rocky planet or planets in the system. “We speculate that these observations can be explained by the engulfment of a rocky planet sometime during the system’s evolution. This presents us with an exciting glimpse into the system’s violent planet formation history.”
One star in the pair, HAT-P-4 A, also hosts a gas giant planet orbiting at only 0.04 AU from the star. This same star also displays a higher Lithium abundance than its stellar companion, which is another unexpected feature in this type of binary system. The authors use these data to exclude other possible explanations, such as a peculiar composition of the stars or different rotational velocities. The team concludes that HAT-P-4-A formed the known gas giant planet while rocky (refractory) material accreted closer to the star, possibly due to migration of the gas giant. Saffe concludes, “This scenario explains the higher metallicity of HAT-P-4-A, the higher refractory abundance, and the higher Lithium content.”
The results are accepted for publication in Astronomy & Astrophysics Letters and available online.
To explore the possible chemical signature of planet formation in the binary system HAT-P-4, by studying abundance vs condensation temperature Tc trends. The star HAT-P-4 hosts a planet detected by transits while its stellar companion does not have any detected planet.We also study the Lithium content, which could shed light on the problem of Li depletion in exoplanet host stars.
We derive, for the first time, both stellar parameters and high-precision chemical abundances by applying a line-by-line full differential approach. The stellar parameters were determined by imposing ionization and excitation equilibrium of Fe lines, with an updated version of the FUNDPAR program, together with ATLAS9 model atmospheres and the MOOG code. We derived detailed abundances of different species with equivalent widths and spectral synthesis with the MOOG program.
The exoplanet host star HAT-P-4 is found to be ∼0.1 dex more metal rich than its companion, which is one of the highest differences in metallicity observed in similar systems. This could have important implications for chemical tagging studies, disentangling groups of stars with a common origin. We rule out a possible peculiar composition for each star as λ Boötis, δ Scuti or a Blue Straggler. The star HAT-P-4 is enhanced in refractory elements relative to volatile when compared to its stellar companion. Notably, the Lithium abundance in HAT-P-4 is greater than in its companion by ∼0.3 dex, which is contrary to the model that explains the Lithium depletion by the presence of planets. We propose a scenario where, at the time of planet formation, the star HAT-P-4 locked the inner refractory material in planetesimals and rocky planets, and formed the outer gas giant planet at a greater distance. The refractories were then accreted onto the star, possibly due to the migration of the giant planet. This explains the higher metallicity, the higher Lithium content, and the negative Tc trend detected. A similar scenario was recently proposed for the solar twin star HIP 68468, which is in some aspects similar to HAT-P-4. We estimate a mass of at least Mrock ∼ 10 M⊕ locked in refractory material in order to reproduce the observed Tc trends and metallicity.
News Archive Filter
The GEMMA Podcast
A podcast about Gemini Observatory and its role in the Era of Multi-Messenger Astronomy. Featuring news related to multi-messenger astronomy (MMA), time-domain astronomy (TDA), our visiting instrument program, and more through interviews with astronomers, engineers, and staff both here at Gemini (North and South) and abroad. | 0.864133 | 4.036754 |
In the fall of 2018, when the James Webb Space Telescope launches to an orbit four times farther away than the Moon, it will have an unprecedented ability to see distant events and objects in the universe. Six times larger than the Hubble Space Telescope, Webb will be able to detect remnants of the earliest stars and galaxies, and answer fundamental questions about how our world formed.
The namesake for the most powerful telescope ever developed, James Webb graduated from UNC in 1928 and went on to become the second administrator at NASA. He served from the beginning of the Kennedy administration through the end of the Johnson administration, overseeing all the critical first manned launches until just before the first astronaut-led Apollo flight.
But Webb is not the only Tar Heel connected to NASA or deep space exploration. Since the university opened its doors, Carolina scientists have been posing questions — and finding answers — in the stars.
The first astronomical observatory
In the early 19th century, back when Franklin Street was a dirt road, and UNC’s enrollment totaled just a few dozen students — a man ahead of his time helped shape the culture of learning here. Joseph Caldwell, the university’s first president, was a mathematician and Presbyterian minister, and he was also an astronomy buff who saw great physical and philosophical value in looking toward the sky. When he asked for university funds to purchase astronomical tools, though, his requests fell on deaf ears.
Undeterred, Caldwell used his own money to travel to Europe and came back with several thousand dollars’ worth of scientific materials for the university, including a handful of telescopes. In 1830, he constructed an observatory in the backyard of his house — the first one in the United States intended solely for educational purposes.
Despite this promising foundation, it would be another 150 years before the study of astronomy became an official major at UNC. Chris Clemens, senior associate dean for natural sciences in the College of Arts & Sciences, attributes that to the deadliest conflict in our nation’s history.
“The Civil War ended the astronomical aspirations of many southern universities — in particular the University of Mississippi,” he says. “They had ordered the biggest refracting telescope lens ever made, and then the war broke out and they couldn’t complete the project. That telescope went to Wisconsin instead. Because of the war, astronomy in the South didn’t take off until generations later.”
The original telescopes that Caldwell purchased from France in 1824 are still on campus today — on display at UNC’s Morehead Planetarium and Science Center. Roughly 100 years after Caldwell built his observatory, John Motley Morehead, III met with UNC’s then-president Frank Porter Graham. The two men chatted about Morehead’s illustrious career in chemistry. Shortly after graduating from UNC, he helped uncover an economical process for manufacturing calcium carbide — a discovery that made him very wealthy. Morehead attributed his success to UNC, and wanted to find a way to give back to his alma mater.
In addition to endowing the John Motley Morehead Foundation to provide financial assistance to UNC students, Morehead wanted to inspire young North Carolinians to explore the world of science. He and Graham discussed different possibilities, and ultimately decided on a planetarium.
When it first opened in 1949, Morehead Planetarium was unprecedented. It was only the sixth planetarium to be built in the United States, the first one in the South, and the first one on a university campus.
The planetarium not only fulfilled Morehead’s wish of inspiring young people to engage with science — it also served as a training center for professional space explorers. From 1960 to 1975, over 60 NASA astronauts including Neil Armstrong and John Glenn came to Morehead Planetarium to study celestial navigation — a critical skill in the event that automatic navigation systems failed while they were in space.
The training saved lives on three occasions — during the Mercury Atlas 9 mission, Apollo 12, and Apollo 13, according to Todd Boyette, the current director of Morehead Planetarium.
To this day, it remains the only planetarium in the world to train astronauts in celestial navigation.
The first astronomers at UNC
As NASA astronauts were honing their skills at Morehead Planetarium, and the country became more engaged with the international space race, UNC’s Department of Physics started recruiting new faculty like Morris Davis, who arrived from Yale in the early 1970’s to become Carolina’s first official astronomer. Wayne Christiansen and Bruce Carney joined the faculty just a few years later. They advocated for adding “astronomy” to the department’s title, and started an official astronomy major.
By 1985, the Department of Physics and Astronomy was on the forefront of astronomical study, boasting a brand-new $45,000 “super-microcomputer” with extensive memory and operations capabilities. The SUN 2-170 system included a 2-MB, 32-bit processing unit, a tape drive, and a 130-MB hard disk — a fraction of the operating power of a standard smart phone today.
Radio technology and radio telescopes were also considered cutting-edge in 1985. Christiansen would travel to the middle of the desert, 120 miles southwest of Albuquerque, New Mexico, to spend time peering through the most sophisticated radio telescope at the time — the Very Large Array (VLA). With it, he was able to observe quasars — extremely remote celestial objects — several billion light years away.
But getting time on the VLA was a challenge. Christiansen and Carney wanted a telescope that UNC could claim as its own — a massive undertaking that would come to fruition 20 years later.
The value of SOAR
In the Andes mountain range of central Chile is a small peak called Cerro Pachón. Rising almost 9,000 feet above sea level, the mountain is home to some of the driest conditions — and clearest air — on Earth. It is the perfect place to observe the night sky.
There are only a handful of 4-meter telescopes in the world, and one of them came to be on this mountain in 2004 thanks to a $32 million public-private partnership among the U.S. National Optical Astronomy Observatory (NOAO), the Ministry of Science of Brazil, Michigan State University, and UNC.
The Southern Astrophysical Research telescope (SOAR) boasts first-rate optics but its true innovation lies in its adjustability. Other 4-meter telescopes have equipment that weighs thousands of pounds and can take an entire day to change. The “quick change” instruments on SOAR, though, allow astronomers to measure the mass and temperature of a white dwarf star, or capture two binary stars orbiting each other.
Roughly 5,000 miles away, new technology and new instrumentation for SOAR is developed in the Goodman Laboratory for Astronomical Instrumentation on UNC’s campus, where students have the ability to observe these phenomena in real time.
The colors of the universe
On a sunny afternoon in early February, J.J. Hermes, a Hubble Fellow in the Department of Physics and Astronomy, sits in a room with no windows on the ground floor of Chapman Hall. “This is sort of the front line where the data is coming in — in real time,” he says.
Astronomers from UNC spend roughly 60 nights a year observing from this room, remotely controlling instruments more than 4,500 miles away in Chile. But their astronomical laboratories are truly remote: The nearest stars UNC researchers observe are still several light years away, tens of trillions of miles from Earth.
SOAR is one of the most efficient telescopes at capturing blue, near-ultraviolet light, which is often produced from very hot stars.
On this February evening, Hermes and collaborators were using SOAR to measure the mass and temperature of stars at the end of their life cycle, white dwarfs, which have surface temperatures more than twice as hot as the Sun.
“SOAR is helping us better understand white dwarfs that pulsate,” Hermes says. “Just as earthquakes tell us about what’s happening at the core of our planet, these pulsations cause ‘starquakes’ that give us access to phenomena at pressures and densities we simply cannot access from Earth.”
The competitive advantage: UNC undergraduates
While Chris Clemens and many UNC students study blue light across the universe, other researchers who use SOAR wanted to replace the blue camera with one that would better study cooler, redder objects — but this would reduce capabilities in the blue and ultraviolet. To compromise, Clemens suggested they add a red camera to the Goodman Spectrograph. The instrument, though, was not designed to host two cameras.
“So I got a grad student and an undergrad, and I helped them define what they were going to do,” Clemens says. They didn’t need to build a whole new camera from scratch — they needed to engineer a new optical interchange on the existing instrument that would allow them to permanently attach a second camera without interfering with any of the existing capabilities. The graduate student, Erik Dennihy, supervised the undergraduate, Stephen Fanale, to write the software and conduct finite element engineering analysis.
“Stephen flew through it,” Dennihy says. “He’s now our primary software engineer and is working on some ambitious projects to eventually allow the cameras to take sets of images on their own.”
The opportunity to work on SOAR is a big part of the reason Dennihy chose UNC for graduate school. “SOAR is in a bit of a sweet spot when it comes to providing that hands on experience for students,” he says. “It comes with all the challenges of working within a large, international collaboration, and is still a small enough consortium to allow significant contributions from students.”
Clemens has received some criticism during design reviews with professional astronomers who believe undergraduate students shouldn’t conduct software development. “They would tell me, ‘They don’t take it seriously, they’re only here for four years. We’ve never seen undergrads deliver like a professional team,’” Clemens recalls. “And I would say, ‘You don’t know UNC undergrads.’”
Clemens built the Goodman spectrograph for SOAR in the early 2000s. An undergraduate helped design the entire software control system for the spectrograph. Dan Reichert built the PROMPT network — small telescopes pointing toward explosive events in the sky that are detected by orbiting X-ray and gamma-ray satellites. Nicholas Law built the EVERYSCOPE in Chile.
“Everyone who has come to our department has built this, or built that. So we hire people now who are known for building interesting stuff.” As senior associate dean of natural sciences, and former chair of the Department of Physics and Astronomy, Clemens hopes to see UNC gain international recognition in the coming years for our astronomy prowess and unique astrophysics.
“Really good schools are also hubs,” Clemens says. “So if an astronomer or physicist in England wants to take a sabbatical to the U.S., we want them to come here instead of Princeton or Harvard.”
That wish could become a reality with the inauguration of a new center devoted to the study of gravity, cosmology, astrophysics, astronomy, nuclear physics, and particle physics. The goal of the Institute for Cosmology, Subatomic Matter and Symmetries (CoSMS) is to bring together scientists from different disciplines by creating open and interactive workspaces. “We have a chance to be the center for fundamental nuclear physics research in RTP with these three major universities,” Clemens says. “The CoSMS Institute will lay the groundwork, not just for the next 10 years at UNC, but for the next 50 years, the next 100 years.” | 0.832744 | 3.349135 |
Our Milky Way is a pretty vast and highly-populated space. All told, its stars number between 100 and 400 billion, with some estimates saying that it may have as many as 1 trillion. But just where did all these stars come from? Well, as it turns out, in addition to forming many of its own and merging with other galaxies, the Milky Way may have stolen some of its stars from other galaxies.
Such is the argument made by two astronomers from Harvard-Smithsonian Center for Astrophysics. According to their study, which has been accepted for publication in the The Astrophysical Journal, they claim that roughly half of the stars that orbit at the extreme outer edge of the Milky Way were actually stolen from the nearby Sagittarius dwarf galaxy.
At one time, the Sagittarius Dwarf Elliptical Galaxy was thought to be the closest galaxy to our own (a position now held by the Canis Major dwarf galaxy). As one of several dozen dwarf galaxies that surround the Milky Way, it has orbited our galaxy several times in the past. With each passing orbit, it becomes subject to our galaxy’s strong gravity, which has the effect of pulling it apart.
The long-term effects of this can be seen by looking to the farthest stars in our galaxy, which consist of the eleven stars that are at a distance of about 300,000 light-years from Earth (well beyond the Milky Way’s spiral disk). According the study produced by Marion Dierickx, a graduate student at Harvard University’s Department of Astronomy, half of these stars were taken from the Sagittarius dwarf galaxy in the past.
Professor Avi Loeb, the Frank B. Baird, Jr. Professor of Science at Harvard and Marion Dierickx PhD advisor, co-authored the study – titled, “Predicted Extension of the Sagittarius Stream to the Milky Way Virial Radius“. As he told Universe Today via email:
“We see evidence for streams of stars connected to the core of the galaxy, and indicating that this dwarf galaxy passed multiple times around the Milky Way center and was ripped apart by the tidal gravitational field of the Milky Way. We are all familiar with the tide in the ocean caused by the gravitational pull of the moon, but if the moon was a much more massive object – it would have pulled the oceans apart from the Earth and we would see a stream of vapor stretched away from the Earth.”
For the sake of their study, Dierickx and Loeb ran computer models to simulate the movements of the Sagittarius dwarf over the past 8 billion years. These simulations reproduced the streams of stars stretching away from the Sagittarius dwarf galaxy to the center of our galaxy. They also varied Sagittarius’ velocity and angle of approach to see if the resulting exchanges would match current observations.
“We attempted to match the distance and velocity data for the core of the Sagitarrius galaxy, and then compared the resulting prediction for the position and velocity of the streams of stars,” said Loeb. “The results were very encouraging for some particular set of initial conditions regarding the start of the Sagittarius galaxy journey when the universe was roughly half its present age.”
What they found was that over time, the Sagittarius dwarf lost about one-third of its stars and nine-tenths of its dark matter to the Milky Way. The end result of this was the creation of three distinct streams of stars that reach one million light-years from galactic center to the very edge of the Milky Way’s halo. Interestingly enough, one of these streams has been predicted by simulations conducted by projects like the Sloan Digital Survey.
The simulations also showed that five of Sagittarius’ stars would end becoming part of the Milky Way. What’s more, the positions and velocities of these stars coincided with five of the most distant stars in our galaxy. The other six do not appear to be from Sagittarius dwarf, and may be the result of gravitational interactions with another dwarf galaxy in the past.
“The dynamics of stars in the extended arms we predict (which is the largest Galactic structure on the sky ever predicted) can be used to measure the mass and structure of the Milky Way,” said Loeb. “The outer envelope of the Milky Way was never probed directly, because no other stream was known to extend that far.”
Given the way the simulations match up with current observations, Dierickx is confident that more Sagittarius dwarf interlopers are out there, just waiting to be found. For instance, future instruments – like the Large Synoptic Survey Telescope (LSST), which is expected to begin full-survey operations by 2022 – may be able to detect the two remaining streams of stars which were predicted by the survey.
Given the time scales and the distances involved, it is rather difficult to probe our galaxy (and by extension, the Universe) to see exactly how it evolved over time. Pairing observational data with computer models, however, has been proven to test our best theories of how things came to be. In the future, thanks to improved instruments and more detailed surveys, we just might know for certain!
And sure to check out this animation of the computer simulation, which shows the effects on the Milky Way’s gravity on the Sagittarius dwarf galaxy’s stars and dark matter.
Further Reading: CfA | 0.800785 | 3.772389 |
- Express Letter
- Open Access
Autonomous spectrographic system to analyse the main elements of fireballs and meteors
Earth, Planets and Space volume 70, Article number: 2 (2018)
We present a meteor observation system based on imaging CCD cameras, wide-field optics and a diffraction grating. This system is composed of two independent spectrographs with different configurations, which allows us to capture images of fireballs and meteors with several fields of view and sensitivities. The complete set forms a small autonomous observatory, comprised of a sealed box with a sliding roof, weather station and computers for data storing and reduction. Since 2014, several meteors have been studied using this facility, such as the Alcalá la Real fireball recorded on 30 September 2016.
Meteor spectra studies started in the 1860s by means of the observations taken by A.S. Herschel (Millman 1963). Photographic techniques have been used to study meteor spectra since the end of the nineteen century (Millman 1980), and transmission gratings started to replace prisms in meteor spectrographs since the 1950s. Broad spectroscopy programmes were carried out in USA, Canada, the former USSR and Czechoslovakia (Ceplecha et al. 1988). New video techniques to study meteor spectra started to be used in the early 1970s (Hemenway et al. 1971), as well as new methods and TV processes for data reduction, described by Millman and Clifton (1975), Borovicka and Bocek (1995) and Zender et al. (2004). Meteor spectroscopy is based on the emission of atomic lines (emission spectra), along with other molecular bands and continuous radiation. Early on, Halliday (1961), Ceplecha (1971) and Borovička (1994a) provided significant identification lists of lines in high-dispersion photographic spectra. Meteor emission lines can be divided into two components according to their temperature (high and low) (Borovička 1994b).
Video techniques allow the recording of relatively faint meteors (Espartero and Madiedo 2016 and references therein) in comparison with photographic images, so only certain emission lines can be detected, such as Na, Mg, Ca and Fe, in addition to the O, N and N2 atmospheric emissions (obtained by low-resolution spectroscopy). With our video systems, we can capture meteors with apparent visual magnitude as faint as 3 ± 1 (Madiedo et al. 2016), but the spectrographic equipment is limited to the spectral study of fireballs with visual apparent magnitude of − 4 and brighter.
Light emitted by meteors during the ablation process in the terrestrial atmosphere allows us to study, by means of spectrographs, the chemical nature of their parent bodies. Thus, the analysis of the spectrum of a given meteor can provide distinct information about the plasm, the ablation process and the chemical composition of the meteoroid (Borovička 1993, 1994a; Trigo-Rodríguez et al. 2003) and even relevant information about its parent body.
This new system for capturing spectroscopic images has been designed in order to obtain more detailed and complete emission spectra from bright bolides and meteors with higher spectral resolution when compared to video techniques. This system is the first in a series of three stations that are foreseen to be located at a minimum distance of 100 km from each other, in order to be able to calculate the atmospheric trajectory, radiant of origin and orbit of its progenitor in the solar system (Ceplecha 1987) from at least two stations, in addition to analysing the corresponding meteor spectra.
The existing spectrographic equipment we have developed is located at the Andalusian Astronomical Observatory (37°24′54″N, 3º57′12″W), a dark location at 1030 m above the sea level, in south Spain (close to the Alcalá la Real village). The equipment has been connected to a weather station that regulates the proper functioning of the spectrographs. The station allows the equipment to automatically start operating at sunset and being disconnected at sunrise on a daily basis.
We use two different spectrographs, with different optical configurations and CCD cameras, to attempt to get images with different fields of view and sensitivity for the same fireball. The combination of these images allows to capture the complete fireball phenomenon and obtain precise details thereof.
The two spectrographs have the same design, but different size. Each of them is composed by a CCD camera with a wide-field telephoto lens, a holographic diffraction grating and adequate protection against weather (Fig. 1). Both the CCDs and the lenses are different models, and thus, we have had to adopt two different settings in order to obtain two images simultaneously, with different spectral resolution each other.
To assemble all the elements that form the spectrograph, firstly, all elements were adjusted manually to obtain a precise optical focus and its stability. For each of the two spectrographs, the resulting block (CCD case + adapter + objective + grating) was then inserted inside two concentric polyvinyl chloride (PVC) tubes. These tubes are covered at their upper end with a special glass, perfectly sealed with a silicone elastomer, which allows both waterproofing and preventing temperature differences from impairing the connection joint (Fig. 1).
The spectrographs are located in an automatic enclosure system, which serves as support and protection. This system has an electromechanical device which opens or closes a sliding double roof above them (Fig. 2). The system is connected to a weather station that measures the cloud rate to close the roof and turns the system off in case of risk of rain.
The equipment is connected to two computers in which the recorded images are saved to the hard drive. Moreover, all the devices that form this system can be controlled at distance and programmed in advance.
The main elements of the spectrographs (CCD cameras, wide-field objectives and diffraction gratings, support and protection) are described below.
Two CCD cameras with different configurations have been used for each of the spectrographs. Details are listed in Table 1.
Wide-field objectives and diffraction gratings
Two different photographic lenses are used. On the one hand, a Sigma 4.5 mm f/2.8 EX DC HSM objective is attached to the Atik 314L + CCD, which provides a 120º field of view and is adapted by a male/female aluminium adapter to achieve a good focus. On the other hand, a 50 mm f/1.2 Nikon objective that provides a field of view of 15° is also attached to the Atik 11000 CCD via an adapter cap.
Facing each objective and with only a 0.67 mm maximum separation, the 1000 lines per mm holographic grating are connected over a filter adaptor, which varies in each device depending on its size. This allows for a quick and easy handling for its maintenance, given that every 6 months the grating must be replaced by a new one to obtain optimum results and prevent its deterioration (as solar radiation and temperature changes deteriorate the joint between the grating and the objective, causing its detachment).
Support and protection
Protection systems for the spectrographs have been specifically designed and created for this set of elements, as per the dimensions and needs of each device. The individual PVC protection consists of two concentric tubes whose dimensions fit the CCD and other elements that shape our device. The PVC tubes only have a 8-mm difference in diameter between them, in the case of spectrograph #1 (96/88 mm) and a 6-mm difference in spectrograph #2 (130/124 mm) as Fig. 1a shows. This lets both tubes fit inside each other and move relative to one another. They serve as fastening and anchoring for the cameras and optical systems. In the first experimental and test phase, adaptors with different height overlapping rings threaded between the CCD detector and the objective were placed to obtain the adequate focal length that would allow us to get sharp images. These elements were inserted inside two PVC tubes, which allow the whole set to be handled and moved without any relevant optical disturbances. The upper part of the tube is covered by 1-mm-thick float glass and with the same diameter as the tube, in order to correctly fit and being sealed with a special silicon cord for glass and exterior.
The last element that comprises this system is the regulated heating tape, which is connected to the upper part of the tube, surrounding the protection glass. This tape prevents frost formation as well as the condensation of water vapour (mist), both inside and outside. It has been built with a printed flexible circuit and surface mounted device (SMD) resistance, isolated with silicone and thick fabric to avoid heat loss.
Automatic enclosure (opening/closing) system (AES)
For the spectrographs to be operated in a reliable and durable way, an AES (Fig. 2) has been designed and built, which can be manipulated remotely via the Internet. The automatic module is built with a structure of 10 × 10 mm square section steel bars with electrowelded joints, which allows us to place the necessary trays and supports for the mechanical elements that give mobility to the leaning roof. As outer coating, panels of 2-mm-thick galvanized sheet have been placed in both walls and the sliding roof. The roof of the observatory has been designed with a double leaning slope whose opening and closing are done in an opposed and synchronized way (Fig. 2).
Inside, the spectrographs are placed on the supports, as well as the various devices that allow for the opening and closing of the roof. The activation of the roof of this small observatory is achieved by two 24-V electric engines, which are activated through two relays, current intensity transformers and a programmer. These electronic devices are programmed and regulated through the control computer and allow us to move the roof accordingly. This ensemble is connected to the 220 V electric current through a system of uninterrupted power source, which also allows us to control the possible oscillations in voltage and amperage that may damage the equipment. The AES controller is based on the astronomical weather station input.
Astronomical weather station
A weather station for astronomy (dubbed EMA) weather station was specifically designed to control and measure the atmospheric and sky quality parameters in order to guarantee that observations are performed in safe conditions.
The EMA weather station measures, among other parameters, the sky brightness (using a Sky Quality Meter), the speed of air (by means of an anemometer) or the cloud index (thanks to a Peltier system that measures the difference in infrared radiation between the ground and the sky), the latter being the most relevant indicator for our protection system, as we choose to close the protection if it surpasses the 70% fraction of clouds in the sky. At this point, the EMA sends a signal to the AES to close its sliding roof, while the CCDs are switched to ‘standby’ mode until the cloud cover value decreases below the threshold and the system resumes operation again.
The process that allows the correct functioning of the system (protection module, spectrographs and computers) is the following one. The ensemble is connected to the EMA of the Andalusian Astronomy Observatory, which activates the system at sunset and deactivates it at sunrise, thus allowing it to stay disconnected and the protection module to remain closed during the daytime hours. The switching on/off depends on the magnitude of sky brightness, and it is not necessary to update an astronomical clock or timer with the passage of days, since its autoregulation is autonomous (Trueblood and Russel 1985).
Daily operations begin with the aperture of the AES soon after twilight, provided the sky’s brightness value is < 12 mag/arcsec2, as these lower values would saturate the images obtained. This value drops again shortly before the sunrise, at which time the systems stop functioning and the AES closes. The computers remain on hibernation mode every day and are activated automatically at twilight, continuing to store the images into the corresponding hard drives.
The spectrographs obtain different types of images depending on their optical lens and CCDs combinations. With spectrograph #1 (the wide-field spectrograph), images of up to 250 kB providing a field of view of 120° are obtained, and with spectrograph #2 (the narrow field spectrograph), images of up to 2.2 MB providing a field of 15° are gathered, reaching limiting magnitudes of 9 and 11, respectively (when comparing to the stellar catalogue USNO-B1.0), if atmospheric conditions and seeing are optimal. Download time is 2 and 5.2 s for spectrographs #1 and #2, respectively, with optimal exposure times being 60 s for spectrograph #1 and 90 s for spectrograph #2. These times are halved during the previous and following days around the full moon phase, thus avoiding the saturation of the images to a great extent.
The data are stored in the hard drives of two computers (one for each spectrograph), so when a fireball alert is received (by e-mail) through the Spanish Meteor Network (SPMN), the images can be pinpointed by date and time. Capturing images is done with the original ARTEMI software provided by the Atik CCD manufacturer, and the data are saved in FITS format.
The image reduction process is done by subtracting the previous or following image to the image containing the fireball, with the dark and bias being subtracted with the MAXIM DL software.
The first and second orders of the spectrum are present, and in some cases, due to the brightness of the fireball, the signal corresponding to the first order can saturate during a part of its atmospheric trajectory. The CHIMET software (Madiedo et al. 2011) has been used, as it can provide valuable information of the studied objects through a synthetic spectrum. The basic procedure has been described in Trigo-Rodríguez et al. (2003).
In the case of fireballs with apparent visual magnitude of − 4 and brighter, the system can provide their low-resolution spectra, thanks to the holographic diffraction grating. A minimum integration time of 2 s is required in order to obtain high quality. Sometimes, the result obtained may not be good enough, since it also depends on the geometric position of the diffraction grating with respect to the angle of incidence of the spectral emission. The first and second orders of the spectrum may be present depending on the time and apparent magnitude of the meteor, but in some cases and due to the intense brightness of the fireball, the signal corresponding to the first order may become saturated during part of its atmospheric trajectory. For its correct analysis, it is necessary then to resort to the second order of the spectrum.
To properly obtain the spectrum, we first determine the intensity profile by comparing the pixel brightness (in arbitrary intensities) versus the number of pixels along the given direction. The spectrum is analysed and calibrated automatically in intensity and wavelength by means of the CHIMET software mentioned above (Madiedo et al. 2011), in order to identify the main wavelengths with different chemical species, such as Na, Mg, Fe, Ca or Cr. To this end, the program uses a database containing the main frequencies and typical emissions of meteor spectra. These frequencies have been taken from the NIST Atomic Spectra Database (http://physics.nit.gov/PhysRefData/ASD/lines_form.html). Thus, the software can superimpose the theoretical spectral lines with the new lines of the observed spectrum. Then, it selects some known lines of the spectrum, such as Na and Mg, and the software automatically sets the different positions of other well-known theoretical lines.
The spectra of the Alcalá la Real fireball
In this work, we have applied the above-mentioned procedure to the meteor M20160930_213851, captured by both spectrographs on 30 September 2016 at 21 h 38 m 51 s U.T. (Fig. 3). The naming convention corresponds to M for meteor, followed by the date (year YYYY, month MM, day DD) and UT time (hour HH, minute MM and seconds SS).
The video cameras of the SPMN showed that its brightness reached -7. As it was not possible to identify the origin of this meteor, it was considered to be of sporadic origin. Our analysis of its spectral lines clearly indicates the most prominent emission features due to the Na I-1 (5889 Å) and Mg I-2 (5167 Å) lines together with the Fe I-15 multiplets (5269 and 5429 Å). The numbers of the multiplets are given according to Moore (1945), with the most relevant ionized species being highlighted according to the most intense lines and peaks.
In addition, the contributions of the Fe I-41 (4404 Å) triplets, Fe I-42 (4380 Å), Cr I-1, Fe-I-43, Mn I-2 lines and the presence of Ba-I are clearly prominent in the first order of the spectrum. In the second order, the presence of the Na I-5 and Fe I-318 lines is observed in the infrared, in addition to other compounds such as N2 (Fig. 4).
On the other hand, it is worth noting the scarce presence of refractory elements such as Ca and Al, which is a common phenomenon in the case of a meteoroid with a low heliocentric velocity (Trigo-Rodríguez 2002; Trigo-Rodríguez et al. 2003). This is due to the inefficiency of providing all the available Ca or Al in its vapour phase. Thus, it was previously reported (Trigo-Rodríguez et al. 2003) that, in the chondritic meteoroids, the elements Ca and Al are associated with refractory minerals that do not complete their vaporization during the ablation phase (Trigo-Rodríguez 2002; Trigo-Rodríguez et al. 2003; Trigo-Rodríguez and Llorca 2007).
The chemical abundances of the main spectral elements of a meteor provide a more detailed information if we consider the classification of its populations (Borovička et al. 2005) and the comparison of the ratios of its chemical elements by means of ternary diagrams (Trigo-Rodríguez et al. 2003). These techniques allow us to study the nature of fireballs that are captured by our spectrographs from 2013 to 2016 and that are analysed in Espartero et al. (2017). In some cases, it has been possible to gather video images from two or more stations, which allows us to complete our work with the orbital analysis of their parent bodies, providing their radiant and most relevant parameters.
We have described the spectrographic system developed and installed in the Andalusian Astronomical Observatory and showed an example of the fireball spectra that can be analysed with it. The main conclusions are the following one:
The spectra images obtained with this method allow us to analyse fireballs with apparent magnitude of − 4 and brighter and whose trajectory, with the aforementioned brightness, lasts at least 2 s.
The spectra obtained cover the range from 3700 to 10000 Å, including the first- and second-order spectra.
The chemical abundances analysed in the Alcalá la Real fireball spectrum presented in this work indicate that it could be a sporadic object with a chondritic nature.
For the future, we aim at expanding the network of spectrographs, incorporating two new stations, at > 100 km distance each other, which will allow altogether to determine the atmospheric trajectory, the apparent radiant in the sky, and the orbit of the parent object. We also plan to use fish-eye optics for the future spectrographs, in order not to lose the fireballs that happen to occur close to the horizon. The image acquisition must be also configured alternatively in order to continuously cover the visible sky. This will ensure the full performance of these devices.
Borovička J (1993) A fireball spectrum analysis. Astron Astrophys 279:627–645
Borovička J (1994a) Line identifications in a fireball spectrum. Astron Astrophys Suppl Ser 103:83–96
Borovička J (1994b) Two components in meteor spectra. Planet Space Sci 42:145–150
Borovička J, Boček J (1995) Television spectra of meteors. Earth Moon Planet 71:237–244
Borovička J, Koten P, Spurný P, Boček J, Stork R (2005) A survey of meteor spectra and orbits: evidence for three populations of Na-free meteoroids. Icarus 174:15–30
Ceplecha Z (1971) Spectral data on terminal flare and wake of double-station meteor No. 38421 (Ondrejov, April 21, 1963). Bull Astron Inst Czechoslov 22:219–304
Ceplecha Z (1987) Geometric, dynamic, orbital and photometric data on meteoroids form photographic fireball networks. Bull Astron Inst Czechoslov 38:222–234
Ceplecha Z, Borovička J, Elford WG et al (1988) Meteor phenomena and bodies. Space Sci Rev 84:327–471
Espartero FA, Madiedo JM (2016) The Norterm ω-scorpiid meteoroid stream: orbits and emission spectra. Earth Moon Planet 118:81–89
Espartero FA et al (2018) In preparation
Halliday I (1961) A study of spectral line identifications in Perseids meteor spectra. Publications of the Dominion Observatory, Ottawa
Hemenway CL, Swider A, Bowman C (1971) Meteor spectroscopy using an image orthicon. Can J Phys 49:1361–1364
Madiedo JM, Toscano FM, Trigo-Rodríguez JM (2011) Software tools for the analysis of video meteors emission spectra. In: Abstracts of the EPSC-DPS joint meeting 2011, Nantes, pp 2–7
Madiedo JM, Espartero F, Trigo-Rodríguez JM, Castro-Tirado AJ, Pujols P, Pastor S, De los Reyes JA, Rodríguez D (2016) Observations of the Quadrantid meteor shower from 2008 to 2012: orbits and emission spectra. Icarus 275:193–202
Millman PM (1963) A general survey of meteor spectra. Smithson Contrib Astrophys 7:119–127
Millman PM (1980) One hundred and fifteen years of meteor spectra spectroscopy. In: Halliday I, McIntosh BA (eds) IAU Symposium on solid particles in the solar system, vol 90. Reidel, Dordrecht, pp 121–128
Millman PM, Clifton KS (1975) SEC Vidicon spectra of Geminid meteors, 1972. Can J Phys 53:1939–1947
Moore CE (1945) A multiplet tablet of astrophysical interest. Contrib Princet Obs 20:1–110
Trigo-Rodríguez JM (2002) Spectroscopic analysis of cometary and asteroidal fragments during their entry into the terrestrial atmosphere, Ph.D. thesis, University of Valencia, Spain (In Spanish)
Trigo-Rodríguez JM, Llorca J (2007) Erratum: the strength of cometary meteoroids: clues to the structure and evolution of comets. MNRAS 375:415
Trigo-Rodríguez JM, Llorca J, Borovička J, Fabregat J (2003) Chemical abundances determined form meteor spectra- I: ratios of the main chemical elements. Meteorit Planet Sci 38:1283–1294
Trueblood M, Russel G (1985) Microcomputer control of telescopes. Editions Willmann-Bell, Inc., Richmond
Zender J, Koschny D, Witasse O, et al (2004) Video intensified camera setup of visual and meteor spectroscopy. In: Proceedings the international meteor conference on 22nd IMC, Bollmannsruh, Germany, pp 163–167
Espartero performed the instrumentation set-up and data analysis and drafted the manuscript. Martínez, Frias and Montes participated in designing the instrumentation and helped draft the manuscript. Castro-Tirado participated in designing the study and interpreting the results, and helped draft the manuscript. All authors read and approved the final manuscript.
We thanks the support of the M.I. Ayuntamiento de Alcalá la Real, the Diputación de Jaén, the Spanish Meteor Network (SPMN) and the Spanish Ministry through Project AYA 2015-71718-R (including FEDER funds). We thank A. Castellón (University of Málaga) for fruitful discussions. We also acknowledge the useful comments from the referees, as they have helped to significantly improve this manuscript.
The authors declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Cite this article
Espartero, F.Á., Martínez, G., Frías, M. et al. Autonomous spectrographic system to analyse the main elements of fireballs and meteors. Earth Planets Space 70, 2 (2018). https://doi.org/10.1186/s40623-017-0768-2 | 0.833742 | 3.243953 |
Comet ISON to fly by Mars
August 23, 2013: Around the world, astronomers are buzzing with anticipation over the approach of Comet ISON. On Thanksgiving Day 2013, the icy visitor from the outer solar system will skim the sun's outer atmosphere and, if it survives, could emerge as one of the brightest comets in years.
First, though, it has to fly by Mars.
"Comet ISON is paying a visit to the Red Planet," says astronomer Carey Lisse of the Johns Hopkins University Applied Physics Lab. "On Oct 1st, the comet will pass within 0.07 AU from Mars, about six times closer than it will ever come to Earth."
Mars rovers and satellites will get a close-up view. It’s too early to say whether Curiosity will be able to see the comet from the surface of Mars—that depends on how much ISON brightens between now and then. Lisse says the best bet is NASA’s Mars Reconnaissance Orbiter. The MRO satellite is equipped with a powerful half-meter telescope named HiRISE that is more than capable of detecting the comet’s atmosphere and tail. Observations are planned on four dates: August 20th, Sept 29th, and Oct 1st and 2nd.
HiRISE wasn't sent to Mars to do astronomy, notes the telescope’s principal investigator Alfred McEwen of the University of Arizona. "The camera is designed for rapid imaging of Mars. Our maximum exposure time is limited compared to detectors on other space telescopes. This is a major limitation for imaging comets. Nevertheless, I think we will detect Comet ISON."
The Mars flyby comes at a key time in Comet ISON’s journey. It will have just crossed the "frost line," a place just outside the orbit of Mars where solar heating is enough to start vaporizing frozen water.
"The volatiles in a comet are 80% to 90% water ice," notes Lisse. "Right now in August almost all the water is still frozen, and the outgassing we see in ISON is driven by carbon dioxide and other lesser constituents. Probably only isolated patches of the comet's nucleus are active."
But when ISON crosses the frost line, "the whole comet could erupt in geysers of gas," says Lisse. "Mars orbiters will have a ringside seat."
The amount of outgassing at Mars will give researchers clues to the size of ISON’s nucleus, which is hidden from view deep within the comet’s dusty atmosphere.
"If ISON's nucleus is much bigger than 0.5 km, it will probably survive its Thanksgiving Day brush with the sun," says Lisse. "It could turn into one of the most spectacular comets in many years."
McEwen sees this as a tune-up for another comet encounter next year. "The science value of observing Comet ISON is hard to predict. We've never tried such a thing before. However, this is good practice for Comet Siding Spring, which will pass much closer to Mars in 2014."
For now all eyes are on Comet ISON. An unprecedented number of NASA spacecraft - 16 - will be observing the comet. Astronauts on board the International Space Station will be watching, too.
Meanwhile back on Earth, Lisse is working with NASA to organize a worldwide observing campaign for Comet ISON. "Our goal is to have every telescope on Earth pointed at the comet when it emerges from the sun," says Lisse. "The Mars flyby will give us a sneak preview, providing data we need to predict what we might see."
Comet of the Century? -- ScienceCast video
Comet ISON Meteor Shower -- ScienceCast video
Collision Course? A Comet Heads for Mars -- ScienceCast video
NASA Comet ISON Observing Campaign -- get involved! | 0.832149 | 3.69348 |
This year is the 60th anniversary of the Space Age, which has already seen many giant leaps for humanity. We've gone from Sputnik to space stations to Pluto probes in one human lifetime, unleashing a galaxy of science and technology in the process.
Unfortunately, we've also unleashed a galaxy of garbage. Our trash already accumulates in remote earthly locations from Midway Atoll to Mount Everest, but like many frontiers before it, Earth's exosphere is increasingly cluttered, too. Hopefully the same ingenuity that helped us reach space can still help us clean it up, too.
Waste in space
Earth's orbital environment contains about 20,000 pieces of human-made debris larger than a softball, 500,000 pieces larger than a marble and millions of others that are too small to be tracked. (Image: ESA)
Commonly known as space junk, this orbital trash mainly consists of old satellites, rockets and their broken parts. Millions of pieces of human-made debris are currently hurtling through space overhead, moving at speeds of up to 17,500 mph. Because they're whizzing by so quickly, even a tiny piece of space junk could cause catastrophic damage if it collides with a satellite or spacecraft.
But the space around Earth is too important for us to let ourselves ruin it with garbage. Satellites alone are key to services like GPS, weather forecasting and communication, plus we need to safely pass through this region for bigger-picture missions into deeper space. It's obvious we need to remove space junk, but for a place that's already a vacuum, space can be surprisingly hard to clean up.
Even just figuring out how to grab a piece of space junk is tricky. The first rule is to avoid making more space junk, which can easily happen when pieces collide, so it's helpful for any junk-collecting spacecraft to keep a safe distance from its target. That may mean using some kind of tether, net or robotic arm to do the actual corralling.
Suction cups don't work in a vacuum, and the extreme temperatures in space can render many adhesive chemicals useless. Harpoons rely on high-speed impact, which could chip off new debris or push an object in the wrong direction. Yet the situation isn't hopeless, as some recently proposed ideas suggest.
A magnetic, tugboat-esque chaser satellite would corral derelict satellites by targeting electromagnetic components known as 'magnetorquers,' which use Earth's magnetic field to adjust satellites' orientation. (Image: Emilien Fabacher/ISAE-Supaero)
The European Space Agency (ESA), which actively tracks space debris, supports an array of debris-fighting projects under its Clean Space program. The ESA also announced funding for an idea developed by researcher Emilien Fabacher of the Institut Supérieur de l'Aéronautique et de l’Espace (ISAE-SUPAERO), at the University of Toulouse in France.
Fabacher's idea is to collect space junk from a distance, but not with a net, harpoon or robotic arm. Instead, he hopes to reel it in without even touching it.
"With a satellite you want to deorbit, it's much better if you can stay at a safe distance, without needing to come into direct contact and risking damage to both chaser and target satellites," Fabacher explains in a statement from the ESA. "So the idea I'm investigating is to apply magnetic forces either to attract or repel the target satellite, to shift its orbit or deorbit it entirely."
Target satellites wouldn't need to be specially equipped in advance, he adds, since these magnetic tugboats could take advantage of electromagnetic components, known as "magnetorquers," that help many satellites adjust their orientation. "These are standard issue aboard many low-orbiting satellites," Fabacher says.
This isn't the first concept to involve magnetism. Japan's space agency (JAXA) tested a different magnet-based idea, a 2,300-foot electrodynamic tether extended from a cargo spacecraft. That test failed, but it failed because the tether didn't release, not necessarily due to a flaw in the idea itself.
Still, magnets can only do so much about space junk. Fabacher's idea is mainly focused on removing entire derelict satellites from orbit, since many smaller pieces are too tiny or non-metallic to be reined in with magnets. That's still valuable, though, since one large piece of space junk can quickly become many pieces if it collides with something. Plus, the ESA adds, this principle could also have other applications, like using magnetism to help clusters of small satellites fly in precise formation.
Grabby gecko bots
Another clever idea for collecting space junk comes from Stanford University, where researchers worked with NASA's Jet Propulsion Laboratory (JPL) to design a new kind of robotic gripper that can grab and dispose of debris. Published in the journal Science Robotics, their idea takes its inspiration from sticky-fingered lizards.
"What we've developed is a gripper that uses gecko-inspired adhesives," says senior author Mark Cutkosky, a professor of mechanical engineering at Stanford, in a statement. "It's an outgrowth of work we started about 10 years ago on climbing robots that used adhesives inspired by how geckos stick to walls."
Geckos can climb walls because their toes have microscopic flaps that create something called "van der Waals forces" when in full contact with a surface. These are weak intermolecular forces, created by subtle differences among electrons on the outsides of molecules, and thus work differently from traditional "sticky" adhesives.
The gecko-based gripper isn't as intricate as a real gecko's foot, the researchers acknowledge; its flaps are about 40 micrometers across, compared with just 200 nanometers on an actual gecko. It uses the same principle, though, adhering to a surface only if the flaps are aligned in a specific direction — yet also needing only a light push in the right direction to make it stick.
"If I came in and tried to push a pressure-sensitive adhesive onto a floating object, it would drift away," says co-author Elliot Hawkes, an assistant professor from the University of California, Santa Barbara. "Instead, I can touch the adhesive pads very gently to a floating object, squeeze the pads toward each other so that they’re locked and then I'm able to move the object around."
The new gripper can also tailor its collection method to the object at hand. It has a grid of adhesive squares on the front, plus adhesive strips on moveable arms that let it grab debris "as though it's offering a hug." The grid can stick to flat objects like solar panels, while the arms can help with more curved targets like the body of a rocket.
The team has already tested its gripper in zero gravity, both on a parabolic airplane flight and on the International Space Station. Since those tests went well, the next step is to see how the gripper fares outside the space station.
These are just two of many proposals for cleaning up low-Earth orbit, joined by other tactics like lasers, harpoons and sails. That's good, because the threat of space junk is big and diverse enough that we may need several different approaches.
And, as we should have already learned here on Earth, no giant leap forward is really complete without a few small steps back to clean up after ourselves. | 0.82161 | 3.570567 |
As we all know, the tide is mainly caused by the lunar gravity, and the tide is best on the edge of the river, the big river, the big lake and the sea. Does it mean that the gravity of the moon can only affect these large bodies of water? How much water will respond to the attraction of lunar gravity?
In fact, every water molecule on the earth is affected by the gravity of the moon, no matter how many water molecules around it. However, the gravity of the moon is very weak for each water molecule, and it is often overwhelmed by other short-range forces, such as the interaction between molecules. Only when there are enough water molecules, the effect of lunar gravity can be observed.
Lake Superior in North America is the third largest freshwater lake in the world. Its volume is about 11,600 cubic meters. In such a large body of water, the tide caused by lunar gravity is about 2 cm high. Tidal waves smaller than this are difficult to measure because they are often affected by weather conditions and river flows.
Biometrics is a technology that recognizes you. If you compare a person to a computer, biometrics is a password, and you can access the computer by entering the correct password. The biometric technology that we are generally familiar with is DNA identification. DNA identification seems to be very accurate, but in fact, only a small part of DNA is detected every time DNA is identified, and in this process, the sample DNA is likely to be contaminated. So DNA identification is not as accurate as imagined.
So what is the most accurate biometric technology? Is the tone, signature, fingerprint identification? Is the shape of the retina, iris, and ear identified? No, the most accurate biometrics are often superimposed in several ways, such as DNA identification and retinal and fingerprint identification. Because others may have the same retina, the same ear shape as you, but the chances of having the same DNA and the same fingerprint as you are very small. Therefore, several identifications at the same time can achieve the most accurate biometric identification.
With a command, ignition, the rocket rose in the roar, with a dazzling light group slammed into the sky, after a while, about 100 seconds, you can see several spots out of the light group, falling down These light spots that fall down are the rocket’s boosters.
The Rocket Booster is a power unit that provides additional thrust during the take-off and climb of the rocket. It is usually tied to the first stage of a multi-stage rocket. There are two types of liquid rocket boosters and solid rocket boosters. For the booster, boosting the rocket into a sky is like a skydiving. When the rocket reaches a certain height, the rocket booster can retire, get out of the rocket, and then fall. Boosters that leave the rocket will fall back to Earth, some fall into the sea, and some fall to the ground, and then there will be special personnel to recycle them.
Today, SpaceX’s heavy rocket rocket booster can “go home”. The booster will be equipped with a “homing control system” that can be landed in a designated area by means of automatic control or ground control.
The answer to this question is: Because the celestial body is almost impossible to run along a perfect orbit, it can only run along an elliptical orbit. The orbit of the celestial body is actually the result of gravity and the tendency of the celestial bodies to move along the line. If the two can reach equilibrium, they will get a perfect orbit. In other words, the planet can only make a standard circular motion when the speed of the planet just reaches a certain value and the direction of the speed and the line are strictly perpendicular. If there is a slight deviation, the trajectory of the planet will become elliptical. But this situation is almost non-existent, at least at present, scientists have not found celestial bodies running along a perfect orbit.
Moreover, the quality of the celestial body is not static. In the process of mass change, the gravitation will change accordingly. Under such circumstances, if a certain celestial body has reached the condition of forming a perfect circular orbit at a certain moment, it will be very It is quickly broken and eventually runs along an elliptical orbit. The elliptical orbit is the most stable orbit of the celestial body.
The answer is yes, humans can stop asteroids from hitting the Earth, but the process is difficult.
Perhaps you think that the way to stop the planet from impacting an asteroid is to break the asteroid and disintegrate the large asteroid into a meteor. But in fact, this method is not the first choice. In addition to the huge energy required to crush the asteroid, the broken asteroid may be very large, and it will be dangerous after it has entered the earth. Therefore, the best way is to get the asteroid out of the established orbit and not hit the Earth.
The method proposed by scientists is to use a space detector to launch an object with a certain weight to separate the asteroid from the given orbit, similar to playing billiards. In addition to the impact method, scientists have proposed to place a large airship directly in the orbit of the asteroid. The mutual attraction between the two flying objects will create a new orbit, which will make the asteroid deviate from the original flight path. So as to avoid it hitting the earth.
However, in either case, it takes about five years to prepare, so it is important to observe and monitor the asteroids that may hit the Earth. | 0.850595 | 3.358704 |
One of the big differences between Hubble’s first and latest image of Comet ISON is its jet – or lack thereof. In Hubble’s April image, computer modeling showed a jet streaming away from the comet’s nucleus. In the October image, that jet seems to have vanished.
Where did it go? Well, first let’s talk about why it was there to begin with.
The surface of a comet’s nucleus isn’t smooth. It’s porous and uneven. Because of this structure, the surface area doesn’t warm up equally, and the comet’s ice vaporizes unevenly. The Sun heats the frozen carbon dioxide beneath the surface of the nucleus, changing it directly into a gas, a process known as sublimation. The heated gas wants to expand and escape, and it picks a weak spot in the surface of the comet to break forth.
Gas and dust bursts forth like a geyser – in fact, even the dynamics are somewhat similar: An area below the surface warms up and punches through the surface with explosive force due to its gas content. In comets, the emerging gas carries a stream of dust along with it, instead of the water you would see with a geyser. | 0.807111 | 3.513098 |
Our sun appears to be a typical star: unremarkable in age, composition, galactic orbit, or even in its possession of many planets. Billions of other stars in the milky way have similar general parameters and orbits that place them in the galactic habitable zone. Extrapolations of recent expolanet surveys reveal that most stars have planets, removing yet another potential unique dimension for a great filter in the past.
According to Google, there are 20 billion earth like planets in the Galaxy.
A paradox indicates a flaw in our reasoning or our knowledge, which upon resolution, may cause some large update in our beliefs.
Ideally we could resolve this through massive multiscale monte carlo computer simulations to approximate Solonomoff Induction on our current observational data. If we survive and create superintelligence, we will probably do just that.
In the meantime, we are limited to constrained simulations, fermi estimates, and other shortcuts to approximate the ideal bayesian inference.
While there is still obvious uncertainty concerning the likelihood of the series of transitions along the path from the formation of an earth-like planet around a sol-like star up to an early tech civilization, the general direction of the recent evidence flow favours a strong Mediocrity Principle.
Here are a few highlight developments from the last few decades relating to an early filter:
- The time window between formation of earth and earliest life has been narrowed to a brief interval. Panspermia has also gained ground, with some recent complexity arguments favoring a common origin of life at 9 billion yrs ago.
- Discovery of various extremophiles indicate life is robust to a wider range of environments than the norm on earth today.
- Advances in neuroscience and studies of animal intelligence lead to the conclusion that the human brain is not nearly as unique as once thought. It is just an ordinary scaled up primate brain, with a cortex enlarged to 4x the size of a chimpanzee. Elephants and some cetaceans have similar cortical neuron counts to the chimpanzee, and demonstrate similar or greater levels of intelligence in terms of rituals, problem solving, tool use, communication, and even understanding rudimentary human language. Elephants, cetaceans, and primates are widely separated lineages, indicating robustness and inevitability in the evolution of intelligence.
When modelling the future development of civilization, we must recognize that the future is a vast cloud of uncertainty compared to the past. The best approach is to focus on the most key general features of future postbiological civilizations, categorize the full space of models, and then update on our observations to determine what ranges of the parameter space are excluded and which regions remain open.
An abridged taxonomy of future civilization trajectories :
Civilization is wiped out due to an existential catastrophe that sterilizes the planet sufficient enough to kill most large multicellular organisms, essentially resetting the evolutionary clock by a billion years. Given the potential dangers of nanotech/AI/nuclear weapons - and then aliens, I believe this possibility is significant - ie in the 1% to 50% range.
This is the old-skool sci-fi scenario. Humans or our biological descendants expand into space. AI is developed but limited to human intelligence, like CP30. No or limited uploading.
This leads eventually to slow colonization, terraforming, perhaps eventually dyson spheres etc.
This scenario is almost not worth mentioning: prior < 1%. Unfortunately SETI in current form is till predicated on a world model that assigns a high prior to these futures.
PostBiological Warm-tech AI Civilization:
This is Kurzweil/Moravec's sci-fi scenario. Humans become postbiological, merging with AI through uploading. We become a computational civilization that then spreads out some fraction of the speed of light to turn the galaxy into computronium. This particular scenario is based on the assumption that energy is a key constraint, and that civilizations are essentially stellavores which harvest the energy of stars.
One of the very few reasonable assumptions we can make about any superintelligent postbiological civilization is that higher intelligence involves increased computational efficiency. Advanced civs will upgrade into physical configurations that maximize computation capabilities given the local resources.
Thus to understand the physical form of future civs, we need to understand the physical limits of computation.
One key constraint is the Landauer Limit, which states that the erasure (or cloning) of one bit of information requires a minimum of kTln2 joules. At room temperature (293 K), this corresponds to a minimum of 0.017 eV to erase one bit. Minimum is however the keyword here, as according to the principle, the probability of the erasure succeeding is only 50% at the limit. Reliable erasure requires some multiple of the minimal expenditure - a reasonable estimate being about 100kT or 1eV as the minimum for bit erasures at today's levels of reliability.
Now, the second key consideration is that Landauer's Limit does not include the cost of interconnect, which is already now dominating the energy cost in modern computing. Just moving bits around dissipates energy.
Moore's Law is approaching its asymptotic end in a decade or so due to these hard physical energy constraints and the related miniaturization limits.
I assign a prior to the warm-tech scenario that is about the same as my estimate of the probability that the more advanced cold-tech (reversible quantum computing, described next) is impossible: < 10%.
From Warm-tech to Cold-tech
There is a way forward to vastly increased energy efficiency, but it requires reversible computing (to increase the ratio of computations per bit erasures), and full superconducting to reduce the interconnect loss down to near zero.
The path to enormously more powerful computational systems necessarily involves transitioning to very low temperatures, and the lower the better, for several key reasons:
- There is the obvious immediate gain that one gets from lowering the cost of bit erasures: a bit erasure at room temperature costs 100 times more than a bit erasure at the cosmic background temperature, and a hundred thousand times more than an erasure at 0.01K (the current achievable limit for large objects)
- Low temperatures are required for most superconducting materials regardless.
- The delicate coherence required for practical quantum computation requires or works best at ultra low temperatures.
Assuming large scale quantum computing is possible, then the ultimate computer is thus a reversible massively entangled quantum device operating at absolute zero. Unfortunately, such a device would be delicate to a degree that is hard to imagine - even a single misplaced high energy particle could cause enormous damage.
Stellar Escape Trajectories
The Great Game
If two civs both discover each other's locations around the same time, then MAD (mutually assured destruction) dynamics takeover and cooperation has stronger benefits. The vast distances involve suggest that one sided discoveries are more likely.
Spheres of Influence
Conditioning on our Observational Data
Observational Selection Effects
All advanced civs will have strong instrumental reasons to employ deep simulations to understand and model developmental trajectories for the galaxy as a whole and for civilizations in particular. A very likely consequence is the production of large numbers of simulated conscious observers, ala the Simulation Argument. Universes with the more advanced low temperature reversible/quantum computing civilizations will tend to produce many more simulated observer moments and are thus intrinsically more likely than one would otherwise expect - perhaps massively so.
We estimate that there may be up to ∼ 10^5 compact objects in the mass range 10^−8 to 10^−2M⊙per main sequence star that are unbound to a host star in the Galaxy. We refer to these objects asnomads; in the literature a subset of these are sometimes called free-floating or rogue planets.
Although the error range is still large, it appears that free floating planets outnumber planets bound to stars, and perhaps by a rather large margin.
Assuming the galaxy is colonized: It could be that rogue planets form naturally outside of stars and then are colonized. It could be they form around stars and then are ejected naturally (and colonized). Artificial ejection - even if true - may be a rare event. Or not. But at least a few of these options could potentially be differentiated with future observations - for example if we find an interesting discrepancy in the rogue planet distribution predicted by simulations (which obviously do not yet include aliens!) and actual observations.
Also: if rogue planets outnumber stars by a large margin, then it follows that rogue planet flybys are more common in proportion.
SETI to date allows us to exclude some regions of the parameter space for alien civs, but the regions excluded correspond to low prior probability models anyway, based on the postbiological perspective on the future of life. The most interesting regions of the parameter space probably involve advanced stealthy aliens in the form of small compact cold objects floating in the interstellar medium.
The upcoming WFIST telescope should shed more light on dark matter and enhance our microlensing detection abilities significantly. Sadly, it's planned launch date isn't until 2024. Space development is slow. | 0.865628 | 3.603148 |
Atmospheric Optical phenomena are caused when light from the Sun or Moon interacts with elements in the air or atmosphere, and an observer detects the light after it has interacted with those elements. Often, the light emitted by the Sun or Moon will be scattered, reflected or refracted by the elements before it reaches the observer’s eyes.
Some of these events can easily fall into other categories, such as rainbows.
Large, beautiful circles that appear around the Sun or Moon if the right conditions are present in the atmosphere. Light from the Sun and Moon can be refracted off of ice crystals at high altitudes if the crystals are present, and then detected by the eye.
Alpenglow is a phenomenon that is very similar to the Belt of Venus, and occurs just after sunset. The term was coined because the pink light that appears in the sky, opposite of the sunset, gives mountains a pinkish “glow”.
Resulting from solar particles entering Earth’s atmosphere near the north and south poles, these beautiful phenomena can typically only been seen near the arctic circles.
A pink or red band that sits approximately 10 degrees above the eastern horizon right after the Sun sets in the west, or 10 degrees above the western horizon before Sun rises in the east. The pink band rests on top of a darker grey or blue band which is the Earth’s shadow.
5. Crepuscular Rays
Large rays of sunlight in the sky that appear to meet or converge at the Sun from an observer’s perspective. These rays of sunlight are actually parallel, but they appear to come together due to the long distances between the observer, the horizon and the Sun.
An almost mythical phenomena that results when green in the light spectrum is refracted in the atmosphere as the Sun sets or rises. It lasts only seconds, and those who see it are said to be lucky.
Zodiacal light is a faint light reflected off of planets, dust and asteroid in our solar system. As these objects all lie on the same, flat plane (the ecliptic plane), the light reflected off of them can be seen under special circumstances. This phenomenon is similar to the way dust and stars in the Milky Way create a beautiful band across a dark, nighttime sky. | 0.819738 | 3.464625 |
The combined coronagraph and wavefront control system is characterized by the contrast, inner working angle, and stability achieved. Contrast is the degree to which the instrument can suppress scattered and diffracted starlight in order to reveal a faint companion. Inner Working Angle (IWA) is the smallest angle on the sky at which it can reach its designed contrast. This angle is typically only a few times larger than the theoretical diffraction limit of the telescope. The resulting residual stellar halo must also be stable over the time scale of an observation, so that the halo can be subtracted to reveal an exoplanet or disk.
In principle, with a well-characterized and stable point spread function, various subtraction methods that have been developed and used on both ground and space images can be employed to average the background photon noise and extract faint planets that are below the raw contrast level. The recent history of planet imaging shows that recovering planets with up to factors of 10 fainter contrast than the background is regularly accomplished, both on large ground telescopes and from the Hubble Space Telescope. We thus characterize the coronagraph instrument by its detection limit, that is, the limiting magnitude of a recoverable planet relative to the star from the combination of the coronagraph and wavefront control and data processing.
Only a handful of exoplanets have been imaged to date from the ground and with the Hubble Space Telescope. We have obtained spectra on an even smaller number. All of them are gas giants more massive than Jupiter that reside at great distances (> 10 AU) from their parent stars. Additionally, observational biases have restricted those detections to very young planets — typically less than a hundred million years — that shine brightly at infrared wavelengths through their interior heat. This warm phase constitutes only a small fraction of a planet’s lifetime immediately following its formation. Therefore, the far more numerous population of mature, evolved planets has eluded the current generation of high-contrast imaging instruments. WFIRST provides the first opportunity to observe and characterize planets physically resembling those in our Solar System, spanning ages up to several billion years. The coronagraph on WFIRST will operate in visible wavelengths at flux ratios down to a few parts per billion and an inner working angle of less than 0.2 arcseconds. It will be capable of imaging a dozen known radial velocity planets in reflected starlight at orbital separations ranging from 2 to 10 AU.
Spectroscopic observations of directly imaged exoplanets are challenging, partly due to the extremely low irradiances of planets observed in reflected starlight. Nevertheless, because exoplanet characterization is the chief scientific motivation for advancing high-contrast imaging technology, the WFIRST Coronagraph Instrument is designed to include a modest spectroscopy capability. The prism spectroscopy mode on CGI will disperse the point spread function of an individual exoplanet over the wavelength range 675—785 nm with a spectral resolving power of l/Dl³50. For Jupiter-sized planets with flux ratios in the detection range of CGI, this spectroscopy mode will measure the shape and depth of the methane absorption feature at 720 nm. In conjunction with atmosphere modeling, such observations can place rudimentary constraints on methane gas abundances and cloud properties.
The coronagraph will also be sensitive to debris disks with a few times the solar system's level of dust in the habitable zones of nearby (~10 pc) sun-like stars. The high sensitivity and spatial resolution (0.05 arcsec is 0.5 AU at 10 pc) of WFIRST CGI images will map the structure of these disks, revealing asymmetries, belts, and potentially gaps due to unseen planets. CGI will make the most sensitive measurements yet of the amount of dust in or near the habitable zones of nearby stars. This is important for assessing the difficulty of imaging Earth-like planets with future missions as well as for understanding nearby planetary systems. | 0.872861 | 4.049842 |
Cassini reveals oxygen atmosphere of Saturn's moon Rhea
26 November 2010
A fragile atmosphere infused with oxygen and carbon-dioxide has been discovered at Saturn's moon Rhea by the Cassini-Huygens mission - the first time a spacecraft has captured direct evidence of an oxygen atmosphere at a world other than Earth.
The NASA-led international mission made the discovery using combined data from Cassini's instruments, which includes a sensor designed and built at UCL's (University College London) Mullard Space Science Laboratory.
today in Science Express, results from the mission reveal that the atmosphere
of Rhea, Saturn's second largest moon at 1500 km wide, is extremely thin and is
sustained by high energy particles bombarding its icy surface and kicking up
atoms, molecules and ions into the atmosphere.
The density of oxygen is probably about 5 trillion times less dense than in Earth's atmosphere. However, the formation of oxygen and carbon dioxide could possibly drive complex chemistry on the surfaces of many icy bodies in the universe.
"The new results suggest that active, complex chemistry involving oxygen may be quite common throughout the solar system and even our universe," said Dr Ben Teolis, a Cassini team scientist based at Southwest Research Institute in San Antonio and lead author. "Such chemistry could be a pre-requisite for life. All evidence from Cassini indicates Rhea is too cold and devoid of the liquid water necessary for life as we know it."
Dr Geraint Jones, from the UCL Mullard Space Science Laboratory and a co-author of the paper said: "The discovery of this tenuous atmosphere provides key information on how radiation can drive chemistry on icy surfaces throughout the universe."
Rhea's tenuous atmosphere makes it unique in the Saturn system. Titan has a very thick nitrogen-methane atmosphere, with very little carbon dioxide and oxygen.
UCL's Mullard Space Science Laboratory, supported by the Science and Technology Facilities Council, led the design and building of the electron spectrometer of the Cassini plasma spectrometer (CAPS), which detected negative ions streaming off Rhea's surface in 2005. Another part of CAPS detected positive ions on the opposite side of Rhea in 2005 and 2007. Completing the picture of Rhea's atmosphere, Cassini's ion and neutral mass spectrometer detected neutral particles when Cassini swept within 100 km of the moon's surface in March 2010.
Professor Andrew Coates, also from the UCL Mullard Space Science Laboratory and co-author of the paper, said: "Our instrument turns out to be a fabulous detector of negative ions as well as electrons. We've already found negative ions are important at Titan and Enceladus - and now, tracing back the trajectory of these ions really pinpoints the source of the atmosphere near Rhea's surface."
The ion and neutral mass spectrometer "tasted" peak densities of oxygen of around 50 billion molecules per cubic meter (1 billion molecules per cubic foot). It detected peak densities of carbon dioxide around 20 billion molecules per cubic meter (about 600 million molecules per cubic foot). The plasma spectrometer also saw clear signatures of flowing streams of positive and negative ions, with masses that corresponded to ions of oxygen and carbon dioxide.
"Rhea's oxygen appears to come from water ice on Rhea's surface when Saturn's magnetic field rotates over the moon and showers it with energetic particles trapped in the magnetic field," said Professor Coates.
The carbon dioxide may be the result of "dry ice" trapped from the primordial solar nebula, similar to the case of comets, or it may be due to similar irradiation processes operating on the organic molecules trapped in the water ice of Rhea. The carbon dioxide could also come from carbon-rich materials deposited by tiny meteors that bombarded Rhea's surface.
The finding is consistent with earlier Cassini results that show Rhea to be a particularly dark-looking moon, sporting some carbon-based coating on its surface.
Media contact: Clare Ryan
UCL Mullard Space Science Laboratory delivers a cutting-edge science programme,
underpinned by a capability in space science instrumentation, systems
engineering and project management. Its staff are committed to a broad outreach
programme and are very happy to receive enquiries from the public and fellow
space science professionals alike. | 0.828928 | 3.909481 |
The life cycle of stars
Physics Narrative for 11-14
Stars are not unchanging objects – they don't last for ever. They are born, evolve and die.
The life of a typical star starts when a giant gas cloud begins to collapse under its own gravitational attraction. As the particles and atoms fall towards each other, they speed up and their temperature rises.
Eventually, the temperature becomes sufficient for the forming star to begin radiating visible light at the red end of the spectrum, and so the new star appears as a large, bright, red object. This phase is relatively short (in astronomical terms) and generally lasts less than 1000 million years.
The star soon settles into a stable part of its life during which it converts hydrogen to helium by nuclear fusion. What happens next depends on the mass of the star, being different for low mass stars (like our Sun) as compared with more massive stars like Sirius, the brightest star in the sky, or Betelgeuse, a super giant star in the constellation Orion.
Low and high mass stars
Low mass stars use up all of their hydrogen over several thousand million years, converting it to helium. This results in the core of the star collapsing in on itself, the internal temperature increases and the star
burns the helium. When this cycle is finished, it is followed by a similar cycle with the heavier elements such as carbon and oxygen. The incredibly high temperatures which are generated at the core of the star (of the order of 120 million degrees Celsius) cause the outer layers to expand and cool and the star becomes a red giant. In the case of the Sun, this will lead to it swallowing up Mercury and Venus, and the Earth will become much too hot to live on. Having now used up all of its
fuel, the star collapses to become a very hot, but small, white dwarf star.
yellow dwarf → red giant → white dwarf
Stars of greater mass go through the same cycle initially as smaller stars, apart from the fact that they run at higher internal temperatures leading to a more rapid exhaustion of hydrogen. They then begin to go through the stages of burning helium and carbon to form a red supergiant. Ultimately, the star's nuclear fuel is exhausted and it becomes unstable as there is no energy source to prevent the core collapsing under the force of gravity.
As it does so, a huge amount of energy is released and the star explodes. This is called a supernova and happens very rapidly (in a matter of weeks). The explosion blasts the outer layers of the star off into interstellar space.
The inner remnants of the supernova continue to collapse in on themselves. Protons are converted into neutrons, causing the matter to become increasingly neutron rich, and in some cases a neutron star is formed (a neutron star is thought not to consist of neutrons alone, even though they are believed to account for most of the mass). While this is happening the density increases to such an extent that a matchbox-full of the matter would have a mass of about one million tons.
Rapidly rotating neutron stars can be observed many years later as radio pulsars. The outer remnants of the supernova explosion ultimately produce nebulae – masses of cloud and dust found in the Milky Way.
In the case of stars with a mass greater than about eight solar masses (this is not a definite figure), the collapse continues to the point where the matter is so dense that even light cannot escape and a black hole is created.
blue supergiant → red supergiant → supernova → neutron star or black hole
Why will the Sun not last forever?
The Sun is a finite source of energy. It is depleting its energy stores at the rate of approximately 3.8 × 1026 joule / second.
To put this figure into context, this is equivalent to the output from 380 000 million, million power stations.
Clearly the energy source is not some large coal fire; the Sun produces this energy by the fusion of hydrogen nuclei to make deuterium, followed by further reactions to make helium nuclei. During this process there is a reduction in mass and the release of an equivalent amount of energy as the nuclear store is depleted.
As a result, the Sun is losing around 4 million tons of mass a second. Of course, this is not sustainable in the long term, and models of the Sun's behaviour suggest that it is halfway through its lifetime of 10 000 million years. | 0.841522 | 3.931715 |
For years scientists have seen Saturn's rings as stable and slow to evolve—beautiful but, well, a bit boring. Not anymore.
The most detailed imagery of the rings yet is giving a very different and dynamic feel to the orbiting bands of ice chunks, according to two new studies in this week's issue of the journal Science.
By imaging the rings close up, in many wavelengths, and with unprecedented frequency, NASA's Cassini orbiter has revealed a slew of surprises. Among them are rings that rapidly rearrange themselves, high-speed collisions—not to mention an oxygen atmosphere.
(See Saturn pictures.)
"Here's this giant crystalline structure, stretching two-thirds of the distance from Earth to the moon, and yet parts of it change on a monthly or weekly time scale," said planetary scientist Jeff Cuzzi, from NASA's Ames Research Center in Moffett Field, California.
The edges of the thickest of Saturn's rings, A and B, for example, "kind of flop back and forth, sometimes pointing one way and sometimes another, sloshing around like water in a tank," said Cuzzi, co-author of one the new studies.
These fast-warping edges, he said, underscore the newfound, fluidlike nature of the rings.
Also, recent studies have uncovered dozens of mysterious moonlets, several kilometers in size, bouncing around like bumper cars in the slim, outermost ring, called F.
"These cannonballs are whizzing through the F ring and colliding with things," Cuzzi said. "What are these things? Where did they come from?
"This doesn't strike us as a particularly stable situation."
Oxygen Atmosphere Around Saturn Rings?
Scientists were also surprised to find that the atmosphere around Saturn's rings is largely made up of oxygen.
"Most people thought the ring atmosphere would be water molecules—H2O—and their breakdown products H [hydrogen] and OH [hydroxyl]," Cuzzi said. That the ring system would have the chemistry to turn hydrogen and hydroxyl into oxygen "was not foreseen by most."
The discovery could help solve a long-standing mystery of Saturn's rings: why some of them seem stained red.
Perhaps the color is imparted when metals in ring rocks interact with oxygen, he said. On Earth we have a name for it: rust.
Saturn Rings Hold Keys to Planet Birth?
Saturn's rings seem to be much like the dusty, rocky disks around stars where planets form, said Cassini team member Larry Esposito, of the University of Colorado in Boulder.
If the ring system is in fact a reasonable facsimile for a planet nursery, Saturn may change our understanding of how planetary disks behave. (Explore an interactive solar system map.)
Thanks to Cassini's close-up view of Saturn's rings, "we can see structures and phenomena that we would not have otherwise imagined existed in planetary disks," said Esposito, co-author of one the new Saturn studies.
One such phenomena is clumping, which Esposito called one of the most surprising things he's seen around Saturn. Cassini images reveal that gravity temporarily binds rocky ice chunks together, forming superchunks perhaps 30 feet (10 meters) across.
"The dynamics in the thicker A and B rings are much more complicated than we thought because of this clumpy nature," he said, "and those rings are more massive than we'd thought.
"When you know the mass you can say something about the origins of the rings," he said.
But that knowledge may have to wait until 2017, when Cassini is to measure the rings' masses as it plummets to destruction on Saturn.
So far, "Cassini has helped to refine the questions, but not provide the answers, on where the rings came from and when they were created," Esposito said. "And that is still my number one question." | 0.810921 | 3.933742 |
The dust that is released from the comet nucleus typically has only a small velocity relative to the nucleus. It will therefore follow more or less the orbit of the cometary nucleus, that is, a curved elliptical or parabolic trajectory.
Pushed by the light of the Sun
A large fraction of this dust is very small, with typical dust grain diameters of 0.001 mm. Because of their large surface to mass ratio these grains are very sensitive to the solar radiation pressure, that is, the pressure exerted by the light of the Sun on these particles.
They will therefore be pushed behind the comet, so that the dust grains form a diffuse dust tail trailing behind the comet, more or less along the curved orbit. The degree to which the dust deviates from the comet orbit depends on the size of the dust grains.
Dust reflects sunlight
This dust tail has a yellow-white appearance, as the dust particles simply reflect the incident sunlight.
The straight bluish and highly structured plasma tail and the curved diffuse white dust tail are clearly visible in the accompanying Hale-Bopp photograph. | 0.870725 | 3.690973 |
Last Updated on
This week (14-20 March, 2019) I have an eclectic selection of news items from the world of geoscience, so much so that it’s hard to find any theme that links them. If pushed, though, I’d have to say that the thing they have in common is that they have associations with large scale processes — and even that is a tenuous link.
So what are they? Well, this week I’ve been intrigued by potential new information from the Moon; a glance at how anthropogenic activity might be used to redress some of the changes humans have made to our Earth system; and a visit to our old friend from last year, Kilauea.
A New Look at Moon Rocks
Some geoscience stories are routine; some, especially those involving catastrophic damage or loss of life, are disturbing and distressing; and a very few send shivers of excitement down the spine. One of these appeared in the media this week with the revelation that NASA have selected teams of scientists to conduct experiments on moon rock samples that have been sealed and untouched since the return of Apollo 15 in 1971 and Apollo 17 in 1972.
The rationale for holding these samples back is a sensible one, given that technology (and our understanding of the lunar environment) has advanced since that great leap for mankind. Quoted on NASA’s website, the agency’s Lori Glaze described it as: “…an investment in the future. These samples were deliberately saved so we can take advantage of today’s more advanced and sophisticated technology to answer questions we didn’t know we needed to ask”.
The selected research teams will consider topics that even the most sensational reporter would struggle to make exciting to the layman — topics such as “how curation affects the amount of hydrogen-bearing minerals in lunar soil” or “how airless bodies are affected by exposure to the space environment”.
There are unlikely to be earth-shattering results because, as NASA points out, the samples are really only a snapshot. “NASA has only collected samples from a few places on the Moon so far, but NASA knows from the remote sensing data that the Moon is a complex geologic body”.
There is surely far more to be discovered from possible future missions. The eventual outcome, however, should significantly enhance our knowledge of the Moon and the processes which shaped it. And as we learn more about our nearest neighbour, we will also gain some understanding of how we might approach: “the next era of exploration of the Moon and beyond”.
Geoengineering: A Complex Issue
Climate change remains a matter for considerable debate but it probably isn’t too contentious to say that the scientific community has come to a consensus on the matter — that the climate is changing and that it has serious implications. The problem of how to address it can be tackled (broadly) from two directions — reducing the activities that cause it, and engaging in activities that modify it.
The second of these involves geoengineering, defined (by the website Geoengineering Watch) as: “the artificial modification of Earths climate systems through two primary ideologies, Solar Radiation Management (SRM) and Carbon Dioxide Removal (CDR)”.
There are numerous studies ongoing in this area, so the one that was published this week should be regarded as indicative of the benefits and the complications of the processes. Most of these studies are modelling-related and this one, published in Nature Climate Change and focussing on the impact of injecting aerosols (minute particles) into the stratosphere, is no exception.
It can’t be said often enough that change in one part of the Earth system will have implications elsewhere and this is what the study considered, addressing the issue that: “Solar geoengineering (SG) has the potential to restore average surface temperatures by increasing planetary albedo, but this could reduce precipitation. Thus, although SG might reduce globally aggregated risks, it may increase climate risks for some regions”.
The study addresses the effects of the process rather than its practicalities (another subject entirely) but the results are encouraging, indicating that the perceived problems, while certainly not insignificant, are perhaps not as great as they could be. “…while concerns about the inequality of solar geoengineering impacts are appropriate, the quantitative extent of inequality may be overstated”.
A(nother) Hawaiian Earthquake
Last year, you may remember, I ran the digest for several weeks keeping up to date with the eruption of Hawaii’s Kilauea volcano. It was an eruption that was characterised by repeated earthquake activity, with regular tremors of around M5 occurring as explosive eruptions shook the heart of the volcano.
The eruption officially ended in September 2018, a clear six months ago — so what are we to make of this week’s M5.5 earthquake on the south flank of the volcano?
The answer is that residents of the area around Kilauea can rest easy. The earthquake wasn’t caused, as that series of events last year was, by movement of magma but by the mechanical readjustment of the land in response to large-scale processes. “The location, depth, and waveforms recorded as part of today’s earthquake are consistent with slip along [a] south flank fault” notes the official report on the Hawaiian Volcano Observatory website.
This movement, in other words, is normal. “We see no detectable changes in volcanic activity at the summit or along the rift zones of Kīlauea as a result of this earthquake, Aftershocks are possible and could be felt”.
Decoding Science. One article at a time. | 0.84403 | 3.007964 |
Astronomers have detected radio jets belonging to a neutron star with a strong magnetic field — something not predicted by current theory, according to a new study published in Nature today.
The team, led by researchers at the University of Amsterdam, observed the object known as Swift J0243.6+6124 using the Karl G. Jansky Very Large Array radio telescope in New Mexico and NASA’s Swift space telescope.
“Neutron stars are stellar corpses,” said study co-author Associate Professor James Miller-Jones, from Curtin University’s node of the International Centre for Radio Astronomy Research (ICRAR).
“They’re formed when a massive star runs out of fuel and undergoes a supernova, with the central parts of the star collapsing under their own gravity.
“This collapse causes the star’s magnetic field to increase in strength to several trillion times that of our own Sun, which then gradually weakens again over hundreds of thousands of years.”
University of Amsterdam PhD student Jakob van den Eijnden, who led the research, said neutron stars and black holes are sometimes found in orbit with a nearby “companion” star.
“Gas from the companion star feeds the neutron star or black hole and produces spectacular displays when some of the material is blasted out in powerful jets travelling at close to the speed of light,” he said.
Astronomers have known about jets for decades but until now, they had only observed jets coming from neutron stars with much weaker magnetic fields. The prevailing belief was that a sufficiently strong magnetic field prevents material getting close enough to a neutron star to form jets.
“Black holes were considered the undisputed kings of launching powerful jets, even when feeding on just a small amount of material from their companion star,” Van den Eijnden said.
“The weak jets belonging to neutron stars only become bright enough to see when the star is consuming gas from its companion at a very high rate.
“The magnetic field of the neutron star we studied is about 10 trillion times stronger than that of our own Sun, so for the first time ever, we have observed a jet coming from a neutron star with a very strong magnetic field.
“The discovery reveals a whole new class of jet-producing sources for us to study,” he said.
Astronomers around the world study jets to better understand what causes them and how much power they release into space.
“Jets play a really important role in returning the huge amounts of gravitational energy extracted by neutron stars and black holes back into the surrounding environment,” Associate Professor Miller-Jones said.
“Finding jets from a neutron star with a strong magnetic field goes against what we expected, and shows there’s still a lot we don’t yet know about how jets are produced.” | 0.921284 | 3.920141 |
In this second in NICHOLE OVERALL’s series on Canberra’s role in observing space, she looks at the Molonglo Observatory Synthesis Telescope at Hoskinstown that, for more than half a century, has been on the lookout for some seriously mysterious cosmological phenomena.
THE moon and Canberra’s contribution to that momentous landing 50 years ago has excited local imaginations, but the chance of alien signals could well come from another space observatory in our backyard.
Ensconced in a lonely valley near tiny Hoskinstown, about 40 kilometres from the capital, is the Molonglo Observatory Synthesis Telescope: MOST. For more than half a century, it’s been on the lookout for some seriously mysterious cosmological phenomena.
According to the observatory’s director, Prof Richard Hunstead, a recent collaboration between Sydney and Swinburne Universities enabled it to continue its cutting-edge work.
“If it hadn’t been for the involvement [of Swinburne], and substantial contribution of hardware and software expertise, the telescope would have been forced to close in 2012,” he says.
After this, its name was also upgraded, to UTMOST.
While many think the radio telescope at Parkes, made famous by the movie “The Dish”, is big at 64 metres diameter, UTMOST is the largest antenna of its kind in the southern hemisphere. And it’s not so much a “dish” as a “big steel cross.”
Its huge cylindrical “arms”, consisting of thousands of independent antennae, extend almost a kilometre each. With five times the “viewing” area of Parkes (more than 18,000 square metres), it can search great swathes of the heavens.
Opened in late 1965 and completed two years before Neil Armstrong made that step on to the lunar surface and into history in 1969, UTMOST continues to be a hotspot for radio astronomy.
In scanning for some of the “strangest objects in the universe”, it produces information critical to the study of things such as black holes. It also allows for the better understanding of theories such as Einstein’s Relativity (I’m no rocket scientist but, at its most basic, the impact of space and time on each other; alternatively, try to grasp what’s going on in the movie “Interstellar”).
Radio waves from outer space were discovered as recently as 1932. Five years later, the first parabolic “dish” antenna – at just nine metres – was built by American Grote Reber.
Prof Hunstead points out that on Reber’s death, some of his ashes were sent to all the major observatories around the world.
“At Molonglo, they’re in a small diecast box in the telescope’s reflector,” he says.
Given the distance of astronomical radio sources – planets, stars, nebulas and galaxies – the equipment had to become larger and more sensitive. This also accounts for why they’re built so far from people: they need to avoid interference from other electronic devices.
In 1954, the innovative Mills Cross Telescope was conceived by CSIR(O) engineer and later professor of astrophysics Bernard Mills. Built near a disused World War II air strip, 40 kilometres west of Sydney, in three short years, it was to become “one of the world’s leading radio astronomy field stations”.
The operational parameters of its first telescope – its 450-metre-long arms providing high resolution and a greater ability to detect weak signals – were described as “remarkable”. Notably, it would conduct a detailed survey revealing numerous “extragalactic” radio emissions – that is, from beyond our Milky Way.
With much clamour for even larger antennae, a “Super Cross” Telescope was constructed outside Canberra, at a cost of almost a million dollars (near on $13 million in today’s terms).
“It was based on the original design by Mills from his pioneering work in the early 1950s,” says Prof Hunstead.
Consisting of north-south and east-west arms, the latter would be modified in 1978 to become MOST. After 40 years, the former has only recently been redeployed.
One of MOST’s major coups was the first-time detection of the moment a supernova erupted: SN1987A, the closest observable exploding star in four centuries.
Supernovas are the end of a massive star’s life (massive = more than eight times heavier than the sun). The end of its life means it’s exhausted its fuel supplies and can’t sustain itself (to really cheer you up, this is what astronomers say will eventually happen to that radiant orb in our sky – though it’ll expand as a “red giant” to likely obliterate us). The remnants, neutron stars, are the densest, directly observable objects known.
Rapidly rotating, highly magnetised versions of these relics – think half a million times the earth’s mass in a sphere the size of a small city – are called pulsars. They emit regular, focused beams of radiation detectable as radio pulses. The first in the southern hemisphere were discovered by the original Molonglo Telescope, the year after it commenced operations.
Between 1967 and 1978, more than half the known pulsars of the time were located by it. Among UTMOST’s primary work is the observation of pulsars and magnetars – another type of neutron star and the most magnetic objects in the universe.
Then there’s its job detecting another of “astronomy’s biggest puzzles” – fast radio bursts (FRBs). These intense, short-lived “cosmic blips” are even further in the nether regions of space. So elusive are they, in the first decade after their 2007 discovery (from archival data collected by the Parkes Observatory), less than 20 were identified. The importance of the still unexplained events could lead to revelations on the composition and mass of the universe.
Heavy stuff, indeed.
In conjunction with other organisations and universities, the ongoing program to search for them has resulted in the 2018 capture of one of the “most energetic FRBs ever detected” (as the energy they produce in a single burst is the equivalent of the output of the sun in a whole day, you get the idea).
A current project setting records for real-time searches for all of this phenomena has also been given another adorable acronym: SMIRF (Survey for Magnetars, Intermittent pulsars, Rotating radio transients and FRBs). It allows for a sweep of the entire southern arc of the Milky Way every 10 days as opposed to once a decade. The volume of information collected means the facility’s recently introduced supercomputers conduct trillions of calculations a second, processing a billion gigabytes of data in a year.
Parkes is one of the telescopes that’s part of SETI – the Scientific Search for Extraterrestrial Intelligence – and Breakthrough Listen, the most comprehensive quest for alien communication using radio wave and light observations. Perhaps though, given the incredible work going on down a backroad of the capital region, just like those first minutes of footage from the moon landing, the next world-stopping moment from outer space will come from Canberra.
More information at anoverallview.wixsite.com/blog. | 0.867287 | 3.571656 |
Next year will be the anniversary of a rather earth-shattering event. May 29, 2019 will be 100th anniversary of the famed first confirmation of Einstein’s Theory of Relativity.
One of the key tenets of Einstein’s theory is that space-time can be distorted by the motion and mass of objects moving through it. The light from one distant object would appear to bend as it passed near the body of another sufficiently large body on its way to still a third body.
One scientist came up with a way to test this outlandish idea: the effect, although small, might still be measurable not near any body we might encounter on Earth, but on the largest body in our Solar system: the Sun: during an eclipse, and given the right conditions, we might be able to measure the slight change in position of a distant object beyond our solar system consistent with the prediction of Einstein’s theory.
This photograph from the May 29, 1919 total solar eclipse shows one of the stars used to confirm Albert Einstein’s general theory of relativity. The red dot shows where the star would have been without the sun’s interference.
Credit: Royal Observatory, Greenwich
On May 29, 1919, this measurement was successfully accomplished, changing the natural sciences forever. Our conception of the universe was no longer that of a flat, static, unchanging space-time. Within a few decades of this confirmation of Einsteins new theory, the now expanding universe was populated by all sorts of strange new theoretical objects, including black hole singularities where the known laws of the physical universe — including Einstein’s — may no longer hold.
Now, you may ask, what does any of this have to do with Moseley’s book, “Money and Totality”?
Einstein’s theory of relativity was the answer to contradictory observations of natural phenomenon for which existing theory could not account. To explain these contradictory observations, Einstein was forced to re-conceptualize space-time itself. This new space-time was no longer flat and unvarying. Gravity, rather than affecting the trajectory of objects, described the shape of the space-time through which objects moved.
Similarly, Marx’s labor theory of value was the answer to persistent contradictions that arise in labor theory of value once prices have to account for the division of socially necessary labor time into the wages of the working class and the profits of capital. Bizarrely, it appears capitalistically produced commodities do not have prices that express their labor values. They have prices of production that no longer directly express the socially necessary labor time required to produce them.
According to Marx’s solution, once the value of labor power was converted into wages, the prices of commodities were converted into capitalistic prices of production, i.e., into the costs of the constant capital and variable capital plus an average rate of profit. The average rate of profit was calculated on the basis of the total social capital and apportioned among individual capitalists as if they were shareholders in a single capitalist firm according to the relative share of their stake.
Contrary to our expectation, division of the social product of the exploitation of the working class takes place not according the relative mass of surplus value squeezed out of the individual work forces of each capital, but by the relative share of capital controlled by each capital in the process of accumulation generally. The manner in which the average rate of profit forms means that even in the case of capitals that employ no labor power and thus create no surplus value they will realize the average rate of profit based on their total mass of employed capital.
Thus, although, ultimately, labor is the only source of profit in the mode of production, empirically it appears each capitalist firm can create its own profit by progressively shedding the costs of wage labor.
This then sets the stage for the self-negation of the capitalist mode of production. | 0.812319 | 3.715854 |
Press Releases Archive
As the Earth orbits the sun, it plows through a stream of fast-moving particles that can interfere with satellites and global positioning systems. Now, a team of scientists at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) and Princeton University has reproduced a process that occurs in space to deepen understanding of what happens when the Earth encounters this solar wind.
Vincent Graber, a doctoral student in mechanical engineering at Lehigh University, has won a highly competitive award from the U.S Department of Energy (DOE) that he will use to conduct research at the DOE’s Princeton Plasma Physics Laboratory (PPPL) on the design of a critical device to help bring the fusion energy that powers the sun and stars to Earth.
Blobs can wreak havoc in plasma required for fusion reactions. This bubble-like turbulence swells up at the edge of fusion plasmas and drains heat from the edge, limiting the efficiency of fusion reactions in doughnut-shaped fusion facilities called “tokamaks.” Researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have now discovered a surprising correlation of the blobs with fluctuations of the magnetic field that confines the plasma fueling fusion reactions in the device core.
New aspect of understanding
A major roadblock to producing safe, clean and abundant fusion energy on Earth is the lack of detailed understanding of how the hot, charged plasma gas that fuels fusion reactions behaves at the edge of fusion facilities called “tokamaks.” Recent breakthroughs by researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have advanced understanding of the behavior of the highly complex plasma edge in doughnut-shaped tokamaks on the road to capturing the fusion energy that powers the sun and stars.
Mike Bonkalski, the Princeton Plasma Physics Laboratory’s (PPPL) new head of Environment, Safety, and Health (ES&H), brings almost 30 years of experience at two national laboratories to the position that oversees health and safety at a crucial time for the Laboratory as it begins several major projects.
Bonkalski begins his new position in the midst of the curtailment of operations at PPPL during the coronavirus pandemic. Bonkalski is communicating remotely from 829 miles away in Geneva, Illinois, with his staff of 48 people in New Jersey.
David Graves, an internationally-known chemical engineer, has been named to lead a new research enterprise that will explore plasma applications in nanotechnology for everything from semiconductor manufacturing to the next generation of super-fast quantum computers.
A key challenge to capturing and controlling fusion energy on Earth is maintaining the stability of plasma — the electrically charged gas that fuels fusion reactions — and keeping it millions of degrees hot to launch and maintain fusion reactions. This challenge requires controlling magnetic islands, bubble-like structures that form in the plasma in doughnut-shaped tokamak fusion facilities.
Ian Ochs, a graduate student in the Program in Plasma Physics, has won a Porter Ogden Jacobus Fellowship, the most prestigious of the honorific fellowships that the University awards annually for academic excellence. The award goes to only one student in each of the four graduate school divisions — humanities, social sciences, natural and physical sciences, and engineering.
A key issue for scientists seeking to bring the fusion that powers the sun and stars to Earth is forecasting the performance of the volatile plasma that fuels fusion reactions. Making such predictions calls for considerable costly time on the world’s fastest supercomputers. Now researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have borrowed a technique from applied mathematics to accelerate the process.
Carefully manipulating the outer skin of plasma can create cascades of effects that help create the stability needed to sustain fusion reactions, scientists have found. The research, led by physicist Dylan Brennan of the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL), could provide insight into the physics required to stabilize plasma in doughnut-shaped fusion facilities known as tokamaks. These include ITER, the multinational facility being built in France to demonstrate the practicality of fusion power.
Mercury, the planet nearest the sun, shares with Earth the distinction of being one of the two mountainous planets in the solar system with a global magnetic field that shields it from cosmic rays and the solar wind. Now researchers, led by physicist Chuanfei Dong of the Princeton University Center for Heliophysics and the U.S.
Scientists seeking to bring the fusion that powers the sun and stars to Earth must deal with sawtooth instabilities — up-and-down swings in the central pressure and temperature of the plasma that fuels fusion reactions, similar to the serrated blades of a saw. If these swings are large enough, they can lead to the sudden collapse of the entire discharge of the plasma. Such swings were first observed in 1974 and have so far eluded a widely accepted theory that explains experimental observations.
Consistent with observations
Creating and controlling on Earth the fusion energy that powers the sun and stars is a key goal of scientists around the world. Production of this safe, clean and limitless energy could generate electricity for all humanity, and the possibility is growing closer to reality. Now a landmark report released this week by the American Physical Society Division of Plasma Physics Community Planning Process proposes immediate steps for the United States to take to accelerate U.S.
An international team of scientists led by a graduate student at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) has demonstrated the use of Artificial Intelligence (AI), the same computing concept that will empower self-driving cars, to predict and avoid disruptions — the sudden release of energy stored in the plasma that fuels fusion reactions — that can halt the reactions and severely damage fusion facilities.
Risk of disruptions
In an abundance of caution around the coronavirus pandemic, and in light of presumptive cases in the Princeton area, the Princeton Plasma Physics Laboratory is curtailing o
In an abundance of caution around the coronavirus pandemic, and in light of presumptive cases in the Princeton area, the Princeton Plasma Physics Laboratory is curtailing operations and sending employees home to work effective 5 p.m. today, Friday, March 13, until at least March 29, Laboratory Director Steve Cowley announced today. There are no presumptive cases at the Laboratory.
Permanent magnets akin to those used on refrigerators could speed the development of fusion energy – the same energy produced by the sun and stars.
In principle, such magnets can greatly simplify the design and production of twisty fusion facilities called stellarators, according to scientists at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) and the Max Planck Institute for Plasma Physics in Greifswald, Germany. PPPL founder Lyman Spitzer Jr. invented the stellarator in the early 1950s.
Researchers have found that injecting pellets of hydrogen ice rather than puffing hydrogen gas improves fusion performanceat the DIII-D National Fusion Facility, which General Atomics operates for the U.S. Department of Energy (DOE). The studies by physicists based at DOE’s Princeton Plasma Physics Laboratory (PPPL) and Oak Ridge National Laboratory (ORNL) compared the two methods, looking ahead to the fueling that will be used in ITER, the international fusion experiment under construction in France.
Improve the temperature
Researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have used Artificial Intelligence (AI) to create an innovative technique to improve the prediction of disruptions in fusion energy devices — a grand challenge in the effort to capture on Earth the fusion reactions that power the sun and stars.
A key hurdle facing fusion devices called stellarators — twisty facilities that seek to harness on Earth the fusion reactions that power the sun and stars — has been their limited ability to maintain the heat and performance of the plasma that fuels those reactions. Now collaborative research by scientists at the U.S.
Magnetic field lines that wrap around the Earth protect our planet from cosmic rays. Researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have now found that beams of fast-moving particles launched toward Earth from a satellite could help map the precise shape of the field.
Like most teams preparing for a big competition, the 16 middle school teams and 32 high school teams coming to the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) on Feb. 21 and 22 are drilling their hardest, discussing strategy, and getting pep talks from their coaches.
A long-standing puzzle in space science is what triggers fast magnetic reconnection, an explosive process that unfolds throughout the universe more rapidly than theory says it should. Solving the puzzle could enable scientists to better understand and anticipate the process, which ignites solar flares and magnetic space storms that can disrupt cell phone service and black out power grids on Earth.
Turbulence — the unruly swirling of fluid and air that mixes coffee and cream and can rattle airplanes in flight — causes heat loss that weakens efforts to reproduce on Earth the fusion that powers the sun and stars. Now scientists have modeled a key source of the turbulence found in a fusion experiment at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL), paving the way for improving similar experiments to capture and control fusion energy.
State of the art simulations
Researchers led by C.S. Chang of the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have been awarded major supercomputer time to address key issues for ITER, the international experiment under construction in France to demonstrate the practicality of fusion energy. The award, from the DOE’s Innovative and Novel Computational Impact on Theory and Experiment (INCITE) program, renews the third and final year of the team’s supercomputer allocation for the current round.
Among the largest awards
Scientists often make progress by coming up with new ways to look at old problems. That has happened at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL), where physicists have used a simple insight to capture the complex effects of many high-frequency waves in a fusion plasma. These waves can force hot particles to escape from a fusion reactor, potentially impairing fusion energy production and damaging the reactor walls.
Science enthusiasts will get a jolt of excitement along with their coffee at the Princeton Plasma Physics Laboratory’s (PPPL) Ronald E. Hatcher Science on Saturday lecture series, which debuts Jan. 11.
The first talk in the series will be “Visual Perception and the Art of the Brain,” by Sabine Kastner, a professor of psychology and neuroscience at Princeton University.
Arms control robots, a new national facility, and accelerating the drive to bring the fusion energy that powers the sun and stars to Earth. These far-reaching achievements at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) made 2019 another remarkable year. Research at the only national laboratory devoted to fusion and plasma physics — the state of matter that makes up 99 percent of the visible universe — broke new ground in varied fields as vast as astrophysics and as tiny as nanotechnology.
Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.
© 2020 Princeton Plasma Physics Laboratory. All rights reserved. | 0.837813 | 3.159924 |
As the bright Mars-crossing asteroid 433 Eros makes its closest approach to Earth since 1975, astronomers around the globe are taking the opportunity to measure its position in the sky, thereby fine-tuning our working knowledge of distances in the solar system. Using the optical principle of parallax, whereby different viewpoints of the same object show slightly shifted positions relative to background objects, skywatchers in different parts of the world can observe Eros over the next few nights and share their images online.
The endeavor is called the Eros Parallax Project, and you can participate too!
Discovered in 1898, Eros was the largest near-Earth asteroid yet identified. Its close and relatively bright oppositions were calculated by astronomers of the day and used, along with solar transits by Venus (one of which, if you haven’t heard, will also occur this year on June 5!) to calculate distances in the inner solar system.
Having both events take place within the same year offers today’s astronomers an unparalleled opportunity to obtain observational measurements.
Through the efforts of the Astronomers Without Borders organization, along with Steven van Roode and Michael Richmond from the Transit of Venus project, anyone with moderate astrophotography experience can participate in the observation of Eros and share their photos via free online software.
Using the data gathered by individual participants positioned around the world, each with their own specific viewpoints, astronomers will be able to precisely measure the distance to Eros.
The more accurately that distance is known, the more accurately the distance from Earth to the Sun can be calculated – via the orbital mechanics of Kepler’s third law.
The last time such a bright pass of Eros occurred was in January of 1931. Observations of the asteroid made at that time allowed astronomers to calculate a solar parallax of 8″ .790, the most accurate up to that time and the most accurate until 1968, when data acquired by radar measurements gave more detailed measurements.
In many ways the 2012 close approach by Eros – astronomically close, but still a very safe 16.6 million miles (26.7 million km) away – will allow for a re-eneactment of the 1931 event… with the exception that this time amateur skywatchers will also contribute data, instantly, from all over the world!
One has to wonder…when Eros comes this close again in 2056, what sort of technology will we use to watch it then…
And be sure to check out the article about the project on Astronomers Without Borders as well. | 0.887516 | 3.758212 |
Egg-Shaped Orbits of Non-Uniform Oscillators
A simple non-uniform oscillator follows the differential equation (the blue curve). In an imaginary solar system where the planets follow this law of motion, but where angular momentum is conserved, planetary orbits would be egg-shaped (the red curve), with the parameter taking a role akin to the orbit eccentricity.
We are able to plot both the angular velocity (blue curve) and distance from the origin (red curve) on the same axes for comparison by casting the equations in dimensionless form. For visual convenience we also define the functions so that when the oscillation is uniform, both the angular velocity and distance from the origin are equal to unity, as described below:
The curves are related by the need to keep the angular momentum equal to a constant, . As an equation we therefore have, . We define the angular velocity with (you can vary with the slider control), then define , and obtain as a result.
In the case where the non-uniformity is zero, we have constant angular velocity with an intuitively expected circular orbit. When the non-uniformity becomes significant at around 0.9, the angular velocity becomes very small in the region near . To compensate, the orbital radius grows very large, hence an egg-shaped orbit. As approaches unity, the orbital radius must approach infinity and the orbit is then no longer closed. | 0.832481 | 3.368732 |
A new study into where the normal matter produced by the Big Bang is today, has discovered that twenty percent has already turned into stars.
The research, led by the University of St Andrews, involved a survey of over ten thousand giant galaxies, each comprising of up to 10 billion stars as well as bulges, discs and super-massive black holes. The survey was able to determine how much of the Universe’s matter is locked away in black holes, some of which are one million billion times more massive than the Earth. By adding up each key component they found that the Universe has ‘guzzled’ its way through about twenty percent of its original fuel reserves.
Project leader Dr Simon Driver of the University of St Andrews said: “The simplest prognosis is that the Universe will be able to form stars for a further 70 billion years or so after which it will start to go dark. However, unlike our stewardship of the Earth, the Universe is definitely tightening its belt with the rate at which new stars are forming steadily decreasing.”
Tracking down what happened to normal matter dating back to the Big Bang 14 billion years ago has remained one of the most important goals for cosmologists for many years. The new survey reveals that about 20% is locked up in stars, a further 0.1% lies in dust expelled from the massive stars (and from which solid structures like the Earth and man are made), and about 0.01% is in the form of super-massive black holes.
“The remaining 80% are almost completely in gaseous form lying both within and between the galaxies and constitutes the reservoir from which future generations of stars may form,” Dr Driver continued.
The survey involved scientists from Australia, Germany and the UK, and resulted in the Millennium Galaxy Catalogue (MGC), constructed from over 100 nights of telescope time in the Canary Islands, Australia and Chile.
“What is new about the MGC is that it focuses on the structures in which stars are arranged inside galaxies. We have literally dismantled each galaxy so that we can study the main components separately,¿ said Dr Driver.
The survey is the first to catalogue reliable information on the distances, sizes, colours and shapes of both the bulge and disc components of so many galaxies. Dr Driver and his team found that on average half the stars in the Universe lie in the central bulges of galaxies, while the other half are found in discs surrounding the bulges.
“By measuring the concentration of stars in each galaxy’s bulge, we have also been able to determine the super-massive black hole mass at the heart of each galaxy¿, said Dr Alister Graham of the Australian National University.
“It was then a simple matter of summing these up to determine how much of the Universe’s matter is locked away in such monstrous black holes.”
The survey was presented at the General Assembly of the International Astronomical Union in Prague this week. Financial support for this project was jointly provided by the UK Particle Physics and Astrophysics Research Council and the Australian Research Council.
NOTE TO EDITORS: FOR FURTHER INFORMATION CONTACT –
UNITED KINGDOM: Dr Simon Driver, Director of St Andrews’ Observatory, University of St Andrews, St Andrews, Fife, SCOTLAND Mobile: 0791930 5906 (Friday) +44-(0)1334-461680 (after Friday) E-mail: [email protected]
GERMANY: Dr Jochen Liske, European Southern Observatory, Garching, GERMANY +49-(0)89-32006582 E-mail: [email protected]
AUSTRALIA: Drs Alister Graham and Paul Allen, The Australian National University, Canberra, AUSTRALIA +61-(0)2-6125-6713 E-mail: [email protected] & [email protected]
MGC website: http://www.eso.org/~jliske/mgc
Issued by Beattie Media – www.beattiegroup.com on behalf of the University of St Andrews
Contact Gayle Cook, Press Officer on 01334 467227 / 462529, mobile 07900 050 103, or email gec3@st- andrews.ac.uk
Ref: Matter of darkness 180806.doc
View the latest University press releases at http://www.st- andrews.ac.ukResearch | 0.802408 | 3.957469 |
› Asteroids, comets and other small objects in space hold clues to our origins, but may also pose hazards.
› Small worlds likely delivered the ingredients of life to Earth.
› Several NASA missions are either on their way to these small worlds, or are in development.
The entire history of human existence is a tiny blip in our solar system's 4.5-billion-year history. No one was around to see planets forming and undergoing dramatic changes before settling in their present configuration. In order to understand what came before us -- before life on Earth and before Earth itself -- scientists need to hunt for clues to that mysterious distant past.
Those clues come in the form of asteroids, comets and other small objects. Like detectives sifting through forensic evidence, scientists carefully examine these small bodies for insights about our origins. They tell of a time when countless meteors and asteroids rained down on the planets, burned up in the Sun, shot out beyond the orbit of Neptune or collided with one another and shattered into smaller bodies. From distant, icy comets to the asteroid that ended the reign of the dinosaurs, each space rock contains clues to epic events that shaped the solar system as we know it today -- including life on Earth.
NASA's missions to study these "non-planets" help us understand how planets including Earth formed, locate hazards from incoming objects and think about the future of exploration. They have played key roles in our solar system's history, and reflect how it continues to change today.
"They might not have giant volcanoes, global oceans or dust storms, but small worlds could answer big questions we have about the origins of our solar system," said Lori Glaze, acting director for the Planetary Science Division at NASA Headquarters in Washington.
NASA has a long history of exploring small bodies, beginning with Galileo's 1991 flyby of asteroid Gaspra. The first spacecraft to orbit an asteroid, Near Earth Asteroid Rendezvous (NEAR) Shoemaker, also successfully landed on asteroid Eros in 2000 and took measurements that originally hadn't been planned. The Deep Impact mission drove a probe into Comet Tempel 1 in 2005 and prompted scientists to rethink where comets formed. More recent efforts have built on those successes and will continue to teach us more about our solar system. Here's an overview of what we can learn:
This representation of Ceres' Occator Crater in false colors shows differences in the dwarf planet's surface composition. Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Building Blocks of Planets
Our solar system as we know it today formed from grains of dust -- tiny particles of rock, metal and ice -- swirling in a disk around our infant Sun. Most of the material from this disk fell into the newborn star, but some bits avoided that fate and stuck together, growing into asteroids, comets and even planets. Lots of leftovers from that process have survived to this day. The growth of planets from smaller objects is one piece of our history that asteroids and comets can help us investigate.
"Asteroids, comets and other small bodies hold material from the solar system's birth. If we want to know where we come from, we must study these objects," Glaze said.
Two ancient fossils providing clues to this story are Vesta and Ceres, the largest bodies in the asteroid belt between Mars and Jupiter. NASA's Dawn spacecraft, which recently ended its mission, orbited both of them and showed definitively that they are not part of the regular "asteroid club." While many asteroids are loose collections of rubble, the interiors of Vesta and Ceres are layered, with the densest material at their cores. (In scientific terms, their interiors are said to be "differentiated.") This indicates both of these bodies were on their way to becoming planets, but their growth was stunted -- they never had enough material to get as big as the major planets.
But while Vesta is largely dry, Ceres is wet. It may have as much as 25 percent water, mostly bound up in minerals or ice, with the possibility of underground liquid. The presence of ammonia at Ceres is also interesting, because it typically requires cooler temperatures than Ceres' current location. This indicates the dwarf planet could have formed beyond Jupiter and migrated in, or at least incorporated materials that originated farther from the Sun. The mystery of Ceres' origins shows how complex planetary formation can be, and it underscores the complicated history of our solar system.
This artist's concept depicts the spacecraft of NASA's Psyche mission near the mission's target, the metal asteroid Psyche. Image Credit: NASA/JPL-Caltech/Arizona State Univ./Space Systems Loral/Peter Rubin
Although we can indirectly study the deep interiors of the planets for clues about their origins, as NASA's InSight mission will do on Mars, it's impossible to drill down into the core of any sizeable object in space, including Earth. Nevertheless, a rare object called Psyche may offer the opportunity to explore a planet-like body's core without any digging. Asteroid Psyche appears to be the exposed iron-nickel core of a protoplanet -- a small world that formed early in our solar system's history but never reached planetary size. Like Vesta and Ceres, Psyche saw its path to planethood disrupted. NASA's Psyche mission, launching in 2022, will help tell the story of planet formation by studying this metal object in detail.
Artist's impression of NASA's New Horizons spacecraft encountering 2014 MU69, a Kuiper Belt object that orbits the Sun 1 billion miles (1.6 billion kilometers) beyond Pluto, on Jan. 1, 2019. Image Credit: NASA/JHUAPL/SwRI
Farther afield, NASA's New Horizons spacecraft is currently on its way to a distant object called 2014 MU69, nicknamed "Ultima Thule" by the mission. One billion miles farther from the Sun than Pluto, MU69 is a resident of the Kuiper Belt, a region of ice-rich objects beyond the orbit of Neptune. Objects like MU69 may represent the most primitive, or unaltered, material that remains in the solar system. While the planets orbit in ellipses around the Sun, MU69 and many other Kuiper Belt objects have very circular orbits, suggesting they have not moved from their original paths in 4.5 billion years. These objects may represent the building blocks of Pluto and other distant icy worlds like it. New Horizons will make its closestapproach to MU69 on Jan. 1, 2019-- the farthest planetary flyby in history.
"Ultima Thule is incredibly scientifically valuable for understanding the origin of our solar system and its planets,"said Alan Stern, principal investigator of New Horizons, based at Southwest Research Institute in Boulder, Colorado. "It's ancient and pristine, andnotlike anything we've seen before."
Delivery of the Elements of Life
Small worlds are also likely responsible for seeding Earth with the ingredients for life. Studying how much water they have is evidence for how they helped seed life on Earth.
"Small bodies are the game changers. They participate in the slow and steady evolution of our solar system over time, and influence planetary atmospheres and opportunities for life. Earth is part of that story," said NASA's chief scientist Jim Green.
This "super-resolution" view of asteroid Bennu was created using eight images obtained by NASA's OSIRIS-REx spacecraft on Oct. 29, 2018, from a distance of about 205 miles (330 kilometers). Image credit: NASA/Goddard/University of Arizona
One example of an asteroid containing the building blocks of life is Bennu, the target of NASA's OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer) mission. Bennu may be loaded with molecules of carbon and water, both of which are necessary for life as we know it. As Earth formed, and afterward, objects like Bennu rained down and delivered these materials to our planet. These objects did not have oceans themselves, but rather water molecules bound up in minerals. Up to 80 percent of Earth's water is thought to have come from small bodies like Bennu. By studying Bennu, we can better understand the kinds of objects that allowed a barren young Earth to blossom with life.
Bennu likely originated in the main asteroid belt between Mars and Jupiter, and it's thought to have survived a catastrophic collision that happened between 800 million and 2 billion years ago. Scientists think a big, carbon-rich asteroid shattered into thousands of pieces, and Bennu is one of the remnants. Rather than a solid object, Bennu is thought to be a "rubble pile" asteroid -- a loose collection of rocks stuck together through gravity and another force scientists call "cohesion." OSIRIS-REx, which will arrive at Bennu in early December 2018, after a 1.2-billion-mile (2-billion-kilometer) journey, and will bring back a sample of this intriguing object to Earth in a sample-return capsule in 2023.
The Japanese Hayabusa-2 mission is also looking at an asteroid from the same family of bodies thought to have delivered ingredients for life to Earth. Currently in orbit at asteroid Ryugu, with small hopping rovers on the surface, the mission will collect samples and return them in a capsule to Earth for analysis by the end of 2020. We will learn a lot comparing Bennu and Ryugu, and understanding the similarities and differences between their samples.
Tracers of Solar System Evolution
Most of the material that formed our solar system, including Earth, didn't live to tell the tale. It fell into the Sun or was ejected beyond the reaches of our most powerful telescopes; only a small fraction formed the planets. But there are some renegade remnants of the early days when the stuff of planets swirled with an uncertain fate around the Sun.
A particularly catastrophic time for the solar system was between 50 and 500 million years after the Sun formed. Jupiter and Saturn, our system's most massive giants, reorganized the objects around them as their gravity interacted with smaller worlds such as asteroids. Uranus and Neptune may have originated closer to the Sun and been kicked outward as Jupiter and Saturn moved around. Saturn, in fact, may have prevented Jupiter from "eating" some of the terrestrial planets, including Earth, as its gravity counteracted Jupiter's further movement toward the Sun.
Conceptual image of the Lucy mission to the Trojan asteroids. Image credit: NASA/SwRI
Swarms of asteroids called the Trojans could help sort out the details of that turbulent period. The Trojans comprise two clusters of small bodies that share Jupiter's orbit around the Sun, with one group ahead of Jupiter and one trailing behind. But some Trojans seem to be made of different materials than others, as indicated by their varying colors. Some are much redder than others and may have originated beyond the orbit of Neptune, while the grayer ones may have formed much closer to the Sun. The leading theory is that as Jupiter moved around long ago, these objects were corralled into Lagrange points -- places where the gravity of Jupiter and the Sun create holding areas where asteroids can be captured. The Trojans' diversity, scientists say, reflects Jupiter's journey to its present location. "They're the remnants of what was going on the last time Jupiter moved," said Hal Levison, researcher at Southwest Research Institute.
NASA's Lucy mission, launching in October 2021, will send a spacecraft to the Trojans for the first time, thoroughly investigating six Trojans (three asteroids in each swarm). For Levison, the mission's principal investigator, the spacecraft will test ideas he and colleagues have been working on for decades about Jupiter's reshaping of the solar system. "What would really be interesting is what we don't expect," he said.
Processes in an Evolving Solar System
After sundown, under the right conditions, you may notice scattered sunlight in the ecliptic plane, the region of the sky where the planets orbit. This is because sunlight is being scattered by dust left over from the collisions of small bodies such as comets and asteroids. Scientists call this phenomenon "zodiacal light," and it's an indication that our solar system is still active. Zodiacal dust around other stars indicates that they, too, may harbor active planetary systems.
Dust from small bodies has had an important role in our planet in particular. About 100 tons of meteoritic material and dust material fall on Earth every day. Some of it comes from comets, whose activity has direct implications for Earth's evolution. As comets approach the Sun and experience its heat, gases inside the comet bubble up and carry away dusty material from the comet -- including ingredients for life. NASA's Stardust spacecraft flew by Comet 81P/Wild and found that cometary dust contains amino acids, which are building blocks of life.
This view shows Comet 67P/Churyumov-Gerasimenko as seen by the OSIRIS wide-angle camera on ESA's Rosetta spacecraft on September 29, 2016, when Rosetta was at an altitude of 14 miles (23 kilometers). Image Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Occasional outbursts of gas and dust observed in comets indicate activity on or near their surfaces, such as landslides. The European Space Agency's Rosetta mission, which completed its exploration of Comet 67P/Churyumov-Gerasimenko in 2016, delivered unprecedented insights about cometary activity. Among the changes in the comet, the spacecraft observed a massive cliff collapse, a large crack get bigger and a boulder move. "We discovered that boulders the size of a large truck could be moved across the comet's surface a distance as long as one-and-a-half football fields," Ramy El-Maarry, a member of the U.S. Rosetta science team from the University of Colorado, Boulder, said in 2017.
Comets also influence planetary motion today. As Jupiter continues to fling comets outward, it moves inward ever so slightly because of the gravitational dance with the icy bodies. Neptune, meanwhile, throws comets inward and in turn gets a tiny outward push. Uranus and Saturn are also moving outward very slowly in this process.
"Right now we're talking about teeny amounts of motions because there's not a lot of mass left," Levison said.
Fun fact: The spacecraft that has seen the most comets is NASA's Solar & Heliospheric Observatory (SOHO), most famous for its study of the Sun. SOHO has seen the Sun "eat" thousands of comets, which means that these small worlds were spraying material in the inner part of the solar system on their journey to become the Sun's dinner.
This animation portrays a comet as it approaches the inner solar system. Light from the Sun warms the comet's core, or nucleus, an object so small it cannot be seen at this scale. Image credit: NASA/JPL-Caltech
Hazards to Earth
Asteroids can still pose an impact hazard to the planets, including our own.
While the Trojans are stuck being Jupiter groupies, Bennu, the target of the OSIRIS-REx mission, is one of the most potentially hazardous asteroids to Earth that is currently known, even though its odds of colliding with Earth are still relatively small; scientists estimate Bennu has a 1?in?2,700 chance of impacting our planet during one of its close approaches to Earth in the late 22nd century. Right now, scientists can predict Bennu's path quite precisely through the year 2135, when the asteroid will make one of its close passes by Earth. Close observations by OSIRIS-REx will get an even tighter handle on Bennu's journey, and help scientists working on safeguarding our planet against hazardous asteroids to better understand what it would take to deflect one on an impact trajectory.
"We're developing a lot of technologies for operating with precision around these kinds of bodies, and targeting locations on their surfaces, as well as characterizing their overall physical and chemical properties. You would need this information if you wanted to design an asteroid deflection mission," said Dante Lauretta, principal investigator for the OSIRIS-REx mission, based at the University of Arizona in Tucson.
This animation shows how NASA's Double Asteroid Redirection Test (DART) would target and strike the smaller (left) element of the binary asteroid Didymos to demonstrate how a kinetic impact could potentially redirect an asteroid as part of the agency's planetary defense program.
Another upcoming mission that will test a technique for defending the planet from naturally occurring impact hazards is NASA's Double Asteroid Redirection Test (DART) mission, which will attempt to change a small asteroid's motion. How? Kinetic impact -- in other words, collide something with it, but in a more precise and controlled way than nature does it.
DART's target is Didymos, a binary asteroid composed of two objects orbiting each other. The larger body is about half a mile (800 meters) across, with a small moonlet that is less than one-tenth of a mile (150 meters) wide. An asteroid this size could result in widespread regional damage if one were to impact Earth. DART will deliberately crash itself into the moonlet to slightly change the small object's orbital speed. Telescopes on Earth will then measure this change in speed by observing the new period of time it takes the moonlet to complete an orbit around the main body, which is expected to be a change of less than a fraction of one percent. But even that small of change could be enough to make a predicted impactor miss Earth in some future impact scenario. The spacecraft, being built by the Johns Hopkins University Applied Physics Laboratory, is scheduled for launch in spring-summer 2021.
Didymos and Bennu are just two of the almost 19,000 known near-Earth asteroids. There are over 8,300 known near-Earth asteroids the size of the moonlet of Didymos and larger, but scientists estimate that about 25,000 asteroids in that size range exist in near-Earth space. The space telescope helping scientists discover and understand these kinds of objects, including potential hazards, is called NEOWISE (which stands for Near-Earth Object Wide-field Infrared Survey Explorer).
"For most asteroids, we know little about them except for their orbit and how bright they look. With NEOWISE, we can use the heat emitted from the objects to give us a better assessment of their sizes," said Amy Mainzer, principal investigator of NEOWISE, based at NASA's Jet Propulsion Laboratory. "That's important because asteroid impacts can pack quite a punch, and the amount of energy depends strongly on the size of the object."
This artist's concept shows the Wide-field Infrared Survey Explorer, or WISE, spacecraft, in its orbit around Earth. In its NEOWISE mission it finds and characterizes asteroids. Image credit: NASA/JPL-Caltech
Small Worlds as Pit Stops, Resources for Future Exploration
There are no gas stations in space yet, but scientists and engineers are already starting to think about how asteroids could one day serve as refueling stations for spacecraft on the way to farther-flung destinations. These small worlds might also help astronauts restock their supplies. For example, Bennu likely has water bound in clay minerals, which could perhaps one day be harvested for hydrating thirsty space travelers.
"In addition to science, the future will indeed be mining," Green said. "The materials in space will be used in space for further exploration."
How did metals get on asteroids? As they formed, asteroids and other small worlds collected heavy elements forged billions of years ago. Iron and nickel found in asteroids were produced by previous generations of stars and incorporated in the formation of our solar system.
These small bodies also contain heavier metals forged in stellar explosions called supernovae. The violent death of a star, which can lead to the creation of a black hole, spreads elements heavier than hydrogen and helium throughout the universe. These include metals like gold, silver and platinum, as well as oxygen, carbon and other elements we need for survival. Another kind of cataclysm -- the collision of supernova remnants called neutron stars -- can also create and spread heavy metals. In this way small bodies are also forensic evidence of the explosions or collisions of long-dead stars.
Because of big things, we now have a lot of very small things. And from small things, we get big clues about our past -- and possibly resources for our future. Exploring these objects is important, even if they aren't planets.
They are small worlds, after all.
News Media ContactBy Elizabeth Landau | 0.901625 | 3.716009 |
The biggest astronomy story of the past two decades is that the universe is studded with planets. Sweden’s Nobel Prize committee clearly agrees, as they just handed their coveted physics award to Michel Mayor and Didier Queloz — two Swiss astronomers who were the first to find convincing evidence about a world in another normal stellar system. What they uncovered was a bulky planet orbiting 51 Pegasi, an otherwise unremarkable sunlike star about 50 light-years away.
Since that 1995 discovery, more than 4,100 additional exoplanets have been found. That’s an impressive number, so it’s fair to ask whether this new knowledge has changed the way we look for extraterrestrial life.
Few of these exoplanets are the kind you’d expect would cook up intelligent extraterrestrials. The universe boasts many, many second-string exoplanets: large waterlogged worlds, vaporous gas balls and objects that are simply too hot or too cold to be great places for biology.
Yet, preliminary estimates suggest that about 1 in 5 star systems contains a planet that is something like Earth. That adds up to tens of billions in our own Milky Way galaxy, and that doesn’t count all the moons that might also incubate life.
Given all this newly uncovered cosmic real estate, shouldn’t scientists involved in the search for extraterrestrial intelligence (SETI) be assiduously aiming their antennas its way? Wouldn’t doing so better the odds that we’ll trip upon some alien BFF?
Well, yes. And indeed, many of these exoplanet systems have been surveilled by SETI researchers. But the real influence of exoplanets on the hunt for E.T. is more subtle.
To understand why, let’s briefly return to those golden days of yesteryear. When major SETI searches — ones that listened for signals from many hundreds of star systems — got underway in the early 1990s, we didn’t know which might have planets. In fact, it was conceivable (but a poor bet) that none of them did. So SETI scientists preferentially pointed their instruments in the directions of sunlike stellar systems. After all, the sun was the only star we knew that (jokes aside) shone on intelligent beings.
This was a conservative strategy, and hard to fault — a bit like restricting your dining choices to familiar restaurant chains. Doing so confers a reasonable expectation of getting an edible meal, even if better fare might be had elsewhere.
The exoplanet discoveries have expanded the choices for researchers and eased their personal anxieties because they finally can be certain that planets are plentiful. As an example, consider a type of star that scientists had always excluded from the SETI club: red dwarfs. These bantam stars were considered unlikely to host many close-in planets — worlds that orbit near enough to their suns to receive sufficient energy to sustain life.
But exoplanet hunters have proven that assumption wrong. Several red dwarf stars have been found that are ringed by possibly habitable planets. And since 75 percent of all stars happen to be red dwarfs (only 8 percent are similar to the sun), this is like suddenly learning that there are 10 times as many restaurants in your neighborhood as you once thought. Your drive to dinner is shortened, and your menu options have increased.
The practical result of finding lots of planets has been to shift SETI efforts from looking at a certain type of star system to simply looking at the nearest ones. On average, the systems examined today are only half as far away as when only sunlike stars were examined. Any signals would be four times stronger and, of course, if we find someone at home, a back-and-forth conversation might be more practical.
Mayor and Queloz weren’t looking for planets when they found one around 51 Peg, but they’re being justly credited with paying attention to their data and realizing what it implied. Like many discoveries in science, theirs was accidental, but realizing its importance was not.
Want more stories about the search for alien life?
- Space aliens are breeding with humans, university instructor says. Scientists say otherwise.
- 'Zoo hypothesis' may explain why we haven't seen any space aliens
- Why alien megastructures may hold key to making contact with extraterrestrials | 0.8789 | 3.807991 |
The moon’s orbit about the Earth is not a perfect circle—it is slightly eccentric. As a result, during part of its orbit it is a little closer to us than at other times.
The closest approach is called perigee, while the greatest separation is called apogee.
On average, the moon’s distance from Earth is 239,228 miles (385,000 kilometers).
At perigee it is a bit closer at 221,643 miles (356,700 kilometers), whereas at apogee it is somewhat farther away at 252,463 miles (406,300 kilometers).
Saturday’s full moon has been called a supermoon, because the moon was closer to us than it had been at any time in the last 18 years, making it appear unusually large in the night sky.
After the event many pictures were posted of this super full moon. But many of my visual observer friends tell me it didn’t look much different from any other full moon. So, how much different was it?
It just so happens that I took a picture of the almost full moon on December 19, 2010—just a day and a few hours before the famous “solstice lunar eclipse” (pictures).
Fortunately, I used the exact same camera and telescope to take a picture of the March 19 supermoon.
Hence, a side-by-side comparison, such as the one shown above, of the two pictures gives a good idea of the relative apparent sizes of these two full moons.
My planetarium program tells me that on December 19 the center of the moon was 233,523 miles (375,820 kilometers) from my home in New Jersey. The same program tells me that on March 19 it was 220,084 miles (354,192 kilometers) away.
Measuring the height of each moon in the picture and dividing, I get that the diameter of the moon on March 19 was 6 percent larger than the December 19 moon, making it 12.4 percent larger in area.
Robert J. Vanderbei is chair of the Operations Research and Financial Engineering department at Princeton University and co-author of the National Geographic book Sizing Up the Universe. Vanderbei has been an astrophotographer since 1999, and he regularly posts new images on his astro gallery website. | 0.866808 | 3.21669 |
Many of us heard that the spacecraft New Horizons launched on a mission to Pluto by NASA 9 and a half years ago, has successfully reached its destination few days ago. This was a very thrilling news and I believe what the authors of this mission and the rest of the world have been curious to know is what does Pluto look like. in the extract below, CNN’s Amanda Barnett brings us the latest on the early pictures and information downloaded from Pluto:
It had been downgraded to a dwarf planet. It looked like a fuzzy blob in our best telescopes. And it was often referred to as just an icy orb. Even scientists working on the first mission to Pluto expected to find an old, pockmarked world.
But Pluto is turning out to be full of surprises.
“I’m completely surprised,” said Alan Stern, principal investigator for NASA’s New Horizons spacecraft.
The first zoomed-in image of Pluto was released on Wednesday, a day after the spacecraft made its closest pass over Pluto, cruising about 7,700 miles over the surface. The probe traveled more than 3.6 billion miles to snap the photo, and scientists think it was well worth the trip.
The new image shows a crisp, clear view of Pluto’s surface, and it’s covered with wide smooth areas, lumpy terrain and mountains. Huge mountains.
“They would stand up respectably against the Rocky Mountains,” said John Spencer, a planetary scientist on the New Horizons mission.
The height of the mountains is important because it’s a clue that there may be water on Pluto. Scientists know that Pluto’s surface is covered with nitrogen ice, methane ice and carbon monoxide ice. But Spencer says, “You can’t make mountains out of that stuff. It’s too soft.”
That leaves H20 — water ice like we have here on Earth.
“The steep topography means that the bedrock that makes those mountains must be made of H2O — of water ice,” said Stern. “We can be very sure that the water is there in great abundance.”
“Who would have supposed that there were ice mountains?” said Hal Weaver, another new Horizons project scientist.
“It’s just blowing my mind,” he said.
Before New Horizons was launched, scientists thought Pluto probably had a rocky core surrounded by a mantle of water ice. But they were having a hard time finding evidence of the water ice, Weaver said. He expects more data from the spacecraft will confirm that the ice mountains mean there is lots of water on Pluto.
“That’s the only way to get these huge mountains, and that’s a big surprise I think.”
Finding water on another world is important because water is considered one of the key ingredients to life as we know it.
Weaver says they’ll learn a lot more about the makeup of Pluto’s ice mountains in the days ahead. It will take about 16 months to download all of the information gathered by New Horizon’s seven instruments during the flyby. | 0.801863 | 3.344014 |
The modern astronomy has gifted us with the great pleasure of knowing our far-off planetary neighbors with more details than ever before. Whether it’s Jupiter’s intimidating Great Red Spot or Saturn’s mesmerizing planetary rings, we now have much better understandings of outer planets in our solar system than anytime else in the entire human history staring from the ancient Babylonians and Chinese.
Today we will reveal much more about the planet Saturn, possibly more than you may know. For starters, Saturn is the second largest planet in our solar system and sixth from the Sun. It is named after the Roman god of agriculture. In many ways, Saturn is similar to Jupiter, but there are many more things about Saturn that you should know. Here are some of the facts about about Saturn.
First Known Observation: By the Ancient Babylonians
Equatorial Diameter: 120,536 km
Orbital Period: 29.5 years
Satellites or Moons: 62 Known Moon
Mass: 5.6834×1026 kg
Density: 0.687 g/cm3
Surface Gravity: 10.44 m/s2
Image Courtesy: NASA
Do you Know that almost 1,600 Saturn can Fit inside the Sun? Now that you know, can you guess how many Earths can fit inside the Sun? The answer is roughly 1.3 million Earths.
14. Chemical Composition
Just like its gaseous neighbor Jupiter, Saturn also has a small rocky core surrounded by mainly hydrogen and Helium. Its inner core is much denser than most of the planets in our solar system with the mass as much as 22 times higher than that of the planet Earth.
Despite the fact that most of its atmosphere is composed of hydrogen and helium, a large amount of Saturn’s mass is actually not in gaseous phase. Traces of other gases like methane, ammonia, hydrogen deuteride and ethane are also found in its atmosphere similar to Jupiter.
13. Physical characteristics
Saturn is the second largest planet in our solar system only after Jupiter. While it has one-eighth of the total density of the Earth, its mass is more than 95 times of the Earth’s and 90 times of its radius. The planet is perhaps famous for its distinguishable, and complex ring system.
Yellow and orange bands of different shades on Saturn’s atmosphere is due to the ultra-fast winds along with the planetary heat flowing in its upper atmosphere. Right now nearly 62 moons are identified orbiting around the planet of which 53 are officially named.
12. Rotation & Orbit
The estimated distance between the Sun and Saturn is about 9AU or 1.4 billion in kilometers. Compared to the Earth, it takes about 29.5 years to complete one rotation around the Sun. Saturn has the second fastest rotation (on its axis) after Jupiter completing one in every 10 hours and 30 minutes. There is a slight difference of several minutes in this rotational speed due to the phenomena of differential rotation which is effective on the planet.
11. It’s Visible in the Night Sky
With a bond albedo of 0.342, Saturn is the fifth brightest the farthest planet we can see with our bare eyes, while telescopes are needed to observe some of its features such as its planetary rings. The far reaches of Saturn are the limit of human eyes. Many times over the course of a year, the planet presents itself slightly brighter than the star Antares.
10. The Planet Was Well Known to the Ancient Babylonians
Saturn has been known to humans since the prehistoric times. The ancient Babylonians were probably the first to observe and record its movements. Early Greeks to their god Cronus while the Romans dedicated the planet to Saturnus, their god of agriculture after which the planet was named. One of the first scientific calculations of its Orbit was performed by Ptolemy when Saturn was in opposition.
9. Saturn is the flattest planet
Saturn is perhaps the flattest planet (near the poles) in the solar system and that’s due to its very low density and relatively higher rotational speed. The planet takes a peculiar shape of a spheroid, which is much flattened at the poles.
8. Bands of Clouds
Image Courtesy: NASA
Saturn’s atmosphere exhibits a banded pattern similar to Jupiter’s, but Saturn’s bands are much fainter and are much wider near the equator. The nomenclature used to describe these bands is the same as on Jupiter. Saturn’s finer cloud patterns were not observed until the flybys of the Voyager spacecraft during the 1980s. The top layers are mostly ammonia ice. Below them, the clouds are largely water ice. Below are layers of cold hydrogen and sulfur ice mixtures.
7. Saturn’s Magnetic Field is Weaker than Earth’s
Unlike Jupiter, Saturn’s magnetic field is much simpler and symmetric in shape. Near its equator, the strength of its magnetic field is around 0.2 Gauss, which is weaker than that of the Earth’s and about one-twentieth that around the planet Jupiter. It is believed that the magnetic field around the planet is generated by the currents from the liquid metallic-hydrogen layer near its core. Even though weak, its magnetosphere is effective in deflecting solar winds coming from the Sun.
6. It’s Second Largest Moon Rhea
Rhea was first discovered by Giovanni Cassini during his observation of Saturn in 1672. It is the second largest moon of Saturn and ninth largest in the entire solar system. Back in 2005, scientists hypothesized the existence of a small ring system, which, if proven will make Rhea the first natural satellite to have its own ring system. But numerous observations done by NASA’s Cassini spacecraft on the icy moon resulted in nothing.
Then again in 2010, NASA revealed the discovery of a weak exosphere around the moon for the first time. This exosphere is mainly composed of carbon dioxide and oxygen in a ratio of 2 to 5. Scientists believe that the oxygen present in the moon’s atmosphere is a result of radiolysis of water ice by the ions present Saturn’s magnetosphere. While the source of carbon dioxide is rather not clear, but its maybe due to some organics present in Rhea’s surface.
5. Eerie Sounds of Saturn’s Radio Transmission
Saturn has been long known as a prominent source of radio emissions in our solar system. But in 2002, Cassini spacecraft detected mysterious radio emissions originated from Saturn’s poles for the first time from about 380 million kilometers from the planet. According to NASA, these eerie sounds are somehow closely related to the auroras near the poles of the planet. These radio emissions were only audible to human ears after they were downsized by the factor of 44.
4. Saturn’s Moon Titan
Titan is the second largest moon in our solar system after Jupiter’s Ganymede and it’s the largest of all 62 known moons of Saturn. Titan is not just larger than most of the moons, but it also outsize Mercury, the smallest planet revolving around the Sun. Due to its special characteristics, Titan is sometimes classified as a planet-like moon.
Its dense Nitrogen-rich atmosphere is somehow similar to that of our Earth. In 2004, data collected by the Cassini spacecraft indicated that the moon might be “super-rotator“, where the atmosphere rotates at much faster rates than the surface. It also features a vortex near its south pole.
3. Cloud Patterns and Vortexes
Saturn’s rather famous hexagon cloud pattern was first detected in 1981 by the two Voyager probes and was again visited by NASA’s Cassini spacecraft in 2006. The enormity of Saturn’s hexagon can be estimated by the fact that each of its sides is approximately 14,000 km long and rotates once in a period of 10 hours 39 minutes and 24 seconds.
Saturn also has a giant vortex near its south pole which was first observed by the Hubble space telescope, but various data shows that it is not a strong polar vortex nor any kind of standing wave like the one on the north pole. According to NASA, this polar vortex may have been there for the last few billion years. There is a second vortex inside the northern hexagon.
2. Saturn’s Iconic Rings
From Jupiter to Neptune, all of the gas giants in our solar system have rings, but Saturn’s are the brightest and significant of all. Although they were first discovered by Italian genius Galileo Galilei in the early 1600s, the first detailed study of these rings was made by Christiaan Huygens in 1655. He also discovered of Saturn’s largest moon Titan. Saturn’s rings stretch from about 6,600 km to 120,700 km from its equator. They are predominantly composed of water with small traces of tholin and amorphous carbon.
1. Recent Researches and Explorations
900 million miles far, Earth shines bright among the many stars. Image Courtesy: NASA
We were able to get close-up images of Saturn for the first time in 1979, when NASA’s Pioneer 11 reached within less than 22,000 km of the planet. That encounter revealed presence of a strong magnetic field and also two of its outer rings. Then the planet was again visited by the Voyagers in 1980-81, and this time we were able to get better images of the gas giant. The probes also discovered some of its new moons.
After the Voyagers, Cassini was the only space probe, which studied the planet in detail. Before its demise, Cassini was able to collect tons of valuable data like the liquid water deposits on Saturn’s Enceladus and detailed images of Phoebe, one of its moons and Titan. In the case of Titan, it was able to take some unique images of lakes and mountains on that moon for the first time. | 0.891926 | 3.461681 |
Get ready, stargazers. On October 21 and 22, the Orionid meteor shower will reach its peak, and you won’t want to miss it.
The Orionid shower occurs when Earth passes through the remnants of Halley’s comet, called meteorites, which burn up in Earth’s atmosphere and leave streaks of light across the sky. Because the meteor shower occurs around the same time each year (mid-October), it’s pretty easy to predict and watch.
For the best chance of seeing the shower, go outside between 10:00 PM and 12:00 AM, as the moon’s light after midnight will make seeing the meteors a bit more difficult. Over 15 meteors will be visible each hour, but the shower’s peak is projected to be around 11:30 PM.
The Orionids got their name because they seem to radiate from the Orion constellation, which is easily recognized by its three stars arranged in a line. While the Orionid meteor shower is relatively small — about 15 meteors per hour in a moonless sky — it’s known to be one of the brightest, most impressive celestial phenomenons. It’s also one of the easiest to spot.
That said, for the best viewings, NASA recommends that you observe them during the hours after midnight, in an area with little light pollution, while lying flat on your back with “your feet facing southeast if you are in the Northern Hemisphere or northeast if you are in the Southern Hemisphere.” It takes about 30 minutes for your eyes to adjust to the dark, so be patient and you’ll be rewarded with a beautiful shower.
A version of this article was previously published on October 2, 2018 and was updated on October 21, 2019. | 0.804138 | 3.293173 |
Nov 21, 2012
Rather than being a stellar nursery the famous dust clouds in the Eagle Nebula may already be gone.
On November 2, 1995, NASA released the now-famous image of M16, the Eagle Nebula, in the constellation Serpens. Jeff Hester, an astronomer from Arizona State University, was quoted as saying:
“For a long time astronomers have speculated about what processes control the sizes of stars — about why stars are the sizes that they are. Now in M16 we seem to be watching at least one such process at work right in front of our eyes.”
Star-forming regions within nebular dust clouds have been discussed many times in previous Picture of the Day articles. The prevailing opinion among astronomers is that stars are created from the collapse of such clouds through gravitational attraction: the Nebular Hypothesis. The theory seems plausible because astronomical images portray what appear to be clouds so dense that they are opaque to visible light and span tens of light-years. What is not usually mentioned in the press releases is that the nebulae are composed of gases and dust a thousand times less dense than a puff of smoke.
The Hubble Space Telescope photographed the similarly diffuse three pillars in 1995 using its optical sensors, but according to observations by the Spitzer Space Telescope a shock wave from a nearby supernova may have already destroyed them. In fact, the Pillars of Creation may have ceased to exist about 6,000 years ago, since there are several candidates for such explosions scattered throughout nearby space.
Stellar ignition is dependent on compressive forces, so most astronomers conclude that shock waves of some nature are necessary for nebular clouds to condense. Supernova blasts are supposed to provide the impetus needed for the initial collapse and to “seed” the region with larger granules that will cause more dust to be attracted to them, as well. Thus, nebulae are deemed “star-forming regions”.
Apparently, Spitzer confirmed that there is an arc-shaped wavefront of luminous material moving through the Eagle Nebula. Due to the great distance involved, infrared radiation emitted from the shell of expanding gas is visible as it was 2000 years ago, so in “real time” it already impacted the Pillars. The visible-light from the supernova might have been seen on Earth about that time as a “new star” in the night sky.
Conventional theory suggests that a compression wave from the supernova as we see it now will both destroy the cloud formations in M16 and begin the process of star birth from the ashes of their destruction. Has science actually increased knowledge with theories such as these? Or has it spun an elaborate tale based on the slimmest of evidence?
The birth and death of stars is illustrated in such stories of gravity and inertia, but they are missing key ingredients that provide continuity to the plot. Where is electricity and conducting plasma filaments to carry the current? Both are ignored. How does the heated gas collapse instead of dissipate, as thermodynamic physics would insist?
The Electric Universe theory relates a more reasonable account. Instead of “hot gas and compressed dust”, it is plasma and electric currents that form electric stars.
Birkeland currents power and shape the galaxy and are constricted by the magnetic fields they generate. Hot gases and dust are prevented from dispersing inside their multi-light-year-long helical coils. When the current density inside the twisted filaments gets high enough the plasma that carries the current begins to glow and to “pinch” into plasmoids that eventually become stars.
When the electrical stress is low and the plasma contains a lower concentration of dust, only the star “lights up” in arc-mode discharge. Where the electrical stress is greater, as in the Eagle Nebula, disks, jets, and the surrounding gas clouds can also light up. Of course, dust clouds can reflect the light from nearby stars, but these glowing plasma formations show the characteristic filaments and cell-like behavior seen in plasma computer simulations. | 0.904104 | 3.788639 |
Jupiter is the biggest planet in our nearby planetary group. It is the fifth planet from the sun, delegated a gas planet and a monster simply like Uranus, Saturn and Neptune. Made up generally of hydrogen, and a littler level of helium, Jupiter does not have an extremely all around characterized surface. It was first found in the seventeenth century by telescope, yet space experts have been watching and recording Jupiter since antiquated circumstances. The planet was named after the ruler of Roman divine beings, Jupiter. There is a ring framework around Jupiter however it is black out. Around evening time, Jupiter is regularly the fourth brightest protest in the sky. The sun, the moon and Venus are brighter.
Jupiter was discovered in 1610 by Galileo Galilei. Galileo also discovered 4 of the moons of Jupiter. These moons are aptly called the Galilean moons in honor of their discoverer. The four moons discovered by Galileo were Callisto, Ganymede, Europa and Io.
The planet Jupiter is the fifth planet out from the Sun, and is two and a half times more massive than all the other planets in the solar system combined.
Jupiter is the giant of the Solar System, with a mass more than 300 times the mass of the Earth and is called after the ancient Roman sky-god, Jupiter, known to the Greeks as Zeus.
The mass of the core of Jupiter is 10 times the mass of our Earth. The layer of fluid metallic hydrogen that covers the core extends up to 90% of the diameter of the planet. Some scientists believe that the core of Jupiter is made of rocks, metals, water ice, ammonia ice and methane ice.
Jupiter is the fourth brightest object in the solar system.Only the Sun, Moon and Venus are brighter. It is one of five planets visible to the naked eye from Earth.
Jupiter takes only 9 hours and 55 minutes to spin on its axis. This means a day on Jupiter is less than 10 hours long. Its fast rotation causes the planet to be squashed, being wider at the equator than from North to South.
Jupiter is the planet with the strongest pull of gravity in the Solar System. If we were able to stand on the surface of Jupiter, we would weigh three times as much as we would weigh on Earth. The only other object in the Solar System with a stronger pull of gravity is the Sun.
Jupiter’s moon Ganymede is the largest moon in the solar system.Jupiter’s moons are some times called the Jovian satellites, the largest of these are Ganymeade, Callisto, Io and Europa. Ganymeade measures 5,268 km across, making it larger than the planet Mercury.
Jupiter is 7% wider at its equator compare to its width at the poles. This is because of its extreme spinning speed that makes the planet bulge out at its waistline.
The atmosphere of Jupiter is composed of 10.2% helium, 89.8% molecular hydrogen and trace amounts of ammonia hydrosulfide aerosols, water ice aerosols, water, ethane, hydrogen deuterite, ammonia and methane.
The core of Jupiter is massive and dense. Its composition is uncertain. The core is surrounded by a layer of helium-rich fluid metallic hydrogen and the whole thing is then wrapped up in an atmosphere that primarily consists of molecular hydrogen.
There are 63 moons in total, four of which are large enough to be easily observed with a small telescope.
The first person to discover and observe Jupiter’s moons was Galileo (1564-1642).
Jupiter orbits the Sun once every 11.8 Earth years.From our point of view on Earth, it appears to move slowly in the sky, taking months to move from one constellation to another.
Jupiter has a very strong magnetic field. This is around 14 times stronger than the magnetic field found on Earth – the largest of any planet in the solar system.
Thick, colorful clouds of deadly poisonous gases surround Jupiter. The quick spinning of the planet whips up the atmosphere, creating the bands around the planet.
The white clouds are formed by frozen ammonia crystals while the dark clouds are the results of other chemicals that are found in the darker belts.
Blue clouds can be seen at the deepest visible levels of Jupiter’s atmosphere.
The Great Red Spot is the most extraordinary feature of Jupiter. It is actually a storm akin to a hurricane on Earth. This storm has been visible for at least 300 years. There are times when the Great Red Spot completely disappears. This Great Red Spot, at the widest points, is 3 times as wide as Earth’s diameter. The edges of the spot spin around its center in a counterclockwise direction at a speed of 360 kilometers per hour or 225 miles per hour.
Interestingly, if Jupiter had managed to grab 80 times more mass than its current mass, it would actually end up being a star instead of a planet.
Jupiter’s atmosphere is very similar to that of our Sun. The atmosphere is made up to mostly helium and hydrogen.
Jupiter has colored bands. These are visible in form of light zones and dark belts. These colored bands originate because of the strong east-west winds that travel in the upper atmosphere of the planet at a speed of 640 kilometers per hour or 400 miles per hour.
Jupiter is the fastest spinning planet in Solar System. It completes one rotation around its axis in just under 10 hours.
Jupiter has a liquid metal ocean (metallic hydrogen) at its center, surrounded by thousands of kilometers of hydrogen and helium gas.
Jupiter has a big red spot known as Jupiter’s Great Red Spot.The red spot is a huge storm that has been
continuously going on Jupiter for over 350 years. Winds inside this storm reach speeds of about 435 km/h (270 mp/h).
Jupiter is so massive that its total mass is twice as much as the mass of all planets in Solar System combined together. Jupiter is capable of holding 1300 Earths in it. However, the mass of Jupiter is only 1 thousandths of the total mass of Sun.
Jupiter is the vacuum cleaner of the Solar System. It sucks in comets, asteroids and meteorites which could be on a collision course for Earth.
Eight spacecraft have visited Jupiter.Pioneer 10 and 11, Voyager 1 and 2, Galileo, Cassini, Ulysses, and New Horizons missions. The Juno mission is its way to Jupiter and will arrive in July 2016.
The first recorded sighting of Jupiter were by the ancient Babylonians in around 7th or 8th BC.
The magnetic field of Jupiter is 20,000 times stronger to that of Earth’s magnetic field.
Because of its gargantuan magnetic field, the planet is capable of trapping electronically charged particles such as electrons and other particles. These particles form a belt around the planet. The moons and the rings of Jupiter are regularly blasted with radiations.
The radiations from this belt is 1000 times stronger than the lethal dose of radiation for humans. The radiations are so intense that they even damaged the Galileo probe of NASA that was heavily shielded.
The entire magnetosphere of Jupiter (the magnetic fields and the charged particles) extend out to some 600 million miles behind the planet and some 600,000 miles to 2 million miles towards the Sun. | 0.846413 | 3.035141 |
NASA’s super exciting Dawn mission to the Asteroid Belt marked a major milestone in human history by becoming the first ever spacecraft from Planet Earth to achieve orbit around a Protoplanet – Vesta – on July 16. Dawn was launched in September 2007 and was 117 million miles (188 million km) distant from Earth as it was captured by Asteroid Vesta.
Dawn’s achievements thus far have already exceeded the wildest expectations of the science and engineering teams, and the adventure has only just begun ! – so say Dawn’s Science Principal Investigator Prof. Chris Russell, Chief Engineer Dr. Marc Rayman (think Scotty !) and NASA’s Planetary Science Director Jim Green in exclusive new interviews with Universe Today.
As you read these words, Dawn is steadily unveiling new Vesta vistas never before seen by a human being – and in ever higher resolution. And it’s only made possible via the revolutionary and exotic ion propulsion thrusters propelling Dawn through space (think Star Trek !). That’s what NASA, science and space exploration are all about.
“Dawn is in orbit, remains in good health and is continuing to perform all of its functions,” Marc Rayman of the Jet Propulsion Laboratory, Pasadena, Calif., told me. “Indeed, that is how we know it achieved orbit. The confirmation received in a routine communications session that it has continued thrusting is all we needed.”
Dawn entered orbit at about 9900 miles (16000 km) altitude after a nearly 4 year journey of 1.73 billion miles.
Over the next few weeks, the spacecrafts primary task is to gradually spiral down to its initial science operations orbit, approximately 1700 miles above the pock marked surface.
Vesta is the second most massive object in the main Asteroid Belt between Mars and Jupiter. Dawn is the first probe to orbit an object in the Asteroid Belt.
I asked Principal Investigator Chris Russell from UCLA for a status update on Dawn and to describe what the team can conclude from the images and data collected thus far.
“The Dawn team is really, really excited right now,” Russell replied.
“This is what we have been planning now for over a decade and to finally be in orbit around our first ‘protoplanet’ is fantastic.”
“The images exceed my wildest dreams. The terrain both shows the stress on the Vestan surface exerted by 4.5 billion years of collisions while preserving evidence [it seems] of what may be internal processes. The result is a complex surface that is very interesting and should be very scientifically productive.”
“The team is looking at our low resolution images and trying to make preliminary assessments but the final answers await the higher resolution data that is still to come.”
Russell praised the team and described how well the spacecraft was operating.
“The flight team has been great on this project and deserves a lot of credit for getting us to Vesta EARLY and giving us much more observation time than we had planned,” Russell told me.
“And they have kept the spacecraft healthy and the instruments safe. Now we are ready to work in earnest on our science observations.”
Dawn will remain in orbit at Vesta for one year. Then it will fire its ion thrusters and head for the Dwarf Planet Ceres – the largest object in the Asteroid Belt. Dawn will then achieve another major milestone and become the first spacecraft ever to orbit two celestial objects.
Jim Green, Director of Planetary Science for the Science Mission Directorate (SMD) at NASA HQ in Washington, DC, summed up his feelings about Dawn in this way;
“Getting Dawn into orbit is an amazing achievement,” Green told me.
“Instead of the ‘fire the thrusters full blast’ we just sort of slid into orbit letting gravity grab the spacecraft with a light tug. This gives us great confidence that the big challenge down the road of getting into orbit around Ceres can also be accomplished just as easily.”
Sharper new images from Vesta will be published by NASA in the next day or so.
“We did take a few navigation images in this last sequence and when they get through processing they should be put on the web this week,” Russell informed. “These images are from a similar angle to the last set and with somewhat better resolution and will not reveal much new.”
However, since Dawn is now orbiting Vesta our upcoming view of the protoplanet will be quite different from what we’ve seen in the approach images thus far.
“We will be changing views in the future as the spacecraft begins to climb into its science orbit,” stated Russell.
“This may reveal new features on the surface as well as giving us better resolution. So stay tuned.”
Marc Rayman explained how and why Dawn’s trajectory is changing from equatorial to polar:
“Now that we are close enough to Vesta for its gravity to cause a significant curvature in the trajectory, our view is beginning to change,” said Rayman. “That will be evident in the pictures taken now and in the near future, as the spacecraft arcs north over the dark side and then orbits back to the south over the illuminated side.”
“The sun is over the southern hemisphere right now,” added Russell. “When we leave we are hoping to see it shine in the north.”
Dawn is an international mission with significant participation from Germany and Italy. The navigation images were taken by Dawn’s framing cameras which were built in Germany.
Exploring Vesta is like studying a fossil from the distant past that will immeasurably increase our knowledge of the beginnings of our solar system and how it evolved over time.
Vesta suffered a cosmic collision at the south pole in the distant past that Dawn can now study at close range.
“For now we are viewing a fantastic asteroid, seeing it up close as we zero in on its southern hemisphere, looking at the huge central peak, and wondering how it got there,” explained Jim Green
“We know Vesta was nearly spherical at one time. Then a collision in its southern hemisphere occurred blowing off an enormous amount of material where a central peak now remains.”
That intriguing peak is now obvious in the latest Dawn images from Vesta. But what does it mean and reveal ?
“We wonder what is that peak? replied Green. “Is it part of the core exposed?
“Was it formed as a result of the impact or did it arise from volcanic action?”
“The Dawn team hopes to answer these questions. I can’t wait!” Green told me.
As a result of that ancient south pole collision, about 5% of all the meteorites found on Earth actually originate from Vesta.
Keep your eyes glued to Dawn as mysterious Vesta’s alluring secrets are unveiled.
Read my prior features about Dawn
Dawn Closing in on Asteroid Vesta as Views Exceed Hubble
Revolutionary Dawn Closing in on Asteroid Vesta with Opened Eyes | 0.863237 | 3.227991 |
This astronomical event will be broadcast live via the channel sky-live.tv in the early hours of January 4th, with the collaboration of the European project EELabs. Together with the Geminids and the Perseids, this is the most intense meteor shower of the year.
The three most spectacular meteor showers of the year are the Perseids (in August) the Geminids (in December) and the Quadrantids in the first week of January. Although the Perseids are the best known, the maximum is in a holiday period with mild night-time temperatures, the Geminids and the Quadrantids never let us down, with an activity which reaches 100 meteors per hour (zenith hourly rate, ZHR) and remains constant year by year (the activity of the Quadrantids in 2019 in IMO).
The Quadrantids are at their maximum during the first week of January. For 2020 this maximum is predicted for 08:20 UT on January 4th. So that in Europe the night of January 3rd-4th will be the best moment to observe them. It is best to wait until the early morning of the 4th of January, when the constellation of Bootes is high in the sky, and there will not be a Moon. The final activity of meteors is predicted at an average rate of one every 4 minutes, some of them very bright, if we are at a dark site with a clear view to the horizon.
As the radiant, the point in the sky from which the meteors appear to diverge, is near to the Plough, in fact within the constellation of Bootes, which occupies a part of the now no longer used constellation of Quadrans Muralis, (which is why they are called the Quadrantids) their activity is not seen in the southern hemisphere.
The Quadrantids and the Geminids are special meteor showers
So called “shooting stars” are really tiny particles of dust with a range of sizes, some smaller than grains of sand, which are left behind by comets during their orbits around the Sun. The current of particles produced this way (called meteoroids) produced by the thawing of the comet as it is affected by the Sun’s heat, is dispersed along the comet’s orbit, and it is traversed every year by the Earth in its orbit round the Sun.
During the encounter the particles of dust disintegrate when they enter the Earth’s atmosphere, making the well know luminous trails which are called, scientifically, meteors. This general picture is valid for most meteor showers, but for the Quandrantids and the Geminids there is not comet whose path around the Sun coincides with this cloud of “debris”.Their progenitors are asteroids, 3200 Phaeton, for the Geminids, and 2003 EH for the Quadrantids.
Live from the Teide Observatory
Within the popularization initiatives of the European Project EELabs (eelabs.eu), the channel sky-live.tv will offer a live broadcast of the meteor shower from the Teide Observatory (IAC, Tenerife, Islas Canarias).
The appointment is in the early morning of Saturday, January 4th at 6.30 UT (which is local time in the Canaries and the UK, and 7.30 Central European Time)
“It`s never eay to get up at six in the morning, especially in early January, with holidays and cold weather, but it is worth it.This year there will be no Moon,so that we should seen a pretty spectacle with activity at almost a hundred meteors per hour” comments Miquel Serra-Ricart, an IAC astronomer.
EELabs (eelabs.eu) is a project funded by the Programme INTERREG V-A MAC 2014-2020, cofinanced by FEDER (The European Fund for Regional Development) of the European Union, under contract MAC2/4.6d/238. There are 5 centres in Macaronesia working within EELbs (IAC, ITER; ULPGC, SPEA-Azores, SPEA-Madeira). The aim of EELabs is to create Laboratories to measure the energy efficiency of the artificial night lighting in the natural protected areas of Macaronesia (the Canaries, Madeira, and the Azores).
Three Spanish Supercomputer Centres: the Extremadura Centre for Advanced Technology (CETA-CIEMAT, the Consortium of University Servers of Catalonia (CSUC) and the Instituto de Astrofísica de Canarias (IAC) collaborate in the distribution and the broadcasting of the web portal (sky-live.tv).
Star counters and app (www.contadoresdeestrellas.org)
The best Quadrantids of the year 2017 (https://flic.kr/p/2i583k6)
Images and videos of meteor showers (https://flic.kr/s/aHsjH2BFa4)
CAPTION: Meteors registered at the Teide Observatory (IAC) between 06:13 h and 06: 38 h UT (Local Canary time) on 4th January 2107. The brightest star to the left is Procyon (alpha Canis Minoris) while Castor and Pollux (alpha and beta Geminis respectively) are almost in the centre. The cluster which in the upper part of the picture is Praesepe (the Beehive) in the constellation of Cancer. Most of the meteors recorded are Cuandrantids. High resolution image at https://flic.kr/p/J1T4Yn | 0.870514 | 3.723621 |
Japanese engineers hurriedly redesigned the rock-collector and science payloads on the Hayabusa 2 spacecraft set to launch on an asteroid-sampling mission in late 2014, hoping to trump a problem which limited the load of asteroid rock fragments brought home by a preceding mission.
With the launch of Hayabusa 2 scheduled in less than 2 years, engineers did not have time to make major alterations to the probe based on lessons learned from the Hayabusa mission, which returned the first samples from the surface of an asteroid to Earth in June 2010, according to Shogo Tachibana, a researcher from Hokkaido University in Japan and lead scientist for the Hayabusa 2 sampling system.
The 1,320-pound Hayabusa 2 probe, slightly larger than the preceding Hayabusa spacecraft, is due for launch on a Japanese H-2A rocket in December 2014, and its destination is asteroid 1999 JU3, an object about 3,000 feet in length. Hayabusa 2 will arrive at 1999 JU3 in 2018 and loiter around the asteroid for about 18 months. Hayabusa spent about three months near asteroid Itokawa, a smaller rock than 1999 JU3.
After up to three close approaches to acquire samples, Hayabusa 2 will depart the asteroid and deploy a sample-bearing re-entry capsule into Earth’s atmosphere in December 2020.
Although the first Hayabusa mission made history, it collected substantially fewer samples than expected because the spacecraft’s rock-gathering device failed to function when the probe approached Itokawa.
Hayabusa also suffered from a crippling fuel leak, ion engine failures, reaction wheel problems, battery issues and a break in communications with Earth for two months, and Japanese officials grew concerned they would lose the spacecraft.
But controllers delayed Hayabusa’s return to Earth by three years, buying time for engineers to devise a method of using the craft’s remaining ion propulsion engines to control its orientation and guide the probe home.
When scientists opened Hayabusa’s re-entry capsule after it landed in Australia, they found more than 1,500 tiny rock and soil grains, most of which were confirmed to be from Itokawa.
Launched in May 2003, Hayabusa made two descents toward Itokawa in late 2005 to collect samples, and the spacecraft was supposed to fire a tantalum pellet into the asteroid and scoop up bits of rock blasted away by the projectile.
The tantalum bullet did not fire on either sampling attempt, and scientists feared the mission was a failure.
But an analysis of telemetry from Hayabusa showed the probe inadvertently landed on the asteroid for up to a half-hour, leaving officials hopeful some surface specimens made their way through the craft’s sampling horn and into a collection chamber.
It turns out that is what happened.
Before the Hayabusa probe returned to Earth, scientists proposed a follow-on mission named Hayabusa 2, which received approval from the Japanese government in January 2012.
But with the mission slated to launch in late 2014, engineers had to prioritize what upgrades to make to the spacecraft, which will use much the same technology flown on Hayabusa.
Like its predecessor, Hayabusa 2 carries four ion engines, but the efficient electrically-propelled engines will generate more power on the new spacecraft. And Hayabusa 2 will have a Ka-band communications antenna to beam data and imagery back to Earth at higher speeds than Hayabusa, according to Makoto Yoshikawa, Hayabusa 2’s project manager at the Japan Aerospace Exploration Agency.
NASA’s Deep Space Network will support communications with the Japanese probe.
And with the benefit of a decade’s progress in computer development, Hayabusa 2 will use upgraded software to keep the probe resilient to faults caused by radiation and other threats.
Once it arrives at asteroid 1999 JU3, Hayabusa 2 will survey the rock with an array of instruments, including imagers, a spectrometer, and a terrain-mapping altimeter.
The craft will also release a small Japanese rover named MINERVA to hop across the surface of the asteroid and deploy the MASCOT lander developed by the German Aerospace Center, or DLR.
Led by the DLR Institute of Space Systems in Bremen, Germany, with support from the French space agency, the Mobile Asteroid Surface Scout will measure the asteroid’s magnetic field, surface temperature, rock composition, and take pictures during descent and after landing, according to a presentation by Ralf Jaumann, a planetary scientist at DLR.
Scientists will compare data from MASCOT and the Japanese lander to analyses of samples returned to Earth by Hayabusa 2.
Hayabusa 2’s destination is a different type of miniature world than Itokawa. Asteroid 1999 JU3 is a C-type asteroid, a classification of primitive objects made of organic and hydrated minerals
Itokawa is an S-type asteroid composed of rocks and metals heated and modified over the solar system’s 4.5 billion year history, causing the material to lose chemical markers left over from the dawn of the solar system.
Scientists expect the Hayabusa 2 samples to hold a record of the tumultuous early phases of the solar system’s formation, including the basic building blocks of life such as amino acids.
“These C-type asteroids could be the bridge from the start of the evolution of the solar system to the beginning of life on Earth,” Tachibana said in an interview at the 44th Lunar and Planetary Science Conference near Houston.
Mission planners designed Hayabusa 2 to make three sampling attempts at its target asteroid, one more than Hayabusa made at Itokawa. On each attempt, Hayabusa 2 will approach 1999 JU3 at low speeds and try to scoop up pebbles with a 3-foot-long sampling horn during brief touchdowns on the asteroid.
Two of the sampling attempts will focus on regions identified to be rich in hydrated, water-rich minerals and organic molecules. Hayabusa 2’s sampling system will fire a tantalum projectile into the asteroid to kick up rocks into the 5.5-inch opening of a funnel leading into a storage container.
The sampling gun did not fire on Hayabusa’s visit to asteroid Itokawa, limiting the probe’s haul of samples for return to Earth to tiny grains of dust. Engineers blamed the failure on a software coding error.
Tachibana is confident the tantalum bullet will fire on Hayabusa 2, but even with another glitch, engineers devised a backup method to ensure the probe comes home with more samples than Hayabusa. The end of the new sampling horn has teeth like a comb to dig into the asteroid’s gravely surface to pick up some material even if the sampling gun does not fire, according to Tachibana.
“Even if the bullet does not shoot, as long as we touch down, we will get samples,” Tachibana said.
Hayabusa 2 will collect a third sample with the help of a small copper impactor, which was not aboard the Hayabusa mission to Itokawa.
Slamming into the asteroid at more than 4,000 mph, the grapefruit-sized impactor will blast a crater and excavate material from beneath the rock’s surface. After the collision, Hayabusa 2 will glide to a soft landing at or near the impact site, collecting material from the newly-formed crater.
Scientists say the subsurface samples are more pristine than surface rocks, which are exposed to weathering from radiation and the solar wind.
Each sample will be funneled into three separate holding chambers to separate the specimens, then the containers will be sealed to trap volatile compounds like hydroxides.
Depending on the texture of the rocks on 1999 JU3, Hayabusa 2 should pick up between a gram and several grams of samples.
That is much less than the 60-gram, or 2.1-ounce, sampling goal of NASA’s OSIRIS-REx asteroid mission scheduled for launch in September 2016. Some scientists say OSIRIS-REx could corral more than 4 pounds of asteroid material under the right conditions.
“We get much less samples than OSIRIS-REx, but we think we can do a lot of science with our samples,” Tachibana said. “Of course, we want to have more.”
OSIRIS-REx is targeting another primitive carbon-rich asteroid similar to Hayabusa 2’s target. It will arrive at asteroid 1999 RQ36 in 2020 and return to Earth in 2023.
Tachibana said OSIRIS-REx and Hayabusa 2 are complementary.
“They get more samples, but we get samples with better quality,”Tachibana said, adding that Hayabusa 2’s sample container has the advantage of differentiating each batch of asteroid material from three sampling attempts. | 0.811184 | 3.464629 |
The life cycle of stars comes full circle in a new photo taken by NASA's Chandra X-ray Observatory and the Smithsonian's Submillimeter Array (SMA), which may reveal new clues for studying star evolution.
The photo captures a large cloud called Cygnus X-3 and another smaller cloud, nicknamed the "Little Friend." Cygnus X-3 contains a massive, short-lived star that is slowly being eaten by a companion black hole or neutron star and, as a result, produces bright, powerful X-rays. The Little Friend, on the other hand, is a dense cloud of gas and dust that gives birth to new stars called a Bok globule. You can take a video tour of the "Little Friend" here.
The two stellar bodies are located relatively close to one another. The Little Friend — which is roughly 0.7 light-years in diameter — acts as a mirror, "reflecting some of the X-rays generated by Cygnus X-3 towards Earth," according to a statement from NASA. [Monster Black Hole Eats Star, Returns Leftovers]
"We nicknamed this object the 'Little Friend' because it is a faint source of X-rays next to a very bright source that showed similar X-ray variations," Michael McCollough, an astronomer from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, and lead author of the study, said in the statement.
The faint X-rays radiating from the Little Friend were first spotted in 2003, using Chandra's high-resolution X-ray telescope. In 2013, astronomers later found the Little Friend had a mass between two and 24 times that of the sun, and deduced that it was likely a nursery for infant stars (a Bok globule).
Using the Submillimeter Array — a series of eight radio dishes atop Mauna Kea in Hawaii — astronomers detected molecules of carbon monoxide, confirming the Little Friend was, in fact, a Bok globule. A jet or outflow was also found within the Little Friend, indicating a star has started to form inside. "This discovery provides a new way to study how stars form," officials said in the statement.
"Typically, astronomers study Bok globules by looking at the visible light they block or the radio emission they produce," Lia Corrales, a study co-author from the Massachusetts Institute of Technology, said in the statement. "With the Little Friend, we can examine this interstellar cocoon in a new way using X-rays — the first time we have ever been able to do this with a Bok globule."
What's more, the Little Friend is located approximately 20,000 light-years from Earth, making it the most distant Bok globule ever recorded, NASA officials said.
The close proximity of the two stellar bodies provides astronomers with a unique opportunity to measure how far away Cygnus X-3 is from Earth.
"Since the early 1970s, astronomers have observed a regular 4.8-hour variation in the X-rays from Cygnus X-3," officials said in the statement. "The Little Friend, acting as an X-ray mirror, shows the same variation, but slightly delayed because the path the reflected X-rays take is longer than a straight line from Cygnus X-3 to Earth."
Based on the delay time between Cygnus X-3 and the Little Friend, astronomers estimate Cygnus X-3 is about 24,000 light-years from Earth, according to the study, published in The Astrophysical Journal Letters.
That distance puts Cygnus X-3 outside the Milky Way's four spiral arms, which is particularly surprising, the astronomers said.
Cygnus X-3 contains a massive, short-lived star and therefore likely "originated in a region of the Galaxy where stars are still likely to be forming," NASA officials said in the statement. However, "these regions are only found in the Milky Way's spiral arms," which means Cygnus was relocated (at speeds between 400,000 and 2 million miles per hour), following the supernova explosion that formed its companion black hole or neutron star.
"In some ways it's a surprise that we find Cygnus X-3 where we do," Michael Dunham, an astronomer from the CfA and co-author of the study, said in the statement. "We realized something rather unusual needed to happen during its early years to send it on a wild ride." | 0.910327 | 3.829648 |
There may be far more black holes wandering space, consuming all in their path, says worrying new research
The team from Montana State University targeted dwarf galaxies, which are 100 times less massive than our own Milky Way, for study as these are the smallest known to possibly host black holes. Given the size of the galaxies, it follows that their black holes would also be relatively small, though still somewhere in the region of 400,000 times the mass of our sun.Also on rt.com ‘Impossible black hole’ discovery in Milky Way may have been just that, as scientists spot major errors in research
The team began by surveying galaxies in the NASA-Sloan Atlas, a catalog of readily visible galaxies, before cross-referencing potential candidates with the National Radio Astronomy Observatory's Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey, to form a candidate list of 111 galaxies.
Using the National Science Foundation's Karl G. Jansky Very Large Array (VLA), the team discovered 13 such black holes in dwarf galaxies less than a billion light years away. However, these massive, predatory black holes were found to be roving around their galaxies and consuming surrounding material such as stars, planets and moons as opposed to remaining stationary at the galaxy’s center.Also on rt.com Milky Way soiree: Our galaxy was filled with almost 100k supernovae roughly 1bn years ago
This indicates that the galaxies likely merged with others in the past, and leads to the rather terrifying conclusion that there may be far more black holes wandering out there than we thought, consuming everything in their path.
“This work has taught us that we must broaden our searches for massive black holes in dwarf galaxies beyond their centers to get a more complete understanding of the population and learn what mechanisms helped form the first massive black holes in the early universe,” said Amy Reines of Montana State University.
Think your friends would be interested? Share this story! | 0.815039 | 3.324766 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.