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The long standing view on the formation of stars is that they form in clusters. This theory is supported by understanding of the formation process that requires large clouds of gas and dust to be able to condense. Small clouds with enough mass to only form one star just can’t meet the required conditions to condense. In a large cloud, where conditions are sufficient, once one star begins, the feedback effects from this star will trigger other star formation. Thus, if you get one, you’ll likely get lots.
But a new paper takes a critical look at whether or not all stars really form in clusters.
The main difficulty in answering this question boils down to a simple question: What does it mean to be “in” a cluster. Generally, members of a cluster are stars that are gravitationally bound. But as time passes, most clusters shed members as gravitational interactions, both internal and external, remove outer members. This blurs the boundary between being bound and unbound.
Similarly, some objects that can initially look very similar to clusters can actually be groups known as an association. As the name suggests, while these stars are in close proximity, they are not truly bond together. Instead, their relative velocities will cause the the group to disperse without the need for other effects.
As a result, astronomers have considered other requirements to truly be a member of a cluster. In particular for forming stars, there is an expectation that cluster stars should be able to interact with one-another during the formation process.
Its these considerations that this new team uses as a basis, led by Eli Bressert from the University of Exeter. Using observations from Spitzer, the team analyzed 12 nearby star forming regions. By conducting the survey with Spitzer, an infrared telescope, the team was able to pierce the dusty veil that typically hides such young stars.
By looking at the density of the young stellar objects (YSOs) in the plane of the sky, the team attempted to determine just what portion of stars could be considered true cluster members under various definitions. As might be expected, the answer was highly dependent on the definition used. If a loose and inclusive definition was taken, they determined that 90% of YSOs would be considered as part of the forming cluster. However, if the definition was drawn at the narrow end, the percentage dropped as low as 40%. Furthermore, if the additional criterion of needing to be in such proximity that their “formation/evolution (along with their circumstellar disks and/or planets) may be affected by the close proximity of their low-mass neighbours”, the percentage dropped to a scant 26%.
As with other definition boundaries, the quibbling may seem little more than a distraction. However, with such largely varying numbers attached to them, these triflings carry great significance since inconsistent definitions can greatly distort the understanding. This study highlights the need for clarity in definitions for which astronomers constantly struggle in a muddled universe full overlapping populations and shades of gray. | 0.859796 | 3.995208 |
The first 1.5 billion years of Earth's evolution is subject to considerable uncertainty due to the lack of any significant rock record prior to four billion years ago and a very limited record until about three billion years ago. Rocks of this age are usually extensively altered making comparisons to modern rock quite difficult. In new research conducted at LSU, scientists have found evidence showing that komatiites, three-billion-year old volcanic rock found within the Earth's mantle, had a different composition than modern ones. Their discovery may offer new information about the first one billion years of Earth's development and early origins of life. Results of the team's work has been published in the October 2017 edition of NATURE Geoscience.
The basic research came from more than three decades of LSU scientists studying and mapping the Barberton Mountains of South Africa. The research team, including LSU geology professors Gary Byerly and Huiming Bao, geology PhD graduate Keena Kareem, and LSU researcher Benjamin Byerly, conducted chemical analyses of hundreds of komatiite rocks sampled from about 10 lava flows.
"Early workers had mapped large areas incorrectly by assuming they were correlatives to the much more famous Komati Formation in the southern part of the mountains. We recognized this error and began a detailed study of the rocks to prove our mapping-based interpretations," said Gary Byerly.
Within the rocks, they discovered original minerals called fresh olivine, which had been preserved in remarkable detail. Though the mineral is rarely found in rocks subjected to metamorphism and surface weathering, olivine is the major constituent of Earth's upper mantle and controls the nature of volcanism and tectonism of the planet. Using compositions of these fresh minerals, the researchers had previously concluded that these were the hottest lavas to ever erupt on Earth's surface with temperatures near 1600 degrees centigrade, which is roughly 400 degrees hotter than modern eruptions in Hawaii.
"Discovering fresh unaltered olivine in these ancient lavas was a remarkable find. The field work was wonderfully productive and we were eager to return to the lab to use the chemistry of these preserved olivine crystals to reveal clues of the Archean Mantle," said Kareem
The researchers suggest that maybe a chunk of early-Earth magma ocean is preserved in the approximately 3.2 billion year-old minerals.
"The modern Earth shows little or no evidence of this early magma ocean because convection of the mantle has largely homogenized the layering produced in the magma ocean. Oxygen isotopes in these fresh olivines support the existence of ancient chunks of the frozen magma ocean. Rocks like this are very rare and scientifically valuable. An obvious next step was to do oxygen isotopes," said Byerly.
This study grew out of work taking place in LSU's laboratory for the study of oxygen isotopes, a world-class facility that attracts scientists from the U.S. and international institutions for collaborative work. The results of the study were so unusual that it required extra care to be certain of the results. Huiming Bao, who is also the head of LSU's oxygen isotopes lab, said that the team triple and quadruple checked the data by running with different reference minerals and by calibrating with other independent labs.
"We attempted to reconcile the findings with some of the conventional explanations for lavas with oxygen isotope compositions like these, but nothing could fully explain all of the observations. It became apparent that these rocks preserve signatures of processes that occurred over four billion years ago and that are still not completely understood," said Benjamin Byerly.
Oxygen isotopes are measured by the conversion of rock or minerals into a gas and measuring the ratios of oxygen with the different masses of 16, 17, and 18. A variety of processes fractionate oxygen on Earth and in the Solar System, including atmospheric, hydrospheric, biological, and high temperature and pressure.
"Different planets in our solar system have different oxygen isotope ratios. On Earth this is modified by surface atmosphere and hydrosphere, so variations could be due either to heterogeneous mantle (original accumulation of planetary debris or remnants of magma ocean) or surface processes," said Byerly. "Either might be interesting to study. The latter because it would also provide information about the early surface temperature of Earth and early origins of life."
This work was supported by a National Science Foundation grant awarded to Byerly, a NASA grant awarded to Bao, and general support from LSU. | 0.800104 | 3.346935 |
Scientists working with data from NASA's Cassini mission have developed a new way to understand the atmospheres of exoplanets by using Saturn's smog-enshrouded moon Titan as a stand-in. The new technique shows the dramatic influence that hazy skies could have on our ability to learn about these alien worlds orbiting distant stars.
The work was performed by a team of researchers led by Tyler Robinson, a NASA Postdoctoral Research Fellow at NASA's Ames Research Center in Moffett Field, California. The findings were published May 26 in the Proceedings of the National Academy of Sciences.
"It turns out there's a lot you can learn from looking at a sunset," Robinson said.
Light from sunsets, stars and planets can be separated into its component colors to create spectra, as prisms do with sunlight, in order to obtain hidden information. Despite the staggering distances to other planetary systems, in recent years researchers have begun to develop techniques for collecting spectra of exoplanets. When one of these worlds transits, or passes in front of its host star as seen from Earth, some of the star's light travels through the exoplanet's atmosphere, where it is changed in subtle, but measurable, ways. This process imprints information about the planet that can be collected by telescopes. The resulting spectra are a record of that imprint.
Spectra enable scientists to tease out details about what exoplanets are like, such as aspects of the temperature, composition and structure of their atmospheres.
Robinson and his colleagues exploited a similarity between exoplanet transits and sunsets witnessed by the Cassini spacecraft at Titan. These observations, called solar occultations, effectively allowed the scientists to observe Titan as a transiting exoplanet without having to leave the solar system. In the process, Titan's sunsets revealed just how dramatic the effects of hazes can be.
Multiple worlds in our own solar system, including Titan, are blanketed by clouds and high-altitude hazes. Scientists expect that many exoplanets would be similarly obscured. Clouds and hazes create a variety of complicated effects that researchers must work to disentangle from the signature of these alien atmospheres, and thus present a major obstacle for understanding transit observations. Due to the complexity and computing power required to address hazes, models used to understand exoplanet spectra usually simplify their effects.
"Previously, it was unclear exactly how hazes were affecting observations of transiting exoplanets," said Robinson. "So we turned to Titan, a hazy world in our own solar system that has been extensively studied by Cassini."
The team used four observations of Titan made between 2006 and 2011 by Cassini's visual and infrared mapping spectrometer instrument. Their analysis provided results that include the complex effects due to hazes, which can now be compared to exoplanet models and observations.
With Titan as their example, Robinson and colleagues found that hazes high above some transiting exoplanets might strictly limit what their spectra can reveal to planet transit observers. The observations might be able to glean information only from a planet's upper atmosphere. On Titan, that corresponds to about 90 to 190 miles (150 to 300 kilometers) above the moon's surface, high above the bulk of its dense and complex atmosphere.
An additional finding from the study is that Titan's hazes more strongly affect shorter wavelengths, or bluer, colors of light. Studies of exoplanet spectra have commonly assumed that hazes would affect all colors of light in similar ways. Studying sunsets through Titan's hazes has revealed that this is not the case.
"People had dreamed up rules for how planets would behave when seen in transit, but Titan didn't get the memo," said Mark Marley, a co-author of the study at NASA Ames. "It looks nothing like some of the previous suggestions, and it's because of the haze."
The team's technique applies equally well to similar observations taken from orbit around any world, not just Titan. This means that researchers could study the atmospheres of planets like Mars and Saturn in the context of exoplanet atmospheres as well.
"It's rewarding to see that Cassini's study of the solar system is helping us to better understand other solar systems as well," said Curt Niebur, Cassini program scientist at NASA Headquarters in Washington.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology, Pasadena, manages the mission for NASA's Science Mission Directorate in Washington. The VIMS team is based at the University of Arizona in Tucson.
More information about Cassini is available at the following sites:
News Media ContactPreston Dyches 818-354-5011
Jet Propulsion Laboratory, Pasadena, California
NASA's Ames Research Center, Moffett Field, California | 0.858072 | 4.081887 |
U-M space weather model picked to improve US warning system
ANN ARBOR—A University of Michigan space weather model beat out four other contenders for a spot in the national Space Weather Prediction Center’s forecasting toolbox.
It is the first time that computer models based on a firm understanding of physics have overtaken simpler, statistics-based models to predict magnetic disturbances due to space weather. The new model can also give information about where the effects of a geomagnetic storm will be weaker or stronger around Earth.
Space weather forecasts are important for protecting satellites, predicting when GPS signals become unreliable, and in the worst case, preventing far-reaching and long-term electrical power outages.
Most of the time, Earth’s magnetic field unflinchingly deflects most of the charged particles shed by the sun, known collectively as the solar wind. Yet every now and again, the sun ejects a chunk of material—still charged particles but a lot more of them.
“You can have eruptions like coronal mass ejections or solar flares, and these propagate all the way from the sun to the earth,” said Gábor Tóth, a research scientist in atmospheric, oceanic and space sciences and one of the model’s main developers.
In a gale-force solar wind brought on by these eruptions, Earth’s magnetic field shakes. The main fear is that this shaking could knock out the big transformers in the electrical grid.
“These power grids always operate on the edge, and if you put an extra load on, they can fail,” Tóth said.
As Earth’s magnetic field moved, it would create its own currents in the high-voltage cables that carry electricity across hundreds of miles. At substations, where transformers convert the electricity to lower voltages for delivery into cities and towns, that extra current would likely push transformers over the edge.
Since crisscrossing the Earth with high-voltage cables and sending satellites into orbit, humans haven’t experienced space weather that could cause worldwide disruption. The last event of that magnitude was in September 1859. Only the telegraph system was around to preview how Earth’s roiling magnetic field can fry long-distance electrical systems.
Because large transformers take between five months and five years to build, a modern version of that storm could mean prolonged, extensive blackouts.
“It would really be a disaster much worse than a major hurricane,” Tóth said.
Fortunately, a crisis could be averted by reducing the voltage or switching off parts of the grid entirely. Then, magnetically induced currents would be much less likely to burn out transformers. Also, powering down satellites could prevent the crippling of communications systems. To take such precautions wisely, grid and satellite operators need accurate space weather forecasting.
Direct observations of the solar flares aren’t clear enough to tell whether any extreme plasma from the sun is heading toward us. For that, our first responder is on a small orbit around a point where the gravitational pull of the sun and Earth are equal, roughly a million miles from Earth. This satellite, the Advanced Composition Explorer, measures the solar wind.
Using measurements from ACE, the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center has been making forecasts from statistics-based, or empirical, models for space weather. These models work reasonably well for estimating the strength of magnetic fluctuations on a global level within the range of space weather observed before. However, these models cannot predict events outside their statistical comfort zones, like the 1859 storm, or where around Earth magnetic disturbances will occur.
That’s why NOAA put out a call for new models that could provide more accurate predictions. They tested two empirical models with local forecast capabilities and three physics-based models, including Michigan’s. The physics models outperformed the empirical models and Michigan’s came out tops.
The model is called the Space Weather Modeling Framework. The main developers are Tóth, Darren De Zeeuw, Igor Sokolov and Bart van der Holst, all research scientists in atmospheric and space sciences. Professor Aaron Ridley and research scientist Daniel Welling played important roles in the model development and the U-M participation in the competition. The Center for Space Environment Modeling is led by Tamas Gombosi, the Rollin M. Gerstacker Professor of Engineering and professor of atmospheric, oceanic and space sciences and aerospace engineering. | 0.827645 | 3.328219 |
STRANGE parents should have unusual offspring. Sure enough, when two carbon “onions” collide, a nanodiamond is born. It’s an insight into the weird chemistry that arises in outer space.
Meteorites are home to diamonds a few nanometres wide but how these tiny crystals form is a mystery. A precursor could be the equally exotic nested carbon cages called carbon onions that lurk in interstellar space. When Nigel Marks of Curtin University in Perth, Australia, and colleagues simulated collisions between two carbon onions, and carbon onions and dust grains, both produced nanodiamonds (Physical Review Letters, DOI: 10.1103/PhysRevLett.108.075503).
Clouds of dust around ageing, carbon-rich stars and dusty planet-forming discs could host such collisions. When the dust gets baked into asteroids, chips can fall to Earth as meteorites.
Read more: Click here to read a longer version of this story
ROLLING stones on Mars suggest the Red Planet still rocks with quakes, which could be good for life.
At about half the diameter of Earth, Mars is thought to have radiated away its internal heat quickly, essentially dying geologically many millions of years ago. But boulders that rolled into faults and channels in a region called Cerberus Fossae suggest the planet’s rock ‘n’ roll days may not be over quite yet.
Gerald Roberts at Birkbeck, University of London, and colleagues compared the distribution of the boulders to that of boulders displaced by the 2009 earthquake in mountainous L’Aquila, Italy. In that quake, the size and number of boulders decreased with distance from the epicentre. The same pattern is seen around Cerberus Fossae (Journal of Geophysical Research, DOI: 10.1029/2011JE003816).
“This is consistent with the hypothesis that boulders had been mobilised by ground-shaking,” Roberts says.
The quakes may have occurred only months ago, since the boulders left trails in the Martian dust that had not yet been swept away by wind. If so, it might signal that some magma still flows beneath a nearby dormant volcano. That could be good for the search for Martian life, since magma could melt ice, providing wet, life-friendly habitats.
A DRUG which minimises brain damage when given three hours after stroke has proved successful in monkeys and humans.
A lack of oxygen in the brain during a stroke can cause fatal brain damage. There is only one approved treatment – tissue plasminogen activator – but it is most effective when administered within 90 minutes after the onset of stroke. Immediate treatment isn’t always available, however, so drugs that can be given at a later time have been sought.
In a series of experiments, Michael Tymianski and colleagues at Toronto Western Hospital in Ontario, Canada, replicated the effects of stroke in macaques before intravenously administering a PSD-95 inhibitor, or a placebo. PSD-95 inhibitors interfere with the process that triggers cell death when the brain is deprived of oxygen.
To test its effectiveness the team used MRI to measure the volume of damaged brain for 30 days following the treatment, and conducted behavioural tests at various intervals within this time.
Monkeys treated with the PSD-95 inhibitor one hour after stroke had 55 per cent less damaged tissue in the brain after 24 hours and 70 per cent less after 30 days, compared with those that took a placebo. These animals also did better in behavioural tests. Importantly, the drug was also effective three hours after stroke (Nature, DOI: 10.1038/nature10841).
An early stage clinical trial in humans, run by firm NoNO in Ontario has also seen positive results.
IS IT possible to tell whether a planet hosts life just from its glow? A new analysis of Earthshine, sunlight reflected off Earth then bounced back by the moon, suggests this is a viable way to seek life on exoplanets.
Life co-exists with certain chemicals that leave their imprint on the light Earth reflects, while plants reflect light differently to rocks. The trouble is that exoplanets are too faint compared with their host stars for such distinctions to be detected.
So Michael Sterzik of the European Southern Observatory in Santiago, Chile, and colleagues used a spectrograph mounted on the Very Large Telescope to examine polarised Earthshine, its light waves aligned in one plane. The reflection of light off a planet’s surface and passage through the atmosphere cause it to become polarised, making it visible amid the glare of unpolarised starlight.
The team found light signatures of oxygen, ozone and water, as well as an increase in reflected wavelengths characteristic of vegetation (Nature, DOI: 10.1038/nature10778). Future telescopes such as the European Extremely Large Telescope could look for these signs in exoplanet-shine.
WHEN a new leader takes control of a troop of gelada monkeys, he is likely to kill the offspring of his predecessor. His arrival is also bad news for young yet to be born: they’ll be aborted within weeks.
Named for Hilda Bruce who first observed it in mice, the “Bruce effect” is common in lab animals. In fact, some biologists suspect it is an artefact of keeping animals in labs. Jacinta Beehner of the University of Michigan in Ann Arbor and colleagues have now found evidence of the effect in wild geladas (Theropithecus gelada), an Ethiopian monkey related to baboons.
They found that the number of births fell sharply in the six months after a new dominant male took over a group, suggesting females were aborting their fetuses. As a check, Beehner took hormone samples from females’ faeces, allowing her to track 60 pregnancies closely. Of nine failures, eight occurred in the two weeks after the father was replaced.
Beehner says the strategy makes sense, because females don’t want to waste energy on offspring likely to be killed after they are born.
We don’t know how the females do it, says Peter Brennan of the University of Bristol, UK, who was not part of the study. It may simply be a response to the stress of the takeover.
Journal reference: Science, DOI: 10.1126/science.1213600 | 0.850082 | 3.556026 |
The Green Peas were first identified from Sloane Digital Sky Survey data – and then in Hubble Space Telescope archive images. Now radio observations of Green Pea galaxies (from GMRT and VLA) have led to some new speculation on the role of magnetic fields in early galaxy formation.
Green Pea galaxies were so named from their appearance as small green blobs in Galaxy Zoo images. They are low mass galaxies, with low metallicity and high star formation rates – but, surprisingly, are not all that far away. This is surprising given that their low metallicity means they are young – and being not very far away means they formed fairly recently (in universal timeframe terms).
Most nearby galaxies reflect the 13.7 billion year old age of the universe and have high metallicity resulting from generations of stars building elements heavier than hydrogen and helium through fusion reactions.
But Green Peas do seem to have formed from largely unsullied clouds of hydrogen and helium that have somehow remained unsullied for much of the universe’s lifetime. And so, Green Peas may represent a close analogue of what the universe’s first galaxies were like.
Their green color comes from strong OIII (ionised oxygen) emission lines (a common consequence of lots of new star formation) within a redshift (z) range around 0.2. A redshift of 0.2 means we see these galaxies as they were when the universe was about 2.4 billion years younger (according to Ned Wright’s cosmology calculator). Equivalent early universe galaxies are most luminous in ultraviolet at a redshift (z) between 2 and 5 – when the universe was between 10 and 12 billion years younger than today.
Anyhow, studying Green Peas in radio has yielded some interesting new features of these galaxies.
With the notable exception of Seyfert galaxies, where the radio output is dominated by emission from supermassive black holes, the bulk radio emission from most galaxies is a result of new star formation, as well as synchrotron radiation arising from magnetic fields within the galaxy.
Based on a number of assumptions, Chakraborti et al are confident they have discovered that Green Peas have relatively powerful magnetic fields. This is surprising given their youth and smaller size – with magnetic field strengths of around 30 microGauss, compared with the Milky Way’s approximately 5 microGauss.
They do not offer a model to explain the development of Green Pea magnetic fields, beyond suggesting that turbulence is a likely underlying factor. Nonetheless, they do suggest that the strong magnetic fields of Green Peas may explain their unusually high rate of star formation – and that this finding suggests that the same processes existed in some of the first galaxies to appear in our 13.7 billion year old universe.
Chakraborti et al Radio Detection of Green Peas: Implications for Magnetic Fields in Young Galaxies
Cardamone et al Galaxy Zoo Green Peas: Discovery of A Class of Compact Extremely Star-Forming Galaxies. | 0.833205 | 4.14044 |
Vitamin B3 is one of the most essential nutrients for life on Earth. It is used to build NAD (nicotinamide adenine dinucleotide), a vital component to metabolism, and probably a necessary element for the beginnings of life on our planet. But now new NASA-funded research suggests that much of the vitamin B3 found on Earth may actually have an extraterrestrial origin.
The study builds on previous research which found that vitamin B3 is present in carbon-rich meteorites at concentrations ranging from about 30 to 600 parts-per-billion. Scientists were even able to reproduce these results in a lab designed to simulate space-like conditions. Vitamin B3 was produced from a mixture of pyridine, a basic organic compound, and carbon dioxide ice.
The new experiments went a step further by adding water ice to the mixture. This is particularly important because water ice is abundant on comets and icy dust grains found throughout the cosmos. Sure enough, vitamin B3 could still be generated under space-like conditions from this heartier meteorite-like stew.
"We found that the types of organic compounds in our laboratory-produced ices match very well to what is found in meteorites," said Karen Smith of NASA's Goddard Space Flight Center. "This result suggests that these important organic compounds in meteorites may have originated from simple molecular ices in space. This type of chemistry may also be relevant for comets, which contain large amounts of water and carbon dioxide ices. These experiments show that vitamin B3 and other complex organic compounds could be made in space and it is plausible that meteorite and comet impacts could have added an extraterrestrial component to the supply of vitamin B3 on ancient Earth."
This is exciting news for those who expound the theory that life on Earth may have started elsewhere in the universe and traveled to our planet on comets and meteors. At the very least, the experiments demonstrate that the building blocks for life on Earth did not have to originate here. Furthermore, if the basic constituents of life are free-floating throughout space, this could increase the odds that life could form on other planets besides Earth.
Researchers hope that their results will further be validated by the Rosetta orbiter, which is currently circling comet 67P. This is the same comment that the dormant Philae lander is sitting on. If some of the same complex organic molecules used in these experiments is found in the gases released by the comet or in the comet’s nucleus, that would lend strong support to the idea that early Earth was seeded with vitamin B3 from beyond our solar system.
Related on MNN:
- Most of Earth's water came from asteroids, not comets
- Scientists may have discovered the origin of life
- New study overturns 'primordial soup' theory | 0.831143 | 3.721861 |
It seems Titan is getting more Earth-like all the time. There are lakes, rainfall (never mind that any liquids on Titan are frigid hydrocarbons), dust storms, lightning and all sorts of other activity going on it the atmosphere, along with clouds. And now, not just any clouds but cirrus clouds, very similar to what we have on Earth: thin, wispy clouds of ice particles high in the atmosphere. A team of researchers at NASA’s Goddard Space Flight Center say that unlike Titan’s brownish haze, the ice clouds are pearly white.
“This is the first time we have been able to get details about these clouds,” said Robert Samuelson, an emeritus scientist at Goddard and the co-author of a new paper published in the journal Icarus. “Previously, we had a lot of information about the gases in Titan’s atmosphere but not much about the [high-altitude] clouds.”
Using the Composite Infrared Spectrometer (CIRS) on NASA’s Cassini spacecraft scientists can get a “weather report” of sorts. Previously, scientists have found that Titan’s intriguing atmosphere has a one-way cycle that delivers hydrocarbons and other organic compounds to the ground as precipitation.
Those compounds don’t evaporate to replenish the atmosphere, but somehow the supply has not run out.
Additionally, puffy methane and ethane clouds had been found before by ground-based observers and in images taken by Cassini. But these new clouds are much thinner and located higher in the atmosphere.
“They are very tenuous and very easy to miss,” said Carrie Anderson, the paper’s lead author. “The only earlier hints that they existed were faint glimpses that NASA’s Voyager 1 spacecraft caught as it flew by Titan in 1980.”
So what are these cirrus clouds made of?
More than a half-dozen hydrocarbons have been identified in gas form in Titan’s atmosphere, but many scientists feel there are probably many more that haven’t yet been identified.
The clouds on Titan can’t be made from water because of the planet’s extreme cold. “If Titan has any water on the surface, it would be solid as a rock,” said Goddard’s Michael Flasar, the Principal Investigator for CIRS.
Instead, the key ingredient is likely methane. High in the atmosphere, some of the methane breaks up and reforms into ethane and other hydrocarbons, or combines with nitrogen to make materials called nitriles. Any of these compounds can probably form clouds if enough accumulates in a sufficiently cold area.
To find these cloud, the team focuses on the observations made when CIRS is positioned to peer into the atmosphere at an angle, grazing the edge of Titan. This path through the atmosphere is longer than the one when the spacecraft looks straight down at the surface. Planetary scientists call this “viewing on the limb,” and it raises the odds of encountering enough molecules of interest to yield a strong signal.
So, when the researchers look at the data, they can separate the telltale signatures of ice clouds from the other aerosols in the atmosphere. “These beautiful, beautiful ice clouds are optically thin, and they’re diffuse,” said Anderson. “But we were able to pick up on them because of the long path lengths of the observations.” | 0.812333 | 3.950426 |
This is an image of Ganymede.
Ganymede was first discovered
by Galileo in 1610, making it one of the Galilean Satellites
. Of the 60 moons it is the 7th closest to Jupiter, with a standoff distance of 670,900 km. It is the largest moon in the solar system, much larger than the Earth's moon, with a diameter that is about the distance across the United States, of 5262 km (3270 miles).
Ganymede is named after Jupiter's favorite cup bearer, from Greek/Roman mythology. Ganymede is one of the Icy Satellites, meaning that it is mostly made of ice. Its main characteristic is the grooved terrain on its cratered surface.
The Galileo spacecraft made an amazing discovery-- this moon, which is larger than the planet Mercury, generates its own magnetosphere, one that is bigger than Mercury’s magnetosphere. Ganymede also has a very thin atmosphere.
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phrase that explains what the equinox, assumes at least a basic knowledge of astronomical terms, because the very Equinox is a phenomenon being studied is this science.
necessary knowledge astronomical terms
our star makes his move along the ecliptic, which is the saying unscientific language, the plane of Earth's orbit.And the moment when the sun, making their way along the ecliptic intersects the celestial equator, is a large range of air and airless space, parallel the Earth's equator (the plane of the same, and both are perpendicular to the axis of the world), is called the equinox.Terminator (this is also the astronomical concept has nothing to do with Schwarzenegger) is a line that divides any celestial body in the sunlit part and "night".So, on the day of the equinox is the terminator passes through the geographic poles of the Earth and divides it into two equal semi-ellipse.
characteristic feature encased in the title
In the name laid down the notion that the day of the equinox night and day are equal.From a scientific point of view, the night is always a little shorter and the sun rises and sets are not exactly in the east and west and a little north.Still, since childhood, we know that on June 22 - is not only the first day of the war, and school graduation balls (as in Soviet times), but also the day of the summer equinox.However, it is called and 22 December days of summer and winter solstice.This happens because the sun during these periods of time, or is at the highest point above the horizon, or the lowest and farthest from the celestial equator.That is the day of the equinox light and dark part of the day is almost equal.
number, characteristic for dates days equinoxes and solstices
During the solstices, some of them - either day or night - more than most other.Equinoxes and solstices are notable for the fact that are the beginning of the change of seasons.It is noteworthy these dates, and always someone from the family members said that, they say, now the longest or shortest day, or what day it is night.And that it highlights in a series of consecutive days.Almost always, the date of these moments becomes the number 22, but in fact there are leap years, and other aspects of astronomy and the phenomena affecting the displacement of the date of 21 or 23 numbers.Months of March, June, September and December are the ones that fall on the equinoxes and solstices.
Holidays, came from ancient times
Of course, they are known since ancient times.Our ancestors observed them and communicate with these dates his life, to take dozens of witnesses.The ancient Slavs with each of these days is associated a certain holiday, and it lasts usually a week (Christmas carols, Rusal, Shrovetide).So, on the winter solstice falls Kolyada, holiday, later dedicated to Christmas.Velikden or Komoeditsa, aka Mardi Gras - the name marks the vernal equinox, the birth of the young sun.From this day begins the astrological solar year, and our star goes into the Northern Hemisphere from the South.Maybe that's why March 20, the feast has to astrology.Midsummer (aka Ivan-day Solstice), or a summer confrontation - the big summer holiday of ancient Slavs, covered with legends, the glory of the brave men walking in the night to look for a fern flower.Ovsenev-Tausen, autumnal equinox, after which winter slowly begins to come into its own, and the nights grow longer.So our ancestors Svyatovit (another name) lit candles - the most beautiful was put on a place of honor.
special climatic zone of the Earth
All these serve as a benchmark date for the commencement of certain activities necessary for life - seasonal types of farming, construction or reserves for the winter.The days of vernal and autumnal equinox is characterized by the fact that the sun gives its light and warmth in equal measure and the Northern and Southern hemisphere, and its rays reach both poles.These days it is over the territory of a climatic zone of the Earth, as the tropics (in Greek language means the turntable).The opposite sides of the equator to 23 degrees with a slight, are parallel to the northern and southern tropics.A characteristic feature of the area enclosed between them is that on them twice a year, the sun reaches its zenith - once on June 22 over the northern tropics and the Tropic of Cancer, the second time - over the South, and the Tropic of Capricorn.There is 22 December.Typically this for all latitudes.North and south of the zenith of the sun in the tropics does not happen ever.
One of the consequences of the displacement direction of the Earth's axis
at the equinoxes and solstices it intersects the celestial equator at a point in the constellation Pisces (spring) and Virgin (autumn), and in the days of maximum and minimum distance from the equator, thethere during the summer and winter solstice - in the constellation Taurus and Sagittarius respectively.From the zodiacal constellation Gemini into Taurus point of the summer solstice has moved in 1988.Under the influence of gravity of the Sun and the Moon slow the Earth's axis shifts its direction (precession - another astronomical term), resulting in a shift, and the point of intersection of the light with the celestial equator.Spring dates are different from the number of autumn, and if falls on the September 22-23 th, then the question, "When the day of the vernal equinox?" The answer would be as follows - 20 March.It should specify that the date for the Southern Hemisphere will be swapped - will spring autumn, because there is the opposite.
role zodiacal constellations
As noted above, the equinoxes are called points of intersection of the celestial equator and the ecliptic, and they have their zodiac symbols corresponding to the constellations in which there are: spring - Aries, summer - CancerAutumn - Libra winter - Capricorn.It should be noted that the period of time between the two equinoxes of the same name is called the tropical year, the number of sunny days which is different from the Julian calendar by about 6 hours.And only thanks to a leap year, repeated once in 4 years, fleeing forward the date of the next equinox, returning to the previous number.On the Gregorian year, the difference is negligible (tropical - 365.2422 days, Gregorian - 365.2425), because the modern calendar is designed so that even in the long term, the date of solstices and equinoxes occur in the same number.This happens because in the Gregorian calendar provides a pass 3 days once in 400 years.
One of the most important practical problems in astronomy - the establishment of the equinox
dates range from 1 to 2, not more days.So how do you determine in the coming years, when the equinox?It has been observed that due to the presence of small fluctuations, the earliest date that is 19 numbers account for leap years.Naturally, the most recent (22) fall directly onto the previous leap year.Very rarely earlier and later dates, their memory is kept for centuries.So, back in 1696, the vernal equinox fell on March 19, and in 1903 - Autumn on September 24.Such deviations will not see contemporaries, because the repetition of the record in 1696 will be in 2096-th, and the latest equinox (September 23) will not happen before the 2103rd.There are nuances associated with local time - deviation in the figure of the world happens only when the exact date falls on 24:00.After west of the starting point - the zero meridian - a new day has not yet come. | 0.837923 | 3.579619 |
From HubbleCast. Before NASA’s New Horizons probe flew past Pluto in July 2015, almost all of the information scientists had about this mysterious dwarf planet came from observations made by Hubble. What discoveries did Hubble make in the Pluto system and how will the greatest telescope ever built advance our knowledge of this distant, icy world following New Horizons’ flyby?
From ESO-Cast. Giant telescopes are being used to search for the subtle signs of magnetic fields in other stars and even to map out the star spots on their surfaces. This information is beginning to reveal how and why so many stars, including our own Sun, are magnetic, and what the implications might be for life on Earth and elsewhere in the Universe. Astronomers are beginning to use signs of magnetic fields generated by stars to assess the habitability of planets that orbit them.
From Hubblecast. Using images from the NASA/ESA Hubble Space Telescope and ESO’s Very Large Telescope, astronomers have discovered unique and totally unexpected structures within the dusty disc around the star AU Microscopii. These fast-moving wave-like features are unlike anything ever observed, or even predicted. What are they, and what do they tell us about the restless early years of a solar system in the making?
Among the methods astronomers have used to discover extra solar planets, the most successful is a technique called transit photometry. It measures changes in a star’s brightness caused when a planet crosses in front of its star along our line of sight.
Astronomers using NASA’s Kepler Space Telescope have employed this technique to become the most successful planet-hunting spacecraft to date, with more than a thousand established discoveries and many more awaiting confirmation. Future missions carrying improved technology are now in the works.
How much can they tell us about alien planetary systems similar to our own?A great deal, according to a recently published study. It shows that in the best-case scenarios, these upcoming missions could uncover planetary moons, ringed worlds similar to Saturn, and even large collections of asteroids.
NASA’s Kepler Space Telescope has used this technique to become the most successful planet-hunting spacecraft to date, with more than a thousand established discoveries and many more awaiting confirmation. Missions carrying improved technology are now planned, but how much more can they tell us about alien planetary systems similar to our own?
A great deal, according to recently published studies by Michael Hippke at the Institute for Data Analysis in Neukirchen-Vluyn, Germany, Continue reading Finding Earth’s Twin
This is the story of a discovery made on St. Patrick’s Day, 2015. We learned just how much Mars is at the mercy of our sun. During a solar outburst that hit Mars that day, the NASA spacecraft Maven measured an accelerated loss of molecules in its upper atmosphere.
In its early days, Mars appears to have had enough surface water to cover the entire planet to a depth of 140 meters, and an atmosphere that was thick enough to hold it there. But a more active sun in those days began a long slow process of steadily eroding the Martian air and sending it out into space. The water dried up, and whatever life forms had developed had no chance to thrive and evolve on the surface.
Music by Epidemic Sound (http://www.epidemicsound.com)
Mars Express, the first planetary mission of the European Space Agency, was sent to the Red Planet in 2003. It sent a lander down to the surface, and although it failed to fully deploy , the orbiter has been taking pictures and mapping the surface ever since. It has produced high-resolution mineralogical maps, radar soundings of permafrost, and probing the composition of the atmosphere.
Its images, now released for general use, show the dramatic landscapes of Mars, sculpted by ancient volcanoes, water flows, and the scouring action of dust storms. Now we an revel in these cinematic images and imagine what it’s like to fly over the surface of Mars.
Decades before the Hubble Space Telescope, Dr. Edwin Powell Hubble revolutionised the field of astronomy. Take a look at the life and work of this brilliant American astronomer for whom the Hubble Space Telescope is named. From Hubblecast.
May 22nd, 2011. A powerful tornado cut a mile-wide swath through Joplin, Missouri. It was the costliest tornado disaster in history, with insured losses close to two billion dollars. It was also one of the deadliest, with 161 lives lost… and one thousand injured.
The scale of the Joplin disaster drew teams of scientists hoping to find out what made this storm so destructive. And what can be done to protect communities and people in the future. What did they learn by peering inside the violent realm of a Super Tornado?
This stirring film recounts the flight many consider to be NASA’s most daring and important. Interviews with Apollo 8 astronauts, their wives, mission control staff, and journalists take viewers inside the high-stakes space race of the late 1960s to reveal how a bold decision by NASA administrators put a struggling Apollo program back on track and allowed America to reach the moon before the Soviets.
Uploaded under license from American Public TV.
As night falls, astronomers at Chile’s La Silla observatory are just starting their observations. Suddenly, a strange red flash of light appears on the horizon. An alert photographer is there to take a closer look! From ESO Cast. | 0.885428 | 3.429855 |
Earth has just one moon but it offers astronomers a lot to study between the blue planet and the natural satellite. But there’s a planet in our solar system which has close to 100 moons. Saturn, which is the sixth planet of the solar system, has 82 moons. This number significantly increased after scientists discovered 20 new moons on the planet. This makes the ringed planet ‘moon king’ knocking Jupiter off the throne, said the International Astronomical Union’s Minor Planet Center. Jupiter, which stands fifth in the solar system, has 79 moons. Astronomer Scott Sheppard, of the Carnegie Institution for Science in Washington, D.C., said that Saturn will is likely to keep this tag as it has about 100 moons. However, the remaining ones are very hard to identify as they are very small.
“We used some of the largest telescopes in the world to find that Saturn is the king in terms of having a maximum number of moons. We are now completing the list of small moons around the ringed gas giant Saturn,” Sheppard said. The newly discovered moons will play a crucial role in helping researchers to determine how the solar system of our planets formed and evolved, he added. Talking about the size of newly discovered moon astronomers said each one of them is 5 kilometres in diameter. Out of 20, 17 orbit the planet in a retrograde or backward direction. In other words, they move in the opposite direction of Saturn’s rotation around its axis. The remaining three natural satellites orbit in the same direction as the planet. These moons are so minuscule that it takes them two to three years to complete a single orbit.
Last year, Sheppard and his team had discovered 12 new moons orbiting Jupiter and a moon-naming online contest was started by the Carnegie Institution. Now, a similar contest is being planned for the ringed planet’s moons. “We were overwhelmed with the amount of public engagement for Jupiter moon-naming contest and this is why we have decided to go for another one for newly discovered 20 moons,” Sheppard said. | 0.821162 | 3.040765 |
Scientists have paired NASA’s Cassini spacecraft with the National Science Foundation’s Very Long Baseline Array (VLBA) radio-telescope system to pinpoint the position of Saturn and its family of moons to within about 2 miles (4 kilometres). The measurement is some 50 times more precise than those provided by ground-based optical telescopes. The feat improves astronomers’ knowledge of Saturn’s orbit and benefits spacecraft navigation and basic physics research.
The team of researchers used the VLBA — a giant array of radio-telescope antennas spread from Hawaii to the Virgin Islands — to pinpoint the position of Cassini as it orbited Saturn over the past decade by receiving the signal from the spacecraft’s radio transmitter. They combined this data with information about Cassini’s orbit from NASA’s Deep Space Network. The combined observations allowed the scientists to make the most accurate determinations yet of the position of the center of mass, or barycenter, of Saturn and its numerous moons.
The study team included researchers from NASA’s Jet Propulsion Laboratory in Pasadena, California, and the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico. The scientists presented the results of their work on 8th January at the American Astronomical Society’s meeting in Seattle.
The new measurement was made possible by two factors: Cassini’s long-term presence in the Saturn system and the VLBA’s ability to discern extremely fine detail. The result is a greatly improved table of predicted positions of objects in the Saturn system, known as an ephemeris. An ephemeris is one of the basic tools of astronomy.
“This work is a great step toward tying together our understanding of the orbits of the outer planets of our Solar System and those of the inner planets,” said Dayton Jones of JPL, who led the study.
The improved positional information will help enhance precise navigation of interplanetary spacecraft and help refine measurements of the masses of Solar System objects. It will also improve predictions of when Saturn or its rings will pass in front of background stars — events that provide a variety of research opportunities for astronomers.
VLBA measurements of Cassini’s position have even helped scientists who seek to make ever-more-stringent tests of Albert Einstein’s theory of general relativity by observing small changes in the apparent positions of actively feeding black holes, or quasars, as Saturn appears to pass in front of them on the sky.
Cassini’s navigation team, charged with plotting the spacecraft’s course around Saturn, began using new positional information provided by the ongoing study in 2013. The new ephemeris has enabled them to design better manoeuvres for the spacecraft, leading to mission-enhancing savings in propellant. Previously, the navigators performed their own estimates of the positions of Saturn and its satellites using data gleaned by tracking Cassini’s radio signal during its communications with Earth. The new calculations, enhanced by VLBA data, are about 20 times more accurate.
Jones and colleagues plan to continue the joint observations with Cassini and the VLBA through the end of Cassini’s mission in late 2017. The team plans to use similar techniques to observe the motion of NASA’s Juno spacecraft when it reaches Jupiter in mid-2016. They hope to improve the orbital knowledge of that giant planet as well. | 0.835763 | 3.884606 |
Quarter* ♋ Cancer
Moon phase on 30 September 2094 Thursday is Waning Gibbous, 21 days old Moon is in Gemini.Share this page: twitter facebook linkedin
Previous main lunar phase is the Full Moon before 6 days on 24 September 2094 at 08:33.
Moon rises in the evening and sets in the morning. It is visible to the southwest and it is high in the sky after midnight.
Lunar disc appears visually 4.3% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1836" and ∠1917".
Next Full Moon is the Hunter Moon of October 2094 after 23 days on 23 October 2094 at 17:47.
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 21 days old. Earth's natural satellite is moving from the middle to the last part of current synodic month. This is lunation 1171 of Meeus index or 2124 from Brown series.
Length of current 1171 lunation is 29 days, 16 hours and 13 minutes. This is the year's longest synodic month of 2094. It is 15 minutes longer than next lunation 1172 length.
Length of current synodic month is 3 hours and 29 minutes longer than the mean length of synodic month, but it is still 3 hours and 34 minutes shorter, compared to 21st century longest.
This lunation true anomaly is ∠190.4°. At the beginning of next synodic month true anomaly will be ∠216.5°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
7 days after point of perigee on 23 September 2094 at 11:57 in ♓ Pisces. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 5 days, until it get to the point of next apogee on 5 October 2094 at 23:56 in ♌ Leo.
Moon is 390 446 km (242 612 mi) away from Earth on this date. Moon moves farther next 5 days until apogee, when Earth-Moon distance will reach 405 919 km (252 226 mi).
Moon is in ascending node in ♊ Gemini at 20:19 on this date, it crosses the ecliptic from South to North. Moon will follow the northern part of its orbit for the next 14 days to meet descending node on 15 October 2094 at 09:00 in ♑ Capricorn.
At 20:19 on this date the Moon is completing its previous draconic month and is entering the new one.
11 days after previous South standstill on 18 September 2094 at 21:55 in ♑ Capricorn, when Moon has reached southern declination of ∠-23.617°. Next day the lunar orbit moves northward to face North declination of ∠23.728° in the next northern standstill on 1 October 2094 at 13:29 in ♋ Cancer.
After 9 days on 9 October 2094 at 12:44 in ♎ Libra, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.83659 | 3.079387 |
Not all auroras are created equal. Jupiter’s auroral glow is much stronger than Earth’s, so researchers assumed it was caused by the same process that generates our planet’s brightest auroras. But new observations from NASA’s Juno spacecraft show that’s not true.
“For many years we thought we understood Jupiter’s aurora,” says John Clarke at Boston University. “But then Juno got there and it went through these magnetic fields right above an active aurora, and it didn’t see what we thought it would.”
Now, Barry Mauk at Johns Hopkins University in Maryland and his colleagues have analysed Juno’s data and found that the likely cause of powerful auroras on Jupiter is one that does something quite different on Earth.
On our planet, most intense auroras are the result of powerful electric fields building up along Earth’s magnetic field lines. This creates wells of electric potential – areas where the electric field changes sharply – that accelerate electrons from the solar wind toward the ground.
Those electrons collide with atoms in the upper atmosphere and give up some of their energy. When the atoms release that energy, they emit tiny bursts of light that together make up the aurora.
“On Earth, these electric potentials cause the most intense auroras – these are the beautiful twisting snake-like undulations that people marvel at when they go see the aurora in northern regions,” says Mauk.
But even though Jupiter’s electric potential wells are up to 30 times stronger than Earth’s, Mauk and his team found that they don’t align with the auroras.
“These electric potentials are not the source of the most intense aurora at Jupiter. That’s a surprise,” Mauk says. Instead, Jupiter’s auroras might come from a process that only causes dim auroras on Earth.
These weaker auroras can be caused by ripples in Earth’s magnetic field that accelerate electrons just a smidge. Some of these electrons can build up enough energy to light up the sky when they hit gas in the upper atmosphere.
Because Jupiter is so large, the electric potentials there could get so strong that they become unstable, turning into waves and random turbulence. It is these phenomena that can accelerate electrons so much that they produce a dazzling display, he says.
We often use models of Earth’s atmosphere and magnetic field as jumping-off points for describing other planets, but the Juno observations could force us to re-examine our assumptions, especially when it comes to understanding exoplanets – many of which are more like Jupiter than Earth.
Journal reference: Nature, DOI: 10.1038/nature23648
More on these topics: | 0.817599 | 3.988997 |
Ethan Siegel discusses neutrinos, the one last Big Bang prediction that has yet to be verified. via Medium:
The mass-and-energy of these neutrinos tell us that they’ve fallen into the large-and-small-scale structures in the Universe, including in our own galaxy. They tell us that they’re a small percentage of the dark matter — between about 0.5%-and-1.4% of it — but cannot be all of it. There’s about as much mass in neutrinos as there is mass in the form of stars currently burning through their fuel today. Not a lot, but still interesting!
But what’s maybe most amazing about these neutrinos is that we have no practical idea about how we could experimentally detect them!
We can detect neutrinos, but only neutrinos with about a billion times the energy of these cosmic relics. Because of how quickly (exponentially) the cross-section falls off, we really have no hope for how to detect something with such a small signature; all of the neutrino detectors we’ve built and successfully implemented rely on ultra-high-energy neutrinos.
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand. | 0.801479 | 3.196982 |
It has been the farthest planet from the Sun since Pluto's 'relegation', but despite Neptune's remoteness in our solar system, it still holds plenty of interest for physicists – not least because of the unusual things going on in its atmosphere.
A new paper published in the journal Nature Communications by Dr Karen Aplin of Oxford University's Department of Physics attempts to get to the bottom of the 'wobbles' observed in Neptune's atmosphere over the past 40 years.
The study, written with Professor Giles Harrison of the University of Reading, evaluates two competing hypotheses for why we can see changes in the planet's brightness – a phenomenon essentially connected to its cloud cover. The results solve a long-standing conundrum in planetary science.
Dr Aplin says: 'Neptune's great distance from the Sun means that its atmosphere is very cold, but despite this it has some interesting weather, including clouds, winds, storms and perhaps lightning. It provides an entirely different environment to help us test our knowledge of atmospheres.
'Unlike Earth's atmosphere, which is mostly nitrogen, Neptune's atmosphere is mainly hydrogen and helium, with some methane. The methane absorbs much of the red light in the atmosphere, making the planet seem blue to us.
'Neptune’s atmosphere contains clouds made of a range of substances, such as ammonia and methane, whereas clouds on Earth are almost always made of water. Neptune's atmosphere is also a lot colder than ours – around -170C – because it receives 900 times less sunlight. Despite this, the Sun can still affect its clouds in subtle ways.'
Since the early 1970s, Neptune's brightness has been measured with great care by Dr Wes Lockwood of Lowell Observatory in Arizona. Because Neptune rotates around the Sun once every 165 years, each of its seasons is about 40 Earth years. Most of the ups and downs seen in Neptune's brightness since the 1970s are therefore due to its slowly changing seasons. However, even when the seasonal changes are accounted for, there are still some other small 'wobbles' in Neptune's clouds – and these are the subject of Dr Aplin's study.
Dr Aplin says: 'The "wobbles" in Neptune's cloudiness appeared to follow the Sun’s 11-year activity cycle, which could mean that they were influenced by small changes in sunlight. Another suggestion was that particles from outer space, called cosmic rays, which are also affected by the solar cycle, were changing the clouds. Using the different physics of the two mechanisms, we showed that the combined effect of the two "rival" hypotheses explained the changes in cloudiness more successfully than each would do individually.
'We also looked for a known marker of cosmic ray effects, a kind of fingerprint, in Neptune's cloud data. During the 1980s, when the Voyager 2 mission was nearing Neptune, we were able to compare both cosmic rays and clouds at Neptune and show that they had the same fingerprint. We were therefore able to confirm the effects of cosmic rays in planetary atmospheres.'
Another mission to Neptune would allow for even more scientific insight into this distant planet. But, with nothing currently planned, scientists will continue to rely on telescopic observations combined with simulation experiments of the type carried out in Dr Aplin's laboratory. | 0.895939 | 3.960095 |
Back in March, a project known as BICEP2 held a press conference where they announced the discovery of inflation in the early universe. This created quite a stir in the press. When the announcement was made, the results had just been made public, and their paper had not been peer reviewed. As everyone started analyzing the work, what initially looked like a pretty strong result started to look less strong. Then there started to be murmurings that perhaps the announcement had been premature.
The key aspect of the BICEP2 results is the analysis of polarization within the cosmic microwave background (CMB). Specifically there is a type of polarization known as B-mode polarization. This type of polarization can be caused by gravitational lensing of the CMB by galaxies and the like, but it can also be caused by primordial gravitational waves formed during the earliest moments of the universe. Distinguishing between these two types of B-modes requires a detailed analysis of the CMB data, which is very tricky to do. The BICEP2 team ran their analysis, and found a polarization signature too strong to be caused by gravitational lensing alone, thus pointing to inflation as a cause.
But the real challenge is making sure your data is relatively free of foreground effects. The CMB is the most distant thing we can observe in the universe, and that means everything else is between the CMB and us. All of that stuff can distort the CMB, which can give you a false positive result. This is particularly true in the region around the plane of our galaxy, which is sometimes referred to as the zone of avoidance. These foreground effects are the Achilles heel of any inflation result.
Soon after the BICEP2 announcement, some initial results from the Planck telescope mapped our galaxy’s magnetic field through the polarization of gas and dust within the Milky Way. This is exactly the type of foreground effect that can distort results. Another paper noted that an effect known as radio loops could produce similar B-mode polarization, and it wasn’t clear whether BICEP2 had taken this into account. Later it was found that the BICEP2 team had used some tentative data from Planck by extracting the data from a PDF slide.
Now a couple1 of new papers2 argue that there are sufficient foreground effects to wash out the results of BICEP2, thus the BICEP2 result neither confirms nor denies the existence of early inflation. The BICEP2 team argues that even with foreground corrections the results are still strong enough to be valid.
It is important to keep in mind that the BICEP2 results are still going through peer review. Whether the result holds up or not is an ongoing question. But this is happening very publicly, and it was initiated with a very public announcement that a great discovery had been made. If it turns out the results don’t pan out, it can give an impression that we really don’t understand the universe, or that this kind of public point-counterpoint is how peer review works. If that’s the case, how is that any different from the public debates we see on global warming, or the safety and effectiveness of vaccines?
Of course there is a difference between intense discussion over BICEP2, which is an initial discovery of a new effect, and the endless debate over arguments that have been refuted by the evidence again and again. I have in the past compared peer review to whacking a result like a piñata, but there also comes a point where you stop whacking and come to a conclusion. Both are a part of peer review.
Much of this public drama began because BICEP2 decided to make a public announcement. Maybe they shouldn’t have. Maybe the professionals should keep results to themselves until it passes peer review. Only then should results be announced. It would reduce the drama, and maybe we wouldn’t have such skepticism on controversial topics strongly supported by the evidence.
While I can see the benefit of that approach, I’m not sure that I agree. I think there is value in discussing results that are tentative, and in a public discussion of its strengths and weaknesses. Perhaps we shouldn’t be so eager to have press conferences, but once the paper was released, it was public. That’s true of most research these days. In my field preprints appear on the arxiv long before they are published in a journal. Trying to keep results private would only make it more difficult to peer review work. I also think there is a responsibility to ensure science is done publicly. Most of the work in astrophysics is funded through government support. The general public pays for it, and should have access to not only the results, but also the data supporting it.
That said, I think there is also a responsibility to be honest and thoughtful about scientific discoveries. Journalists need to move beyond copy-pasta press releases and point-counterpoint simply for the sake of argument. When results are tentative that should be made clear, and when the data is conclusive, that should be made clear as well. As scientists we also need to be willing to communicate ideas and results clearly. We can’t simply disseminate our work among our peers and consider the job done. As a society we’ve moved beyond that. And as readers we need to be mindful not to feed the hype machines so prevalent among online media. Science is not simply about data and facts. It is a process that pushes us to be better. To be honest and to think critically.
I’m not sure whether the BICEP2 results will hold up or not. What I can say is that as it whatever the outcome you’ll hear about it here. Because it’s not about the results, it’s about the process. In the end, that’s what makes science so cool.
ht to Phillip Buckhaults for prompting this post.
Mortonson, Michael J., and Uroš Seljak. “A joint analysis of Planck and BICEP2 B modes including dust polarization uncertainty.” Journal of Cosmology and Astroparticle Physics 2014.10 (2014): 035. ↩︎
Flauger, Raphael, J. Colin Hill, and David N. Spergel. “Toward an understanding of foreground emission in the BICEP2 region.” Journal of Cosmology and Astroparticle Physics 2014.08 (2014): 039. ↩︎ | 0.84161 | 4.096714 |
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.
This same limit is often thought to hold for other objects, such as active galactic nuclei (AGNs) powered by black holes, but it also isn’t an absolute limit. When Eddington derived the limit he assumed a star that is spherical and non-rotating. Black holes are known to rotate, and their accretion disks are not spherical, so there have been proposed models that allow AGNs and other black holes to emit more power than the Eddington limit. There have been searches for such super-Eddington luminosity, but so far results have been inconclusive.
Now a new paper in Science has analyzed the energy output of a black hole in the galaxy M83, and found that it has emitted sustained levels of energy beyond the Eddington limit.1 Since the black hole was in a quiet phase when it was observed, the team could make an accurate determination of its mass by analyzing its accretion disk. They then looked at the effect of its jets, which were produced in an active period. They found that the energy of the jets clearly exceeded the Eddington limit.
By demonstrating that energy generated near black holes can exceed the Eddington limit, the authors have demonstrated that black holes can affect their environment in a more powerful way that originally thought.
Soria, Roberto, et al. “Super-Eddington mechanical power of an accreting black hole in M83.” Science 343.6177 (2014): 1330-1333. ↩︎ | 0.824243 | 4.161664 |
false-color composite image, constructed from data obtained by VIMS, shows the glow of auroras streaking
out about 1,000 kilometers (600 miles) from the cloud tops of Saturn's south polar region.
See Volume 1-Mission Overview, Science Objectives and Results
for full science report. The technical report is in other volumes archived at the Jet Propulsion Lab.
Mission Science Highlights and Science Objectives Assessment
provides a brief overview of the mission
The Visible and Infrared Mapping Spectrometer (VIMS) was designed to generate spectral maps of the Saturn system at visible
and near-infrared wavelengths. It was also frequently used to record the occultation of stars by Saturn and its
moons, as well as by Saturn's rings. VIMS was assembled at NASA's Jet Propulsion Laboratory (JPL) for the Cassini
Mission to Saturn. Its components were supplied by JPL, the Agenzia Spaziale Italiana in Italy and France's Centre
Nationale de la Recherche Scientifique.
Scientific objectives of VIMS include the following:
- Determine the distribution of the gases and aerosols in Saturn's atmosphere and their time variability
- Study Saturn's atmospheric dynamics, including the characterization of its ammonia clouds
- Map the radial, azimuthal and vertical distribution of the material in Saturn's rings
- Discern the mineralogical composition and surface properties of the particles comprising Saturn's rings
- Constrain and identify the mineralogical properties of Saturn's icy satellites, including the non-icy contaminants
found across the system
- Map the composition and geology of Titan's surface
- Determine the distribution of the gases and aerosols in the atmosphere of Titan and their variability with time
- VIS: Visible-spectrum spectrometer
- IR: Infrared spectrometer
- Often the two spectrometers were operated together, and data was merged into a single data cube spanning the
full wavelength range. During data processing, each of the main detector channels can be separated out.
VIMS Instrument Characteristics*
* values taken from Tables I and II in Brown
et al. (2004) in
Space Science Reviews
a 0.3 - 1.0 by special command
b in normal mode (five spectral pixel binning); 1.46 nm spectral resolution in high-resolution mode
|Spectral Range (µm)
|Spectral Sampling (nm)
|# of Bands
|Instantaneous Field of View (mrad)
||0.17 x 0.17
||0.25 x 0.5
|Effective IFOV (mrad)
||0.5 x 0.5 (3 x 3 sum)
||0.5 x 0.5 (1 x 2 sum)
|Total FOV (mrad)
||32 x 32 (64 x 64 pixels)
||32 x 32 (64 x 64 pixels)
The design of the VIMS instrument was largely based on the Near-Infrared Mapping Spectrometer (NIMS) which flew on the Galileo
mission to Jupiter. Both the VIMS and NIMS benefited from the long history of imaging spectrometers that preceded
them. VIMS incorporated two channels to cover its full wavelength range. The Italian-built VIMS Visual Channel
(VIS) recorded light at wavelengths between 0.35 and 1.05 µm in 96 individual spectral channels, with a spectral
resolution of 7.3 nm. The VIMS Infrared Spectral Region Component (IR) which was built by JPL, picked up in the
near infrared at 0.85 µm and extended the coverage of the VIMS instrument out to 5.1 microns with 256 spectral
channels, at a spectral resolution of 16.6 nm. Separate telescopes collected light for each spectrometer, and each
spectrometer operated in a variety of observational modes. However, they were usually operated together in compatible
modes to generate a single data cube spanning the full wavelength range available to both portions of the instrument.
In addition to its standard imaging mode, with data-cube sizes up to 64x64 pixels, VIMS was able to operate in continuous
LINE-mode (used for close Titan flybys and some radial ring scans) and in POINT-mode (for stellar occultations).
The instrument also contained an off-axis solar port which was used to obtain spectra of the Sun for calibration
purposes and to monitor solar occultations by Titan, Saturn and the rings.
The engineering details of the VIMS instrument and the science objectives it was built to address are described in further
detail in the
Space Science Reviews
Brown et al. (2004)
Data Search Tools
about searching for VIMS images of rings, or for close encounters with moons using the OPUS
and the Image Atlas search tools listed below.
OPUS search engine allows for an interactive search of the VIMS data in the PDS archive based on a wide
variety of search parameters, including observation geometry and target.
PDS Imaging Atlas is another image-search tool with VIMS data, where parameter search and thumbnail evaluation
Master Schedule is a time-ordered listing of observations by all instruments. This may help find data based
on particular events, however the OPUS tool and Image Atlas linked above will be much simpler to use in most
Event Calendar is an interactive event-finding tool that can be used to search for data associated with
- Catalogs of VIMS
Stellar and Solar Occultations Observations are available. They include information on the latitudes and ranges of Titan
and Saturn occultations, as well as the radial coverage and opening angle of ring occultations
Browse Raw Data Products
Derived Data Products
VIMS Rings Occultation Data
- The Occultation Data is a set of peer-reviewed data sets located at the PDS Ring-Moon Systems Node
- The data contains reduced and calibrated optical depth profiles for Saturn's rings derived from VIMS stellar
occultation observations at the Rings Node.
- The data includes radial profiles at 1 and 10 km resolution derived from more than 60 VIMS occultations.
Analyzing VIMS Data
Processing VIMS Data
- The ISIS 3 is a software package can be used to process VIMS data.
- Users should use these
Step-by-Step Instructions for cartographic and science data if they wish to create their own products.
(Note: this applies only to imaging and LINE-mode data, and not to occultation data, though the format of the
raw data is the same in all cases)
IR Pixel Timing
VIMS-IR Pixel Timing
- VIMS was used in modes that were not a part of the initial instrument design. The VIMS infrared channel used
an articulating secondary mirror to produce a raster scan of the scene being observed.
- Users who wish to construct geometry for individual pixels within the scan must deal with characteristics of
the VIMS internal clock.
- The VIMS-IR Pixel Timing linked above is a white paper which has been generated and the resulting refinement
has been included in the ISIS 3 software.
VIMS Final Report of Radiometric Calibration 1/25/2018
The VIMS instrument underwent shifts in the wavelength calibration of the spectrometer since the mission launch. Large shifts occurred
during the Jupiter fly-by in 2000, followed by a period of stability until Saturn orbit insertion. Small shifts
occurred throughout the orbital tour until the end of mission in September 2017. The wavelength shifts require
a time-dependent radiometric calibration technique to be deployed to preserve radiometric accuracy. The final report
covers unresolved issues, quantifies the time-dependent wavelength shift, and described a compensatory scheme that
provides an accurate calibration for both specific intensity and intermediate frequency for the VIMS measurements
made throughout the Cassini Mission.
Other Useful Products and Resources for Interpreting the Data
The VIMS team has archived operational details for each observation, including command and mode data. These archives are
These files require knowledge of mission planning to be useful to the user.
IOI Files: Instrument command files used to acquire data for specific requests 126 MB TXT file
Requests: Observation details (e.g. primary bv, secondary bv) for each observation - 5.6 MB CSV file
SFOFs: Short forms generated for each observation - 350 MB TXT file | 0.862584 | 3.793422 |
The glowing cloud in Orion’s sword, the Orion Nebula is a thing of beauty in the night sky; it is also the closest center of massive star formation—a stellar nursery that reproduces the conditions in which our own Sun formed some 4.5 billion years ago. The study of the Orion Nebula, focused upon by ever more powerful telescopes from Galileo’s time to our own, clarifies how stars are formed, and how we have come to understand the process. C. Robert O’Dell has spent a lifetime studying Orion, and in this book he explains what the Nebula is, how it shines, its role in giving birth to stars, and the insights it affords into how common (or rare) planet formation might be.
An account of astronomy’s extended engagement with one remarkable celestial object, this book also tells the story of astronomy over the last four centuries. To help readers appreciate the Nebula and its secrets, O’Dell unfolds his tale chronologically, as astrophysical knowledge developed, and our knowledge of the Nebula and the night sky improved.
Because he served as chief scientist for the Hubble Space Telescope, O’Dell conveys a sense of continuity with his professional ancestors as he describes the construction of the world’s most powerful observatory. The result is a rare insider’s view of this observatory—and, from that unique perspective, an intimate observer’s understanding of one of the sky’s most instructive and magnificent objects. | 0.842805 | 3.39284 |
With an equator diameter of around 143,000 kilometers, Jupiter is the largest planet in the solar system and has 300 times the mass of the Earth. The formation mechanism of giant planets like Jupiter has been a hotly debated topic for several decades. Now, astrophysicists of the Swiss National Centre of Competence in Research (NCCR) PlanetS of the Universities of Bern and Zürich and ETH Zürich have joined forces to explain previous puzzles about how Jupiter was formed and new measurements. The research results were published in the magazine Nature Astronomy.
“We could show that Jupiter grew in different, distinct phases,” explains Julia Venturini, postdoc at the University of Zürich. “Especially interesting is that it is not the same kind of bodies that bring mass and energy,” adds Yann Alibert, Science Officer of PlanetS and first author of the paper. First, the planetary embryo rapidly accreted small, centimeter-sized pebbles and quickly built a core during the initial one million years. The following two million years were dominated by slower accretion of larger, kilometer-sized rocks called planetesimals. They hit the growing planet with great energy, releasing heat. “During the first stage the pebbles brought the mass,” Yann Alibert explains: “In the second phase, the planetesimals also added a bit of mass, but what is more important, they brought energy.” After three million years, Jupiter had grown to a body of 50 Earth masses. Then, the third formation phase started dominated by gas runaway accretion leading to today’s gas giant with more than 300 Earth masses.
Solar system divided into two parts
The new model for Jupiter’s birth matches the meteorite data that were presented at a conference in the US last year. At first, Julia Venturini and Yann Alibert were puzzled when they listened to the results. Measurements of the composition of meteorites showed that in the primordial times of the solar system the solar nebula was divided into two regions during two million years. It could therefore be concluded that Jupiter acted as a kind of a barrier when it grew from 20 to 50 Earth masses. During this period, the forming planet must have perturbed the dust disk, creating an over-density that trapped the pebbles outside of its orbit. Therefore, material from outward regions could not mix with material of the inner ones until the planet reached enough mass to perturb and scatter rocks inwards.
“How could it have taken two million years for Jupiter to grow from 20 to 50 Earth masses?” asked Julia Venturini. “That seemed much too long,” she explains: “That was the triggering question that motivated our study.” A discussion by email started among NCCR PlanetS researchers of the Universities of Bern and Zürich and ETH Zürich and the following week the experts in the fields of astrophysics, cosmochemistry and hydrodynamics arranged a meeting in Bern. “In a couple of hours we knew what we had to calculate for our study,” says Yann Alibert: “This was only possible within the framework of the NCCR, which links scientists from various fields.”
Explanation for delayed growth
With their calculations, the researchers showed that the time the young planet spent in the mass range of 15 to 50 Earth masses was indeed much longer than previously thought. During this formation phase the collisions with the kilometer-sized rocks provided enough energy to heat the gaseous atmosphere of the young Jupiter and prevented rapid cooling, contraction and further gas accretion. “Pebbles are important in the first stages to build a core quickly, but the heat provided by planetesimals is crucial to delay gas accretion so that it matches the timescale given by the meteorite data,” the astrophysicists summarize. They are convinced that their results provide as well key elements for solving long-standing problems of the formation of Uranus and Neptune and exoplanets in this mass regime.
Publication: Yann Alibert, et al., “The formation of Jupiter by hybrid pebble–planetesimal accretion,” Nature Astronomy (2018) | 0.876916 | 3.856617 |
Saturn is one of the most distinctive planets in the solar system thanks to its iconic rings, but surprising new research suggests that those rings weren't always there. In fact, they may have formed during the age of dinosaurs here on Earth.
In other words, Saturn's rings — and many of its moons too — might not just be babies on a galactic timescale. They might be babies on a geological timescale. If a time-traveling scientist went back to the Age of Dinosaurs and peered through a telescope at Saturn, it might have been a far different looking system.
NASA scientists recently analyzed data from the Cassini spacecraft's final missions in 2017. Towards the end of Cassini's mission, the spacecraft performed 22 dives between the planet and its rings to measure mass of the rings. Cassini calculated the mass by feeling the gravitational pull. From that, the scientists were able to study the rings' age.
"Only by getting so close to Saturn in Cassini's final orbits were we able to gather the measurements to make the new discoveries," said Cassini radio science team member and lead study author Luciano Iess, of Sapienza University of Rome. "And with this work, Cassini fulfills a fundamental goal of its mission: not only to determine the mass of the rings, but to use the information to refine models and determine the age of the rings."
The researchers knew that lower mass means a younger age. So from the data, they knew that the rings were likely formed by a comet that was ripped apart by Saturn's gravity or another event that broke apart icy moons because the rings are bright and made of ice. If the rings were similar in age to the planet, they would likely be darker and contaminated from debris.
This new analysis supports previous evidence proving that Saturn's rings are younger than the planet.
Still young at 100 million years old
In 2016, researchers calculated the age of Saturn's rings by studying the orbital tilt of the planet's inner moons. Orbital tilt is what happens to an orbiting body when it gets tugged and yanked by the gravity from other nearby objects, essentially making it more elongated. As an object like a moon becomes elongated, it begins to tilt out of its original orbital plane. By comparing the current orbital tilt of Saturn's inner moons to predictions made through computer simulations about their implied age, scientists calculated that they are probably only around 100 million years old.
"Moons are always changing their orbits. That's inevitable," Matija Cuk, principal investigator at the SETI Institute, told Phys.org. "But that fact allows us to use computer simulations to tease out the history of Saturn's inner moons. Doing so, we find that they were most likely born during the most recent two percent of the planet's history."
It's a profound thing to fathom. Up until now, the working assumption about Saturn's rings was that they were primordial, as old as the planet itself. It's humbling to think that such a prominent feature of one of the largest planets in our solar system could be a recent development. The fact that we're able to witness them today is an incredibly lucky moment in the history of the solar system.
Such an event would probably have been spectacular to witness in time lapse — if only we were born about 100 million years earlier to witness it.
Editor's note: This article has been updated since it was originally published in March 2016. | 0.867769 | 4.032519 |
About four months ago, in December 2019, the interstellar comet known as 2I/Borisov made its closest approach to our sun. After its initial discovery by Crimean amateur astronomer Gennady Borisov in August 2019, astronomers raced to observe the object—only the second known visitor from another star since the asteroidlike ‘Oumuamua in 2017—before it drifted out of view. But aside from merely watching 2I/Borisov, they were hoping for something else: that the warmth of our sun would crack the comet apart, releasing material from its innards that was scarcely, if at all, altered after forming billions of years ago in an alien star system.
In late March those hopes were fulfilled. Observations from two teams of astronomers using the Hubble Space Telescope have confirmed that a large chunk of debris up to 100 meters in size has broken off from the comet’s solid icy core, known as the nucleus, which is itself up to 500 meters across. This fragment was moving away from the comet at about 0.5 meter per second and was seen more than 180 kilometers from its nucleus. “A small fragment of the primary nucleus has come off,” says David Jewitt of the University of California, Los Angeles, who leads one of the teams. “Something came out.” Later images from Hubble revealed the fragment has since disintegrated—but the comet could well continue to cast off debris.
Ever since 2I/Borisov, often referred to as Comet Borisov, was discovered, astronomers have been eagerly studying its reflected light, using a process called spectroscopy to discover its composition and compare it to more familiar homegrown objects in our solar system. They have detected traces of water, cyanide, oxygen, and more. Those findings could be but a prelude, though, to the treasure trove of data from observations of Borisov as it breaks apart. “Cracking it open is even more exciting, because what we’re really interested in is what this thing’s made of,” says Dennis Bodewits of Auburn University, who is part of the other Hubble team. “If you crack [it] open, you get material that’s never been heated before, the building blocks of another solar system.”
Borisov made its closest approach to the sun on December 8, 2019, reaching about twice the Earth-sun distance. While the origin of the object is not known, this event may have been the first time it has ever been significantly heated by a star, a process that causes ices to boil off comets as gases, lending them their distinctive tail. It was not until early March, however, that Borisov showed any signs of responding to this heating when it let out multiple outbursts of material.
These outbursts may have increased the comet’s rotation speed, resulting in the subsequent fragmentation that has now been observed. “If the nucleus spins itself up because of these outgassing torques, it can spin so fast that it basically flies apart,” Jewitt says. “We can calculate the gravitational escape speed for this nucleus, and we can guess the density to be like other comets. The test of that will come in the future—if we ever get to see the nucleus without dust around it.”
As to why it took the comet until now to fragment, Michele Bannister of the University of Canterbury in New Zealand says she was a “little surprised,” considering the closest approach to the sun was four months ago. She notes, however, that Borisov’s high speed, as compared with the sun, may have played a part, swooping the object past our star much faster than native comets and thus subjecting it to less overall heating. “You do have to shift your expectations a bit relative to the solar system stuff,” Bannister says.
Hubble alone will be able to tell us a great deal about this event and any subsequent activity from Borisov. Yet astronomers have lamented the unfortunate timing of this never before seen breakup happening now, when most of the world’s major observatories are shuttered because of the coronavirus pandemic. “The comet is now only visible in the southern hemisphere. And all major facilities in the Southern Hemisphere—from Chile to Australia to South Africa—are closed,” says Quanzhi Ye of the University of Maryland.
Bannister notes she and her colleagues would normally now be measuring the composition of the interior in earnest with instruments such as the Very Large Telescope in Chile—observations that, for now, are simply not possible. “Hubble is a beautiful thing, but it has a bunch of different tools that are specialized to very particular purposes,” she says. “I’m not sure that [Borisov’s] going to be bright enough in some of the parts of the spectrum [for which] we have the available instrumentation on Hubble. What we can measure about the composition will be substantially limited.”
Although Borisov will remain visible to Hubble for up to another year, ground telescopes will only have a couple of months before it becomes too faint to study. Whether the pandemic’s grip on the globe will have loosened by then is unclear, but for the time being, the grand finale of one of our solar system’s most extraordinary events is airing without a full house. | 0.900579 | 3.981552 |
Astronomers studying ALIEN radio signals discover 8 NEW sources, one from nearby galaxy
While these curious signals are alien in origin, no one should be expecting little green men contacting their friends in Area 51 about the allegedly impending September raid. We currently don’t know what these bursts are or what causes them, though some suspect they may be the death rattles of neutron stars or young magnetars, extremely dense star cores spinning in a magnetic field.
The eight new repeating FRBs detected by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) radio telescope now bring the total number of known repeating FRBs to 10. These perplexing, ‘alien’ signals have captured humanity’s attention for over a decade, as the world’s best and brightest try to figure out both what they are and what causes them.
The majority of FRBs are only detected once and then they disappear, but a select few are repeaters which may provide unprecedented insights into the composition of our universe.Also on rt.com Aliens phoning home? Mysterious deep-space radio signals are more frequent than we thought
These brief, immensely powerful but short-lived bursts (often lasting just milliseconds) typically release the energy of 500 million suns, so naturally they have captured astrophysicists’ attention the world over.
In January 2019, just one, FRB 121102, was known to flash repeatedly, though a second, FRB 180814, was discovered weeks later. In just a few short months, humanity has increased that number five-fold.
Scientists have also localized the eight new repeaters to known galaxies, determining their rough location by how dispersed the signal is. Researchers have also discovered that not all FRBs come from extreme gravity environments, which means that there could be several different classes of objects or events that create FRBs.
Furthermore, repeater flashes last longer than one-off bursts indicating there may be two distinct underlying mechanisms that create them. Repeat bursts get weaker and less frequent in what the researchers dub the ‘sad trombone’ effect.
Another important milestone from our discovery with CHIME: this is the first time in the history of astrophysics that the phrase “sad trombone” has appeared in a scientific paper. pic.twitter.com/QEeYsYide2— Bryan Gaensler 📡🧲 (@SciBry) August 12, 2019
“There is definitely a difference between the sources, with some being more prolific than others,” physicist Ziggy Pleunis of McGill University told ScienceAlert.Also on rt.com ‘The big breakthrough’: Extraterrestrial radio signal source finally pinpointed for 1st time
Think your friends would be interested? Share this story! | 0.843161 | 3.119667 |
Where did the water go that was once so plentiful on the surface of Mars?
Simple question, but the answer has profound consequences.† Water was once very plentiful on the surface of Mars.† Evidence indicates vast areas were covered with water much like the oceans of the Earth.† Now the surface of Mars has very little water.† At one time the question was, ďDoes Mars have intelligent life?Ē† Now the question is does Mars have any life at all?† Does Mars have enough water to support life?† Did Mars at one time have all the elements to include intelligent life?† It did have plentiful water.† What happened to it?†
But more important to us, can the same thing happen to Earth?† At one time the Earth had much more abundant life than it now has.† During the time of the Dinosaurs, life was much more abundant.† Rainforests existed where there is now nothing but desert.† What has happened to Earth to cause this.† Could it be that the worst ecological disaster that ever happened on Earth was the loss of the material which sustains the cycle of life?† Is the Earth a dying planet, similar to the history of Mars?†
Mars has lost itís water.† The Earth has lost much of its Carbon due to burial.† Both are vital elements in the cycle of hydrocarbon life.† The answer to where the water of Mars went may be in the answer to where did it come from in the first place.† The answer to where the carbon went on earth may be burial in the form of fossil life.† We have been accustomed to calling it fossil fuel, but in reality it is fossil life.† Without restoring the fossil life to availability in the carbon cycle of life, the ecological history of the Earth may be on collision course with disaster.† We see all around us the steady eroding of the number of species as many go extinct each year.† What can we do to restore the Earth to itís former glory.† Does the answer lie in restoring the fossil life material to availability so ecology can take itís natural course?
So, where did the water that was on Mars come from in the first place?† Could it have come from the same place that water on Earth came from?† Recent evidence indicates that water is arriving on Earth at nearly the equivalency of one thousandth of an inch of rain worldwide each year.† This arriving water is in the form of soft blobs of ice and hydrocarbons similar to the composition of† a comet.† Evidence indicates there is a water cycle in our solar system similar to the water cycle on earth.† These snowballs have been heretofore undiscovered due to their dark surface from long exposure to erosion of outer space and their soft impacts.† The dark surface makes them very hard to see.† Their soft impact makes† them dissipate high in the upper atmosphere without the hot flare of an incoming meteorite.† We may have detected them but not recognized the detection in the unexplained source of clear air turbulence which is such a hazard to modern aviation.†
If water is arriving on Earth at such a rapid rate, are we loosing it at a similar rate to prevent being drowned?† Where is it going?† Is there a water cycle in space from which we are gaining water and to which we are loosing water, keeping the water supply on Earth constant?† In the past was there more water available in that water cycle such that Mars once had a sustainable supply?
So, what is this possible water cycle in outer space?† Is there a giant snowstorm in the plane of the planets of our solar system.† It has long been known that there is a dark cloud in the plane of the planets.† It has been assumed to be dust just floating out there.† Could it be the dark snowballs of a giant snowstorm in space? | 0.814489 | 3.107131 |
The proposed Tomographic Hydrogen Emission Observatory (THEO) mission is designed to investigate the physical mechanisms that control the production and loss of atomic hydrogen (H) in the outermost layer of the terrestrial neutral atmosphere known as the exosphere. Although the thermal evaporation of gaseous planetary atmospheres into space is a ubiquitous process in the universe, it is complicated at Earth by the strong charge exchange coupling between exospheric H atoms and ionospheric, magnetospheric, and solar wind ions. This ion-neutral coupling serves to enhance the permanent gravitational escape of exospheric H while dissipating plasma energy, particularly during geomagnetic storms. Studies of the Earth's exosphere thus address key NASA goals of assessing long-term changes in atmospheric composition as well as understanding the response of the terrestrial system to solar and geomagnetic energy input. In addition, accurate quantification of exospheric H is a crucial requirement for reliable remote sensing of the Earth's magnetospheric ring current via energetic neutral atom imaging. Despite the importance of Earth's H exosphere to the solar-terrestrial system, however, current understanding of its global structure and dynamical evolution is poor, such that the origin of significant discrepancies between measurements, models, and theory remains unresolved. Observation of solar ultraviolet (UV) radiation scattered by H atoms is a potential means to infer the underlying exospheric density distribution, but prior investigations have not provided sufficiently high-resolution, high-sensitivity, or global measurements to advance exospheric science. The proposed THEO mission is designed to overcome historical measurement limitations and significantly advance our understanding of H abundance and escape. The THEO mission concept is based on 3-D photometric sensing of ultraviolet H emission at 121.6 nm (Lyman-a) at unprecedented spatial resolution and angular coverage, along an ideal trans-lunar trajectory enabled by the EM-1 launch opportunity. THEO is designed to operate as a month-long, sounding-rocket mission, implementing a highly autonomous, three-axis-stabilized, 6U CubeSat platform, supported by a closed-loop ground-tracking system, orbit predictor, and redundant high-capacity ground stations. The THEO bus and science photometer share significant flight-heritage elements from the successful NSF CINEMA, USAF SENSE, and NASA POLAR satellite missions. The THEO bus includes operational redundancy for on-board elements, including the tracking transponder, the science data transmitter, and the electrical power subsystem. The operational flight software, heavily leveraged from the CINEMA mission, allows THEO to adapt to the instantaneous range-limited RF link capacity and to provide the first reliable means for quantifying global, 3-D H density from a vantage throughout and beyond the limits of the Earth's exosphere. | 0.883425 | 4.002714 |
Crescent ♌ Leo
Moon phase on 7 July 2054 Tuesday is Waxing Crescent, 2 days young Moon is in Leo.Share this page: twitter facebook linkedin
Previous main lunar phase is the New Moon before 2 days on 5 July 2054 at 10:34.
Moon rises in the morning and sets in the evening. It is visible toward the southwest in early evening.
Moon is passing about ∠14° of ♌ Leo tropical zodiac sector.
Lunar disc appears visually 4.4% wider than solar disc. Moon and Sun apparent angular diameters are ∠1972" and ∠1887".
Next Full Moon is the Buck Moon of July 2054 after 12 days on 19 July 2054 at 17:47.
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 2 days young. Earth's natural satellite is moving from the beginning to the first part of current synodic month. This is lunation 674 of Meeus index or 1627 from Brown series.
Length of current 674 lunation is 29 days, 7 hours and 14 minutes. This is the year's shortest synodic month of 2054. It is 16 minutes shorter than next lunation 675 length.
Length of current synodic month is 5 hours and 30 minutes shorter than the mean length of synodic month, but it is still 39 minutes longer, compared to 21st century shortest.
This lunation true anomaly is ∠336°. At the beginning of next synodic month true anomaly will be ∠352.3°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
1 day after point of perigee on 6 July 2054 at 21:10 in ♋ Cancer. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 14 days, until it get to the point of next apogee on 22 July 2054 at 05:49 in ♒ Aquarius.
Moon is 363 461 km (225 844 mi) away from Earth on this date. Moon moves farther next 14 days until apogee, when Earth-Moon distance will reach 405 947 km (252 244 mi).
12 days after its descending node on 25 June 2054 at 04:56 in ♒ Aquarius, the Moon is following the southern part of its orbit for the next day, until it will cross the ecliptic from South to North in ascending node on 8 July 2054 at 11:43 in ♌ Leo.
26 days after beginning of current draconic month in ♍ Virgo, the Moon is moving from the second to the final part of it.
2 days after previous North standstill on 5 July 2054 at 00:45 in ♋ Cancer, when Moon has reached northern declination of ∠19.186°. Next 10 days the lunar orbit moves southward to face South declination of ∠-19.176° in the next southern standstill on 18 July 2054 at 03:03 in ♑ Capricorn.
After 12 days on 19 July 2054 at 17:47 in ♑ Capricorn, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.848363 | 3.216825 |
As implied from the question, does the sun rotate? If so, do other stars not including the sun also rotate? Would there be any consequences if the sun and other stars didn't rotate? Me and my friends have differing views on this, and would like some clarification. Thanks!
Yes, the sun and nearly all other stars do rotate.
One can see the rotation of the sun by looking at the motion of sunspots on its surface. Over time, the sunspots will move across the sun's surface - proof of its rotation. Furthermore, the rate of the sun's rotation is not constant throughout the sun; it is higher near the equator and slower near the poles.
Other stars rotate as well. To imagine why this would be requires some thought about the creation of a star. A star begins as an enormous cloud of dust and gas. When these clouds form, they always have some rotation - even if this rotation is incredibly small and imperceptible. Gravity, however, begins pulling the cloud together into a smaller and more compact object (a star). The shrinking of the large cloud into a smaller body hugely decreases its moment of inertia, causing its angular velocity to significantly increase by the conservation of angular momentum. (This is much like how a figure skater increases her rate of spinning by pulling in her arms.) Because of this, even the slightest hint of rotation of the large gas cloud is amplified into a rapid spinning once the compact star forms.
Rotation is notable in pulsars, which are rapidly rotating neutron stars. Rapidly spinning neutron stars produce magnetic fields, causing electromagnetic radiation (often in the form of X-rays). Beams of the radiation can strike Earth, allowing observatories to observe the rapidly pulsating stars.
The sun does rotate. We can see the rotation of the sun by the doppler shift of the light we get from the sun.
(Image from this page.)
Since we know the characteristic spectrum of light from a hot body of a given temperature, we can use the same effect to determine if other stars rotate as well. Note that this only gives the spread in velocities along the line of sight, so a star may be rotating much more than the amount measured.
Draksis' answer is more than enough...
As implied from the question, does the sun rotate?
Yes, it does rotate. There's an evidence similar to the sunspots. It's not much historical. Yet, we can observe it -The 2012 Venus transit. I noticed this in three of my images (1, 2, 3) which I got during the transit. These are the images from NASA's SDO, captured in the visible spectrum. On viewing these images consecutively, you can clearly see sun's rotation. Or you can also download their amazing video based on the same time-lapse. If you observe it closely, you can see the sun's rotation in the background quite relative to Venus.
Do other stars not including the sun also rotate?
Though Dan's answer provide an excellent evidence, Draksis' answer gives an amazing explanation. As far as we've observed, almost every celestial body in the observable universe rotates about its axis, due to the conservation of angular momentum $mr^2\omega$. As the distance (radius of orbital motion) decreases, $\omega$ should increase. Inertia does this automatically. Interstellar clouds (a few or few thousand LYs long) are massive enough to experience a gravitational collapse. Once this collapse leads to proto-star phase, the center is dense enough, so that the surrounding matter can swirl and finally spiral into it. As the lengthy cloud slowly spiral inwards it spins faster. Hence, almost all stellar objects spin.
Would there be any consequences if the sun and other stars didn't rotate?
Let's assume that the sun and other stars along with the planets suddenly stopped rotating themselves. There won't be a consequence or any effects now. (This necessarily doesn't happen due to conservation of angular momentum). But as Frank says (which according to the currently accepted hypothesis), if the clouds had stopped rotating (no initial angular momentum), there would be no proto-planetary disks surrounding the nebula-forming region, leading to a central non-rotating star with no planets. These proto-stellar disks are the accretion disks (dense arms of the clouds) which sometimes acquire enough density to form a star-like object (unable to fuse further) ending up as a planet.
The photosphere of the Sun rotates with a 25 day period at equator and more than a 36 day period at the poles. Below the photosphere we have the convection zone and below the convection zone everything rotate as it was one solid spherical body. This spherical body is 70 % of the volume of the Sun and even more of the mass and rotates with a period of 26,3 days. The surface of this sphere is called the tachocline and its extremely thin, less than 3% of the solar diameter.
Often magnetic confinement are used as a explanation of how the interior of the Sun can behave like one solid rotating spherical body, and the magnetic field are again hypothesized to come from motion in the convection zone, but this theory is not yet developed to level where it can fully explain what we observe.
Alternatively the interior of the sun is a fluid or solid body, but this conflicts with current fusion theory where the core of the sun is a hot, high pressure, nuclear fusion furnace.
Yes the rotation of stars have some implications, like neutron stars that rotate faster than a dentists drill. If they where made of ordinary matter the centrifugal forces would rip them apart, so we postulated that they where made of neutrons with huge gravity forces holding them together. Our Sun is the most spherical object we know of and we would excpect it to be like a compressed oval ball due to centrifugal forces, but current theory states that it is the magnetic field which confines the hot plasma ball into the perfect sphere we observe. | 0.878402 | 3.804183 |
Tiniest Alien Solar System Discovered: 5 Packed Planets
The most crowded alien planetary system found yet possesses five worlds all orbiting a star at least 12 times closer than Earth does the sun, researchers say. KOI-500 is a super-compact planetary system, the most tightly packed one seen yet, hosting at least five planets ranging from 1.3 to 2.6 times the size of Earth. These planets orbit so near KOI-500 that their “years,” or the time it takes to circle their star, are only 1.0, 3.1, 4.6, 7.1, and 9.5 days long. The planets are so close together that their mutual gravity slightly pushes and pulls on their orbit
Recent theories for the formation of the giant planets of our outer solar system involve planets moving during the formation process, as scientists suspect happened with KOI-500. As these giants shifted their orbits, researchers suggest their gravitational pulls hurled asteroids and comets toward the inner solar system, causing the so-called Late Heavy Bombardment about 4.1 billion to 3.8 billion years ago, which pummeled Earth, the moon and the inner planets with a barrage of countless impacts. As scientists have discovered more and more exoplanets, they have found that most observed worlds orbit much closer to their stars than any planet in our solar system orbits the sun, including so-called hot Jupiters, which are giant planets orbiting closer to their stars than Mercury does the sun. Scientists still don’t understand why most observed alien planetary systems look so unlike ours. | 0.886455 | 3.053043 |
From: Planetary Science Institute
Posted: Tuesday, September 20, 2011
Two small depressions on Mars found to be rich in minerals that formed by water could have been places for life relatively recently in the planet's history, according to a new paper in the journal Geology.
"We discovered locations at Noctis Labyrinthus that show many kinds of minerals that formed by water activity," said Catherine Weitz, lead author and senior scientist at the Planetary Science Institute. "The clays we found, called iron/magnesium (Fe/Mg)-smectites, are much younger at Noctis Labyrinthus relative to those found in the ancient rocks on Mars, which indicates a different water environment in these depressions relative to what was happening elsewhere on Mars."
Smectites are a specific type of clay mineral that readily expands and contracts with adsorbed water. They contain silica, plus aluminum, iron or magnesium in their structures. They form by the alteration of other silicate minerals in the presence of non-acidic water.
Weitz and her co-authors studied approximately 300 meters of vertically exposed layered rocks within two 30 to 40 kilometer depressions, called troughs, near the western end of the Valles Marineris canyon system. Using high-resolution images from the High Resolution Imaging Science Experiment (HiRISE) camera and hyperspectral data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on the Mars Reconnaissance Orbiter (MRO) spacecraft, combined with Digital Terrain Models (DTMs) to determine elevations and view geometric relationships between units, the team was able to map hydrated minerals and understand how the water chemistry varied with time within each trough, said Weitz, a HiRISE team member.
Each trough probably experienced multiple episodes where water partially filled in low-lying regions and deposited minerals. As each trough continued to enlarge and experience collapse over time, older minerals became buried and separated, followed by deposition of younger minerals, then finally erosion to re-expose buried units. Volcanism from the Tharsis volcanoes to the west may have created subsurface water that was subsequently transported through the ground and into the troughs. Localized volcanism that produced ash and gases, hydrothermal activity, and melting snow/ice within the troughs could have also produced some of the minerals. The observed minerals indicate water varied in pH levels over time, in one trough from acidic to neutral, and in the other trough from neutral to acidic and back to neutral.
Other occurrences of Fe/Mg-smectites have been found on Mars but almost exclusively in association with older, Noachian-age (more than 3.6 billion years ago) rocks, or produced by younger impact events. Following the deposition of Fe/Mg-smectites in the Noachian period, the climate on Mars is believed to have changed during the Hesperian time to favor formation of minerals under more acidic conditions, such as salts rich in sulfur (sulfates).
Weitz and her co-authors identified the same sulfates and Fe/Mg-smectites in the Noctis Labyrinthus troughs found elsewhere on Mars, but the progression of minerals over time, from sulfates to Fe/Mg-smectites, indicates a reverse order relative to what happened globally across Mars.
"These clays formed from persistent water in neutral to basic conditions around 2 to 3 billion years ago, indicating these two troughs are unique and could have been a more habitable region on Mars at a time when drier conditions dominated the surface," said co-author and CRISM team member Janice Bishop from the SETI Institute and NASA Ames Research Center.
"These troughs would be fantastic places to send a rover, but unfortunately the rugged terrain makes it unsafe both for landing and for driving," Weitz said.
# # #
The study was funded by grants to PSI from NASA, the Jet Propulsion Laboratory and the University of Arizona.
The Planetary Science Institute is a private, nonprofit 501(c)(3) corporation dedicated to solar system exploration. It is headquartered in Tucson, Arizona, where it was founded in 1972. PSI scientists are involved in numerous NASA and international missions, the study of Mars and other planets, the Moon, asteroids, comets, interplanetary dust, impact physics, the origin of the solar system, extra-solar planet formation, dynamics, the rise of life, and other areas of research. They conduct fieldwork in North America, Australia and Africa. They also are actively involved in science education and public outreach through school programs, children's books, popular science books and art. PSI scientists are based in 17 states, the United Kingdom, France, Switzerland, Russia and Australia.
Public Information Officer
+1 520-382-0411; +1 520-622-6300
Catherine M. Weitz
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// end // | 0.860896 | 3.912905 |
In practice, however, Venus's orbit is very close to circular; its distance from the Sun varies by only about 1.5% between perihelion and aphelion. This makes Venus's orbit more perfectly circular than that of any of the Solar System's other planets. As a result, its surface receives almost exactly the same amount of energy from the Sun at perihelion (closest approach to the Sun) and aphelion (furthest recess from the Sun).
The exact position of Venus at the moment it passes aphelion will be:
|Object||Right Ascension||Declination||Constellation||Angular Size|
The coordinates above are given in J2000.0.
From Ashburn, Venus will be visible in the dawn sky, rising at 03:25 (EDT) – 2 hours and 29 minutes before the Sun – and reaching an altitude of 23° above the eastern horizon before fading from view as dawn breaks around 05:33.
|The sky on 10 July 2020|
19 days old
All times shown in EDT.
The circumstances of this event were computed using the DE405 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).
This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.
|10 Jul 2020||– Venus at aphelion|
|12 Aug 2020||– Venus at dichotomy|
|13 Aug 2020||– Venus at greatest elongation west|
|07 Sep 2020||– Venus reaches highest point in morning sky| | 0.894611 | 3.522365 |
This is a photo of a Gibeon meteorite (iron, IVA class) fragment from Namibia, featuring the Thomson (Widmanstatten) patterns. I believe the darker areas are kamacite and lighter areas taenite/plessite (1, 2). Nitric acid is used to etch/reveal the patterns on the surface, with kamacite being more easily dissolved by the acid than taenite (3).
Approximate Photo Location (Side 1)
Field of view: ~1/4” x 3/8“ (6.7mm x 10.0mm)
Images in focus stack: 42
The Gibeon meteorite landed in present-day Namibia possibly 5,000-30,000 years ago (5). It is estimated to have been larger than 3m before it broke up in the atmosphere, and could have originally been larger than 600km during the early stages of the formation of the solar system (4, 6). The illustration below shows the octahedral crystal structure of the meteorite. (An octahedron has eight faces, as if you connected two pyramids at their bases. If you imagine each face of the octahedron as a plane, you have four unique orientations, as opposite faces are parallel)(8). The taenite forms along (parallel) to these four unique directions/planes. It also serves as a boundary for the growth of the kamacite (7). The crystallization process/formation of the patterns occurs between a specific range of temperatures as the asteroid slowly cools in space (6, 8). It takes hundreds of thousands, if not millions of years for the crystals to form (7). The exact appearance of the Thomson patterns is determined by the plane on which the meteorite is cut (7, 8). For example, if you cut perpendicular to the octahedron’s axis (e.g., cutting off the top of the pyramid shape as shown in figure II), the patterns will intersect at right angles. If you cut parallel to a face (figure III), the patterns will intersect at 60/120 degree angles (8). The photographed specimen was cut at a different angle that these (which I can’t quite visualize at the moment) :). The image below the illustration shows the specimen and setup for the photo. The fragment has a shiny metallic appearance. The lighting determines whether the kamacite is light/taenite is dark or vice-versa.
1. Nowell, M. (2015). Space rocks rock! Retrieved from EDAX.
2. Hogue, F., and Sheybany, S. (2002). A comparative look at microstructures of iron meteorites. Microscopy Microanalysis, 8(Suppl. 2). Retrieved from Cambridge University Press.
3. Hartman, R. (2002). Etching iron meteorites (or…”the myth of nitric acid”). Retrieved from the Meteorite Times Magazine.
4. Buhl, S. (n.d.). Gibeon iron meteorites: Part 1: Discovery, history, and study. Retrieved from Meteorite Recon.
5. Buhl, S. (n.d.). Gibeon iron meteorites: Part 4: Research after Buchwald. Retrieved from Meteorite Recon.
6. Buhl, S. (n.d.). Gibeon. Retrieved from Meteorite Studies.
7. Irons. (n.d.). Retrieved from the Utas Collection of Meteorites.
8. Oskay, W. (2014). A fragment of muonionalusta. Retrieved from the Evil Mad Scientist Laboratories.
Copyright © 2016–2019 by Aaron-Emile W. Osborn, all rights reserved. | 0.833939 | 3.434213 |
The Juno project is taking public participation in a space mission to a new level by inviting amateur astronomers to upload telescope images of Jupiter directly to the Junocam website. Eventually the photos will be voted on, and the top targets will be targeted by the spacecraft’s camera—provided the atmospheric features don’t disappear in the meantime.
While amateur involvement in space projects is nothing new, Juno’s team will rely on non-professionals more heavily than previous missions have, says Candice Hansen, a senior scientist at the Planetary Science Institute responsible for operating Junocam. She compares this effort to HiWish, whereby the public can suggest viewing targets for the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter. Junocam will need even more help, says Hansen (who also works on HiRISE) because Juno’s team is tiny.
“With [Jupiter’s] dynamic atmosphere, you cannot just get one map and plan from there. We need up-to-date knowledge of where the big storms are, what’s going on with the belts and zones, etc.,” Hansen says.
Telescopes run by professional astronomers will be viewing Jupiter, too, of course, but amateur observers get more competitive with the big guys every day. Backyard telescopes can capture far better images of Jupiter than they could during the last major Jupiter mission, Galileo, in the 1990s. Amateurs even caught the collision of a small body with Jupiter earlier this year.
Even modest-size telescopes can track features on Jupiter, whereas features on more distant planets like Neptune are much more challenging, says Glenn Orton of the Jet Propulsion Laboratory, who is co-ordinating the amateur campaign. Mars is well photographed by spacecraft in Martian orbit, but Juno will be the only camera in orbit around Jupiter.
Roughly 50 active amateurs are already uploading images to the Junocam website, says Orton. The website’s full features, including voting, won’t be turned on until November.
Hansen says that another distinction between Juno and other opportunities for amateurs is that previous campaigns have been mainly student-focused. The International Space Station’s EarthKAM, for example, allows students to pick a single image per day, while Cassini’s “scientist for a day” allows a few winning essay writers every year to pick a science target.
As with the Cassini mission at Saturn and the Curiosity and Opportunity rovers at Mars, raw images from Juno will be available for the public to download and even enhance. “We will invite the public to process them,” Hansen says. “The resources within our team are limited, and we won’t have the luxury of producing enhanced color, special crops, montages, etc.” | 0.848678 | 3.336145 |
Washington, Oct 31 (IANS) NASA has decided to retire its Kepler space telescope that had run out of fuel needed for further science operations.
Working in deep space for nine years, Kepler has discovered more than 2,600 planets from outside our solar system, many of which could be promising places for life, Xinhua news agency reported on Tuesday.
The spacecraft will be retired within its current, safe orbit, away from Earth, according to NASA, the report said.
“As NASA’s first planet-hunting mission, Kepler has wildly exceeded all our expectations and paved the way for our exploration and search for life in the solar system and beyond,” said Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate in Washington.
“Not only did it show us how many planets could be out there, it sparked an entirely new and robust field of research that has taken the science community by storm. Its discoveries have shed a new light on our place in the universe, and illuminated the tantalising mysteries and possibilities among the stars,” said Zurbuchen.
A recent analysis of Kepler’s discoveries suggested that 20 to 50 per cent of the stars visible in the night sky were likely to have small, possibly rocky, planets similar in size to Earth, and located within the habitable zone of their parent stars, which means they’re located at distances from their parent stars where liquid water, a vital ingredient to life as we know it, might pool on the planet surface.
“When we started conceiving this mission 35 years ago, we didn’t know of a single planet outside our solar system,” said the Kepler mission’s founding principal investigator, William Borucki, now retired from NASA’s Ames Research Center in California’s Silicon Valley.
“Now that we know planets are everywhere, Kepler has set us on a new course that’s full of promise for future generations to explore our galaxy,” said Borucki.
Launched on March 6 in 2009, the Kepler space telescope combined cutting-edge techniques in measuring stellar brightness with the largest digital camera outfitted for outer space observations at that time.
Originally positioned to stare continuously at 150,000 stars in one star-studded patch of the sky in the constellation Cygnus, Kepler took the first survey of planets in our galaxy and became NASA’s first mission to detect Earth-size planets in the habitable zones of their stars.
Four years into the mission, after the primary mission objectives had been met, some mechanical failures temporarily halted observations. But the mission team managed to devise a fix, switching the spacecraft’s field of view roughly every three months.
This enabled an extended mission for the spacecraft, dubbed K2, which lasted as long as the first mission and bumped Kepler’s count of surveyed stars up to more than 500,000.
“We know the spacecraft’s retirement isn’t the end of Kepler’s discoveries,” said Jessie Dotson, Kepler’s project scientist at NASA’s Ames Research Center in California’s Silicon Valley.
Kepler’s more advanced successor is the Transiting Exoplanet Survey Satellite (TESS), launched in April.
TESS builds on Kepler’s foundation with fresh batches of data in its search of planets orbiting some 200,000 of the brightest and nearest stars to the Earth. | 0.873082 | 3.143888 |
One of the most important obstacles for the exploration of the night sky is the brightening of the night sky by artificial lights, such as streetlights. The night sky is not really dark in the vicinity of towns or cities, which reduces the visibility of objects bejond the solar systems enourmously. Depending on the type of the celestial object it is possible to increase the contrast dramatically by blocking the annoying artifical light. The Explore Scientific O-III filter uses a characteristic property of the so called emmission nebulae. Those objekcts glow in special colors, the so called emmission lines. Those emmission lines are linked to chemical elements – in this case oxygen. The Explore Scientific O-III nebula filter blocks all other colors (and thereby nearly all of the artificial light) and only the two emmission lines of the oxygen can pass the filter. The result is astonoishing: suddenly nebulae are visible at locations that were completely empty without filters. In suburbian skies for example the veil nebula NGC 6992 is almost not visible with a 200mm telescope. By using this filter you can see the nebula and its structures without problems. A must for every visual observer.
|Optics material||optical glass|
|Eyepiece barrel diameter||2” (50.8mm)| | 0.821196 | 3.187436 |
The Parker Solar Probe is ready to smash more cosmic records as it prepares to make its closest ever approach to the sun.
The spacecraft’s second closest approach, the perihelion is expected to take place on April 4, 2019.
Image: Parker Solar Probe’s position, speed and round-trip light time as of Jan. 28, 2019. Track the spacecraft online. Image Credit: NASA.
161 days have gone by since the Parker Solar Probe was launched into space, and scientists report the space probe has successfully orbited the sun for the first time.
Now, the Parker Solar Probe is set to smash new records as it gears up to start it second orbit around the sun, which will take the spacecraft closer to the sun than ever before.
As reported by NASA, the spacecraft has begun the second of a total of twenty-four planned orbits, which will take the spacecraft closer to the sun like never before.
“It’s been an illuminating and fascinating first orbit,” said Andy Driesman, Project Manager at the Johns Hopkins University’s Applied Physics Laboratory.
“We’ve learned a lot about how the spacecraft operates and reacts to the solar environment, and I’m proud to say the team’s projections have been very accurate,” Driesman added.
During its first orbit around the sun, the spacecraft gathered a plethora of scientific data that will help experts understand how our sun functions.
Data gathered by the spacecraft is expected to shed light on how solar particles and solar material are accelerated out into space at such extreme speeds, and how the Sun’s atmosphere, known as the corona, is much hotter than its surface below.
According to reports, the Parker Space Probe has been delivering data gathered via the Deep Space Network, and to date, more than 17 gigabits of science data has been downloaded by NASA mission scientist.
In fact, the spacecraft gathered so much data that scientists expect the full data set of its first orbit around the sun will be downloaded by April of 2019.
“We’ve always said that we don’t know what to expect until we look at the data,” said Project Scientist Nour Raouafi, also of APL.
“The data we have received hints at many new things that we’ve not seen before and at potential new discoveries. Parker Solar Probe is delivering on the mission’s promise of revealing the mysteries of our Sun.”
While gathering the scientific data that’s being transmitted by the spacecraft, mission scientists are preparing for the ‘second solar encounter’ expected to take place in about two months.
In addition to unpreceded scientific data, we expect to see new, fresh images snapped by the spacecraft from ‘inside’ the sun’s atmosphere. | 0.842839 | 3.286967 |
Jupiter will align with Earth and the sun tonight, standing alongside our planet and the fiery star in a perfect straight line.
This phenomenon, known as opposition, occurs just once every 13 months and finds the gas giant reaching its closest distance to Earth. Most significantly for space enthusiasts, opposition marks the year’s most optimal Jupiter viewing conditions, enabling binocular-equipped watchers to easily spot the planet and perhaps even a few of its 79 moons.
According to Vox’s Brian Resnick, Jupiter will grace the southeastern sky at dusk and remain visible until setting in the west at dawn. Those with binoculars should be able to see both the enormous planet, officially the largest in our solar system, and its four brightest moons—Io, Europa, Callisto and Ganymede. If you own a telescope, you may also be able to make out individual cloud bands and Jupiter’s characteristic Great Red Spot.
To locate Jupiter, simply look to the southeast and find the brightest object in the sky, excluding Venus and the moon, as Inverse’s Scott Snowden points out. Although the precise moment of opposition will take place at 6 p.m. Eastern time, Sky & Telescope’s Bob King writes that the planet will reach ideal viewing height around 11:30 p.m. and will remain visible through sunrise, or roughly 7 a.m.
From Minneapolis, it will be visible between 21:43 and 04:38. It will become accessible at around 21:43, when it rises 7° above your south-eastern horizon, and then reach its highest point in the sky at 01:13, 22° above your southern horizon. It will become inaccessible at around 04:38 when it sinks to 7° above your south-western horizon.
Jupiter has aurorae. Like Earth, the magnetic field of the gas giant funnels charged particles released from the Sun onto the poles. As these particles strike the atmosphere, electrons are temporarily knocked away from existing gas molecules. Electric force attracts these electrons back. As the electrons recombine to remake neutral molecules, auroral light is emitted. In the featured recently released composite image by the Hubble Space Telescope taken in ultraviolet light, the aurorae appear as annular sheets around the pole. Unlike Earth’s aurorae, Jupiter’s aurorae include several bright streaks and dots. Jupiter’s Great Red Spot is visible on the lower right. Recent aurorae on Jupiter have been particularly strong — a fortunate coincidence with the arrival of NASA’s Juno spacecraft at Jupiter last week. Juno was able to monitor the Solar Wind as it approached Jupiter, enabling a better understanding of aurorae in general, including on Earth. | 0.833435 | 3.614457 |
After successfully launching Thursday night, NASA’s Ionospheric Connection Explorer (ICON) spacecraft is in orbit for a first-of-its-kind mission to study a region of space where changes can disrupt communications and satellite orbits, and even increase radiation risks to astronauts.
A Northrop Grumman Stargazer L-1011 aircraft took off at 8:31 p.m. EDT from Cape Canaveral Air Force Station in Florida carrying ICON, on a Northrop Grumman Pegasus XL rocket, to launch altitude of about 39,000 feet. The first launch opportunity around 9:30 was skipped due to communication issues between the ground team at Cape Canaveral and the aircraft. On the second attempt, the aircraft crew released its payload at 9:59 p.m. EDT and automated systems on the Pegasus rocket launched ICON, a spacecraft roughly the size of a refrigerator, into space.
The spacecraft’s solar panels successfully deployed, indicating it has power with all systems operating. After an approximately month-long commissioning period, ICON will begin sending back its first science data in November.
ICON will study changes in a region of the upper atmosphere called the ionosphere. In addition to interfering with communications signals, space weather in the ionosphere can also prematurely decay spacecraft orbits and expose astronauts to radiation-borne health risks. Historically, this critical region of near-Earth space has been difficult to observe. Spacecraft can’t travel through the low parts of the ionosphere and balloons can’t travel high enough.
“ICON has an important job to do – to help us understand the dynamic space environment near our home,” said Nicola Fox, director for heliophysics at NASA Headquarters in Washington. “ICON will be the first mission to simultaneously track what’s happening in Earth’s upper atmosphere and in space to see how the two interact, causing the kind of changes that can disrupt our communications systems.”
ICON explores the connections between the neutral atmosphere and the electrically charged ionosphere with four instruments. Three of the instruments rely on one of the upper atmosphere’s more spectacular phenomena: colorful bands called airglow.
Airglow is created by a similar process that creates the aurora – gas is excited by radiation from the Sun and emits light. Though aurora are typically confined to extreme northern and southern latitudes, airglow happens constantly across the globe, and is much fainter. But it’s still bright enough for ICON’s instruments to build up a picture of the ionosphere’s density, composition and structure. By way of airglow, ICON can observe how particles throughout the upper atmosphere are moving.
ICON’s fourth instrument provides direct measurements of the ionosphere around it. This instrument characterizes the charged gases immediately surrounding the spacecraft.
“We put as much capability on this satellite that could possibly fit on the payload deck,” said Thomas Immel, the principal investigator for ICON at the University of California, Berkeley. “All those instruments are focused on the ionosphere in a completely new science mission that starts now.”
ICON’s orbit around Earth places it at a 27-degree inclination and altitude of about 360 miles. From there, it can observe the ionosphere around the equator. ICON will aim its instruments for a view of what’s happening at the lowest boundary of space, from about 55 miles up to 360 miles above the surface. This rapid orbit circles Earth in 97 minutes while precessing around the equator, allowing ICON to sample a wide range of latitude, longitude and local times.
ICON is an Explorer-class mission. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the Explorer Program for NASA’s Science Mission Directorate in Washington. The University of California at Berkeley developed the ICON mission and the two ultraviolet imaging spectrographs, Extreme Ultra-Violet instrument and the Far Ultra-Violet instrument. The Naval Research Laboratory in Washington developed the Michelson Interferometer for Global High-resolution Thermospheric Imaging instrument. The University of Texas in Dallas developed the Ion Velocity Meter. The spacecraft was built by Northrop Grumman in Dulles, Virginia. The Mission Operations Center at UC Berkeley’s Space Sciences Laboratory is tasked with operating the ICON mission.
For more information on ICON, visit:
Rod is a blogger, writer, filmmaker, photographer, daydreamer who likes to cook. Rod produces and directs the web series, CUPIC: Diary of an Investigator. | 0.822001 | 3.415544 |
The current cosmological paradigm includes two significant and unknown physical entities called "dark matter" and "dark energy," which are used to model the Universe as we know it. Understanding the distribution of dark matter remains one of the most fundamental problems in astronomy and is the focus of this project. There are many discrepancies between dark matter sub-structure in the existing computer simulations and in observations. There are too few massive satellites relative to simulations, and at low Galactic latitudes there are hardly any Milky Way satellites. This project aims to extract essential information on the dark matter distribution in spiral galaxies by building on the investigator's ongoing work in characterizing galactic satellites from analysis of disturbances in extended disks of hydrogen gas.
Communicating scientific results to a broad audience and promoting diversity benefits the astronomy community and our society at large. This project will be carried out at Rochester Institute of Technology (RIT), which has historically been primarily an undergraduate institution:
(1) Women in Science: The PI will organize regular meetings with visiting women colloquium speakers, with the goal of gathering advice on professional development. Dr. Chakrabarti will also continue participating in the Expanding Your Horizons program, which is geared towards engaging middle school girls in science.
(2) Computational Bootcamp: Every summer, the PI will provide a two-week, intensive computational bootcamp geared towards entering graduate students. The goal of this bootcamp is to serve as a bridge---providing an introduction to computational astrophysics, with hands-on lectures that illustrate the basics of computing and applications to astronomy. The PI will work through simple examples in IDL and Python, and she will encourage women and minority students to attend the bootcamp, and assign mentors for entering students.
(3) Visualization Laboratory: The PI will continue producing 3-D animations of galaxy collisions, which will be showcased in the Viz-Lab at RIT. Three-D movies are becoming an increasingly popular tool to engage the public and are effective in widely disseminating research on galaxy evolution.
The PI will carry out the following technical tasks:
(1) The Milky Way: By matching simulated orbits of the Milky Way satellites with HST proper motions and tidal debris, the PI will derive constraints on the orbital parameters, as well as the initial stellar (and dark matter) distribution of the Milky Way satellites. The PI will produce models that are consistent with both the HI and stellar data of our galaxy, which displays large ripples in the outskirts, a prominent warp, and vertical waves in the galactic disk.
(2) Probing The Dark Matter Halo: Dark matter halos evolve as a function of time, and they may have complex shapes. The PI will determine if the inference of the halo potential from stellar streams is viable for time-varying potentials. By deconstructing the hydrodynamical cosmological simulation ERIS, the PI will study if the distribution of satellites and the morphology of the gas and stellar disk is representative of the Milky Way or local spirals.
(3) Shaking and Rattling The Local Spirals: By simulating a wide range of encounters with sub-halos from cosmological simulations, and mapping to multiple observational constraints in a statistically robust manner using a Monte Carlo Markov Chain analysis, the PI will produce realistic mock catalogs and evolutionary histories of HI disks and their satellite populations.
(4) Strong Spiral Lenses in HI: As the SWELLS sample is a sufficiently low redshift sample of strong spiral lenses (z_avg ~ 0.1) showing visible signs of interaction, the PI will compare and contrast the team's HI analysis and gravitational lensing to derive two independent constraints on the dark matter distribution. | 0.899567 | 3.491967 |
Quarter ♊ Gemini
Moon phase on 20 February 2002 Wednesday is First Quarter, 7 days young Moon is in Gemini.Share this page: twitter facebook linkedin
First Quarter is the lunar phase on . Seen from Earth, illuminated fraction of the Moon surface is 50% and growing larger. The 7 days young Moon is in ♊ Gemini.
* The exact date and time of this First Quarter phase is on 20 February 2002 at 12:02 UTC.
Moon rises at noon and sets at midnight. It is visible high in the southern sky in early evening.
Moon is passing first ∠2° of ♊ Gemini tropical zodiac sector.
Lunar disc appears visually 5.5% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1837" and ∠1940".
Next Full Moon is the Snow Moon of February 2002 after 6 days on 27 February 2002 at 09:17.
There is medium ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at very acute angle, so their combined tidal force is moderate.
The Moon is 7 days young. Earth's natural satellite is moving through the first part of current synodic month. This is lunation 26 of Meeus index or 979 from Brown series.
Length of current 26 lunation is 29 days, 18 hours and 22 minutes. This is the year's longest synodic month of 2002. It is 1 hour and 3 minutes longer than next lunation 27 length.
Length of current synodic month is 5 hours and 38 minutes longer than the mean length of synodic month, but it is still 1 hour and 25 minutes shorter, compared to 21st century longest.
This lunation true anomaly is ∠155.3°. At the beginning of next synodic month true anomaly will be ∠180.3°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
5 days after point of apogee on 14 February 2002 at 22:22 in ♓ Pisces. The lunar orbit is getting closer, while the Moon is moving inward the Earth. It will keep this direction for the next 7 days, until it get to the point of next perigee on 27 February 2002 at 19:47 in ♍ Virgo.
Moon is 390 205 km (242 462 mi) away from Earth on this date. Moon moves closer next 7 days until perigee, when Earth-Moon distance will reach 356 898 km (221 766 mi).
12 days after its descending node on 7 February 2002 at 15:33 in ♐ Sagittarius, the Moon is following the southern part of its orbit for the next day, until it will cross the ecliptic from South to North in ascending node on 22 February 2002 at 06:26 in ♊ Gemini.
25 days after beginning of current draconic month in ♋ Cancer, the Moon is moving from the second to the final part of it.
11 days after previous South standstill on 8 February 2002 at 20:59 in ♑ Capricorn, when Moon has reached southern declination of ∠-24.309°. Next 2 days the lunar orbit moves northward to face North declination of ∠24.418° in the next northern standstill on 23 February 2002 at 11:48 in ♋ Cancer.
After 6 days on 27 February 2002 at 09:17 in ♍ Virgo, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.848363 | 3.286091 |
You’re looking at the center of our galactic home, the Milky Way, as imaged by 64 radio telescopes in the South African wilderness.
Scientists released this image today to inaugurate the completed MeerKAT radio telescope. But these scopes form part of an even more ambitious project: the Square Kilometer Array, a joint effort to build the world’s largest telescope, spanning the continents of Africa and Australia.
This image shows filaments of particles, structures that seem to exist in alignment with the galaxy’s central black hole. It’s unclear what causes these filaments. Maybe they are particles ejected by the spinning black hole; maybe they are hypothesized “cosmic strings;” and maybe they’re not unique, and there are other, similar structures waiting to be found, according to a 2017 release from Harvard-Smithsonian Center for Astrophysics.
“This image from MeerKAT is awesome to me because the fine filaments seen in the radio image are excellent tracers of the galactic magnetic field, something we don’t get to see in most optical and infrared data,” Erin Ryan, research space scientist at the NASA Goddard Space Flight Center, told Gizmodo. “High-resolution data like this will help the study of galactic magnetic fields and how they may be important for galaxy evolution.”
Each one of MeerKAT’s 64 radio receivers is a 44-foot radio antenna. They collect radio waves from cosmic sources (like the center of the galaxy) with a timestamp, convert it to digital information, and send it to a central location. The information from each dish is then correlated together into an image. Imagine how a regular telescope works—light is collected by mirrors and focused in the center. In this case, it’s as if each of the radio telescopes is itself a mirror, and the “center” is where the fiber optic cables meet to create the main image.
Ultimately, MeerKAT will form part of the larger Square Kilometer Array (SKA), named because it will have a square kilometer of collecting area, potentially with higher resolution than the Hubble Space Telescope in the radio band. By the late 2020s, it should consist of 2,000 radio dishes in the Karoo region of South Africa and Murchison Shire in Western Australia, and the total project could one day consist of 3,000 dishes in other African countries, reports South Africa’s News24.
News24 reports that MeerKAT alone cost over $330 million (USD), while the total SKA cost hasn’t yet been determined.
A telescope like this could have many important uses: perhaps it could measure the history of the Universe’s expansion to help understand the mysterious dark energy. It could also offer insight into the laws of gravity at the Universe’s largest scales, and more generally see details of our galaxy and Universe that are invisible to other telescopes.
There are many cosmic mysteries yet to be solved. And some of the answers may come from an enormous array of dishes in South Africa and Australia.
Correction: This post has been updated to correct Dr. Ryan’s affiliation. Sorry about that! | 0.900593 | 3.526956 |
Sirius is the brightest star in the night sky. Its name is derived from the Greek word Σείριος Seirios "glowing" or "scorching". With a visual apparent magnitude of −1.46, Sirius is twice as bright as Canopus, the next brightest star. Sirius is a binary star consisting of a main-sequence star of spectral type A0 or A1, termed Sirius A, a faint white dwarf companion of spectral type DA2, termed Sirius B; the distance between the two varies between 8.2 and 31.5 astronomical units as they orbit every 50 years. Sirius appears bright because of its proximity to the Solar System. At a distance of 2.64 parsecs, the Sirius system is one of Earth's nearest neighbours. Sirius is moving closer to the Solar System, so it will increase in brightness over the next 60,000 years. After that time, its distance will begin to increase, it will become fainter, but it will continue to be the brightest star in the Earth's night sky for the next 210,000 years. Sirius A is about twice as massive as the Sun and has an absolute visual magnitude of +1.42.
It is 25 times more luminous than the Sun but has a lower luminosity than other bright stars such as Canopus or Rigel. The system is between 300 million years old, it was composed of two bright bluish stars. The more massive of these, Sirius B, consumed its resources and became a red giant before shedding its outer layers and collapsing into its current state as a white dwarf around 120 million years ago. Sirius is known colloquially as the "Dog Star", reflecting its prominence in its constellation, Canis Major; the heliacal rising of Sirius marked the flooding of the Nile in Ancient Egypt and the "dog days" of summer for the ancient Greeks, while to the Polynesians in the Southern Hemisphere, the star marked winter and was an important reference for their navigation around the Pacific Ocean. The brightest star in the night sky, Sirius is recorded in some of the earliest astronomical records, its displacement from the ecliptic causes its heliacal rising to be remarkably regular compared to other stars, with a period of exactly 365.25 days holding it constant relative to the solar year.
This rising occurs at Cairo on 19 July, placing it just prior to the onset of the annual flooding of the Nile during antiquity. Owing to the flood's own irregularity, the extreme precision of the star's return made it important to the ancient Egyptians, who worshipped it as the goddess Sopdet, guarantor of the fertility of their land; the Egyptian civil calendar was initiated to have its New Year "Mesori" coincide with the appearance of Sirius, although its lack of leap years meant that this congruence only held for four years until its date began to wander backwards through the months. The Egyptians continued to note the times of Sirius's annual return, which may have led them to the discovery of the 1460-year Sothic cycle and influenced the development of the Julian and Alexandrian calendars; the ancient Greeks observed that the appearance of Sirius heralded the hot and dry summer and feared that it caused plants to wilt, men to weaken, women to become aroused. Due to its brightness, Sirius would have been seen to twinkle more in the unsettled weather conditions of early summer.
To Greek observers, this signified emanations. Anyone suffering its effects was said to be "star-struck", it was described as "burning" or "flaming" in literature. The season following the star's reappearance came to be known as the "dog days"; the inhabitants of the island of Ceos in the Aegean Sea would offer sacrifices to Sirius and Zeus to bring cooling breezes and would await the reappearance of the star in summer. If it rose clear, it would portend good fortune. Coins retrieved from the island from the 3rd century BC feature dogs or stars with emanating rays, highlighting Sirius's importance; the Romans celebrated the heliacal setting of Sirius around April 25, sacrificing a dog, along with incense, a sheep, to the goddess Robigo so that the star's emanations would not cause wheat rust on wheat crops that year. Ptolemy of Alexandria mapped the stars in Books VII and VIII of his Almagest, in which he used Sirius as the location for the globe's central meridian, he depicted it as one of six red-coloured stars.
The other five are class M and K stars, such as Betelgeuse. Bright stars were important to the ancient Polynesians for navigation of the Pacific Ocean, they served as latitude markers. Sirius served as the body of a "Great Bird" constellation called Manu, with Canopus as the southern wingtip and Procyon the northern wingtip, which divided the Polynesian night sky into two hemispheres. Just as the appearance of Sirius in the morning sky marked summer in Greece, it marked the onset of winter for the Māori, whose name Takurua described both the star and the season, its culmination at the winter solstice was marked by celebration in Hawaii, where it was known as Ka'ulua, "Queen of Heaven". Many other Polynesian names have been recorded, including Tau-ua in the Marquesas Islands, Rehua in New Zealand, Ta'urua-fau-papa "Festivity of original high chiefs" and Ta'urua-e-hiti-i-te-tara-te-feiai "Festivity who rises with prayers and religious ceremonies" in Tahiti; the Hawaiian people had many names for Sirius, including Aa, Hoku-kauopae, Ka
Maurice Garland Fulton was an American historian and English professor. He was History at the New Mexico Military Institute for three decades, he was the author or editor of several books, "an authority on the Lincoln County War and Southwestern history." Maurice Garland Fulton was born on December 1877, in Lafayette County, Mississippi. His father, Robert Burwell Fulton, served as the seventh chancellor of the University of Mississippi in Oxford, Mississippi, his maternal grandfather, Landon Garland, was a slaveholder who served as the second president of Randolph-Macon College in Ashland, Virginia from 1836 to 1846, the third president of the University of Alabama in Tuscaloosa, Alabama from 1855 to 1865, the first chancellor of Vanderbilt University in Nashville, Tennessee from 1875 to 1893. Fulton had a sister. Fulton graduated from the University of Mississippi, where he earned a Ph. B. in English in 1898, followed by an A. M. in 1901. He attended graduate school at the University of Michigan, but came short of earning a PhD.
Fulton taught at his alma mater, the University of Mississippi, from 1900 to 1901, followed by the University of Michigan until 1903, the University of Illinois in 1904, back at the University of a year. He taught at Centre College from 1905 to 1909, followed by Davidson College until 1918, he took a hiatus to serve as a colonel in the United States Army during World War I in 1918, returned to academia, teaching at Indiana University from 1919 to 1922. He was a professor of English and History at New Mexico Military Institute in Roswell, New Mexico from 1922 to 1955. Fulton taught the courses about William Shakespeare and Charles Lamb as well as Mississippi poet Irwin Russell, he was the chair of the English department at NMMI. Fulton authored or edited several books, he became "an authority on the Lincoln County War and Southwestern history." He edited the writings of Theodore Roosevelt, who served as the 26th president of the United States from 1901 to 1909, Pat Garrett's biography of Billy the Kid.
He edited a history of New Mexico and two volumes of Josiah Gregg's diary and letters with Paul Horgan. He was active in the Chaves County Historical Society. Fulton married Vaye McPhearson Callahan, he died on February 12, 1955 in Roswell, New Mexico, at 77. He was buried in South Park Cemetery, Roswell, NM, his papers are at the University of Arizona. Fulton, Maurice G.. Expository Writing: Materials for a College Course in Exposition by Analysis and Imitation. New York: Macmillan. OCLC 367449881. Fulton, Maurice G. ed.. College Life, Its Conditions and Problems: A Selection of Essays for Use in College Writing Courses. New York: Macmillan. OCLC 561071500. Fulton, Maurice G.. Southern Life in Southern Literature. Boston: Ginn and Co. OCLC 320938032. Fulton, Maurice G.. National Problems. New York: Macmillan – via Internet Archive. Fulton, Maurice G. ed.. Roosevelt's Writings: Selections from the Writings of Theodore Roosevelt. New York: Macmillan. OCLC 17993757. Garrett, Pat. Fulton, Maurice G.. Authentic Life of Billy the Kid.
New York: Macmillan. OCLC 459886698. Fulton, Maurice G.. Charles Lamb in Essays and Letters. New York: Macmillan. OCLC 2093756. Fulton, Maurice G.. Writing Craftsmanship: Models and Readings. New York: Macmillan. OCLC 1060526160. Fulton, Maurice G.. New Mexico's Own Chronicle. Dallas, Texas: B. Upshaw and Co. OCLC 49597488. Fulton, Maurice G.. Diary and Letters of Josiah Gregg. Norman, Oklahoma: University of Oklahoma Press. OCLC 500377799. Fulton, Maurice G.. History of the Lincoln County War. Tucson, Arizona: University of Arizona Press. OCLC 166484144. Maurice Garland Fulton at Find a Grave Works written by or about Maurice Garland Fulton at Wikisource Worldcat Overview & works, Maurice G. Fulton
Shapeshifter is the debut album by American metalcore band The Dead Rabbitts. It was released on July 1, 2014; this album was released a year. Before the announcement, the band toured with Metalcore band Eyes Set to Kill in the Arizona, US. In November 2013, the band signed with Tragic Hero Records and announced that they will be releasing an album sometime in 2014. and In December 2013. They began recording songs with Andrew Wade; the album was announced by the band a month prior to its release on May 16 and stated that the album would be released on July 1, 2014 through Tragic Hero Records. "My Only Regret" was released as the debut single off the album on May 16, 2014, along with its lyric video. The second single "Shapeshifter" was released on June 3, 2014; the third single "Bats In the Belfry" was released on June 21, 2014. and the band premiered a music video for "Deer In the Headlights" on November 7, 2014. In support of the album, The band embarked on ShapeshifTour, which took place from June 20 to July 26, 2014.
Support for the tour included The Relapse Symphony, Myka Relocate, Nightmares. for the 28-date summer trek. Shapeshifter was met with positive reception by critics. In a four-star review for Revolver, David McKenna averring, "Fans of post-hardcore will want to check this album out." All tracks are written by The Dead Rabbitts. Shapeshifter" album personnel as listed on Allmusic | 0.83402 | 3.942282 |
A stellar heart that defies predictions: this is what reveals the first mapping of the interior of a white dwarf star by an international team led by Noemi Giammichele, a young researcher from the Institut de Recherche en Astrophysique et Planétologie. This breakthrough will allow to better understand the physical mechanisms involved in the evolution of stars and of our Sun. This result is published in the journal Nature on January 8,2018.
Using data from NASA’s Kepler satellite on the pulsations of the star KIC 08626021, an international team of astrophysicists, led by Noemi Giammichele, a young researcher from the Institut de Recherche en Astrophysique et Planétologie (IRAP) in Toulouse, mapped the internal composition of a white dwarf, a distant successor of a star similar to our Sun. The luminosity oscillations observed on the surface of this star could be deciphered using “asterismological” techniques, similar to the methods used by geophysicists to study the inner structure of our planet through the seismic waves caused by earthquakes.
White dwarf stars are the relics of the hearts of nearly 97% of the stars filling the Universe. These true stellar fossils carefully retain the imprint of past physical processes, such as nuclear burning and convective mixing episodes, which are still very uncertain in the current models of stellar evolutionary theories. Obtaining a clear view of the composition of these stars will therefore allow to better decipher the phenomena at stake during the earlier phases of their evolution.
During the white dwarf slow agony, during which they cool down inexorably, these stars pass through phases of instability or start to vibrate. These deep vibrations – or star shakes – are the keys leading to lift the veil on the very interior of these stellar residues. The internal chemical stratification of the white dwarf generates a unique signature on the luminous modulations emerging from the star which, once deciphered, allows the structure to be mapped.
And what is revealed from the deepest of these stars? Not only that the heart is significantly larger and richer in oxygen than predicted, but also the distribution profile of the main chemical elements present. This discovery thus provides a highly accurate test bed for finely calibrating the physical processes of nuclear burning and convective mixing at work within most stars, particularly during the phases of white pre-dwarf stellar evolution. Precise knowledge of the internal chemical composition of white dwarfs is also invaluable to use them as “cosmic chronometers” for dating the stellar populations filling our Galaxy.
- Nature Publication :« Large oxygen-dominated core from the seismic cartography of a pulsating white dwarf » N. Giammichele, S. Charpinet, G. Fontaine, P. Brassard, E.M. Green, V. Van Grootel, P. Bergeron, W. Zong,& M.-A. Dupret
- CNRS-INSU Press Release : Voyage au centre d’une étoile naine blanche
- Noemi Giammichele – [email protected]
- Stéphane Charpinet– [email protected] | 0.811369 | 4.041829 |
Shortly after NASA's OSIRIS-REx spacecraft flew past Earth at a distance of about 11,000 miles on Sept. 22, an ASU-built spectrometer onboard looked at Earth and detected methane, ozone, carbon dioxide and water vapor. Taken together these gases in our atmosphere set Earth apart from other planets.
While hardly a discovery, the findings helped scientists calibrate the ASU-built instrument and show that it is working perfectly after a year in space.
The OSIRIS-REx spacecraft was launched Sept. 8, 2016, from the Kennedy Space Center in Florida. It is now about halfway on the journey to its target, a primitive carbonaceous asteroid named Bennu. The gravity assist the spacecraft received in the Earth flyby changed its trajectory so that it is now on track to arrive at Bennu in August 2018.
OSIRIS-REx stands for Origins, Spectral Interpretation, Resource Identification, Security – Regolith Explorer. The mission's goals are to return a sample of surface rocks, soil and dust from Bennu, map the asteroid's global properties, document the surface at the sample site down to centimeter scales, characterize its type of asteroid for comparison with meteorites, and measure a subtle effect of sunlight that can alter an asteroid's orbit.
The latter two goals are the main scientific tasks for the ASU-built OSIRIS-REX Thermal Emission Spectrometer, or OTES for short. Philip Christensen, Regents’ Professor of geological sciences in Arizona State University’s School of Earth and Space Exploration, designed the instrument, which was constructed on ASU's Tempe campus.
"OTES is the first complex space instrument to be designed and built entirely at ASU," Christensen said. "We're very proud that this instrument is on its way and operating as designed."
With an orbit that comes inside Earth's orbit, Bennu is the most accessible asteroid rich in organic materials from the early solar system. It reflects only 3 percent of the sunlight falling on it, making it about as dark as charcoal.
When OSIRIS-REx arrives at Bennu, OTES will make a global mineral map of the asteroid, which is roughly spherical and about 1,600 feet (500 meters) across. The map will help mission scientists decide the best place to collect surface samples for eventual return to Earth.
Given its Earth-crossing orbit, Bennu is also a space rock scientists want to keep an eye on. They estimate that it has a 1-in-2,700 chance of hitting Earth in the year 2170.
Which directly leads to OTES' other major task: measuring the temperature and heat emission over Bennu's surface as it spins through its 4.3-hour-long day. This is to help scientists gauge the strength of the Yarkovsky effect on Bennu.
The Yarkovsky effect is a weak but steady thrust produced by sunlight as it falls on a spinning object. The effect comes from the fact that sunlit ground is warmer in the afternoon than the same ground is in the morning, because sunlight has had longer to heat it.
This means that the afternoon side of a rotating object radiates more heat than the morning side, thus producing an extremely small thrust. The effect is negligible for massive objects like planets, but for small bodies like Bennu the effect could shift its orbit.
Using OTES data, OSIRIS-REx will help scientists assess how fast Bennu's orbit is changing and gather information useful for future generations, which may have to take action to deflect the asteroid.
OSIRIS-REx will remain at Bennu until 2021. Then with the sample of rocks and dust safely packed into a sealed re-entry capsule, the spacecraft will fire its engine and go into an orbit to meet with Earth in 2023.
After releasing the sample return capsule, OSIRIS-REx will fly past Earth and continue in its solar orbit. The capsule with the samples will enter the atmosphere behind a heat shield and land under a parachute in Utah.
Christensen said, "This Earth flyby gave us our first real data. Up to now we have just looked at an onboard test target. It's exciting to collect spectral data on a real solar-system body. OTES has performed exactly as we hoped."
The spectrometer works by examining infrared (heat) wavelengths.
"The infrared is great for identifying minerals," Christensen explained. "Rocks and minerals may look similar to the eye, but they show unique spectra when studied in the infrared, where their 'colors' stand out differently."
As it happened, the flyby trajectory gave OTES a view of Earth dominated by the Pacific Ocean. Almost no land areas came within the instrument's field of view, which saw clouds and seawater.
Even so, the instrument worked as designed. In addition to identifying minerals, the infrared also excels at detecting gases such as methane, ozone, carbon dioxide and water vapor, which are common in our atmosphere.
"We measured them with OTES and got good 'ground truth' results," Christensen explained.
"Earth isn't our prime target, however," Christensen said. "That will come about a year from now. But the Earth flyby was a great test for OTES and the other instruments on the spacecraft.
NASA’s Goddard Space Flight Center provides overall mission management, systems engineering, and the safety and mission assurance for OSIRIS-REx. Dante Lauretta of the University of Arizona, Tucson, is the principal investigator, and the University of Arizona also leads the science team and the mission’s science observation planning and data processing. Lockheed Martin Space Systems in Denver built the spacecraft and is providing flight operations. Goddard and KinetX Aerospace are responsible for navigating the OSIRIS-REx spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers Program. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the agency’s New Frontiers Program for its Science Mission Directorate in Washington. | 0.847373 | 3.825886 |
IF EXTRATERRESTRIAL life were to exist, it would need a planet on which to evolve. All but one of 200-or-so planets outside the solar system that have so far been discovered by astronomers would be quite unsuitable. That is because they are composed of gas. Yet the one whose discovery was announced this week is different. Astronomers think it is rocky, like the Earth, and that it may harbour liquid water. This makes it the best candidate yet for supporting life.
The new planet orbits a star, called Gliese 581, that lies a mere 20 light years away in the constellation Libra. The temperature of the sun is such that it supports a nuclear-fusion reaction that generates bright sunlight. By contrast, Gliese 581 is a red dwarf, so-called because the star is small and the fusion reaction proceeds slowly, creating a dim glow. Nevertheless, because the new planet is much closer to its star than the Earth is to the sun, it lies in what astronomers call the “habitable zone”—the space surrounding a star where water would be in its liquid form.
Seeing remote planets is difficult. Astronomers used to detect them indirectly, by spotting a small wobble in the position of the star, which indicated that it was being pulled very slightly to and fro by an orbiting planet. New telescopes and techniques have found other planets outside the solar system—so-called “exoplanets”—directly, from the slight dip in the luminosity of the star as the planet crosses its face. But these techniques work only with giant planets and, in general, giant planets are gaseous.
Looking for planets orbiting red dwarfs is easier because the stars are less massive. This not only means that any planets are likely to circle it more closely (to remain in orbit) but also that the wobbles are more readily seen. The researchers—led by Stéphane Udry of the University of Geneva—used an indirect method called the “radial velocity” technique. This exploits the Doppler effect—familiar when a siren changes pitch as a fire engine passes you—to reveal changes in the velocity of the star as it wobbles. This is sensitive because it is easier to measure small changes in the wavelength of light than luminosity.
The new planet, dubbed Gliese 581c, is more than three times the size of the Earth. It has five times the mass of this planet and orbits its star every 13 days. The astronomers who discovered it had earlier found another planet, a gaseous giant similar to Neptune, orbiting the same star every 5.4 days. They say they have strong evidence for a third planet in the same system that has about eight times the mass of the Earth and orbits every 84 days. The evidence is reported in a paper submitted to Astronomy and Astrophysics.
According to theory, a planet the size and mass of Gliese 581c should be rocky, like the Earth. It could be covered in oceans, perhaps completely. The mean temperature on the surface of the planet is thought to be between 0°C and 40°C, making it far more hospitable than either Venus or Mars, Earth's nearest neighbours.
The race is now on to detect whether the planet has an atmosphere and whether it contains water. Just a fortnight ago, astronomers using the Hubble space telescope identified for the first time water vapour in the atmosphere of an exoplanet, albeit a gaseous one some 150 light years away. The planet, called HD209458b, shows its face to Earth every three-and-a-half days, giving plenty of chances to take measurements. If water exists on Gliese 581c, detecting it there will be far harder.
Even if Gliese 581c is not yet inhabited by little green men, there is plenty of time for that to change. The Earth gets its warmth from a sun that is thought to be about 5 billion years old and halfway through its lifetime as a “main sequence” star. After that it is expected to become a red giant, at which time the Earth's atmosphere and water will be boiled away, leaving it uninhabitable.
Red dwarfs, by contrast, burn for hundreds of billions of years. This not only gives plenty of time for life to evolve on the recently discovered planet. It may make Gliese 518c a useful bolthole in some 5 billion years' time.
This article appeared in the Science & technology section of the print edition under the headline "Sister Earth" | 0.916234 | 3.986644 |
On February 5, 1974, space probe Mariner 10 passed by at planet Venus shooting 4,165 high resolution pictures and continued its journey to Mercury, using the slingshot maneuver.
The Mariner Program
Mariner 10 was the last of NASA‘s Mariner program and executed to measure the environment of Mercury as well as its surface and its atmosphere. The spacecraft was the second of all time to perform the gravitational slingshot maneuver, using Venus to bend its flight path and adapt it to Mercury‘s. The maneuver was developed by Guiseppe Colombo, an Italian scientists, mathematician, and engineer, whose calculations took a major influence in the success of the mission. Colombo was able to send the spacecraft into an orbit repeatedly bringing it back to Mercury. The spacecraft was also the first to use active solar pressure control and took over 7000 pictures of Mercury during its flybys.
The Mariner 10 Mission
The mission’s first goal was to explore the north polar region of the Moon and take images so cartographers were able to update their lunar maps. After a correction maneuver and an ultraviolet observation of the long-period Comet Kohoutek, named after the Czech astronomer Luboš Kohoutek, the spacecraft cruised its way to Venus, arriving on February 4, 1974. Through Mariner’s ultraviolet camera filters, the planet’s chevron clouds were explored in detail before heading to Mercury, passing its shadow side at first. Mercury was then to complete two full orbits before ‘meeting’ again with Mariner 10, which looped around the Sun while Mercury’s orbits. The second approach to Mercury was completed on September 21, 1974 below its southern hemisphere and the third focused on its north pole.
Orbiting the Sun
Until March 24, 1975, several tests continued while Mariner 10 began its orbit around the Sun. Then its transmitter was turned off and up to this day, the spacecraft is orbiting the Sun according to Dave Williams of NASA’s National Space Science Data Center:
“Mariner 10 has not been tracked or spotted from Earth since it stopped transmitting. We can only assume it’s still orbiting [the Sun], but the only way it would not be orbiting would be if it had been hit by an asteroid or gravitationally perturbed by a close encounter with a large body. The odds of that happening are extremely small, so it is assumed to still be in orbit.“
However, its electronics have probably been damaged by the Sun’s radiation. Mariner 10 has not been spotted or tracked from Earth since it stopped transmitting. During its three approaches to Mercury, the spacecraft was able to map about 45% of the planet’s surface, revealing a surface very much alike the one’s of the Moon. Through the mission, scientists discovered, that the planet’s atmosphere consists of helium, a magnetic field and an iron-rich core.
Planning for MESSENGER, a spacecraft that surveyed Mercury until 2015, relied extensively on data and information collected by Mariner 10.
At yovisto academic video search, you may enjoy a video on the planets Mercury, Venus and Mars by Professor Robert Nemiroff.
References and Further Reading:
- Mariner 10 Mission at NASA
- The Voyage of Mariner 10: Mission to Venus and Mercury (NASA SP-424) 1978 [PDF]
- Apollo 17 – The Last Men on the Moon (so far) , SciHi Blog, December 11, 2018
- The Arecibo Radio Telescope – Looking for Extraterrestrial Signals , SciHi Blog, November 1, 2018
- Eris – The Planet of Discord , SciHi Blog, October 21, 2018
- The Sputnik Shock and the Start of the Space Race , SciHi Blog, October 4, 2018
- A4 – The First Human Vessel To Touch Outer Space, SciHi Blog, October 3, 2018
- The First Image from Abroad – Earth Rising and Lunar Orbiter 1 , SciHi Blog, August 23, 2018
- Mariner 10 at Wikidata
- Venus Images at Wikidata | 0.869791 | 3.532682 |
Current images of the second interstellar comet It is known that visited the s olar sy tribe, which seems to reveal a fragment or fragments that fall away from its core.
Comet 2I / Borisov came last summer with a lot of fanfare when scientists realized that it was a hyperbolic orbit – which means that it was a visitor from outside the solar system. But unlike the first known visitor Borsiov allowed a closer look when he orbited the sun. Recent observations have shown that it loses matter .
"We have been looking at this thing with space telescopes for months since its discovery," UCLA astronomer David Jewitt told Gizmodo. "We noticed this change in appearance – that it split in two – this week."
A picture taken by Jewitt yesterday with the Hubble space telescope shows the comet as one piece already on March 23 but seems to be divided into two parts by March 28 .
But the comet probably didn't break it in half, said Jewitt . Other comets have changed the appearance like this before; Borisov has probably just lost a fragment that is less than 1 percent of its mass. However, this small fragment is extremely bright, which, according to astronomers is due to the fact that it was a piece of ice that had not been exposed before, which has now become extremely active due to the energy of the sun is. 19659007] Jewitt is not the only team to observe comet fragmentation. Another astronomer telegram post yesterday also reported references to a small fragment that separates from the rock. One ll follows two comet outbreaks reported on March 12 by a team of astronomers in Poland .
amateur a stronomer Gennady Borisov who was first discovered this interstellar visitor on August 30 last year and scientist soon confirmed as the second interstellar object (the first was 2017 & # 39; Oumuamua ). But in contrast to the rocky Oumuamua, the comet Borisov looked surprisingly familiar – this is like an icy comet of the solar system with a cloud called coma and a tail that happened to have arrived from outside the solar system.
Scientists have been tracking the object with space-based telescopes since it came closest to the sun in December. You have already learned more about it, said Jewitt. Initial estimates indicated that Borisov was large (maybe 8 kilometers wide), but later observations instead set his radius to a few hundred meters. It has a composition similar to that of comets in the solar system, with water ice quickly turning into gas. But, Jewitt said, it appears to have larger dust particles and more carbon monoxide than comets in the solar system. Carbon monoxide is a volatile element that would otherwise m from the surface of the sun separate from solar energy but not in the case of Borisov. "This thing was in a cold place for a long time," said Jewitt.
Does that mean Borisov split up? Its not clear yet. Jewitt hopes that this is the case – for one thing it would be a cool show, but it would also provide knowledge about the composition of its core and other physical properties.
Scientists continue to monitor comet Borisov. We hope that it will crumble to pieces. | 0.886112 | 3.617411 |
Remember when you were a kid and blowing bubbles was such great fun? Well, stars kind of do that too. The “bubbles” are partial or complete rings of dust and gas that occur around young stars in active star-forming regions, known as stellar nurseries. So far, over 5,000 bubbles have been found, but there are many more out there awaiting discovery. Now there is a project that you can take part in yourself, to help find more of these intriguing objects.
The Milky Way Project, part of Zooniverse, has been cataloguing these cosmic bubbles thanks to assistance from the public, or “citizen scientists” – anyone can help by examining images from the Spitzer Space Telescope, specifically the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) and the Multiband Imaging Photometer for Spitzer Galactic Plane Survey (MIPSGAL).
They have been seen before, but now the task is to find as many as possible in the newer, high-resolution images from Spitzer. A previous catalogue of star bubbles in 2007 listed 269 of them. Four other researchers had found about 600 of them in 2006. Now they are being found by the thousands. As of now, the new catalogue lists 5,106 bubbles, after looking at almost half a million images so far. As it turns out, humans are more skilled at identifying them in the images than a computer algorithm would be. People are better at pattern recognition and then making a judgment based on the data as to what actually is a bubble and what isn’t.
The bubbles form around hot, young massive stars where it is thought that the intense light being emitted causes a shock wave, blowing out a space, or bubble, in the surrounding gas and dust.
Eli Bressert, of the European Southern Observatory and Milky Way Project team member, stated that our galaxy “is basically like champagne, there are so many bubbles.” He adds, “We thought we were going to be able to answer a lot of questions, but it’s going to be bringing us way more questions than answers right now. This is really starting something new in astronomy that we haven’t been able to do.”
There are currently about 35,000 volunteers in the project; if you would like to take part, you can go to The Milky Way Project for more information. | 0.905339 | 3.403985 |
Jupiter’s moon Europa has been the subject of intense research and speculation ever since it was determined that this celestial body more than likely has a liquid ocean beneath its icy crust. NASA is in the process of planning a flyby mission to Europa, but now the agency is actively looking into adding a lander to the payload. Our first close encounter with Europa might be even closer than expected.
This news comes by way of Robert Pappalardo, a project scientist on NASA’s Europa project at the Jet Propulsion Laboratory. He says NASA is actively pursuing the possibility of a lander on the upcoming Europa mission, which could laun in the early 2020s. This aspect of the mission is still in the early phases. NASA is looking into the cost and feasibility of getting a payload to the surface of Europa, which could answer a lot of questions you just can’t adequately investigate from a flyby.
Europa is often cited as a possible home for alien life in our own solar system. Its surface is very smooth compared to other moons that lack an atmosphere. This indicates there is some sort of constant remodeling of the crust, which is believed to be about 50 miles thick. What makes this happen is still up in the air. Some scientists favor a model of Europa with a layer of warm convecting ice that slowly rises to the surface. However, most think there’s a liquid ocean under the surface that escapes through cracks in the ice sheet, and could harbor life. In either case, the heat to melt the ice comes from tidal stresses on Europa as it orbits Jupiter.
The draft Europa mission currently in the planning phase calls for a probe that would enter orbit of Jupiter, then make 45 flybys of Europa over the course of about 2.5 years. Some of these passes would be low enough that the probe could pass through a plume of water erupting from the moon, which is often observed when it is at its furthest point from Jupiter.
NASA scientists have previously expressed skepticism about including a lander on the flyby mission. We don’t know enough about the surface to design something that can survive long term (the eel-rover will have to wait). However, that doesn’t make much difference if all you need to do is reach the surface with a stationary instrument package. You could also simply run into the surface at high speed. NASA previously talked to the European Space Agency about the possibility of building an ice-impacting probe for the mission. This could help scientists characterize the surface of Europa without a traditional lander.
If NASA does end up adding a lander to the mission, it will be a low-cost addition rather than a main focus. There are still too many unknowns when it comes to Europa’s surface to put all our eggs in that basket. The data gathered from this mission could, however, give us what we need to make a true Europa lander mission possible in the future. | 0.860139 | 3.226246 |
The Most Distant Object Ever Confirmed
This week, an international team of astronomers have confirmed the sighting of the most distant object ever seen. Ben Valsler spoke to Bristol University's Professor Malcolm Bremer to find out more.
Malcolm - We were trying to identify extremely distant galaxies - in this case, a single galaxy - so that we can understand the very early stages of galaxy evolution. We're seeing this galaxy very early on in the history of the universe. We think therefore that it will tell us a lot about the early stages of how galaxies form and then evolve from the very small building blocks, such as this galaxy, into the larger galaxies like the Milky Way that we see today. And also, we are seeing this object at a particular time in the universe where there is a transition in the state of the gas that fills the universe, and we hope to be able to use this galaxy as a probe of that.
Ben - So if we come back to using the light from this galaxy as a probe to measure cosmology a bit later on, first of all, tell me a bit more about this galaxy. It's at what we think of as a very large red shift. Now what does that actually mean?
Malcolm - The red shift is a measure of how much the universe has expanded between the time that the photons were emitted by the galaxy, the radiation was emitted by the galaxy, and by the time we receive it. So a red shift of about an 8 ½ actually relates to the universe stretching by about 9 ½ times in linear dimension.
Ben - And what does that mean about how old the light actually is that's getting to us?
Malcolm - That actually means that the light was emitted about 600 million years after the Big Bang, and we are receiving it now, 13.1 billion years later. As well as the time it takes for the light to reach us, also, the light that we're interested in, which is originally emitted in the ultraviolet, we receive in the infrared because the expansion of the universe stretches all of the wavelengths of radiation coming from the galaxy by that much, by the time we actually receive the radiation.
Ben - So, this new galaxy, is there anything particularly special about it that enables us to be able to see it, even though it's that far away?
Malcolm - Well we hope not because what we're trying to characterise is the typical galaxy at these distances. The area of sky that was searched in order to find this object was searched using the Hubble Space telescope with a brand new infrared camera by other astronomers and they came up with a catalogue of objects that they believe to be at these great distances. Any one of them could be at the distance of this object or even slightly larger. So what we're actually hoping for is, this is a typical, very, very distant object. It just happens to be, because it takes an awful lot of effort, that this is the first one that we've confirmed to be this far away.
Ben - So you mentioned earlier that we can use it to probe cosmology really. As this light was emitted when the universe was very young, what can we determine about the state of the universe, just from this light?
Malcolm - Well, we expect that this object is observed as the hydrogen that fills the universe changed in state. Previous to this time, the hydrogen was cool, neutral material like the gas within the atmosphere of Earth. But then, at some point, something ionised that gas, and the effect of that is that the neutral hydrogen is opaque to much of the radiation that's emitted by these galaxies. But then as it gets ionised, charged effectively, and heated, it becomes transparent, and you can see the light escaping from these galaxies. It's an important step in the evolution of the universe. Knowing when it started, when this process ended, and what was causing the heating, the ionisation of the gas, is actually an important set of questions for astronomers. If we understand that, we understand an awful lot more about the early universe than we currently do.
Ben - So looking at the spectrum of light from this enormously distant galaxy - not only can we tell how far away it is, how much space is expanded, but by looking at the bits where this gas has absorbed some of that light in order to become ionised, we can also start to get an idea of the conditions that were around this galaxy.
Malcolm - That's right and one thing that's peculiar about this galaxy is, although we've detected it and we've detected a signature of hydrogen within it, it doesn't seem to be luminous enough for itself to have converted the hydrogen that's around it on the larger scale, by itself, from neutral to ionised gas. We suspect therefore that what we're seeing is the signature of other galaxies that were either very bright before the time that we're actually seeing this galaxy, or just lots of smaller galaxies which are too faint to detect, which have actually done the excavation of the neutral hydrogen for that object. It on itself, I don't think would be able to actually carry out that process.
Ben - So that's evidence of other galaxies that are still too faint for us to see with current technology, but evidence that they must have been around in order to have that effect. What's the next step for us? How do we start to try and look for these galaxies?
Malcolm - These observations clearly push right at the limit of what we're able to do with current technology with both space based and ground based telescopes, but there will be technological improvements that will happen quite soon within astronomy. For example, we will get new instruments on the ground based telescopes that we're using at the moment. But also, over the next few years, there will be the successor to the Hubble Space telescope - this is the James Webb Space telescope. And then on the longer term, we hope to build extremely large telescopes in the ground with mirrors of size 30-40 metres, whereas the current typical size of a large telescope is an 8 metre mirror. That will be much, much more sensitive to these kinds of objects and hopefully we will not just be able to do the detection of these objects, but we will get much better spectra of them, and therefore be able to tell you much more about their physical state. | 0.82836 | 3.662565 |
Captions provided by CCTubes – Captioning the Internet! Blue supergiant stars some of the hottest, biggest young stars in the universe, and their molten cores can reveal more about the formation of everything.
How Scientists Found the Universe’s First Type of Molecule – https://youtu.be/lxepnATltvU
Blue supergiant stars open doors to concert in space
“Stars come in different shapes, sizes and colours. Some stars are similar to our Sun and live calmly for billions of years. More massive stars, those born with ten times or more the mass of the Sun, live significantly shorter and active lives before they explode and expel their material into space in what is called a supernova. Blue supergiants belong to this group. Before they explode, they are the metal factories of the universe, as these stars produce most chemical elements beyond helium in the Periodic Table of Mendeleev.”
Low-frequency gravity waves in blue supergiants revealed by high-precision space photometry
“The discovery of pulsation modes or an entire spectrum of low-frequency gravity waves in these stars allow us to map the evolution of hot massive stars towards the ends of their lives. Future asteroseismic modelling will provide constraints on ages, core masses, interior mixing, rotation and angular momentum transport. The discovery of variability in blue supergiants is a step towards a data-driven empirical calibration of theoretical evolution models for the most massive stars in the Universe.”
Though gravitational waves were predicted to exist in 1916, definitive proof of their existence wouldn’t exist until 1974, 20 years after Einstein’s death. In that year, two astronomers using the Arecibo Radio Observatory in Puerto Rico discovered a binary pulsar. This was exactly the type of system that, according to general relativity, should radiate gravitational waves. Knowing that this discovery could be used to test Einstein’s audacious prediction, astronomers began measuring how the stars’ orbit changed over time.
Elements is more than just a science show. It’s your science-loving best friend, tasked with keeping you updated and interested on all the compelling, innovative and groundbreaking science happening all around us. Join our passionate hosts as they help break down and present fascinating science, from quarks to quantum theory and beyond.
Seeker explains every aspect of our world through a lens of science, inspiring a new generation of curious minds who want to know how today’s discoveries in science, math, engineering and technology are impacting our lives, and shaping our future. Our stories parse meaning from the noise in a world of rapidly changing information.
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Image: Rosetta's comet
(Phys.org) —ESA's Rosetta spacecraft woke up 20 January, after 31 months in deep space hibernation, to catch up with comet 67P/Churyumov–Gerasimenko.
This image shows the most recent observations of the 4 km-wide comet, taken on 5 October 2013 by the Very Large Telescope of the European Southern Observatory (ESO) in Chile. The comet was around 500 million kilometres from Earth, before it passed behind the Sun and out of view from Earth's perspective.
For this image, a long series of observations was processed to reveal both the comet without the background stars (on the left panel), and the star field with the track of the comet marked (on the right). Viewed against a crowded star field in a direction towards the centre of the Milky Way, the comet appears as a simple spot.
The observation marks the start of a close collaboration between ESA and ESO to monitor the comet from the ground during Rosetta's encounter later this year.
Rosetta was launched in 2004 and will become the first space mission to rendezvous with a comet, the first to attempt a landing on a comet and the first to follow a comet as it swings around the Sun.
The comet is on a 6.5-year orbit around the Sun and is currently moving towards the inner Solar System, inside the orbit of Jupiter. It will be closest to the Sun – roughly between the orbits of Earth and Mars – in August 2015. During this approach, the surface will warm up and its ices will sublimate, dragging out dust into a tail and likely causing jets from the surface.
Although there is no evidence in this image to suggest that the comet is already active, scientists will be keen to check in on the comet again in February, when it is next observable by the Very Large Telescope.
In the meantime, the observations carried out late last year have been used to confirm the comet's orbit ahead of a major manoeuvre planned for Rosetta in May, to line it up for its rendezvous in August. Further calculations will be made once Rosetta sights the comet in its own imaging system. | 0.836734 | 3.519194 |
While CERN's vast Large Hadron Collider accelerator gathers all the headlines - allowing humble hacks to become Hollywood blockbuster scriptwriters - an ancient piece of atom hardware is beginning experiments that may prove to be of significance.
CERN's much-anticipated CLOUD experiment has begun, the atom lab says. Using the 50-year-old Proton Synchrotron, the experiment simulates cosmic rays passing through the earth's atmosphere, and hopes to reveal the extent to which the constant background drizzle of charged particles plays a role in cloud formation. Earlier experiments have suggested that ionisation causes clouds to "seed" - and that ionisation is influenced by the type and quantity of cosmic rays that reach the earth.
Both the sun and the earth's magnetic fields act as umbrellas, protecting the surface from the high energy particles, although two particles still reach the surface per second. But small changes in the cosmic ray flux produce significant changes in cloud cover. When fewer cosmic rays reach earth, the planet's climate is warmer, when more reach earth, the climate cools.
"So marked is the response to relatively small variations in the total ionization, we suspect that a large fraction of Earth's clouds could be controlled by ionisation," noted Danish scientist Henrik Svesmark this summer. Svensmark has pioneered the research using smaller experiments, but has waited over a decade to see it tested on such a scale.
Much of the recent interest comes from climate watchers. Clouds are one of the biggest factors in determining global surface temperature, but the UN's IPCC admits the level of scientific understanding of them is poor.
The cosmic ray effect - a factor of the background CBR bombardment itself, and the relative strength of the earth and the Sun's magnetic shields - shows a strong correlation between temperature, CBR and is extraordinary. Here's the relationship over the short term - around 2,000 years.
And here's the correlation into deep time, with CO2 as a comparison.
In addition, "deep freezes" in the Earth's temperatures have coincided with short-lived but intense bursts of cosmic ray activity. Modulation is thought to reflect the Sun's passage through spiral arms of the Milky Way, and also the Sun's oscillation in relation to the plane of the galaxy. The Sun bobs up and down 2.7 times per orbit.
CERN became involved when a visiting lecture by former New Scientist editor Nigel Calder was attended by Jasper Kirkby - CLOUD's project leader. It's taken 12 years to fire up the particles for this major test. CERN has an interview with Kirkby here. ® | 0.836094 | 3.840817 |
Search Results for who first
Galaxy clusters of interest in April’s southern evening sky
Orion stands in the south-west at nightfall as the sparkling skies of winter give way to the less flamboyant constellations of spring, led by Leo and Virgo. By our map times, Orion has mostly set the west and the Milky Way arcs only some 30° above Edinburgh’s north-western horizon as it flows between Auriga and the “W” formation of Cassiopeia.
The Milky Way, of course, marks the plane of our disk-shaped galaxy, itself dubbed the Milky Way, around which our Sun orbits every 240 million years. If we look along it, we encounter numerous distant stars but countless more are forever hidden from sight behind intervening clouds of gas and dust – the raw material from which new stars and planets may eventually coalesce. If we gaze in directions away from the plane of the Milky Way, though, the star numbers fall away and there is negligible gas and dust to hide our view of galaxies far beyond our own.
It follows that we might expect our best view of the distant universe to be in directions at right angles to the plane, towards the galactic poles. Regions around the North Galactic Pole are ideally placed in our April evening sky and host some of the most interesting clusters of galaxies in the entire sky.
The pole itself lies in the less-than-startling Coma Berenices which is approaching the high meridian at our map times. As the only modern constellation named for a historic person, this celebrates Queen Berenice II of Egypt who is said to have sacrificed her long hair as an offering to Aphrodite. Her tresses are represented by a cascade of stars that spill southwards through the “M” of “COMA” on the chart. These make up a dispersed but nearby star cluster at a distance of about 280 light years – the second closest star cluster after the Hyades in Taurus.
Roughly coincident with the “C” of “COMA” is another cluster, but this one of more than 1,000 galaxies at a distance of some 320 million light years. The Coma Cluster’s brightest galaxies are only around the twelfth magnitude and, as such, a challenge for many amateur telescopes. It was by studying this cluster that the Swiss astronomer Fritz Zwicky uncovered evidence as long ago as 1933 for the existence of what we now call dark matter. He found its galaxies were simply moving too fast to be held together unless addition material was present to supply an extra gravitational pull. Now we suspect that up to 90% of the Coma Cluster consists of this still-mysterious dark matter.
Lying south of Coma Berenices, and about 9° to the east (left) of Leo’s star Denebola, is the closer Virgo Cluster of galaxies. This sprawls across 8° of sky and holds about 1,500 galaxies at a distance of 54 million light years or so. Small telescopes show several, though we’d struggle to locate them without a better chart than I can supply here. In fact, The Virgo Cluster lies at the heart of a much larger family of galaxies and galaxy clusters dubbed the Virgo Supercluster which includes the so-called Local Group of galaxies in which the Milky Way is a major player. The Coma Cluster rules another supercluster.
Edinburgh’s sunrise/sunset times change from 06:44/19:50 BST on the 1st to 05:32/20:49 on the 30th as the Moon stands at new on the 5th, first quarter on the 12th, full on the 19th and last quarter on the 26th. As I mentioned last time, satellites may now be spotted at any time of night though the current spell of evening passes by the International Space Station ends on or about the 5th.
Mars stands some 30° high and alongside the Pleiades in our western sky as our nights begin at present. The planet, though, is tracking east-north-eastwards against the stars and passes north of Taurus’ main star, Aldebaran, to lie between the Bull’s horns later in the month. The young earthlit Moon is an impressive sight 9° below Mars on the 8th and stands above Aldebaran and to the left of Mars on the 9th.
Mars no longer glares like an orange beacon in our sky and is now only half as bright as Aldebaran. As its distance grows from 302 million to 335 million km in April, it dims a little more from magnitude 1.5 to 1.6. Even large telescopes reveal little detail on its small ochre disk, less than 5 arcseconds in diameter, and viewing conditions can only deteriorate as it sinks towards the north-western horizon where it sets in the middle of the night.
There are two brighter planets in our predawn sky, both of them low in the south to south-east as the Summer Triangle formed by Vega, Deneb and Altair climbs through the east.
Jupiter, conspicuous at magnitude -2.2 to -2.5, rises in the south-east less than three hours after our map times and stands 11° above Edinburgh’s southern horizon before dawn. Slow-moving in southern Ophiuchus, it reaches a stationary point on the 10th when its motion appears to reverse from easterly to westerly as it begins to be overtaken by the Earth. Saturn, rather fainter at magnitude 0.6 to 0.5 and at its own stationary point on the 30th, lies in Sagittarius some 25° to Jupiter’s left. Catch the Moon near Jupiter on the 23rd and Saturn on the 25th.
Although Venus is brilliant at magnitude -4.0, it rises in the east less than 38 minutes before sunrise and is unlikely to be noticed. Mercury is furthest west of the Sun (28°) on the 11th but is much fainter and lower still in the morning twilight.
Diary for 2019 April
Times are BST
2nd 05h Moon 2.7° S of Venus
3rd 00h Moon 4° S of Mercury
5th 10h New moon
9th 08h Moon 5° S of Mars
9th 17h Moon 2.1° N of Aldebaran
10th 18h Jupiter stationary (motion reverses from E to W)
11th 21h Mercury furthest W of Sun (28°)
12th 20h First quarter
13th 22h Moon 0.1° N of Praesepe
15th 10h Moon 2.8° N of Regulus
16th 23h Mars 7° N of Aldebaran
19th 12h Full moon
23rd 00h Uranus in conjunction with Sun
23rd 13h Moon 1.6° N of Jupiter
25th 15h Moon 0.4° S of Saturn
26th 23h Last quarter
30th 03h Saturn stationary (motion reverses from E to W)
This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on March 30th 2019, with thanks to the newspaper for permission to republish here.
Watch earth satellites transit our vernal equinox sky
The Sun climbs northwards at its fastest for the year in March and crosses the sky’s equator at 21:58 on the 20th, the time of our vernal or spring equinox. As the days lengthen rapidly, the stars in the evening sky appear to drift sharply westwards so that Orion, which is astride the meridian as the night begins on the 1st, stands 45° over in the south-west by nightfall on the 31st.
Another consequence of the Sun’s motion is that the Earth’s shadow, on the night side of the planet, is tilting increasingly southwards so that it no longer reaches so far above Scotland at midnight. Indeed, by the end of March the shadow is shallow enough that satellites passing a few hundred kilometres above our heads may be illuminated by the Sun at any time of night. This allows them to appear as moving points of light against the stars as they take a few minutes to cross the sky. Some are steady in brightness while others pulsate or flash as they tumble or spin in orbit.
Dozens of satellites are naked-eye-visible every night, while many times this number may be glimpsed through binoculars. Predictions of when and where to look, including plots of their tracks against the stars, may be obtained online for free, or example from heavens-above.com, or via smartphone apps. Of particular interest are the so-called Iridium satellites which can outshine every other object in the sky, bar the Sun and Moon, during brief flares when their orientation to the Sun and the observer is just right. Although online predictions also include these, Iridium flares are falling rapidly in frequency since the satellites responsible are being deorbited as they are replaced by 2nd generation (and non-flaring) craft.
The most obvious steadily-shining satellite is, of course, the International Space Station which can outshine Sirius as it transits up to 40° high from west to east across Edinburgh’s southern sky. As it orbits the Earth every 93 minutes at a height near 405 km, it is visible before dawn until about the 15th and begins a series of evening passes a week later.
Sunrise/sunset times for Edinburgh change from 07:05/17:46 GMT on the 1st to 05:47/18:48 GMT (06:47/19:48 BST) on the 31st which is the day that we set our clocks to British Summer Time.
The Moon is new on the 6th and spectacular over the following days as its brightly earthlit crescent stands higher each evening in the west-south-west. Catch the Moon 12° below Mars on the 10th and 6° below and left of the planet on the 11th. Mars itself stands around 30° high in the west-south-west at nightfall and is well to the north of west when it sets before midnight. This month it dims from magnitude 1.2 to 1.4 as it speeds more than 20° north-eastwards from Aries into Taurus to end the period only 3° below-left of the Pleiades.
Mercury has been enjoying its best spell of evening visibility this year, but is now fading rapidly and may be lost from view by the 7th. Binoculars show it shining at magnitude 0.1 on the 1st as it stands 10° directly above the sunset position forty minutes after sunset.
The Moon and planets never stray far from the ecliptic, the line around the sky that traces the apparent path of the Sun during our Earth’s orbit. The ecliptic slants steeply across our south-west at nightfall towards the Sun’s most northerly point which it reaches to the north of Orion at our summer solstice in June.
Given a clear dark evening, this is the best time of year to spy a broad cone of light stretching along the ecliptic from the last of the fading twilight. Dubbed the zodiacal light, this glow comes from sunlight scattering from interplanetary dust particles and was the subject on which Brian May, the lead guitarist of Queen, gained his doctorate.
As the Moon continues around the sky, it reaches first quarter on the 14th and passes just north of the star Regulus in Leo on the night of the 18/19th. Regulus, 45° high on Edinburgh’s meridian at our map times, lies less than a Moon’s breadth above the ecliptic and marks the handle of the Sickle of Leo.
Algieba in the Sickle is a splendid binary whose contrasting orange and yellow component stars lie 4.7 arcseconds apart and may be separated telescopically as they orbit each other every 510 years or so. The larger of the pair has at least one companion which may be a planet much larger than Jupiter or, perhaps, a brown dwarf star.
Between full moon on the 21st and last quarter on the 28th, the Moon passes very close to the conspicuous planet Jupiter on the 27th. The giant planet rises in the south-east in the small hours and is unmistakable at magnitude -2.0 to -2.2 low in the south before dawn where it is creeping eastwards against the stars of southern Ophiuchus.
The red supergiant star Antares in Scorpius lies some 13° to the right of Jupiter while Saturn, fainter at magnitude 0.6, is twice this distance to Jupiter’s left and lower in the twilight. Look for Saturn to the Moon’s left on the 1st and just above the Moon on the 29th.
Venus is brilliant (magnitude -4.1) but becoming hard to spot very low down in our morning twilight. More than 10° to the left of Saturn as the month begins and rushing further away, it rises in the south-east 81 minutes before sunrise tomorrow and only 39 minutes before on the 31st.
Diary for 2019 March
1st 18h Moon 0.3° N of Saturn
2nd 21h Moon 1.2° S of Venus
6th 16h New moon
7th 01h Neptune in conjunction with Sun
11th 12h Moon 6° S of Mars
13th 11h Moon 1.9° N of Aldebaran
14th 10h First quarter
15th 02h Mercury in inferior conjunction
17th 13h Moon 0.1° S of Praesepe
19th 00h Moon 2.6° N of Regulus
20th 21:58 Vernal equinox
21st 02h Full moon
27th 02h Moon 1.9° N of Jupiter
28th 04h Last quarter
29th 05h Moon 0.1° S of Saturn
30th 10h Mars 3° S of Pleiades
31st 01h GMT = 02h BST Start of British Summer Time
This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on February 28th 2019, with thanks to the newspaper for permission to republish here.
Orion and Winter Hexagon in prime-time view
Even though the two brightest planets, Venus and Jupiter, hover low in the south-east before dawn, the shortest month brings what many consider to be our best evening sky of the year. After all, the unrivalled constellation of Orion is in prime position in the south, passing due south for Edinburgh one hour before our star map times. Surrounding it, and ideally placed at a convenient time for casual starwatchers, are some of the brightest stars and interesting groups in the whole sky.
I mentioned some of the sights in and around Orion last time, including the bright stars Procyon, Betelgeuse and Sirius which are prominent in the south at the map times and together form the Winter Triangle.
Like the Summer Triangle, this winter counterpart is defined as an asterism which is a pattern of stars that do not form one of the 88 constellations recognised by the International Astronomical Union. Both triangles are made up of stars in different constellations, but we also have asterisms that lie entirely within a single constellation, as, for example, the Sickle of Leo which curls above Regulus in the east-south-east at our map times, and the Plough which comprises the brighter stars of the Ursa Major, the Great Bear, climbing in the north-east.
Yet another asterism, perhaps the biggest in its class, includes the leading stars of six constellations and re-uses two members of the Winter Triangle. The Winter Hexagon takes in Sirius, Procyon, Pollux in Gemini and Capella in Auriga which lies almost overhead as Orion crosses the meridian. From Capella, the Hexagon continues downwards via Aldebaran in Taurus and Rigel at Orion’s knee back to Sirius.
Edinburgh’s sunrise/sunset times change from 08:08/16:45 on the 1st to 07:07/17:44 on the 28th. The Moon is new on the 4th and at first quarter on the 12th when it stands 12° below the Pleiades in our evening sky. The 13th sees it gliding into the Hyades, the V-shaped star cluster that lies beyond Aldebaran. Both the Pleiades and the Hyades are open clusters whose stars all formed at the same time. Another fainter cluster, Praesepe or the Beehive in Cancer, is visible through binoculars to the left of the Moon late on the 17th. Full moon is on the 19th with last quarter on the 26th.
A number of other open star clusters lie in the northern part of the Hexagon, two of them plotted on our chart. At the feet of Gemini and almost due north of Betelgeuse is M35, visible as a smudge to the unaided eye but easy though binoculars and telescopes which begin to reveal its brighter stars. It lies 3,870 ly (light years) away, as compared with 440 ly for the Pleiades and 153 ly for the Hyades. Further north in Auriga is the fainter M37 (4,500 ly) which binoculars show 7° north-east of Elnath, the star at the tip of the upper horn of Taurus. M36 (4,340 ly) and M38 (3,480 ly) lie from 4° and 6° north-west of M37.
Mars dims a little from magnitude 0.9 to 1.2 but remains the brightest object near the middle of our south-south-western evening sky, sinking westwards to set before midnight. Mars is 241 million km distant when it stands above the Moon on the 10th, with its reddish 5.8 arcseconds disk now too small to show detail through a telescope. As it tracks east-north-eastwards against the stars, it moves from Pisces to Aries and passes 1° above-right of the binocular-brightness planet Uranus (magnitude 5.8) on the 13th.
The usually elusive planet Mercury begins its best evening apparition of 2019 in the middle of the month as it begins to emerge from our west-south-western twilight. Best glimpsed through binoculars, it stands between 8° and 10° high forty minutes after sunset from the 21st and sets itself more than one hour later still. It is magnitude -0.3 on the 27th when it lies furthest from the Sun in the sky, 18°, and its small 7 arcseconds disk appears 45% illuminated.
Venus, brilliant at magnitude 4.3, rises for Edinburgh at 05:11 on the 1st and stands 8° high by 06:30 as twilight begins to invade the sky. That morning also finds it 6° above and right of the waning earthlit Moon. A telescope shows Venus to be 19 arcseconds in diameter and 62% sunlit.
Jupiter is conspicuous 9° to the right of, and slightly above, Venus on the 1st though it is one ninth as bright at magnitude -1.9. Larger and more interesting through a telescope, its 34 arcseconds disk is crossed by bands of cloud running parallel to its equator while its four main moons may be glimpsed through binoculars. Edging eastwards (to the left) in southern Ophiuchus, it is 9° east of the celebrated and distinctly red supergiant star Antares in Scorpius, a star so big that it would engulf the Earth and Mars if it switched places with our Sun.
Our third predawn planet, Saturn rises at 06:38 on the 1st and is more of a challenge being fainter (magnitude 0.6) in the twilight. One hour before Edinburgh’s sunrise on the 2nd, it lies only 2° above the horizon and less than 10 arcminutes above-right of the Moon’s edge. Watchers in south-eastern England see it slightly higher and may glimpse it emerge from behind the Moon at about 06:31.
Venus speeds eastwards through Sagittarius to pass 1.1° north of Saturn on the 18th and shine at magnitude -4.1 even lower in the morning twilight by the month’s end. By then, the Moon has come full circle to stand above-right of Jupiter on the 27th and to Jupiter’s left on the 28th.
Diary for 2019 February
2nd 07h Moon 0.6° N of Saturn
4th 21h New moon
10th 16h Moon 6° S of Mars
12th 22h First quarter
13th 20h Mars 1.1° N of Uranus
14th 04h Moon 1.7° N of Aldebaran
18th 03h Moon 0.3° S of Praesepe
18th 14h Venus 1.1° N of Saturn
19th 13h Moon 2.5° N of Regulus
19th 16h Full moon
26th 11h Last quarter
27th 01h Mercury furthest E of Sun (18°)
27th 14h Moon 2.3° N of Jupiter
This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on January 31st 2019, with thanks to the newspaper for permission to republish here.
Rise early for a total lunar eclipse on the 21st
Any month that has the glorious constellation of Orion in our southern evening sky is a good one for night sky aficionados. Add one of the best meteor showers of the year, a total eclipse of the Moon, a meeting between the two brightest planets and a brace of space exploration firsts and we should have a month to remember
Orion rises in the east as darkness falls and climbs well into view in the south-east by our star map times. Its two leading stars are the blue-white supergiant Rigel at Orion’s knee and the contrasting red supergiant Betelgeuse at his opposite shoulder – both are much more massive and larger than our Sun and around 100,000 times more luminous.
Below the middle of the three stars of Orion’s Belt hangs his Sword where the famous and fuzzy Orion Nebula may be spied by the naked eye on a good night and is usually easy to see through binoculars. One of the most-studied objects in the entire sky, it lies 1,350 light years away and consists of a glowing region of gas and dust in which new stars and planets are coalescing under gravity.
The Belt slant up towards Taurus with the bright orange giant Aldebaran and the Pleiades cluster as the latter stands 58° high on Edinburgh’s meridian. Carry the line of the Belt downwards to Orion’s main dog, Canis Major, with Sirius, the brightest star in the night sky. His other dog, Canis Minor, lies to the east of Orion and is led by Procyon which forms an almost-equilateral triangle with Sirius and Betelgeuse – our so-called Winter Triangle.
The Moon stands about 15° above Procyon when it is eclipsed during the morning hours of the 21st. The event begins at 02:36 when the Moon lies high in our south-western sky, to the left of Castor and Pollux in Gemini, and its left edge starts to enter the lighter outer shadow of the Earth, the penumbra.
Little darkening may be noticeable until a few minutes before it encounters the darker umbra at 03:34. Between 04:41 and 05:46 the Moon is in total eclipse within the northern half of the umbra and may glow with a reddish hue as it is lit by sunlight refracting through the Earth’s atmosphere. The Moon finally leaves the umbra at 06:51 and the penumbra at 07:48, by which time the Moon is only 5° high above our west-north-western horizon in the morning twilight.
This eclipse occurs with the Moon near its perigee or closest point to the Earth so it appears slightly larger in the sky than usual and may be dubbed a supermoon. Because the Moon becomes reddish during totality, there is a recent fad for calling it a Blood Moon, a term which has even less of an astronomical pedigree than supermoon. Combine the two to get the frankly ridiculous description of this as a Super Blood Moon.
Sunrise/sunset times for Edinburgh change from 08:44/15:49 on the 1st to 08:10/16:43 on the 31st. New moon early on the 6th, UK time, brings a partial solar eclipse for areas around the northern Pacific. First quarter on the 14th is followed by full moon and the lunar eclipse on the 21st and last quarter on the 27th.
The Quadrantids meteor shower is active until the 12th but is expected to peak sharply at about 03:00 on the 4th. Its meteors, the brighter ones leaving trains in their wake, diverge from a radiant point that lies low in the north during the evening but follows the Plough high into our eastern sky before dawn. With no moonlight to hinder observations this year, as many as 80 or more meteors per hour might be counted under ideal conditions.
Mars continues as our only bright evening planet though it fades from magnitude 0.5 to 0.9 as it recedes. Tracking through Pisces and well up in the south at nightfall, it stands above the Moon on the 12th. Our maps show it sinking in the south-west and it sets in the west before midnight.
Venus, its brilliance dimming only slightly from magnitude -4.5 to -4.3, stands furthest west of the Sun (47°) on the 6th and is low down (and getting lower) in our south-eastern predawn sky. Look for it below and left of the waning Moon on the 1st with the second-brightest planet, Jupiter at magnitude -1.8, 18° below and to Venus’s left. As Venus tracks east-south-eastwards against the stars, it sweeps 2.4° north of Jupiter in an impressive conjunction on the morning of the 22nd while the 31st finds it 8° left of Jupiter with the earthlit Moon directly between them.
Saturn, magnitude 0.6, might be glimpsed at the month’s end when it rises in the south-east 70 minutes before sunrise but Mercury is lost from sight is it heads towards superior conjunction on the Sun’s far side on the 30th.
China hopes that its Chang’e 4 spacecraft will be the first to touch down on the Moon’s far side, possibly on the 3rd. Launched on December 7 and named for the Chinese goddess of the Moon, it needs a relay satellite positioned beyond the Moon to communicate with Earth.
Meantime, NASA’s New Horizons mission is due to fly within 3,500 km of a small object a record 6.5 billion km away when our New Year is barely six hours old. Little is known about its target, dubbed Ultima Thule, other than that it is around 30 km wide and takes almost 300 years to orbit the Sun in the Kuiper Belt of icy worlds in the distant reaches of our Solar System.
Diary for 2019 January
1st 06h New Horizons flyby of Ultima Thule
1st 22h Moon 1.3° N of Venus
2nd 06h Saturn in conjunction with Sun
3rd 05h Earth closest to Sun (147,100,000 km)
3rd 08h Moon 3° N of Jupiter
4th 03h Peak of Quadrantids meteor shower
6th 01h New moon and partial solar eclipse
6th 05h Venus furthest W of Sun (47°)
12th 20h Moon 5° S of Mars
14th 07h First quarter
17th 19h Moon 1.6° N of Aldebaran
21st 05h Full moon and total lunar eclipse
21st 16h Moon 0.3° S of Praesepe
22nd 06h Venus 2.4° N of Jupiter
23rd 02h Moon 2.5° N of Regulus
27th 21h Last quarter
30th 03h Mercury in superior conjunction
31st 00h Moon 2.8° N of Jupiter
31st 18h Moon 0.1° N of Venus
This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on December 31st 2018, with thanks to the newspaper for permission to republish here.
Comet sweeps near Earth as meteors streak from Gemini
December brings our longest and perhaps most interesting nights of the year. The two stand-out planets are Mars in the evening and Venus before dawn, the latter now as brilliant as it ever gets and the source of a flurry of recent UFO reports. We may also enjoy the rich and reliable Geminids meteor shower and Comet Wirtanen looks set to be the brightest comet of the year.
The comet’s progress is plotted on our charts, beginning low in the south near the Cetus-Eridanus border on the 1st and sweeping northwards and eastwards through Taurus to Auriga and beyond. A small comet with an icy nucleus possibly less than 1 km wide, Wirtanen was discovered in 1948 and orbits the Sun every 5.4 years between the Earth and Jupiter. It was the original destination of the European Space Agency’s Rosetta mission before delays forced the probe to target Comet Churyumov–Gerasimenko instead.
Comet Wirtanen reaches perihelion, its closest to the Sun and just beyond the Earth’s orbit, on the 12th. It is nearest the Earth on the 16th, passing only 11.6 million km away in the tenth closest approach of any observed comet since 1950. On that evening it lies 4° east (left) of the Pleiades and may appear as a large fuzzy ball lacking any obvious tail.
Predictions of its appearance at that time vary, but I suspect that its total brightness may be around the fourth magnitude, a little brighter than the fainter stars plotted on our charts. While this would normally put it well within naked-eye range, the fact that it is so close to the Earth is likely to mean that its light is spread out over an area even wider than the Pleiades. Unless we have a good dark sky, we may struggle to see its extended glow, and it is a pity that the gibbous Moon (63% sunlit) will also hinder observations before midnight. Only a week later, on the evening of the 23rd, it lies only 1° east-south-east of the bright star Capella but will be fading in still brighter moonlight.
The Sun reaches its most southerly point at the winter solstice at 22:23 GMT on the 21st as sunrise/sunset times for Edinburgh change from 08:19/15:44 GMT on the 1st to 08:42/15:40 on the 21st and 08:44/15:48 on the 31st. The Moon is new on the 7th, at first quarter on the 15th, full on the 22nd and at last quarter on the 29th.
Our charts show Andromeda and its Galaxy high in the south as Orion stands proudly in the south-east below Taurus and the Pleiades. Castor lies above Pollux in Gemini in the east and is close to the point in the sky that marks the radiant of the Geminids meteor shower.
The Geminids always produce an abundance of slow bright meteors which streak in all parts of the sky as they diverge from the radiant. The latter climbs to pass high in the south at around 02:00 and sinks into the west before dawn. The shower is active from the 8th to the 17th with the night of 13th-14th expected to be the best as meteor rates build to a peak at around dawn. An observer under an ideal dark sky with the radiant overhead may count upwards of 100 meteors per hour making the Geminids the highest-rated of our annual showers, though most of us under inferior skies may glimpse only a fraction of these.
Mars shines brightly some 25° high in the south as night falls for Edinburgh at present and is almost 10° higher by the month’s end after moving east-north-eastwards from Aquarius into Pisces. Our maps have it sinking in the south-west on its way to setting in the west before midnight. Although the brightest object in its part of the sky, it dims from magnitude 0.0 to 0.5 as it recedes from 151 million to 189 million km. When Mars stands above the Moon on the 14th, a telescope shows its ochre disk to be only 8 arcseconds across.
Saturn, magnitude 0.6, hangs just above our south-western horizon at nightfall as December begins but is soon lost in the twilight. Our other two evening planets, Uranus and Neptune, are visible through binoculars at magnitudes of 5.7 and 7.9 in Pisces and Aquarius respectively. Mars acts as an excellent guide on the evening of the 7th when Neptune stands about one quarter of a Moon’s breadth below-right of Mars.
Venus, now at its best as a dazzling morning star, rises in the east-south-east four hours before the Sun and climbs towards the south by dawn. This month it dims slightly from magnitude -4.7 to -4.5 as it tracks away from Virgo’s brightest star Spica in Virgo into the next constellation of Libra. Telescopes shows its crescent shrink from 40 to 26 arcseconds in diameter. Look for Venus below-left of the Moon on the morning of the 3rd and to the Moon’s right on the 4th.
Mercury is set to become as a morning star very low in the south-east and is soon to be joined by the even brighter Jupiter. Mercury rises more than 100 minutes before the Sun from the 5th to the 24th and stands between 5° and 9° high forty minutes before sunrise. It shines at magnitude 0.8 when it lies 7° below-left of the impressively earthlit Moon on the 5th, and triples in brightness to magnitude -0.4 by the 24th.
Jupiter, conspicuous at magnitude -1.8, emerges from the twilight and moves from 9° below-left of Mercury on the 11th to pass 0.9° south of Mercury on the 21st.
Diary for 2018 December
3rd 19h Moon 4° N of Venus
5th 21h Moon 1.9° N of Mercury
7th 07h New moon
7th 15h Mars 0.04° N of Neptune
9th 06h Moon 1.1° N of Saturn
12th 23h Comet Wirtanen closest to Sun (158m km)
14th 08h Peak of Geminids meteor shower
14th 23h Moon 4° S of Mars
15th 11h Mercury furthest W of Sun (21°)
15th 12h First quarter
16th 13h Comet Wirtanen closest to Earth (11.6m km) and 3.6° SE of Pleiades
20th 02h Jupiter 5° N of Antares
21st 08h Moon 1.7° N of Aldebaran
21st 15h Mercury 0.9° N of Jupiter
21st 22:23 Winter solstice
22nd 18h Full moon
23rd 18h Comet Wirtanen 0.9° SE of Capella
25th 05h Moon 0.3° S of Praesepe in Cancer
29th 10h Last quarter
This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on November 30th 2018, with thanks to the newspaper for permission to republish here.
InSight probe to land on bright evening planet Mars
The Summer Triangle, still high in the south at nightfall, shifts to the west by our map times as our glorious winter constellations climb in the east. Taurus with the Pleiades and its leading star Aldebaran (close to the Moon on the 23rd) stands well clear of the horizon while Orion is rising below and dominates our southern sky after midnight.
In the month that should see NASA’s InSight lander touch down on its surface, the planet Mars continues as a prominent object in the south at nightfall. Venus springs into view as a spectacular morning star but we must wait to see whether the Leonids meteor shower, which has produced some storm-force displays in the past, gives us any more than the expected few meteors this year.
InSight is due to land on the 26th on a broad plain called Elysium Planitia that straddles Mars’ equator. There it will place an ultra-sensitive seismometer directly onto the surface and cover it with a dome-like shell to shield it from the noise caused by wind and heat changes. This should be able of detect marsquakes and meteor impacts that occur all around Mars. Other InSight experiments will hammer a spike up to five metres into the ground to measure Mars’ heat flow, and further investigate the planet’s interior structure by using radio signals to track tiny wobbles in its rotation.
Until recently, Mars has remained low down as it performed a loop against the stars in the south-western corner of Capricornus. That loop, resulting entirely from our changing vantage point as the Earth overtook Mars and came within 58 million km on 31 July, took Mars more than 26° south of the sky’s equator and 3° further south than the Sun stands at our winter solstice.
Now, though, Mars is climbing east-north-eastwards on a track that will take it further north than the Sun ever gets by the time it disappears into Scotland’s night-long twilight next summer. One by-product of this motion is that Mars’ setting time is remarkably constant over the coming months, being (for Edinburgh) within 13 minutes of 23:42 GMT from now until next May.
This month sees Mars leave Capricornus for Aquarius and shrink as seen through a telescope from 12 to 9 arcseconds as it recedes from 118 million to 151 million km. Its path, indicated on our southern chart, carries it 0.5° (one Moon’s breadth) north of the multiple star Deneb Algedi, the goat’s tail, on the 5th. It almost halves in brightness, from magnitude -0.6 to 0.0, but its peak altitude above Edinburgh’s southern horizon early in the night improves from 16° to 25°, though by our map times it is sinking lower towards the south-west.
Mars is not our sole evening planet since Saturn shines at magnitude 0.6 low down in the south-west at nightfall. It is only a degree below-right of the young Moon on the 11th and sets more than 90 minutes before our map times. The two most distant planets, Neptune and Uranus, are also evening objects and may be glimpsed through binoculars at magnitudes 7.9 and 5.7 in Aquarius and Aries respectively.
Edinburgh’s sunrise/sunset times vary from 07:19/16:32 on the 1st to 08:17/15:45 on the 30th. The Moon is new on the 7th, at first quarter and below-right of Mars on the 15th, full on the 23rd and at last quarter on the 30th.
Jupiter is hidden in the solar glare as it approaches conjunction on the Sun’s far side on the 26th. Mercury stands furthest east of the Sun (23°) on the 6th but is also invisible from our northern latitudes.
Venus, though, emerges rapidly from the Sun’s near side into our morning twilight where it stands to the left of the star Spica in Virgo. Shining brilliantly at magnitude -4.1, the planet rises in the east-south-east only 29 minutes before the Sun on the 1st. By the 6th, though, it rises 80 minutes before sunrise and stands 8° below and right of the impressively earthlit waning Moon. Venus itself is 58 arcseconds wide and 4% illuminated on that morning, its slender crescent being visible through binoculars. By the 30th, Venus rises four hours before the Sun, climbs to stand 23° high in the south-south-east at sunrise and appears as a 41 arcseconds and 25% sunlit crescent.
It is just as well that my previous note led on the usually neglected Draconids meteor shower because observers, at least those under clear skies, were thrilled to see it provide perhaps the best meteor show of 2018. For just a few hours around midnight on 8-9th October, the sky became alive with slow meteors at rates of up to 100 meteors per hour or more.
Leonid meteors arrive this month between the 15th and 20th, with the shower expected to hit its usually-brief peak at around 01:00 on the 18th. Although they flash in all parts of the sky, they diverge from a radiant point in the so-called Sickle of Leo which rises in the north-east before midnight and climbs high into the south before dawn. No Leonids appear before the radiant rises, but even with the radiant high in a dark sky we may see fewer than 20 per hour – all of them very swift and many of the brighter ones leaving glowing trains in their wake.
Leonid meteoroids come from Comet Tempel-Tuttle which orbits the Sun every 33 years and was last in our vicinity in 1998. There has not been a Leonids meteor storm since 2002 and we may be a decade or more away from the next one, or are we?
Diary for 2018 November
2nd 05h Moon 2.1° N of Regulus
6th 16h Mercury furthest E of Sun (23°)
7th 16h New moon
11th 16h Moon 1.5° N of Saturn
15th 15h First quarter
16th 04h Moon 1.0° S of Mars
18th 01h Peak of Leonids meteor shower
23rd 06h Full moon
23rd 22h Moon 1.7° N of Aldebaran
26th 07h Jupiter in conjunction with Sun
26th 20h InSight probe to land on Mars
27th 09h Mercury in inferior conjunction on Sun’s near side
27th 21h Moon 0.4° S of Praesepe
30th 00h Last quarter
This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on October 31st 2018, with thanks to the newspaper for permission to republish here.
Draconid meteors glide away from the Dragon’s head
Mars dominates our southern evening sky but most of the other bright planets are poorly placed this month. Even so, our October nights are full of interest, from the Summer Triangle in the evening to the star-fest around Orion before dawn.
Although Mars dims from magnitude -1.3 to -0.6, its reddish light remains prominent as it moves from low in the south-south-east at nightfall to the south-south-west at our map times and onwards to set in the south-west a little before 01:00 BST (midnight GMT). As its distance grows from 89 million to 118 million km, and its diameter shrinks from 16 to 12 arcseconds, the planet speeds through Capricornus to climb 6° northwards and that much higher in our sky. Catch it to the left of the Moon on the 17th and below-right of the Moon on the 18th.
The Sun tracks 11° southwards as Edinburgh’s sunrise/sunset times change from 07:15/18:48 BST (06:15/17:48 GMT) on the 1st to 07:17/16:35 GMT on the 31st. The Moon is at last quarter on the 2nd, new on the 9th, at first quarter on the 16th, full (the Hunter’s Moon) on the 24th and back at last quarter on the 31st.
Our charts show the Plough in the north as it moves below Polaris, the Pole Star. Mizar, in the Plough’s handle, forms a famous double star with the fainter Alcor – the pair being separated by about one third the diameter of the Moon. Once held as a (not very rigorous) test of eyesight, they were dubbed “The Horse and Rider”.
Both lie 83 light years (ly) from us although we can’t be certain that they are tied together by gravity. In any case, we are not talking about just two stars, for Alcor has a faint companion and most telescopes show Mizar to be a binary star – the first to be discovered telescopically in the 17th century. Spectroscopes reveal that each of Mizar’s components is itself binary, so Mizar and Alcor, if they are truly associated, together form a sextuplet star system.
Mizar is the same brightness, magnitude 2.2, as Eltanin which lies 14° to the right of Vega and very high in the west at nightfall, falling into the north-west overnight. It is the brightest star in Draco and a member of a quadrilateral that marks the head of the Dragon whose body and tail twist to end between the Plough and Polaris. It lies 154 ly away but is approaching the Sun and will pass within 28 ly in another 1.5 million years to become the brightest star in Earth’s night sky.
Meteors from the Draconids shower diverge from a radiant point that lies close to Draco’s head (see our north map) between the 7th and 10th. Don’t expect a major display – perhaps no more than 10 meteors per hour, though all of them are very slow as they glide away from the radiant. The shower’s peak is due in a moonless sky around midnight on the 8th-9th and is worth checking because some years surprise us with strong displays and the shower’s parent comet, Comet Giacobini-Zinner, was visible through binoculars when it swept within 59 million km last month.
A better-known comet, Halley, is responsible for the meteors of the Orionids shower which lasts from the 16th to the 30th and has a broad but not very intense peak of fast meteors between the 21st and 24th. The radiant point, between Orion and Gemini, rises in the east-north-east soon after our map times and passes high in the south before dawn. Sadly, the peak coincides with the full moon, so don’t expect much of a show.
From high in the south at nightfall, the Summer Triangle (Vega, Deneb and Altair) tumbles into our western sky by the map times. By then, the less impressive and rather empty Square of Pegasus is in the south and Taurus and the Pleiades star cluster are climbing in the east. Orion rises below Taurus over the next two hours and crosses the meridian as the night ends.
Neptune and Uranus, now well placed in the evening, may be located through binoculars using better charts than I can provide here. A web search, for example for “Neptune finder chart”, should help. Neptune shines at magnitude 7.8 and lies in Aquarius at a distance of 4,342 million km on the 1st. Uranus is 2,824 million km away in Aries, near its border with Pisces, when it stands opposite the Sun in the sky (opposition) on the 24th. Although the full Moon stands close to it on that day, its magnitude of 5.7 makes it just visible to the unaided eye under a good dark and moonless sky.
October should see the launch of the European Space Agency’s BepiColombo mission to Mercury, but the planet itself is too low in our evening twilight to be seen. Venus sweeps around the Sun’s near side at inferior conjunction on the 26th and remains hidden in the Sun’s glare.
Jupiter is bright (magnitude -1.8) but less than 8° high in the south-west at sunset as the month begins. One of our last chances of spotting it in our bright evening twilight comes on the 11th when it lies 4° below-left of the young earthlit Moon.
Saturn, magnitude 0.5 and edging eastwards in Sagittarius, stands less than 10° high above Edinburgh’s south-south-western horizon as the sky darkens and sets in the south-west some 45 minutes before our map times. Look for it to the left of the Moon on the 14th.
Diary for 2018 October
Times are BST until the 28th
2nd 11h Last Quarter
9th 00h Peak of Draconids meteor shower
9th 05h New moon
11th 22h Moon 4° N of Jupiter
15th 04h Moon 1.8° N of Saturn
16th 19h First quarter
18th 14h Moon 1.9° N of Mars
21st – 24th Peak of Orionids meteor shower
24th 02h Uranus at opposition at distance of 2,824m km
24th 18h Full moon
26th 15h Venus in inferior conjunction on Sun’s near side
28th 02h BST = 01h GMT End of British Summer Time
31st 17h GMT Last quarter
This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on September 29th 2018, with thanks to the newspaper for permission to republish here.
Summer Triangle stars as autumn evenings begin
We may be edging towards autumn, but the Summer Triangle, the asterism formed by the bright stars Vega, Altair and Deneb, looms high in the south as night falls and shifts into the high south-west by our star map times later in the evening. Vega, almost overhead as the night begins, is the brightest of the three and lies in the small box-shaped constellation of Lyra the Lyre.
The next brightest, Altair in Aquila the Eagle, stands lower in the middle of our southern sky and, at 16.7 light years (ly), is one of the nearest bright stars to the Sun – eight light years closer than Vega. Flanking Altair, like the two sides of a balance, are the fainter stars Alshain (below Altair) and Tarazed (above) whose names come from “shahin-i tarazu”, the Arabic phrase for a balance.
Deneb, 25° from Vega, lies very high in the south-east at nightfall and overhead at our map times. It marks the tail of Cygnus the Swan which is flying overhead with wings outstretched and its long neck reaching south-westwards to Albireo, traditionally the swan’s beak. Although it is the dimmest corner-star of the Triangle, Deneb is one of the most luminous stars in our galaxy. Current estimates suggest that it shines some 200,000 time more brightly than our Sun from a distance of perhaps 2,600 ly, but its power and distance are hard to measure and the subject of some controversy.
Also controversial is the nature of Albireo. Even small telescopes show it as a beautiful double star in which a brighter golden star contrasts with a dimmer blue one. The mystery concerns whether the pair make up a real binary, with the two stars locked in orbit together by gravity, or whether this is just the chance alignment of two stars at different distances. Now measurement by the European Space Agency’s Gaia spacecraft appear to confirm the chance alignment theory.
The Milky Way, the band of countless distant stars in the plane of our galaxy, flows through the Summer Triangle and close to Deneb as it arches across our evening sky. Scan it through binoculars to glimpse a scattering of other double stars and star clusters.
One interesting stellar group is the so-called Coathanger which lies 8°, a little more than a normal binocular field-of-view, south of Albireo. It is also easy to locate one third of the way from Altair to Vega. Its line of stars, with a hook of stars beneath, gives it the appearance of an upside-down coat hanger. For decades this was regarded as a true star cluster, whose stars formed together, and its alternative designations as Brocchi’s Cluster and Collinder 399 reflect this. In 1998, though, results from the Hipparcos satellite, Gaia’s predecessor, proved that the Coathanger’s stars are at very different distances so that it, like Albireo, is simply a fortuitous chance alignment.
The Sun sinks 11.5° southwards during September to cross the sky’s equator at 02:54 BST on the 23rd. This marks our autumnal equinox and, by one definition, the beginning of autumn in the northern hemisphere. Sunrise/sunset times for Edinburgh change from 06:17/20:07 BST on the 1st at 07:13/18:51 on the 30th. The Moon is at last quarter on the 3rd, new on the 9th, at first quarter on the 17th and full on the 25th.
Venus is brilliant at magnitude -4.4 and 45° from the Sun on the 1st but it is only 4° above Edinburgh’s west-south-western horizon at sunset and sets 35 minutes later as its evening apparition as seen from Scotland comes to an end.
The other inner planet, Mercury, is prominent but low in the east-north-east before dawn until about the 14th. Glimpse it at magnitude -1.1 when it lies 1° above-left of Regulus in Leo on the 6th and 9° below-left of the impressively earthlit waning Moon on the 8th.
Jupiter is conspicuous but very low in the south-west at nightfall, sinking to set in the west-south-west one hour before our map times. Look for it below-right of the Moon on the 13th.
Saturn and Mars are in the far south of our evening sky. Saturn, the fainter of the two at magnitude 0.4 to 0.5, stands above the Teapot of Sagittarius and is just below and right of the Moon on the 17th when a telescope shows that its rings span 38 arcseconds around its 17 arcseconds disk. It sets in the south-west some 70 minutes after our map times.
Mars stands more than 25° east (left) of Saturn, tracks 7° eastwards and northwards in Capricornus and stands near the Moon on the 19th and 20th. It is easily the brightest object (bar the Moon) in the sky at our map times though it more than halves in brightness from magnitude -2.1 to -1.3. As its distance increases from 67 million to 89 million km, its ochre disk shrinks from 21 to 16 arcseconds. The dust storm that blanketed the planet since June has now died down.
Finally, we have a chance to spot the Comet Giacobini-Zinner as it tracks south-eastwards past the bright star Capella in Auriga, low in the north-east at our map times but high in the east before dawn. The comet takes only 6.6 years to orbit the Sun and should appear in binoculars as a small oval greenish smudge only 0.9° to the right of Capella on the evening of the 2nd when it is 60 million km away. Moving at almost 2° per day, it passes less than 7° north-east of Elnath in Taurus (see chart) on the morning of the 11th, just a day after it reaches perihelion, its closest (152 million km) to the Sun.
Diary for 2018 September
Times are BST
2nd 10h Venus 1.4° S of Spica
3rd 03h Moon 1.2° N of Aldebaran
3rd 04h Last quarter
6th 11h Saturn stationary (motion reverses from W to E)
7th 04h Moon 1.1° S of Praesepe in Cancer
7th 19h Neptune at opposition
8th 23h Moon 0.9° N of Mercury
9th 19h New moon
10th 08h Comet Giacobini-Zinner closest to Sun (152 million km)
14th 03h Moon 4° N of Jupiter
16th 14h Mars closest to Sun (206,661,000 km)
17th 00h First quarter
17th 17h Moon 2.1° N of Saturn
20th 08h Moon 5° N of Mars
21st 03h Mercury in superior conjunction
23rd 02:54 Autumnal equinox
25th 04h Full moon
30th 09h Moon 1.4° N of Aldebaran
This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on August 31st 2018, with thanks to the newspaper for permission to republish here.
Perseid meteor shower peaks in planet-rich sky
The persistent twilight that has swamped Scotland’s night sky since May is subsiding in time for us to appreciate four bright evening planets and arguably the best meteor shower of the year.
The Perseid shower returns every year between 23 July and 20 August as the Earth cuts through the stream of meteoroids that orbit the Sun along the path of Comet Swift-Tuttle. As they rush into the Earth’s atmosphere at 59 km per second, they disintegrate in a swift streak of light with the brighter ones often laying down a glowing train that may take a couple of seconds or more to dissipate.
The shower is due to peak in the early hours of the 13th at around 02:00 BST with rates in excess of 80 meteors per hour for an observer under ideal conditions – under a moonless dark sky with the shower’s radiant point, the place from which the meteors appear to diverge, directly overhead. We should lower our expectations, however, for although moonlight is not a problem this year, most of us contend with light pollution and the radiant does not stand overhead.
Even so, observable rates of 20-40 per hour make for an impressive display and, unlike for the rival Geminid shower in December, we don’t have to freeze for the privilege. Indeed, some people enjoy group meteor parties, with would-be observers reclining to observe different parts of the sky and calling out “meteor!” each time they spot one. Target the night of 12th-13th for any party, though rates may still be respectable between the 9th and 15th.
The shower takes its name from the fact that its radiant point lies in the northern part of the constellation Perseus, see the north map, and climbs from about 30° high in the north-north-east as darkness falls to very high in the east before dawn. Note that Perseids fly in all parts of the sky – it is just their paths that point back to the radiant.
Records of the shower date back to China in AD 36 and it is sometimes called the Tears of St Lawrence after the saint who was martyred on 10 August AD 258, though it seems this title only dates from the nineteenth century.
Sunrise/sunset times for Edinburgh change this month from 05:17/21:20 BST on the 1st to 06:15/20:10 on the 31st. The Moon is at last quarter on the 4th, new on the 11th, at first quarter on the 18th and full on the 26th.
A partial solar eclipse on the 11th is visible from the Arctic, Greenland, Scandinavia and north-eastern Asia. Observers in Scotland north of a line from North Uist to the Cromarty Firth see a thin sliver of the Sun hidden for just a few minutes at about 09:45 BST. Our best place to be is Shetland but even in Lerwick the eclipse lasts for only 43 minutes with less than 2% of the Sun’s disk hidden at 09:50. To prevent serious eye damage, never look directly at the Sun.
Vega in Lyra is the brightest star overhead at nightfall and marks the upper right corner of the Summer Triangle it forms with Deneb in Cygnus and Altair in Aquila. Now that the worst of the summer twilight is behind us, we have a chance to glimpse the Milky Way as it flows through the Triangle on its way from Sagittarius in the south to Auriga and the star Capella low in the north. Other stars of note include Arcturus in Bootes, the brightest star in our summer sky, which is sinking in the west at the map times as the Square of Pegasus climbs in the east.
Of the quartet of planets in our evening sky, two have already set by our map times. The first and brightest of these is Venus which stands only 9° high in the west at Edinburgh’s sunset on the 1st and sets itself 68 minutes later. By the 31st, these numbers change to 4° and 35 minutes, so despite its brilliance at magnitude -4.2 to -4.4, it is becoming increasingly difficult to spot as an evening star. It is furthest east of the Sun (46°) on the 17th.
Jupiter remains conspicuous about 10° high in the south-west as darkness falls and sets in the west-south-west just before the map times. Edging eastwards in Libra, it dims slightly from magnitude -2.1 to -1.9 and slips 0.6° north of the double star Zubenelgenubi on the 15th. A telescope shows it to be 36 arcseconds wide when it lies below-right of the Moon on the 17th.
The two planets low in the south at our map times are Mars, hanging like a prominent orange beacon only some 7° high in south-western Capricornus, and Saturn which is a shade higher above the Teapot of Sagittarius almost 30° to Mars’ right. Mars stood at opposition on 27 July and is at its closest to the Earth (57.6 million km) four days later. A planet-wide dust storm has hidden much of the surface detail on its small disk which shrinks during August from 24 to 21 arcseconds as its distance increases to 67 million km. Although Mars dims from magnitude -2.8 to -2.1, so it remains second only to Venus in brilliance. Catch the Moon near Saturn on the 20th and 21st and above Mars on the 24th.
Finally, we cannot overlook Mercury which is a morning star later in the period. Between the 22nd and 31st, it brightens from magnitude 0.8 to -0.7, rises more than 90 minutes before the Sun and stands around 7° high in the east-north-east forty minutes before sunrise. It is furthest west of the Sun (18°) on the 26th.
Diary for 2018 August
Times are BST
4th 19h Last quarter
9th 01h Mercury in inferior conjunction on Sun’s near side
11th 11h New moon and partial solar eclipse
13th 02h Peak of Perseids meteor shower
14th 15h Moon 6° N of Venus
17th 12h Moon 5° N of Jupiter
17th 19h Venus furthest E of Sun (46°)
18th 09h First quarter
21st 11h Moon 2.1° N of Saturn
23rd 18h Moon 7° N of Mars
26th 13h Full moon
26th 22h Mercury furthest W of Sun (18°)
28th 11h Mars stationary (motion reverses from W to E)
This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on July 31st 2018, with thanks to the newspaper for permission to republish here.
Dust storm rages on Mars as it stands closest since 2003
Mars comes closer to the Earth in July than at any time since its once-in-60,000-years record approach in 2003. It is just our luck that a dust storm that began a month ago now engulfs the entire planet so that the surface markings may now be glimpsed only through a patchy reddish haze.
Both current Mars rovers, Opportunity and Curiosity, are also affected. This is the most intense storm to impact Opportunity since it landed in 2004 and the vehicle has shut down because it lost power as the dust hid the Sun and coated its solar panels. It is hoped that, after the storm subsides, friendly gusts of wind will waft the dust from the panels and Opportunity will revive. If not, this would mark the end of a remarkable mission which had been planned, initially, to last for only 90 days. Its sister rover, Spirit, succumbed in 2010 after becoming stuck in soft soil.
Meanwhile, the more advanced Curiosity rover has been operating since 2012. Being nuclear powered, it is less vulnerable to the dust but its cameras are recording a dull reddened landscape beneath dusty orange skies.
For watchers in Edinburgh, Mars rises in the south-east just before midnight at the beginning of July and is conspicuous at magnitude -2.2 but only 11° high in the south during morning twilight. Look for it 4° below the Moon on the 1st as Mars moves westwards in the constellation of Capricornus.
Mars reaches opposition on the 27th when it stands opposite the Sun, rises during our evening twilight and is highest in the south in the middle of the night. By then it blazes at magnitude -2.8, making it second only to Venus in brilliance, and stands 58 million km away. A telescope shows it to be 24 arcseconds wide, with its southern polar cap tilted 11° towards us. Because Mars is edging inwards in its relatively elongated orbit, it is actually around 100,000 km closer to us on the 31st.
As Mars rises at its opposition on the 27th it once again lies below Moon, but this time the Moon is deep in eclipse as it passes almost centrally through the Earth’s shadow. The total phase of the eclipse, the longest this century, lasts from 20:30 to 22:13 BST and it is in the middle of this period, at 21:22, that the Moon rises for Edinburgh. By 22:13, and weather permitting, it may be possible to see the Moon’s dull ochre disk 5° high in the south-east. From then until 23:19, the Moon emerges eastwards from the Earth’s dark umbral shadow, and at 00:29 it is free of the penumbra, the surrounding lighter shadow.
The Earth stands at its furthest from the Sun for 2018 (152,100,000 km) on the 6th. Edinburgh’s sunrise/sunset times change from 04:31/22:01 on the 1st to 05:15/21:22 on the 31st. The Moon is at last quarter on the 6th and new on the 13th when a partial solar eclipse is visible to the south of Australia. First quarter on the 19th is followed by full moon and the total lunar eclipse on the 27th.
Our chart shows the corner stars of the Summer Triangle, Vega in Lyra, Altair in Aquila and Deneb in Cygnus, high in the south to south-east as the fainter corner stars of the Square of Pegasus are climbing in the east. The Plough stands in the middle of our north-western sky and the “W” of Cassiopeia is similarly placed in the north-east.
Venus sets before our chart times but is brilliant in the west at nightfall. It brightens from magnitude -4.0 to -4.2 but is sinking lower from night to night as it tracks southwards relative to the Sun. It passes 1.1° north of the star Regulus in Leo on the 9th as the much fainter planet Mercury (magnitude 0.4) stands 16° below-right of Venus. The little innermost planet stands furthest east of the Sun (26°) on the 12th but is a challenge to glimpse in the twilight this time around.
Venus lies to the left of the young earthlit Moon on the 15th, below-right of the Moon on the 16th and, by month’s end, stands less than 10° high at sunset before setting itself some 70 minutes later.
Jupiter lingers as a conspicuous evening object in the south-south-west at nightfall, sinking to set in the west-south-west one hour after our map times. Moving very little against the stars of Libra, it dims slightly from magnitude -2.3 to -2.1 and shows a 39 arcseconds disk when it lies below-left of the Moon on the 20th.
Saturn reached opposition on June 27 and is at its best at our star map times, albeit low in the south at a maximum altitude of less than 12° for Edinburgh. At magnitude 0.0 to 0.2, it is creeping westwards above the Teapot of Sagittarius where it lies near the Moon on the 24th and 25th. Its disk and wide-open rings appear 18 and 41 arcseconds wide respectively.
Our noctilucent, or “night-shining”, cloud season is now in full swing with sightings of several displays of these high-altitude blue-white clouds since late-May and further ones expected until August.
Often with a wispy cirrus-like appearance, noctilucent clouds are composed of ice-crystals at heights near 82 km and glimmer above our northern horizon where they catch the sunlight long after our more usual lower-level clouds are in darkness. Their nature is still something of a mystery but it may not be coincidental that the first definite record of them dates only as far back as 1885, just two years after the cataclysmic eruption of the Krakatoa volcano in Indonesia.
Diary for 2018 July
Times are BST
1st 03h Moon 5° N of Mars
6th 09h Last quarter
6th 18h Earth farthest from Sun (152,100,000 km)
9th 21h Venus 1.1° N of Regulus
11th 05h Jupiter stationary (motion reverses from W to E)
12th 06h Mercury furthest E of Sun (26°)
13th 04h New moon and partial solar eclipse S of Australia
14th 23h Moon 2.2° N of Mercury
16th 04h Moon 1.6° N of Venus
19th 21h First quarter
21st 01h Moon 4° N of Jupiter
25th 07h Moon 2.0° N of Saturn
27th 06h Mars at opposition at distance of 58 million km
27th 21h Full moon and total lunar eclipse
27th 22h Moon 7° N of Mars
29th Main peak of Delta Aquarids meteor shower
31st 09h Mars closest to Earth (57,590,000 km) | 0.914625 | 3.771123 |
Of or pertaining to → astrophysics.
Fr.: jet astrophysique
A very fast moving, → collimated beam of → ionized gas at high temperatures associated with most classes of compact objects that spin and/or accrete matter from their surroundings, such as → protostars, → X-ray binary systems, and, at a larger scale, with → active galactic nuclei, → gamma-ray bursts, and → quasars. In general, jet sources host → accretion disks and are associated with → magnetic fields. Astrophysical jets, despite their different physical scales and power, are morphologically very similar, suggesting a common physical origin. For example, in one extreme, → active galactic nuclei jets have typical sizes ≥ 106 pc, velocities near that of light c, and parent sources (→ massive black holes) with masses 106-9 Msun and luminosities ~ 1043-48Lsun; while in the other extreme, → young stellar objects jets have typical sizes ≤ 1 pc, velocities ≤ 10-3 c, and emerge from low mass protostars with masses ~ 1 Msun and luminosities (0.1-2 × 104) Lsun. Jets play an important → feedback role in the evolution of their host systems. See also: → jet launching.
Fr.: objet astrophysique | 0.821086 | 3.517199 |
Remote Imaging Platform for Targets of Interest & Lunar Archeology
By Fran Ridge, Coordinator, The Lunascan Project
AbstractThe Earth has weather satellites that give us up-to-the-minute images of the weather on The Weather Channel. SOHO (Solar & Heliospheric Observatory) is keeping us abreast of the latest activity on our nearest star, the Sun. The Deep Space Climate Observatory (DSCOVR) is a NOAA Earth observation and space weather satellite launched by SpaceX on February 11th. It was intended to be positioned at the Sun-Earth L1 Lagrange point, 1,500,000 km (930,000 mi) from Earth, to monitor variable solar wind condition, provide early warning of approaching coronal mass ejections and observe phenomena on Earth including changes in ozone, aerosols, dust and volcanic ash, cloud height, vegetation cover and climate. At this location it has a continuous view of the Sun and the sunlit side of the distant Earth. With the world's plan to return to the Moon it is time for a dedicated, 24/7, live-imaging lunar satellite for our nearest neighbor. This proposal describes the benefits of such a project for science, but it goes farther than just benefits. Our very survival could depend on it.
Simulated LPS view from RIPTILA
13 May 2015, updated 19 July 2019
Current lunar imaging is at the mercy of the observer's location and time of day/night and weather! Speaking from experience, we have had almost a hundred scanning missions since the Lunascan Project began in 1997. The most missions in any given year was a dozen! And many of those were performed under limited sky conditions. It's time to change all of this. We have weather satellites looking at the Earth 24/7. Why can't we have one satellite watching the near side of the Moon? And if that can be done, why not have several, one placed on the far side?
You go to your computer and click on "RIPTILA". The site takes you to a screen with live High Definition images from the Moon similar to the above, being imaged at 30 frames a second. Viewed full screen on your 52' LCD monitor, the bright, contrasted, full image of the Moon floating in the blackness of space in a close-by stationary L-1 orbit is breath-taking. This view is not magnified. It will a filtered, camera eye view, streaming live from RIPTILA's imaging platform. On the bottom of the screen will be fast-running time stamp in Coordinated Universal Time. Anyone will be able to access this site and at almost any time (*) of the month or day and view this live image just like they do with a U.S. weather satellite, but this time it is our nearest neighbor, the Moon.
To get a closer look, using your mouse and a special program, you place a small rectangle over a portion of the Moon. With a right-click you are now looking at that small section pumped up, full screen and in HD, a SIMRANGE of 300 miles and a field of view of 200 miles. This is an unobstructed, clear and sharp view of the lunar surface. Not the latest image, but LIVE images! On command you can zoom in even closer.
Using the mouse, the team slides the camera in the steerable mode to the upper right of the lunar disc and lets the program pan/scan the Moon at the rate of their choice. All the while the live images are being recorded. If the team wants to take a closer look at a target, there is no earth-rotation to deal with here, the system is just in "pan" mode. With another click on the mouse the team can now switch to track mode and hit "zoom". Now at higher power the target is observed extremely clear at a resolution not possible with EBTI or "Earth-Based Telescopic Imaging".
52-mile wide Copernicus in a 200 mile FOV
Does this sound far-fetched? Or a waste of taxpayer's money? At one time weather satellites running 24/7 over the U.S. were just a great idea. We already have the technology. If SOHO can do this with the Sun 93,000,000 miles a way, why can't it be done with the Moon? The DSCOVR satellite is located near the L1 point between the Earth and the Sun. Its position is maintained by firing of rocket motors. (See L1 and "halo" orbit below ). There is a very strong possibility that a project like this could get off the ground with NASA or SPACE-X or some other privately-funded mission. But what would RIPTILA do and why the need to do it?
WHAT ARE TARGETS OF INTEREST?
1. METEORITE IMPACTS
Probably one of the most important aspects of RIPTILA would be the 24/7 scan of the lunar globe for meteorite impact flashes. What is happening on the Moon today is also happening on the Earth, today. Impacts are still occurring and a more comprehensive study of them might help us to understand the rate and periodicity. This could help predict and deter a potential global disaster from the threat from rogue asteroids. In the image at the top of this proposal is a view of the Moon's western hemisphere, perfect for those looking for anomalies and routine targets on the dayside, and great for meteorite impact hunters on the darkside. Even more interesting would be the New Moon's totally black surface with the perfect backdrop for impact flashes. (See below). The other times when watching the Moon would be valuable would be during "meteor showers" which occur about a dozen times a year. Not only would this be live, but a photo-cell type system could even do the tedious work of counting the impacts. State-of-the-art security surveillance systems could store high-quality images for periods as short as a single day. During the last decade many astronomers have been watching the dark side (which also changes every day) for meteorite impacts, and there have been several documented cases. RIPTILA opens up a wonderful opportunity for scientists and researchers to study the Moon live and 24/7. This could be done in MUCH higher resolution than with Earth Based Telescopic Images and scanrate on a daily basis, and recordings reused many times.
2. LUNAR ECLIPSES
Having the full-sized image of the Moon in high-def on a 52" television screen would be a perfect way to observe and study (and record) a lunar eclipse. Not only scientists and researchers could do this, anybody could take part, including the news medias of the world. One problem that will have to be solved is that solar eclipses would be destructive to the sensors/chips used to image the Moon and some type of automatic iris would have to be incorporated in the system. (*) Not only that but once each month the Moon would be aligned with the Sun and there would be a safety shutdown or filter switched on until the Sun was safely out of the way.
3. LUNAR TRANSIENT PHENOMENA4. ROUTINE SCANS
"LTPs") have been observed since 1783, and the reported activity in some cases may be an indicater that the Moon is not as dead as we had once thought. This exciting and promising new idea may change the way we watch the the Moon and there would no longer be any weather problems as we encounter with earth-based telescopes. Teams can be anywhere in the world at any time of the day or night. And requests for viewing "Targets of Interest" at specific times would keep scientists and researchers busy doing very important and exciting work.
Authorized and scheduled teams can observe Targets of Interest, using this steerable high-definition telescopic system "hovering" over the lunar nearside. While they work the mission, people all over the world can watch "the Moon Channel" as live breath-taking images come in. Viewers seeing "flashes" or possible "anomalies" can phone in reports as they occur and be credited for their finds. There is a long list of LTPs with dates and times so that colongitude can predict an occurrence if lighting conditions had anything to do with it. When there is no specific mission, the spacecraft's surveillance would continue its routine "meteor watch" 24/7.
Originally it was thought that teams wanting to do a "meteor watch" during an intense meteor shower known to be going on on the Earth would have to file a "Mission Request" which would allow them priority over the RIPTILA view. But this wouldn't require any more than the image of the full lunar disc to observe the flashes of an impact. A message on the bottom of the screen ("ticker" or "crawler") would inform everyone that some type of mission is going on.
The same with an authorized team for research on a past LTP report. LTP dates and times would have the colongitude data and a computer program would provide the future dates for the exact same seeing conditions to try to duplicate the event if specific lighting caused the anomaly or if lighting conditions betrayed the presence of any unusual feature or outgassing.
Most of the time between these more important activities would be filled in with routine scanning which would still benefit the "meteor watch" aspect. We always see the eastern hemisphere in normal hours and most of the previous 99 missions here at the Lunascan Project involved that area. But the western part of the Moon is for the early bird. It's one of the most interesting sights to see if you like the north-western part of Mare Imbrium with the beautiful Sinus Iridium, and the Jura mountain range which forms its edge. Sinus Iridium is crossed by mare ridges. Luna 17, which landed to the south of Cape Heraclides, transported an automatic mobile laboratory, Lunokhod 1, to the Moon. The interesting target craters Kepler and Aristarchus are always a favorite. But having a mission in the wee hours with good seeing conditions is a long shot in may places of the world. RIPTILA would solve that problem. Teams wouldn't have to have expensive telecopes to set up and maintain. All they would need would be the will to work the scans, a computer, and a recorder.
A word about Lagrange points and halo orbits. A halo orbit is a periodic, three-dimensional orbit near the L1, L2 or L3 Lagrange points in the three-body problem of orbital mechanics. Although a spacecraft in a halo orbit moves in a circular path around the LP, it does not technically orbit the actual Lagrange point, because the LP is just an equilibrium point with no gravitational pull, but travels in a closed, repeating path near the Lagrange point. Halo orbits are the result of a complicated interaction between the gravitational pull of the two planetary bodies and the coriolis and centrifugal accelerations on a spacecraft. Halo orbits exist in many three-body systems, such as the Sun/Earth system and the Earth/Moon system. Continuous "families" of both Northern and Southern halo orbits exist at each Lagrange point. Because halo orbits tend to be unstable, stationkeeping is required to keep a satellite on the orbit. The distance from the Moon is around 384,400 km (240,000 miles) and the LP would be at about 62,000 km (about 39,000 miles) and require more complicated optics on REPTILA. But optics, of Hubble quality, but higher power in space would be fantastic as compared to Earth-bound systems with global atmospheric problems.
If successful, using a relay satellite orbiting the Moon to send the images, another version of our project could be used for the Lunar Far Side in a much more stable L2 Lagrange Point.
RIPTILA is a suggested name only. And how to create an orbiting lunar satellite that would utilize an LP is a problem worth solving. Once we establish enough interest we can work on the issues and those problems. I don't believe the funding would be that difficult. I think the benefits would be scientifically valuable, and that the use of the system would be the beginning of a new era in space as we continue to explore the Moon and prepare for the next generation of more intense explorations and adventures, both private and commercial.
Already on the drawing board are new ways to use the newest technologies. One idea is to use one camera to do the entire operation, the original image being as hi-res as can be obtained. Then, on the ground, using computer programs, zooming in to produce what we use to call MPS and HPS scans. Medium Power Scanning produced images similar to a good telescope where the FOV was over 400 miles and up to 1,000-2000 miles. HPS (High-Powered Scanning) was 400X (or more) with an FOV under 400 miles, such as the pumped up image of Copernicus above with an FOV of 200 miles.
Using a computer program or a RIPTILA "x-box", anyone could do their own experiments without affecting the authorized missions. Rather than just watching scientist and researchers do their work, amateurs would be able to use the system without having to buy a telescope. Telescope suppliers could sell the "R-box" just as they sell telescopes for people to watch the Moon. RIPTILA will never replace the telescope for amateur astronomers who have a wide range of interests in space, but for those interested in the Moon it will open a whole new world in space adventure as we go back to our neighbor a quarter of a million miles away.
Francis L. Ridge
Coordinator,Click here to email us at [email protected]
The Lunascan Project
5847 River Walk Circle
Newburgh, IN 47630Phone: (812) 490-0094
* At times when the Sun would be in the background, and this would be once a month and for a short period, there would have to be a way of turning on a filter or be able to shut down the camera to protect the optics and scanning chip. | 0.881028 | 3.026195 |
Finding the moons of Mars is incredibly hard for the backyard stargazer. These two moons are so small and dim that Mars is about 200,000 times brighter. They are also very close to the planet. Discovered in 1877 by Asaph Hall using a 26in(650mm) telescope at the Naval Observatory.
The Martian satellites are named after the sons of Ares the god of war. Phobos(panic) and Deimos(dread).
Phobos the larger inner moon has an apparent magnitude of 11.3.
this moon orbits Mars so fast it appears in the sky twice a day.
Orbiting from west to east Phobos takes about 4.5 hours to move across the sky.
Smaller in area than the state of Delaware, Phobos is too small to become rounded by its own gravity. Orbiting about 3,700 miles from Mars, this is closer to the parent planet than any other natural satellite in the Solar System. In an equatorial orbit Phobos is not visible above the horizon at +70.4 degrees or -70.4 degrees latitude on Mars.
If you were on Mars you would see Phobos transit the Sun and cast a shadow. Phobos though is too small to cause a total eclipse.
Heavily cratered without an atmosphere for protection from impacts. Stickney crater the most prominent is named after Asaph Hall's wife.
Deimos is the smaller of the two and is the outer moon farthest away from the planet Mars.
Taking slightly longer than 30 hours to orbit Mars, 2.7 days elapse between its rising and setting for an equatorial observer.
For a stargazer on Mars, Deimos would appear to the naked eye as a star. When full it would be about as bright as Venus appears to us on Earth. During the quarter phases it would be about as bright as the star Vega. The apparent magnitude is about 12.4, not very bright.
The 2 largest craters are named for writers who used Martian moons in their writings before their discovery.
Swift Crater and Voltaire Crater are the only named features on Deimos.
Like Phobos, Deimos lies in a very equatorial orbit and observers on Mars would not be able to see it above the horizon after about +80 and -80 degrees latitude.
Finding these two moons will take an incredible amount of patience.
In very dark skies with good seeing conditions you could find them in a 6in(150mm) telescope, but because they are always in the glare of Mars you probably need at least a 12in(300mm) scope to have a chance.
Best time is when the moons are at eastern or western elongation which is maximum separation from the planet.
This article from Sky & Telescope will give you a tip to help you try and find them.
With calm dark skies, time, patience, and luck, you too can find panic and dread Phobos and Deimos...The sons of Ares, the moons of Mars.Celestial Solar System › MOONS › Moons of Mars | 0.874922 | 3.57425 |
Iota Orionis: Pulsating beacon of a constellation
MONTREAL, March 8, 2017 – Astronomers from the BRITE (BRight Target Explorer) Constellation project and Ritter Observatory have discovered a repeating one-per-cent spike in the light of a very massive star which could change our understanding of such stars. Iota Orionis is a binary star system and is easily visible with the naked eye, being the brightest star in the constellation Orion’s sword. Its unique variability, reported in the journal Monthly Notices of the Royal Astronomical Society, was discovered using the world’s smallest astronomical space satellites, referred to as “nanosats”. “As the first functional nanosatellite astronomy mission, the BRITE-Constellation is at the vanguard of this coming space revolution,” said Canadian BRITE-Constellation principal investigator Gregg Wade, of Royal Military College of Canada, Ont.
The light from Iota Orionis is relatively stable 90 per cent of the time but then dips rapidly followed by a large spike. “The variations look strikingly similar to an electrocardiogram showing the sinus rhythms of the heart, and are known as heartbeat systems,” said Herbert Pablo, the project’s principal investigator, a post-doctoral researcher at Université de Montréal and member of the Centre for Research in Astrophysics of Quebec (CRAQ). This unusual variation is the result of the interaction of two stars in a highly elliptical 30-day orbit around each other.
While the two stars spend the majority of their time far apart, they do come nearly eight times closer together for a short time once every orbit. At that point the gravitational force between the two stars becomes so strong that it rapidly distorts their shapes, like pulling on the end of a balloon, causing the unusual changes in light. Iota Orionis represents the first time this effect has been seen in such a massive system (35 times the mass of the Sun), an order of magnitude larger than any in previously known systems, and allows for direct determination of the masses and radii of the components.
A shaking star is like an open book
Even more interesting is that these systems allow us to peer inside the stars themselves. “The intense gravitational force between the stars as they move closer together triggers quakes in the star, allowing us to probe the star’s inner workings, just as we do for the Earth’s interior during Earthquakes,” said Pablo. The phenomenon of quakes is very rare in massive stars in general and this is the first time induced quakes have ever been seen in a star this massive, let alone one whose mass and radius are known. These unprecedented quakes have also led to the first real clues to how such stars will evolve.
Astronomers are hopeful that this discovery will provide the initiative to search for other such systems, creating a fundamental shift in how we study the evolution of massive stars. This is important, since massive stars are laboratories of elements essential to human life. | 0.885465 | 3.864563 |
- Open Access
Far-infrared continuum absorption of olivine at low temperatures
Earth, Planets and Space volume 65, Article number: 10 (2013)
The far-infrared continuum opacity of cold dust is an important quantity for the study of debris disks in planetary systems and of protoplanetary disks. Olivine is considered the most abundant crystalline dust species in such environments. We present spectroscopic absorption measurements on olivine plates of the order of a millimeter thickness at wavelengths between 60 and 400 μ m for temperatures down to 10 K. Our data reveal a strong temperature dependence of the continuum absorption coefficient, i.e. more than an order of magnitude decrease at 100 μ m for 10 K compared to room temperature. The absolute values are generally much lower than those measured with olivine powders embedded into polyethylene pellets, even if the difference between plate and powder samples is taken into account by theoretical models. In contrast to this, the room temperature data are in relatively good agreement with simulations using optical constants determined from reflection measurements. At low temperatures, the absorption coefficient of olivine was measurable with sufficient accuracy only up to 90 μ m for 10 K and up to 110 μ m for 100 K. These data reveal a drastic change in the spectral slope (from β ~ 2.0 to β > 5.0) for the continuum underlying the 69-μ m band, which is not predicted by the low-temperature optical constants determined for forsterite.
Mg-rich olivine (general formula of olivine (Mg,Fe)2SiO4) is probably the most abundant silicate mineral in space. Because of its high thermal stability, it is one of the first minerals that condenses from a cooling gas of solar composition (Gail, 2003). The presence of olivine dust particles of sub-micron size has been detected by the infrared spectroscopy of thermally-emitted radiation from stellar outflows (e.g. Molster et al., 2002), protoplanetary disks (e.g. Juhász et al., 2010), and from warm dust in planetary systems (‘exozodiacal dust’, e.g. Olofsson et al., 2012). The search for olivine in colder environments with the Herschel space telescope has led to a number of detections of the 69-μ m olivine vibration band (e.g. Sturm et al., 2010; de Vries et al., 2012). From the composition-sensitive wavelength position of this band, it has been deduced that the olivines in these cases were Fe-poor (e.g. Sturm et al., 2013), close to the composition of the Mg end member of the olivine series, forsterite (Mg2SiO4). However, in planetary system dust, considerably more iron-rich olivine with an approximate Mg/(Mg + Fe) ratio of 0.8 (in the following, designated as Forsterite80% = Fo80) has been found (Olofsson et al., 2012).
Since infrared bands play the most important role in the diagnostics of dust minerals and can also serve as indicators of the dust temperature, laboratory studies have mostly concentrated on their investigation, examining the dependence of band positions, widths, and strengths on composition, grain size, grain shape, temperature, and structural perfectness (e.g. Koike et al., 2006, and references therein). Several of these studies have especially considered the far-infrared bands at about 50- and 70-μ m wavelengths. It has been proposed that the temperature dependence of their widths and positions makes them usable as a dust thermometer (Chihara et al., 2001; Bowey et al., 2002), which is indeed exploited today with Herschel spectra (e.g. de Vries et al., 2012). Most of the laboratory studies have been performed on powders of olivine and forsterite, while reflection measurements on polished crystals have been used in a few cases in order to determine the complex refractive index of natural olivine (Fabian et al., 2001) at room temperature, and of forsterite even at low temperatures down to 50 K (Suto et al., 2006).
Apart from the diagnostic lattice-vibration bands, the value of the continuum absorption coefficient in adjacent spectral ranges is also important. The absorption of stellar radiation, which determines the temperature of dust in stellar environments, takes place in spectral regions, where minerals are often only weakly absorbing (Zeidler et al., 2011; Pitman et al., 2013), except for conducting, or semiconducting, compounds. Similarly, if dust is located at a larger distance from a star, its thermal radiation may occur at very long infrared wavelengths extending significantly beyond the range of lattice-vibration bands where the emis-sivity is determined by a low continuum opacity as well. Observations at such far-infrared wavelengths (e.g. in the Herschel PACS 100-μ m and 160-μ m bands) are an important tool to study cold dusty structures, such as proto-planetary disks and debris disks (e.g. Eiroa et al., 2011). Consequently, opacity data of relevant dust species are of great importance in order to be able to convert the observed wavelength-dependent fluxes into dust masses, temperatures, and spatial distributions (e.g. Krivov et al., 2008).
Given the diversity of dust minerals, the inventory of spectroscopic data at these long wavelengths is still relatively poor. Some of the data used in models are uncertain due to the methods from which they are derived, or do not take into account the temperature dependence of the continuum opacity. For instance, optical constants derived from reflection measurements at these long wavelengths are actually extrapolations of the band profiles situated shortward and do not contain information about low-energetic continuum absorption processes (see e.g. Henning and Mutschke, 1997, and references therein). Since, for these processes, the imaginary part of the refractive index is typically two or more orders of magnitude smaller than the real part, reflectivity is not sensitive to them. Consequently, the continuum opacity can only be constrained by dedicated absorption measurements.
For olivines, previous far-infrared absorption measure-ments—as already mentioned—have mostly focused on the far-infrared bands and rarely discuss the continuum absorption. Exceptions are provided by Mennella et al. (1998) and Chihara et al. (2001), who performed also temperaturedependent measurements down to 24 K and liquid helium temperature, respectively. While Chihara et al. (2001) cover the wavelength range up to 100 μm (~70 μm at low temperatures), the measurements of Mennella et al. (1998) extend to 2 mm in wavelength. Both find a steepening of the absorption decay at a low temperatures. The absolute values of the absorption index at low temperature, however, differ significantly, which may result from the different samples (forsterite and Fo90 olivine, respectively, see Table 1). On the other hand, both investigations used powder samples embedded in polyethylene (PE) pellets for the measurements. Imai et al. (2009) have demonstrated that such data depend on the shape and the crystal quality (lattice defects) of the powder. In order to obtain data with less dependence on these factors, we present here measurements of the temperature-dependent absorption coefficient using bulk olivine plates. Powder measurements are carried out for comparison. Section 2 describes our measurement set-up and method. In Section 3 we present the absorption spectra obtained, and in Section 4, we discuss the derived temperature-dependent opacity values in relation to those obtained by other authors.
We measured the absorption from two polished crystal plates, which were cut from olivine crystals from San Carlos (Arizona), having the composition Mg1.78Fe0.22SiO4. The thicknesses of the plates were 0.8 mm and about 3.6 mm, respectively. The plates were not crystallographi-cally oriented. Thus, an arbitrary mixture of contributions from vibrational excitations along all three crystal axes have been measured in the absorption spectra. However, we note that the continuum absorption coefficients, predicted by the optical constants published by Fabian et al. (2001) and Suto et al. (2006), are very similar for the principal crystallo-graphic directions. We assume that additional low-energetic excitations would not impose a strong anisotropy, and that the absorption coefficient averaged over the crystal orientations is a meaningful quantity within some limits.
The measurements have been performed with a Bruker 113v FTIR spectrometer using mylar beamsplitters of 12-μ m and 23-μ m thickness, a DTGS detector with PE window, and globar and Hg-lamp sources. This resulted in a wavelength range of 50 μ m to about 400 μ m, in which the spectra have been taken. The olivine samples were cooled down by a liquid helium continuous-flow cryostat with PE windows, inserted into the sample chamber of the spectrometer to measure the transmission through the samples. The cryostat allowed for the removal of the samples from the beam for reference measurements at each temperature. Measurements have been performed at room temperature, 200 K, 100 K, and 10 K for the thinner plate, and at 200 K, 150 K, 100 K, and 10 K for the thicker plate. At room temperature, the 3.6-mm plate was opaque in (more or less) the whole wavelength range.
Besides the absorption from the samples, additional losses to the transmitted spectrometer beam arose from the reflection at the plate surfaces. According to the optical constants derived by Fabian et al. (2001), the average refractive index at λ = 100 μ m of olivine is 2.66, resulting in a reflection loss of 20.6% per surface, which decreases slightly at longer wavelengths (about 19.7% at λ = 300 μ m) and increases slightly at shorter ones. These values depend slightly on the unknown orientation of the plates and have thus to be considered somewhat uncertain (by ±2%), consequently limiting the sensitivity of the measurements to small absorption losses.
Moreover, we found that an additional significant loss of intensity occurred with the thicker plate, which was due to refraction of the beam, caused by a slight non-parallelity of the plate surfaces 1 Footnote 1. Unfortunately, we were not able to determine the magnitude of this loss independently. It also cannot be excluded that the same effect has a small influence (≤3%) on the measurements with the thinner plate as well.
Both the refraction and reflection losses result in additive contributions to the derived absorption coefficient spectra. Consequently, we consider the data obtained with the thinner plate to be uncertain by a (wavelength- and temperature-independent) error of ±0.4–0.6 cm−1, the first value corresponding to the reflectivity error, the second to the possible refraction loss. Fortunately, there was sufficient overlap of the spectra measured with the thicker and thinner plates, so that we could normalize the former data to the latter at wavelengths where the values were a factor of 5 to 10 higher than the mentioned error limit. Identical additive corrections were applied to the spectra measured at all temperatures, resulting in a satisfactory agreement of the slopes of the spectra in the overlap region. Consequently, we assume the data obtained from the thicker plate to have approximately the same possible error of about 1 cm−1 (in this case corresponding to 20% transmission) after the normalization. However, this still means that the slope of the spectra and the absolute values are extremely uncertain at long wavelengths and at low temperatures (see the error bars in Fig. 1).
For comparison, we have measured the spectral absorption of hand-milled olivine powder embedded in polyethylene (PE) pellets from Imai et al. (2009) at low temperatures down to 10 K. We used one of their original pellets with a column density of σ = 2.83 mg/cm2 embedded at a mass ratio of 3.14 wt.% of olivine in PE. A pure PE pellet of the same thickness was used for measuring a reference spectrum, by which the sample transmission spectrum T (λ) was normalized.
Figure 1 shows the resulting absorption spectra in terms of the linear absorption coefficient α. For the powder spectra, we have converted the mass absorption coefficient κ = ln(1/T)/σ into the linear absorption coefficient by multiplying with the mass density of olivine (ρ = 3.3 g/cm3) and dividing by a correction factor of f e = 0.776. This factor converts the linear absorption coefficient of bulk material into the volume-normalized absorption cross-section of ellipsoidal olivine particles (refractive index n = 2.66) embedded in PE (refractive index n m = 1.52) (CDE model- Bohren and Huffman, 1983), provided that the particles are only weakly absorbing 2 Footnote 2. Because the hand-milled olivine particles have irregular grain shapes according to Imai et al. (2009), we consider the CDE model to be appropriate. For spherical particles, the correction factor would be smaller 3 Footnote 3, resulting in increased α values.
The comparison of the spectra reveals significant differences between bulk (olivine plate) data and pellet data. While the α-value measured at room temperature for the former is about 20 cm−1 at λ = 100 μ m (see Fig. 1), the value obtained for the pellet is higher by about a factor of 3.5. At 10 K and the same wavelength, we find α = (1.5 ± 1) cm−1 for the olivine plate, but a value around 35 cm−1 for the pellet, which is about 20 times higher. If these values are compared with calculated absorption coefficients based on the room-temperature optical constants by Fabian et al. (2001)—which result from Lorentzian oscillator fits to reflectivity measurements of olivine crystals—we find a relatively good agreement to the plate measurements. Actually, the reflectivity data give even smaller absorption coefficients (by a factor of 1.7, see Fig. 1, for averaged crystal orientation), for which one explanation could be that Fabian et al. measured an olivine with a lower iron content (Fo92, from Stubachtal, Austria). The forsterite data by Suto et al. (2006) would give a value which is even smaller by a factor of about 2.5 than that of the Fo92 olivine.
Consequently, the pellet data seem to suffer from additional losses, which amount here to 35–50 cm−1 in terms of ρ or to about 8–12 cm2/g in terms of κ (at λ = 100 μ m). We have to note that Imai et al. (2009) found lower mass absorption coefficients at λ = 100 μ m which were not reproduced by our measurements. At shorter wavelengths the data coincide, but beyond the 70-μ m absorption band the absorption falls more steeply in their data. This reflects the fact that, at these longer wavelengths, the absorption of these pellet samples is already quite small, so that it becomes sensitive, for example, to the reference values. We did not use exactly the same reference pellet as Imai et al. (2009), so that deviations are likely to arise from this difference in the procedure. The absorption coefficient obtained by Imai et al. (2009) at λ = 100 μ m amounts to about 23 cm−1 at room temperature (if translated into α-values), which is almost the same as the bulk value measured with the plates. Although, at shorter wavelengths, the big difference between pellet and bulk measurements is definitely valid (a factor of about 3 at λ = 70 μ m, also with the Imai et al. data), a steep decrease beyond this wavelength is not excluded. This uncertainty does of course also affect the 10-K spectrum at these longer wavelengths.
In Table 1, we present a comparison of mass absorption coefficient data obtained by different authors. Data for olivines of different compositions are included, among them also data for pure forsterite measured by Suto et al. (2006) in reflection, and Chihara et al. (2001) measured as a powder in PE pellets. The data have been calculated (or corrected) again for the case of ellipsoidal particles (CDE model), this time assuming a vacuum environment and expressing them as the mass-normalized absorption coefficient (thus divided by the mass density of ρ = 3.3 g/cm3 for olivine). Other pellet data are from Fabian et al. (2001) and Mennella et al. (1998). All the pellet data have been read from graphs in the respective publications, in the case of Chihara et al. (2001) with a small extrapolation done simply by eye from 80-μ m to 100-μ m wavelength. Then, these data have been corrected for the influence of the embedding material (PE) by a factor of 0.765, resulting from the correction factors for embedded and non-embedded ellipsoidal particles of f e = 0.776 (see above) and f ne = 0.594 4 Footnote 4. We note that for spherical particles and , which means that the measured absorption of embedded spherical particles is almost equal to that of non-embedded ellipsoidal particles, while the values for non-embedded spherical particles would be smaller by about a factor of 2.
The values in Table 1 are given with a very low precision, taking into account the inexact way of reading from the figures and the extrapolations. However, they show clearly that bulk data result in much lower absorption coefficients than measured powder spectra. Imai et al. (2009) have demonstrated that irregular grain shapes and lattice distortion introduced by the production of small particles are reasons for increased long-wavelength absorption in powder measurements. However, irregular grain shapes are taken into account by the CDE model in our calculated data. Somewhat higher κ values could be imagined for very elongated grain shapes, but not above the limit of bulk absorption (f ne = 1.0). For the influence of lattice distortion, we note that the hand-milled olivine should have a relatively low lattice distortion, but we cannot exclude that the increased absorption of the powders originates from this effect.
The strong discrepancy between room-temperature pellet spectra and spectra simulated from their reflectivity data had also been noted by Fabian et al. (2001). In their data which extended to 100 μ m in wavelength, they did not see a steep decrease in absorption beyond 70 μ m as did Imai et al. (2009). At 100 μ m, they obtained a factor of 20 enhancement (after correction for the PE’s influence) with the pellets. They assigned this difference tentatively to scattering losses caused by agglomeration of the grains or by boundaries in the pellet. Agglomeration effects on far-infrared spectra had been modeled by Stognienko et al. (1995). They find enhancement factors of up to 3.5 for compact silicate aggregates, which is in agreement with our room-temperature results, but not with those of Fabian et al. and not with our results at low temperatures. Scattering from the polyethylene matrix may thus be another major contribution, although warm-pressed PE pellets are rather homogeneous. We suggest that this enhancement effect should be studied more thoroughly if pellets continue to be used for continuum opacity measurements in future.
The 100-μ m mass absorption coefficient derived from our olivine-plate measurements shows the largest decrease at 10 K compared with 300 K of all data in Table 1. This decrease is connected with an extreme steepening of the spectrum in the wavelength range 50–100 μ m (see Fig. 1). Chihara et al. (2001) have noted such a steepening also in their powder measurements of forsterite. At liquid helium temperature, they derive a power-law exponent of about β = 5.0 for the spectral dependence. In our data, the slope is even steeper in this wavelength range. This could be related to the long-wavelength wings of the lattice-vibration bands at shorter wavelengths (especially at 33 μ m and 50 μ m) and should probably not be taken as a continuum slope. The mentioned bands sharpen at lower temperatures and shift to shorter wavelengths, which will likely result in a steepening of the spectrum in the range of their long-wavelength wings. The slope in this wavelength range may therefore strongly depend on the orientation of the crystal. Unfortunately, we cannot check this effect for olivine by simulations because low-temperature optical constants are not available. When using the optical constants of forsterite at 50 K by Suto et al. (2006), we do not observe this effect (see Fig. 1). However, forsterite bands are located at shorter wavelengths and are somewhat sharper, so that their long-wavelength wings may be of less influence. We are unable to clarify this issue at the present time.
On the other hand, we have to expect that phonon-difference processes 5 Footnote 5 may contribute to the far-infrared absorption. These contributions should disappear at low temperatures due to freezing of the phonon excitations. They may account for part of the deviation of our room-temperature data from the spectrum simulated from the reflectivity-based Lorentzian oscillator model. In our room-temperature data, the spectral slope appears to be somewhat shallower than the β = 2.0 of the oscillator model. At 200 K and 150 K, it seems to converge to β ~ 2.0 for wavelengths beyond 100 μ m. Whether this remains true for lower temperatures, as the forsterite oscillator model suggests, cannot yet be decided because of the limitations in our data (see Section 2). They are so far both consistent with β = 2.0, or with a steeper slope at λ < 100 μ m.
The far-infrared continuum spectrum of olivine is still not well understood. Transmission measurements of thin plates result in much lower absorption coefficients than measurements of powders embedded in PE pellets and may provide more reliable absorption index data. The spectral range below 100 μ m requires further investigations to clarify the origin of the very steep spectral slope measured at low temperature. For the range above 100 μ m, it is not yet known whether this steep slope will continue, or whether it will change to the value of β = 2.0 that is usually assumed based on Lorentzian oscillator models. However, it has to be expected that low-energetic excitations need to be considered, in addition to these models. Measurements on olivine plates with a thickness of centimeters may be required in further studies.
If the emissivity of olivine is confirmed to be as small as derived from the plate measurements, olivine will hardly contribute to the emission of cold dust mixtures if, for example, amorphous silicates are present as well. Vice versa, crystalline olivine dust could be perfectly hidden behind the thermal emission of other cold dust components.
1This was discovered by a non-reproducible signal after removing and remounting the sample, due to different degrees of deflection of the beam depending on the orientation of the sample, it happened only with the thicker plate.
2Within this limit, the volume-normalized absorption cross-section of embedded particles in the CDE model is given by , while the bulk linear absorption coefficient is k × Im(ϵ)/n, with k being the wavenumber.
3For spherical particles, the volume-normalized absorption cross-section of weakly absorbing embedded particles is .
4This value is simply obtained by setting n m = 1 in the formula for f e (footnote 2).
5Phonon-difference process: excitation of a lattice vibration mode during the simultaneous destruction of a lower-energetic one, allowed by the anharmonic lattice potentials, see Henning and Mutschke (1997).
Bohren, C. F. and D. R. Huffman, Absorption and Scattering of Light by Small Particles, John Wiley, New York, 1983.
Bowey, J. E., M. J. Barlow, F. J. Molster, A. M. Hofmeister, C. Lee, C. Tucker, T. Lim, P. A. R. Ade, and L. B. F. M. Waters, The 69-μ m forsterite band as a dust temperature indicator, Mon. Not. R. Astron. Soc,331, L1–L6, 2002.
Chihara, H., C. Koike, and A. Tsuchiyama, Low-temperature optical properties of silicate particles in the far-infrared region, Publ. Astron. Soc. Jap.,53, 243–250, 2001.
de Vries, B. L., B. Acke, J. A. D. L. Blommaert, C. Waelkens, L. B. F M. Waters, B. Vandenbussche et al., Comet-like mineralogy of olivine crystals in an extrasolar proto-Kuiper belt, Nature,490,74, 2012.
Eiroa, C, J. P. Marshall, A. Mora, A. V. Krivov, B. Montesinos, O. Absil, D. Ardila, M. Arévalo, J.-Ch. Augereau, and A. Bayo, Herschel discovery of a new class of cold, faint debris discs, Astron. Astrophys.,536, L4, 2011.
D. Ardila, M. Arévalo, J.-Ch. Augereau, and A. Bayo, Herschel discovery of a new class of cold, faint debris discs, Astron. Astrophys.,536, L4, 2011.
Fabian, D., T. Henning, C. Jäger, H. Mutschke, J. Dorschner, and O. Wehrhan, Steps toward interstellar silicate mineralogy. VI. Dependence of crystalline olivine IR spectra on iron content and particle shape, Astron. Astrophys.,378, 228–238, 2001.
Gail, H.-P, Formation and evolution of minerals in accretion disks and stellar outflows, in Astromineralogy, edited by Th. Henning, 55 pp., Springer, Berlin, 2003.
Henning, T. and H. Mutschke, Low-temperature infrared properties of cosmic dust analogues, Astron. Astrophys.,327,743–754, 1997.
Imai, Y, C. Koike, H. Chihara, K. Murata, T. Aoki, and A. Tsuchiyama, Shape and lattice distortion effects on infrared absorption spectra of olivine particles, Astron. Astrophys.,507, 277–281, 2009.
Juhász, A., J. Bouwman, Th. Henning, B. Acke, M. E. van den Ancker, G. Meeus, C. Dominik, M. Min, A. G. G. M. Tielens, and L. B. F. M. Waters, Dust evolution in protoplanetary disks around Herbig Ae/Be stars? the Spitzer view, Astrophys. J.,721, 431–455, 2010.
Koike, C, H. Mutschke, H. Suto, T. Naoi, H. Chihara, Th. Henning, C. Jäger, A. Tsuchiyama, J. Dorschner, and H. Okuda, Temperature effects on the mid-and far-infrared spectra of olivine particles, Astron. Astrophys.,449, 583–596, 2006.
Krivov, A. V, S. Muller, T. Löhne, and H. Mutschke, Collisional and thermal emission models of debris disks: Toward planetesimal population properties, Astrophys. J.,687, 608–622, 2008.
Mennella, V, J. R. Brucato, L. Colangeli, P. Palumbo, A. Rotundi, and E. Bussoletti, Temperature dependence of the absorption coefficient of cosmic analog grains in the wavelength range 20 microns to 2 millimeters, Astrophys. J.,496, 1058–1066, 1998.
Molster, F J., L. B. F M. Waters, A. G. G. M. Tielens, C. Koike, and H. Chihara, Crystalline silicate dust around evolved stars. III. A correlations study of crystalline silicate features, Astron. Astrophys.,382, 241–255, 2002.
Olofsson, J., A. Juhász, Th. Henning, H. Mutschke, A. Tamanai, A. Moór, and P. Ábrahám, Transient dust in warm debris disks. Detection of Fe-rich olivine grains, Astron. Astrophys.,542, A90, and 547, C1, 2012.
Pitman, K. M., A. M. Hofmeister, and A. K. Speck, Revisiting astronomical crystalline forsterite in the UV to near-IR, Earth Planets Space,65, 129–138, 2013.
Stognienko, R., T. Henning, and V Ossenkopf, Optical properties of coagulated particles, Astron. Astrophys.,296,797, 1995.
Sturm, B., J. Bouwman, Th. Henning, N. J. Evans, B. Acke, G. D. Mulders, L. B. F. M. Waters, E. F. van Dishoeck, G. Meeus, J. D. Green et al., First results of the Herschel key program “Dust, Ice and Gas In Time” (DIGIT): Dust and gas spectroscopy of HD 100546, Astron. Astrophys.,518, L129, 2010.
Sturm, B., J. Bouwman, Th. Henning, N. J. Evans, L. B. F. M. Waters, E. F. van Dishoeck et al., The 69 μ m forsterite band in spectra of protoplanetary disks. Results from the Herschel DIGIT programme, Astron. Astrophys.,553, A5, 2013.
Suto, H., H. Sogawa, S. Tachibana, C. Koike, H. Karoji, A. Tsuchiyama, H. Chihara, K. Mizutani, J. Akedo, K. Ogiso et al., Low-temperature single crystal reflection spectra of forsterite, Mon. Not. R. Astron. Soc,370, 1599–1606, 2006.
Zeidler, S., T. Posch, H. Mutschke, H. Richter, and O. Wehrhan, Near-infrared absorption properties of oxygen-rich stardust analogs. The influence of coloring metal ions, Astron. Astrophys.,526, A68, 2011.
We thank Gabriele Born, Walter Teuschel, and Dirk Fabian for preparational work and help with the measurements. We are grateful to Yuta Imai for providing his samples for comparison measurements. H. M. and S. Z. gratefully acknowledge support by the Deutsche Forschungsgemeinschaft by grant MU 1164/7 within the priority programme “The First 10 Million Years of the Solar System”.
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Mutschke, H., Zeidler, S. & Chihara, H. Far-infrared continuum absorption of olivine at low temperatures. Earth Planet Sp 65, 10 (2013). https://doi.org/10.5047/eps.2013.07.003
- Far-infrared absorption | 0.847415 | 3.75905 |
The ESA's Rosetta spacecraft has crash landed on the surface of comet 67P/Churyumov–Gerasimenko. This brings an end to its 16-year journey across the solar system, having travelled over four billion miles since its launch in 2004.
"Rosetta has entered the history books once again," said Johann-Dietrich Wörner, ESA's Director General. "Today we celebrate the success of a game-changing mission, one that has surpassed all our dreams and expectations, and one that continues ESA's legacy of 'firsts' at comets."
The "collision manoeuvre" saw the spacecraft dive 19km, taking high-resolution images of the comet along the way. It began descending on the evening of 29 September, with the final instructions sent to Rosetta at 8.55am BST. This was to "fine-tune the spacecraft's pointing" ready for impact.
Rosetta was sent to Comet 67P in order to study the make-up of these bodies. The historic mission saw the spacecraft deploy the lander Philae to the surface of the comet, allowing it to analyse the dust and composition of comets – something that will aid our understanding of the evolution of the universe.
The decision to crash Rosetta into the comet was taken after the spacecraft's power began fading, meaning it would no longer be able to transmit back data – and therefore no longer be useful scientifically. Instead of allowing it to fade away, the ESA decided to make its final days useful by getting high-resolution images of the comet that can be studied for years to come.
Upon contact, the spacecraft will shut down. "After Rosetta has touched down, it will not be possible to collect or return any additional data," the ESA said. "The unique measurements obtained during this final descent will be a fitting closing chapter to Rosetta's time spent living with this comet."
Dr Geraint Morgan, of the Open University who worked on a range of Rosetta's instruments, said: "This mission has required over 20 years of effort, as teams designed and then built instruments and spacecraft prior to launch in 2004. We then chased the comet for 10 years over four billion miles across the solar system, so today will be a bittersweet day for many of us."
"This mission was the first to successfully land on a comet. On-board the Philae lander was the Ptolemy Instrument, developed at The Open University and RAL Space in Harwell, which along with the COSAC instrument detected complex organic modules present on the comet surface.
"Space missions push the boundaries of science and technology ... Rosetta is a fantastic example of how an array of science disciplines can work together to expand human knowledge, which can then be applied to change and save lives here on Earth." | 0.848729 | 3.479901 |
The brightest globular cluster in the northern latitudes, the Globular Star Cluster in Hercules M13 (NGC 6205) shines at magnitude 5.8 and is visible to the naked eye from a dark sky site. It is approximately 20 arcminutes in diameter with around 300,000 stars. Located in western edge of the Keystone in the constellation of Hercules. It takes an 11-12″ telescope to resolve the stars decently, like diamond dust on black velvet. Go to a 14″ or larger at a dark sky site and it is a real treasure! The Great Hercules Globular Cluster of stars lies 22,200 light years from earth. This is roughly one quarter the width of our Milky Way Galaxy.
The larger galaxy, upper right-hand corner is NGC 6207 at magnitude 12.2 , 3 x 1.2 arcminutes and 45 million Light years distant, about the distance of the Virgo Galaxy Group . The smaller galaxy, just to the upper right of the globular cluster, in between M13 and NGC 6207. This galaxy is IC 4617 magnitude 15.5, 1.2′ x 22″, at 489 million light years away. A visually challenging object through an eyepiece.
DSLR (Digital Single Lens Reflex) cameras are really opening new doors in astrophotography and the Canon 20d and 20da really preform. Currently in 2018, the Canon 6d (full size) and 7d Mark II (APS) have really made monumental strides in Resolution, QE (Quantum Efficiency), Noise, etc.
2 film exposures 45 min. ea; manual guiding FS/78; 10 DSLR
Slides scanned Nikon 5000 @ 4000dpi 16bit (130 MB files) 3 images stacked; processed in Photoshop CS5 AIP & CCDStack DSLR images stacked with film in CCDStack
7/25/2003 & 8/20/2004
Oregon Star Party 120° 09′ W 44° 18′ N Indian Trail Springs, Ochoco National Forest (Also Eagles Rest 25 miles SE of Dexter, Or.)
5000′ magnitude 6.2 Skies; Clear & Steady
The Pleiades Open Star Cluster M45 is a well known naked eye Open Star Cluster in the constellation of Taurus (The Bull). The Pleiades is a young open cluster of stars enshrouded in gas and dust which is illuminated by several bright stars. Also know as the Seven Sisters covering an area of 2° and lying a mere 415-444 light years away. In fact through binoculars you can see nine prominent stars, two of which are the parents of the seven sisters. The stars are of varying brightness and distances from Earth. They vary from Magnitude 2.9 Alcyone 240 ly to Celaeno magnitude 5.5 and 590 ly distant.
The bright stars are middle aged hot B type Blue stars forming the closets star cluster to earth. They formed approximately 100 million years ago. The nebula is not related to the stars and is just illuminated interstellar dust.
This formation of stars (6) is know as Subaru in Japan (to unite). It was chosen as Subaru brand of cars which united 5 companies into one thus the 6 stars depicted for their logo. | 0.801583 | 3.24023 |
Since its discovery was announced in August of 2016, Proxima b has been an endless source of wonder and the target of many scientific studies. In addition to being the closest extra-solar planet to our Solar System, this terrestrial planet also orbits within Proxima Centauri’s circumstellar habitable zone (aka. “Goldilocks Zone”). As a result, scientists have naturally sought to determine if this planet could actually be home to extra-terrestial life.
Many of these studies have been focused on whether or not Proxima b could retain an atmosphere and liquid water on its surface in light of the fact that it orbits an M-type (red dwarf) star. Unfortunately, many of these studies have revealed that this is not likely due to flare activity. According to a new study by an international team of scientists, Proxima Centauri released a superflare that was so powerful, it would have been lethal to any life as we know it.
The study, titled “The First Naked-Eye Superflare Detected from Proxima Centauri“, recently appeared online. The team was led by Howard Ward, a PhD candidate in physics and astronomy at the UNC Chapel Hill, with additional members from the NASA Goddard Space Flight Center, the University of Washington, the University of Colorado, the University of Barcelona and the School of Earth and Space Exploration at Arizona State University.
As they indicate in their study, solar flare activity would be one of the greatest potential threats to planetary habitability in a system like Proxima Centauri. As they explain:
“[W]hile ozone in an Earth-like planet’s atmosphere can shield the planet from the intense UV flux associated with a single superflare, the atmospheric ozone recovery time after a superflare is on the order of years. A sufficiently high flare rate can therefore permanently prevent the formation of a protective ozone layer, leading to UV radiation levels on the surface which are beyond what some of the hardiest-known organisms can survive.”
In addition stellar flares, quiescent X-ray emissions and UV flux from a red dwarf star can would be capable of stripping planetary atmospheres over the course of several billion years. And while multiple studies have been conducted that have explored low- and moderate-energy flare events on Proxima, only one high-energy event has even been observed.
This occurred on March of 2016, when Proxima Centauri emitted a superflare that was so bright, it was visible to the naked eye. This flare was observed by the Evryscope, an array of telescopes – funded through the National Science Foundation‘s Advanced Technologies and Instrumentation (ATI) and Faculty Early Career Development (CAREER) programs – that is pointed at every part of the accessible sky simultaneously and continuously.
As the team indicates in their study, the March 2016 superflare was the first to be observered from Proxima Centauri, and was rather powerful:
“In March 2016 the Evryscope detected the first-known Proxima superflare. The superflare had a bolometric energy of 10^33.5 erg, ~10× larger than any previously-detected flare from Proxima, and 30×larger than any optically measured Proxima flare. The event briefly increased Proxima’s visible-light emission by a factor of 38× averaged over the Evryscope’s 2-minute cadence, or ~68× at the cadence of the human eye. Although no M-dwarfs are usually visible to the naked-eye, Proxima briefly became a magnitude-6.8 star during this superflare, visible to dark-site naked-eye observers.”
The superflare coincided with the three-month Pale Red Dot campaign, which was responsible for first revealing the existence of Proxima b. While monitoring the star with the HARPS spectrograph – which is part of the 3.6 m telescope at the ESO’s La Silla Observatory in Chile – the campaign team also obtaining spectra on March 18th, 08:59 UT (just 27 minutes after the flare peaked at 08:32 UT).
The team also noted that over the last two years, the Evryscope has recorded 23 other large Proxima flares, ranging in energy from 10^30.6 erg to 10^32.4 erg. Coupled with rates of a single superflare detection, they predict that at least five superflares occur each year. They then combined this data with the high-resolution HARPS spectroscopy to constrain the superflare’s UV spectrum and any associated coronal mass ejections.
The team then used the HARPS spectra and the Evryscope flare rates to create a model to determine what effects this star would have on a nitrogen-oxygen atmosphere. This included how long the planet’s protective ozone layer would be able to withstand the blasts, and what effect regular exposure to radiation would have on terrestrial organisms.
“[T]he repeated flaring is sufficient to reduce the ozone of an Earth-like atmosphere by 90% within five years. We estimate complete depletion occurs within several hundred kyr. The UV light produced by the Evryscope superflare therefore reached the surface with ~100× the intensity required to kill simple UV-hardy microorganisms, suggesting that life would struggle to survive in the areas of Proxima b exposed to these flares.”
Essentially, this and other studies have concluded that any planets orbiting Proxima Centauri would not be habitable for very long, and likely became lifeless balls of rock a long time ago. But beyond our closest neighboring star system, this study also has implications for other M-type star systems. As they explain, red dwarf stars are the most common in our galaxy – roughly 75% of the population – and two-thirds of these stars experience active flare activity.
As such, measuring the impact that superflares have on these worlds will be a necessary component to determining whether or not exoplanets found by future missions are habitable. Looking ahead, the team hopes to use the Evryscope to examine other star systems, particularly those that are targets for the upcoming Transiting Exoplanet Survey Satellite (TESS) mission.
“Beyond Proxima, Evryscope has already performed similar long-term high-cadence monitoring of every other Southern TESS planet-search target, and will therefore be able to measure the habitability impact of stellar activity for all Southern planetsearch-target M-dwarfs,” they write. “In conjunction with coronal-mass-ejection searches from long- wavelength radio arrays like the [Long Wavelength Array], the Evryscope will constrain the long-term atmospheric effects of this extreme stellar activity.”
For those who hoped that humanity might find evidence of extra-terrestrial life in their lifetimes, this latest study is certainly a letdown. It’s also disappointing considering that in addition to being the most common type of star in the Universe, some research indicates that red dwarf stars may be the most likely place to find terrestrial planets. However, even if two-thirds of these stars are active, that still leaves us with billions of possibilities.
It is also important to note that these studies help ensure that we can determine which exoplanets are potentially habitable with greater accuracy. In the end, that will be the most important factor when it comes time to decide which of these systems we might try to explore directly. And if this news has got you down, just remember the worlds of the immortal Carl Sagan:
“The universe is a pretty big place. If it’s just us, seems like an awful waste of space.”
Further Reading: arXiv | 0.911274 | 3.90755 |
The world of astronomy has always been indebted to amateur astronomers for their priceless contribution to the field of astronomy. Big organizations like NASA are constantly working in the field of space exploration and research. They have heavy, modern and quality telescopes and other gears for their research. Yet the history is full of numerous examples of amateur astronomers who with their portable telescopes and limited capability, have made some amazing and path defining contributions in the field of astronomy and space exploration. These people not only contributed to the astronomy but also opened new possibilities to the scientist to understand and explore the vast space.
So here is a list of 5 such path defining and startling discoveries made by amateur astronomers. Which changed the course of astronomy and opened new horizons of space knowledge. Many such discoveries made by amateur astronomers. We are providing you with our best 5 choices. We hope you like, enjoy and learn from them and take inspiration for space exploration yourself.
Discovery of NGC 253-DW2 Galaxy by Micheal Sidonio:
In 2013 Micheal Sidonio who is a strong man competitor and also an amateur astronomer was gazing at NGC 253 galaxy from his portable telescope. He was sitting in a farmer’s filed in Canberra Australia. Suddenly he noticed something that he was sure not seen before. This led to the discovery of a completely new galaxy altogether. Which was after verification named NGC 253-dw2. It was indeed a revolutionary discovery for scientists. The newly discovered galaxy was on the verge of being destroyed by the larger neighboring galaxy. This helped the scientists to conclude that the larger galaxies were in fact made from smaller ones.
Discovery of Uranus by William Herschel:
Uranus was discovered by William Hershel (well-known and respected astronomer now) when he was still an amateur astronomer in 1781. He was, in fact, a music director in the UK at that time. When he was gazing at the sky at night through his telescope searching for double stars, he saw a fuzzy disk-shaped object. He initially thought that it was a comet. But after several nights he saw the same object. Then he became determined that it was not a comet as it was moving too slow.
Through his calculation and after studying the brightness pattern of the object, he was sure that it was positioned beyond Saturn. This is when it dawned on him that he has discovered the farthest planet of the solar system ‘Uranus’. Interestingly it was also the first planet to be discovered that was invisible to the naked eye.
Discovery of the Hale-Bopp comet by Alan Hale and Thomas Bopp:
This was an amazing and interesting discovery because it was done by two different people. Independent of each other but at the same time. On July 23, 1995, Alan Hale and Thomas Bopp who were both amateur astronomers. Both were stars gazing with their own best portable telescopes when their lives changed forever. They discovered the comet which later came to be known as ‘Hale-Bopp comet’. The interesting thing was that they were completely unaware of each other making the same discovery.
Both of them were gazing at the M70 cluster when they saw a never seen before the object. Through its speed, they were determined that it was a comet. Later the International Astronomical Union’s Central Bureau for Astronomical Telegrams confirmed their sightings.
Discovery of 42 planets by amateur astronomers ‘The Planet Hunters’:
In the year 2012, a group of amateur astronomers who have named their group as planet hunters made a startling discovery of not one or two but 42 planets which were not known before to mankind. 15 of these planets were located in the goldilocks zone, which means that their distance from their ‘sun’ or the star they orbit was perfect for supporting life. One particular planet in this zone, which was named PH2 b, is of the same size as Jupiter, though in itself was unlikely to sustain life because of its big size, some of this planets moon is thought to be ideal to sustain life.
Discovery of Cosmic Ghost by Hanny Van Arkel:
In 2007 amateur astronomer and school teacher Hanny Van Arkel was going through the photographs of the galaxies taken with the best telescopes that were on the internet. This is when she made the mind-blowing discovery. Which created ripples in the astronomical world. She discovered a huge hole in the center of mass of bright gas, which she thought to be an irregular galaxy. Astronomers were so fascinated by her discovery that they named it the ‘Cosmic Ghost’.
It is now thought to be a result of the eruption of a black hole. Her discovery was among the significant examples of the power of amateur astronomy. She is also an inspiration to the future generations of kids, who themselves can take their best telescopes for kids and start the amazing journey of space discoveries.
In the field of astronomy, Amateur astronomers are looked on with great respect. Many of the greatest discoveries in astronomy are due to the sheer dedication and excitement of the amateur astronomers. They can be anyone from a school teacher to a construction engineer and from a policeman to a student. The sheer joy of gazing at the night sky with the best portable telescope is irresistible to many. These enthusiasts lead to some amazing and wonderful space discoveries.
Now as the telescopes are coming within the budget and the apparatus like equatorial tracking mount for astrophotography easily available online, more and more people are joining this interesting hobby. Even the inclination of kids is increasing with each day in sky gazing and astrophotography. Parents also cater to their kid’s needs and buy them the best telescopes for kids to satisfy their thirst for space exploration. In short, it is the best time for amateur astronomers. | 0.913014 | 3.225296 |
Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have spotted a circumplanetary disk around a still-forming gaseous exoplanet called PDS 70c.
Source: Sci News
“For the first time, we can conclusively see the telltale signs of a circumplanetary disk, which helps to support many of the current theories of planet formation,” said Dr. Andrea Isella, an astronomer at Rice University.
PDS 70, also known as V1032 Cen, is a K7-type star at a distance of about 370 light-years.
The star is only 5.4 million years old, slightly smaller and less massive than our Sun, and it hosts at least two young gas giants.
The planets are 5-10 times larger than Jupiter, and the innermost, PDS 70b, orbits about 1.8 billion miles from the star, roughly the distance from the Sun to Uranus. PDS 70c is a billion miles further out, in an orbit about the size of Neptune’s.
“Planets form from disks of gas and dust around newly-forming stars, and if a planet is large enough, it can form its own disk as it gathers material in its orbit around the star,” Dr. Isella said.
“Jupiter and its moons are a little planetary system within our Solar System, for example, and it’s believed Jupiter’s moons formed from a circumplanetary disk when Jupiter was very young.”
But most models of planet formation show that circumplanetary disks disappear within about 10 million years, which means circumplanetary disks haven’t existed in the Solar System for more than 4 billion years.
To look for them elsewhere and gather observational evidence to test theories of planet formation, Dr. Isella and colleagues search for very young star systems where they can directly observe disks and the planets still forming inside them.
In the new study, the astronomers analyzed observations made by ALMA in 2017.
“There are a handful of candidate planets that have been detected in disks, but this is a very new field, and they are all still debated,” Dr. Isella said.
“PDS 70b and c are among the most robust because there have been independent observations with different instruments and techniques.”
The findings appear in the Astrophysical Journal Letters. | 0.885363 | 3.816615 |
This striking image combines data gathered with the Advanced Camera for Surveys, installed on the NASA/ESA Hubble Space Telescope and data from the Subaru Telescope in Hawaii. It shows just a part of the spectacular tail emerging from a spiral galaxy nicknamed D100.
Tails such as these are created by a process known as ram-pressure stripping. Despite appearances, the space between galaxies in a cluster is far from empty; it is actually filled with superheated gas and plasma, which drags and pulls at galaxies as they move through it, a little like the resistance one experiences when wading through deep water. This can be strong enough to tear galaxies apart, and often results in objects with peculiar, bizarre shapes and features — as seen here.
D100’s eye-catching tail of gas, which stretches far beyond this image to the left, is a particularly striking example of this phenomenon. The galaxy is a member of the huge Coma cluster. The pressure from the cluster’s hot constituent plasma (known as the intracluster medium) has stripped gas from D100 and torn it away from the galaxy’s main body, and drawing it out into the plume pictured here.
Densely populated clusters such as Coma are home to thousands of galaxies. They are thus the perfect laboratories in which to study the intriguing phenomenon of ram-pressure stripping, which, as well as producing beautiful images such as this, can have a profound effect on how galaxies evolve and form new generations of stars. | 0.809826 | 3.727299 |
Today, Monday June 27 at about 17:00 UT, the asteroid designated 2011 MD will pass only 12,300 kilometers (7,600 miles) above the Earth's surface. The asteroid was discovered by Linear survey with a 1.0-m f/2.15 reflector + CCD on June 22, 2011 at magnitude 18.9.
This object is only 5-20 meters in diameter and it is in a very Earth-like orbit around the Sun. Additional observations have made it possible to exclude that this object is a piece of space junk, as was suggested early on. Calculation by Bill Gray, a well-known expert on orbital dynamics, shows that this asteroid could not have been close enough to Earth any time during the space age to have started off as a rocket booster.
Trajectory of 2011 MD from the general direction of the Sun
We have been able to follow-up this object few hours ago remotely from the GRAS Observatory (near Mayhill, NM) through a 0.25-m, f/3.4 reflector + CCD and from the Faulkes Telescope South through a 2.0-m f/10.0 Ritchey-Chretien + CCD.
At the moment of our images from New Mexico on June 27, 06:50UT, "2011 MD" was moving at about 132"/min and its magnitude was ~15. While the images from FTS were obtained on June 27, 09:30UT when the asteroid was moving at about 176"/min and its magnitude was ~14.5.
At the moment of its close approach later today, 2011 MD will be bright as magnitude ~11.8
Below you can see our image taken with the 0.25-m, f/3.4 reflector + CCD in New Mexico, while 2011 MD was passing nearby a bright star (click on the image for a bigger version):
Here you can see a single 20-second exposure + RGB filter image taken by 2 meters telescope at Faulkes Telescope South (click on the image for a bigger version):
While this is an animation showing the object movement in the sky. Each image was 20-second exposure with Faulkes Telescope South 2 meters telescope. Click on the thumbnail to see a bigger version:
2011 MD's Earth flyby will be a close shave, but not a record for nearby passing asteroids. The record is currently held by the asteroid 2011 CQ1, which came within 5,480 kilometers of Earth on Feb. 4 of this year. See our previous post on this object:
by Ernesto Guido, Nick Howes and Giovanni Sostero | 0.838472 | 3.554504 |
The last thing the planets around the red dwarf star TRAPPIST-1 need is abundant sunshine. Active eruptions and flares from the star would wreak havoc on the rocky planets in orbit. But fortunately, the outer planets might be safe from this barrage of high-energy space weather.
According to a new study in the Proceedings of the National Academy of the Sciences, the outer planets of the system could cling on to their atmospheres. This finding is despite previous studies showing that TRAPPIST-1 might be so active that it blows away planetary atmospheres.
The planetary system was announced as a three planet system in 2016, with an early 2017 discovery bumping that number up to seven total planets. They range from between Mars' size to slightly larger than Earth, and at least three (if not all seven) of those planets could be habitable under the right conditions.
But TRAPPIST-1 is a red dwarf star. It's cooler, smaller, and more active than the sun. Stellar flares can erupt out to millions of miles, which is bad news if your outermost planet is only 5.5 million miles away and each planet is about a quarter-of-a-million-miles away from each other at closest approach.
The new results show that while all seven planets could retain their atmosphere, the more likely scenario is that the outermost two, -1g and -1h, have the best odds (and -1e and -1f have a weaker chance.)
Since -1g is within an Earth-like habitable zone, it could be the most promising candidate out of the seven to hold on to an atmosphere, which gives it a better chance of having liquid water on its surface—a key ingredient for life.
Further studies of the planet will be possible when the James Webb Space Telescope is active in 2019. It will be able to detect traces of the atmospheres of the planets, if there are any atmospheres, and provide a more concrete answer to whether or not they are in fact habitable worlds. | 0.907413 | 3.793044 |
Gottfried Leibniz may have discovered calculus, but really he had the soul of a novelist. You might be forgiven for thinking so, anyway, after reading Adam Ehrlich Sachs’s first novel, The Organs of Sense (227 pages; FSG), which tells the story of a young Leibniz, hungry to understand the world, its inscrutable rules, and its even more inscrutable inhabitants. You might also see the novelistic sensibility in Leibniz’s philosophy. Calculus offered a neat method for the world and its rules, but neat methods aren’t all that useful unless you’re trying to ace the SATs or go to the moon. It’s a genuine boon to human thought that Leibniz’s groundbreaking work in mathematics did not get in the way of his inventing a rather batshit metaphysics of his own, the Monadology, which basically posits a simple substance—the monad—endowed with intention and appetite, busy at work acting as the substrate of the universe. Luckily for Sachs, it’s quite possible, probably even necessary, to be a world-historical genius with an innate understanding of the underlying structure of the universe and a weirdo with a crackpot theory.
Here’s some Monadology:
Since the world is a plenum all things are connected together, and every body acts upon every other, more or less, according to their distance, and is affected by the other through reaction. Hence it follows that each Monad is a living mirror, or a mirror endowed with inner activity, representative of the universe according to its point of view.
It’s just about the perfect metaphor for human interaction and, even though it doesn’t appear in the novel, it’s the kind of deep background that might have made Leibniz an especially appealing investigator into unusual phenomena. The Organs of Sense opens with word reaching a young Leibniz, fresh off a failed attempt at a law degree, of a mysterious astronomer’s prediction:
At noon on the last day of June 1666, the brightest time of day at nearly the brightest time of year, the Moon would pass very briefly, but very precisely, between the Sun and Earth, casting all of Europe for one instant in absolute darkness, ‘a darkness without equal in our history, but lasting no longer than four seconds,’ the astronomer predicted, according to Leibniz, an eclipse that no other astronomer in Europe was predicting…
Note the coiled sentence structure, slightly parodic academic tone, and nested narration—all constant features of the novel. Leibniz’s every thought and action is mediated by a conjectural scrim, and the narrator sometimes draws on extant writings or other, more spurious, attributed language. This narrative voice does, in fact, belong to a character—there is an “I” attached—but the absence of a locus of narration or any identifying clues (except that he is a translator, which is mostly a recurring half-joke) makes it hard not to make your inner novelist queasy by throwing up your hands and saying it’s probably just Sachs himself.
Always get the last word.
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The astronomer, who claims to possess “the longest telescope known to man, and therefore the most powerful, a telescope said to stretch nearly two hundred feet,” is not merely scientifically gifted but possibly oracular, “not merely completely blind…but in fact entirely without eyes.” Being “an assiduous inquirer into miracles and other aberrations of nature,” Leibniz sets off at once, and before too long he finds himself in the astronomer’s tower, somewhere in Bohemia, trying to figure out whether this eyeless man is off his rocker. How is he to know?
The problem of getting inside another head, and seeing what that head was seeing (or not seeing) and what it was thinking (or not thinking), now struck Leibniz as a profoundly philosophical problem. Neither cradling it nor cracking it open would do it, for the barrier involved not only bone but also a thick layer of philosophy. The human skull consists, one might say, Leibniz wrote, of a quarter-inch-thick layer of bone and a quarter-inch-thick layer of philosophy. Of course the brain is also cushioned by various membranes and fluids. A skilled doctor can penetrate the skull with a drill, and he can cut through the membranes with a knife, and he can drain the cerebral fluids with a pump, but his instruments are utterly useless for penetrating that solid, condensed layer of philosophy. “Even the most state-of-the-art medical instrument wielded by the best doctor in Paris will simply bounce off the cerebral-philosophical membrane,” Leibniz wrote. That left language.
Anyone who’s ever been stuck at a party trying to have a meaningful conversation with a philosophy student knows that a quarter inch can seem awfully thick, and language is itself an imperfect instrument. What follows is a self-consciously tangled pattern-building exercise, as the narrator relates the astronomer’s tale, as told to Leibniz, of how he lost his eyes—basically the story of his life as an aspiring chronicler of the cosmos in Bohemia. His father hopes to curry royal favor by presenting a show-stopping mechanical head to Emperor Rudolf, King of Bohemia, descendent of the august Habsburg lineage, and holder of sundry other titles. In the first great Greek tragedy of the astronomer’s life, he betrays his father in order to be installed as the Emperor’s Imperial Astronomer. There is genuine movement and pathos to this part of the story, but it mostly sets up a suspended preamble to the astronomer’s sudden turn into eyeless-ness, meaning it’s an opportunity for copious riffing. To wit:
Then his father went to bed and the astronomer—by the light of a single candle lit only after he heard his father’s sixth snore, for one snore could of course be faked, as could two snores or three, even four simulated snores is not unthinkable if his father had suspicions, and the idea of feigning five snores to catch your son in some verboten act is, if absurd, not impossible, whereas after six snores his father was probably asleep—read, for example, the portions of Friar Bacon’s Opus Majus concerning the physiology of vision or his Letter on the Secret Workings of Art and Nature with its depictions of those ingenious devices of antiquity that according to legend made distant things seem near or near things distant…
The same structure occurs later, when the astronomer slowly recognizes that a room containing a glockenspiel is actually a room containing many glockenspiels, in fact it is lousy with glockenspiels, basically a plenum of glockenspiels. Once the glockenspiel situation has been sorted out, the story continues.
Sachs runs these perspectival recursions often, and while all are smart and some very funny, many only have the tone of being funny, and don’t really work. When they do, though, they follow an absurd and exuberant logical momentum and accrete surprising valences, like a cartoon snowball rolling downhill. In one riff, a ditty about a butcher chopping a pig into limit-approaching sections (quarters, halves eighths, sixteenths, etc.) turns out to be an ode to the beautiful insanity of the infinite: “The song, [the astronomer] realized, had taken a mathematical turn.”
What is the point of all this? One of Sachs’s characters conveniently offers an explanation on his behalf, telling the astronomer that “the true artist walks straight toward the insignificant, while slyly keeping an eye on the significant, and moving at all times away from the gorgeous…” Indeed.
The astronomer finds himself caught up in some palatial intrigue having mostly to do with the Habsburg brats, whose names I couldn’t keep straight. Here, as the novel sprints toward the insignificant, it begins to wobble a bit. It’s not clear whether we’re supposed to care about this submerged plot, or even to follow it. The problem is not necessarily that these sections are syntactically convoluted or demanding. It’s that, as the voice luxuriates in its own convolutions, it teaches you to pay less attention, to gloss. I suspect Sachs knows where the reader’s attention is likely to ebb and flow, and, again, he suggests a larger reason: “One wants above all to understand the Sun,” says the astronomer, “but one cannot aim one’s telescope right at the Sun!” The “sun,” in this case, might also be the thing we want to communicate. Sachs knows that seeing into someone’s head requires their head to do a lot of work with language in order to produce a series of gestures back toward some always-inarticulable idea. Not every utterance is worth paying attention to, unless you’re the one talking.
We are periodically re-situated in the tower, where the clock is ticking on the astronomer’s prediction. A cat, Linus, stalks the room. (A perfect syllogism, courtesy of the astronomer: “A man delighted by a cat is discomfited by existence, a man delighted by existence is discomfited by a cat.”) The astronomer occasionally presses socket to telescope and writes down long strings of numbers, a refrain that mostly works to remind us that Sachs is in control.
But his is a fine control, and it’s surprisingly propulsive, this mystery of whether the forecasted event will occur—at once banal (four seconds in the dark, big deal) and galactically meaningful (the sun occluded for four seconds is a very big deal for those of us who rely on its warmth and light for our survival). It’s a kind of structural suspense, reading to see whether Sachs will pull it off, wondering which threads will be tied neatly, which left frayed. Wondering what, for God’s sake, happened to the astronomer’s eyes! Happily, the dénouement of the novel is excellently wrangled, and its grotesquerie depends in part upon a demonstration of the horrors of a vacuum, which made me wish that more inventors had shown up in its pages to blow everyone’s minds. (To be fair, there’s also the aforementioned mechanical head, a perpetual motion machine, and more.) Sachs’s chosen historical moment bristles with so much metaphysical weirdness in large part because discovery and mysticism are not yet at cross-purposes. Cutting-edge scientific discoveries are intimations of reality’s as-yet-unexplained properties and thus, in their uncanny mixture of the mechanical and the unimaginable, seem tinged with magic.
The Organs of Sense, too, turns out to be more than the sum of its parts. Sachs has written a misdirecting novel about the pleasures and perils of misdirection, and the contraption works exquisitely, proving that it is impossible to be a person on whom nothing is lost. I must be one of those cat-lovers discomfited by existence, because after uncountable moments of frustration, by the novel’s end, I was actually charmed to feel that I, like Leibniz, was the butt of some cosmic joke. The Organs of Sense invites us to wander around in Sachs’s head; of course it’s messy and annoying. On the verge of throwing the book across the room, I would reach an unanticipated reprise or an incredible morsel of history or the end of a deftly completed feedback loop, cackle gleefully, and fall back in love. The people around me might have felt their constituent monads twinge and wondered, if only for a moment, what was going on in my head. | 0.844599 | 3.398726 |
By Sasha Hinkley, Astrophysics Group, University of Exeter
It is now clear that planetary systems around stars other than our own are common, and these extrasolar planetary systems display a stunning diversity of architectures, orbital geometries, and planetary sizes. Yet experiments such as NASA’s Kepler mission, which search for the periodic dimming due to planets transiting the face of their host star in edge-on orbits, rely on indirect detection techniques in which the presence of planetary mass companions is only inferred based on variations in the host starlight. However, astronomers are now able to directly image extrasolar planetary systems using a combination of new technologies described below. Indeed, this technique has now returned a large handful of directly imaged planetary mass companions at wide orbital separations. Just as the discovery of the “Hot Jupiter” 51 Peg b orbiting its host star at a small fraction of an Astronomical Unit (AU) came as a complete surprise in 1995, so have the recent discoveries of planetary mass companions orbiting stars at much wider (20–600 AU) orbital separations using direct imaging. While the indirect techniques such as precision Doppler and transit monitoring work to resolve the signal of an exoplanet in time, the technique of exoplanet direct imaging depends on separating the light from a faint exoplanet from its extremely bright host star directly in an image.
However, as might be expected, imaging these extremely faint planets orbiting their host star is extraordinarily challenging: even young planets, still glowing from the residual heat of their formation, may be a million times fainter than their host stars. The task is analogous to observing a firefly fluttering around a bright searchlight. Now imagine trying to gather an image of this firefly while working in London with the searchlight located in Paris! This analogy accurately describes the sensitivity and resolution necessary for astronomers to uncover the faint light from these exoplanets.
To accomplish this task, astronomers must first correct for aberrations and fluctuations in the incoming light due to turbulence in the Earth’s atmosphere. Just as the turbulent air above a stretch of hot concrete causes the image of a distant object to contort and vary in time, so too does the Earth’s atmosphere affect the signals from distant planets. Those of us working in the field of exoplanet direct imaging use a technique called Adaptive Optics (“AO”, see below). By spatially separating the light of a faint exoplanet from that of its very bright host star, the direct imaging technique can directly resolve the nearby environments of stars, and is thus sensitive to wide companions (tens or hundreds of AUs), probing planetary architectures out of reach of the indirect transit and Doppler techniques.
How it works: AO & Coronagraphy
AO refers to a suite of customized optical components installed in a telescope, typically “downstream” from the primary and secondary mirrors (although several observatories are now building AO systems directly into the secondary mirrors to reduce the number of reflective surfaces). The task of this machinery is two-fold. First, it must use a “wavefront sensor” to sense the extent to which the turbulence in the Earth’s atmosphere has affected the incoming stellar light. Next, to correct for this distorted incoming starlight, AO systems use a “deformable mirror”, which is a flexible mirror that is continuously reshaped by mechanical actuators gently pushing and pulling the mirror hundreds or thousands of times per second. Once the stellar light has been carefully controlled using AO, astronomers use a “coronagraph”, a collection of opaque optical masks, to block out the host star light, similar to the moon passing in front of the sun during a solar eclipse. This combination of AO and coronagraphy provides the contrast needed to image faint exoplanets orbiting close to nearby stars.
New Instruments: GPI and SPHERE
Until recently, the handful of direct images of exoplanets, with orbits even wider than the outermost planets of our own solar system, were obtained with instrumentation not specifically dedicated to this task. Rather, they were obtained using instruments using some kind of custom setting or configuration allowing these extremely challenging observations to happen. Recently, however, several instruments have now been deployed that are dedicated exclusively to the task of obtaining images and spectroscopy of extrasolar planets. In addition to ongoing and planned suites of instrumentation at the Palomar and Subaru telescopes, the most notable projects are the Gemini Planet Imager (GPI), and the Spectro-Polarimetric High-Contrast Exoplanet REsearch (SPHERE) instrument, deployed at the Gemini South telescopes and ESO Very Large Telescopes in Chile, respectively. These instruments have embarked on surveys of hundreds of nearby stars that astronomers speculate could be ripe for hosting wide separation exoplanets.
The Next Generation of 30–40 m Telescopes
At the same time, construction is now underway for the European Extremely Large Telescope (“E-ELT”) at Cerro Armazones, Chile. This telescope will have a mirror with a diameter of 39 meters: a collecting area and sensitivity several times greater than any current telescope. Further, it will be equipped with an ensemble of instruments designed to address a range of astronomical goals. Among the most promising for the direct imaging of extrasolar planets is the Mid-infrared ELT Imager and Spectrograph (“METIS”). The superior contrast and sensitivity of METIS operating on a 39 m telescope will allow exoplanet imaging on orbital scales comparable to our own earth for nearby stars, and METIS will be sensitive to massive planets at slightly further orbital separations from stars residing in the nearest associations of young stars. Even further, conservative calculations suggest METIS will image 20–30 (currently known) planets initially detected by the Doppler methods, as well as a few small—potentially rocky—planets around very nearby stars. When METIS achieves first light in roughly 2025, numerous more Earth-like planets will have been identified, requiring follow up observations with the next generation of 30–40 m class telescopes for more detailed characterization
Direct High Resolution Spectroscopy:
While the images of exoplanets returned by the current and upcoming generation of instruments are particularly exciting, perhaps the greatest legacy of these instruments will be delivered by their ability to provide spectroscopy of the exoplanets. Unlike the transit technique, which fundamentally detects grazing stellar radiation after it has interacted with an exoplanet, by spatially separating the light of the host star and the extremely faint planet, the direct imaging method gives access to photons emitted directly from the exoplanet atmospheres. Obtaining photons directly from the surface of exoplanets will allow astronomers to gather all of the detailed information that has been retrieved for stars using high-resolution spectroscopy (e.g. chemical abundances, compositions, and thermodynamic conditions). This direct spectroscopy will allow unambiguous interpretation of the spectra. As such, the future of comparative exoplanetary science lies in the technique of exoplanet direct imaging.
Sasha Hinkley is a permanent member of Staff in the Astrophysics Group at the University of Exeter in the UK. Prior to arriving in the UK, Dr. Hinkley was a NASA Sagan Fellow as well as a National Science Foundation Astronomy and Astrophysics Postdoctoral Fellow at the California Institute of Technology in Pasadena. He has been involved with development of instrumentation for exoplanet direct imaging at Palomar Observatory, and is an active user of both the W.M. Keck Observatory on Mauna Kea, as well as the ESO SPHERE instrument at Cerro Paranal, Chile. | 0.890197 | 4.069729 |
Images from space show baby planet being born, scientists claim
For the first time ever, scientists believe they have captured the first direct evidence of a baby planet being born.
Images and footage taken by the European Southern Observatory’s Very Large Telescope showed a swirling mass of amber gas and dust, with scientists believing the bright yellow twist at the centre of the formation is proof of a new planet emerging.
The planet was found around the young star AB Aurigae and while astronomers have identified over 4000 exoplanets (a planet found outside the solar system) little is known about how they form, said Anthony Boccaletti who led the study from the Observatoire de Paris, PSL University, France.
“We need to observe very young systems to really capture the moment when planets form,” he said.
It’s believed planets are born when discs of cold gas and dust clump together, creating a ‘swirling motion’. However astronomers were previously unable to capture images sharp or deep enough to identify the telltale ‘twist’.
“The twist is expected from some theoretical models of planet formation,” co-author of the study, Anne Dutrey, from the Astrophysics Laboratory of Bordeaux, said.
“It corresponds to the connection of two spirals – one winding inwards of the planet’s orbit, the other expanding outwards – which join at the planet location. They allow gas and dust from the disc to accrete onto the forming planet and make it grow.”
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Located 520 light-years away from Earth, AB Aurigae is believed to be around 2.4 times the mass of the sun and located within our Milky Way galaxy.
According to Dr Boccaletti, the baby planet is located about 30 times further from AB Aurigae than Earth’s distance from our sun, which is around the same placement as the planet Neptune.
The findings from the study will be published in the scientific journal, Astronomy & Astrophysics.
Originally published as Birth of baby planet captured | 0.867813 | 3.110612 |
This beautiful photograph is of a region in the Orion Nebula called the Trapezium. It was taken by merging images together from two of the Great Observatories: Hubble and Spitzer. The swirls of green are ultraviolet and visible images revealed by Hubble, while the reds and oranges are infrared detected by Spitzer. At the heart of the photograph lurk 4 massive stars, each of which is 100,000 times brighter than our own Sun. The nebula is located about 1,500 light years from the Earth, and can be seen in small telescopes or binoculars.
A new image from NASA’s Spitzer and Hubble Space Telescopes looks more like an abstract painting than a cosmic snapshot. The masterpiece shows the Orion nebula in an explosion of infrared, ultraviolet and visible-light colors. It was “painted” by hundreds of baby stars on a canvas of gas and dust, with intense ultraviolet light and strong stellar winds as brushes.
At the heart of the artwork is a set of four monstrously massive stars, collectively called the Trapezium. These behemoths are approximately 100,000 times brighter than our sun. Their community can be identified as the yellow smudge near the center of the composite.
The swirls of green were revealed by Hubble’s ultraviolet and visible-light detectors. They are hydrogen and sulfur gases heated by intense ultraviolet radiation from the Trapezium’s stars.
Wisps of red and orange detected by Spitzer indicate infrared light from illuminated clouds containing carbon-rich molecules called polycyclic aromatic hydrocarbons. On Earth, polycyclic aromatic hydrocarbons are found on burnt toast and in automobile exhaust.
Additional stars in Orion are sprinkled throughout the image in a rainbow of colors. Spitzer exposed infant stars deeply embedded in a cocoon of dust and gas (orange-yellow dots). Hubble found less embedded stars (specks of green) and stars in the foreground (blue). Stellar winds from clusters of newborn stars scattered throughout the cloud etched all the well-defined ridges and cavities.
Located nearly 1,500 light-years away from Earth, the Orion nebula is the brightest spot in the sword of the hunter constellation. The cosmic cloud is also our closest massive star-formation factory, and astronomers suspect that it contains about 1,000 young stars.
The Orion constellation can be seen in the fall and winter night skies from northern latitudes. The constellation’s nebula is invisible to the unaided eye, but can be resolved with binoculars or small telescopes.
This image is a false-color composite, in which light detected at wavelengths of 0.43, 0.50, and 0.53 microns is blue. Light with wavelengths of 0.6, 0.65, and 0.91 microns is green. Light of 3.6 microns is orange, and 8-micron light is red.
To view the new false-color image, visit http://www.nasa.gov/mission_pages/spitzer/multimedia/pia01322.html
NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena, which manages JPL for NASA.
The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. The Space Telescope Science Institute in Baltimore conducts Hubble science operations. The Institute is operated for NASA by the Association of Universities for Research in Astronomy, Inc., Washington.
For more information about Spitzer, visit http://www.nasa.gov/spitzer or http://www.spitzer.caltech.edu/spitzer. For more information about Hubble, visit: http://www.nasa.gov/hubble or http://hubblesite.org.
Original Source: NASA/Spitzer/Hubble News Release | 0.883913 | 3.803463 |
- A gigantic collision in the asteroid belt between Mars and Jupiter occurred 400 million years before the one that killed the dinos
- It triggered a mini ice age and led to a significant increase in primitive lifeform on Earth
The cataclysmic asteroid impact off Mexico’s coast that doomed the dinosaurs 66 million years ago was not the only time an astronomical event shaped the history of life on Earth.
Scientists said dust spawned by a gigantic collision in the asteroid belt between Mars and Jupiter 400 million years earlier triggered an ice age on Earth that ushered in a significant increase in marine biodiversity.
The event, occurring when life was concentrated in the seas and far before vertebrates first walked on land, set in motion evolutionary changes in invertebrates fundamental to marine ecosystems as they adapted to global cooling.
According to researchers, the inner solar system was filled with enormous amounts of dust after an asteroid more than 150km in diameter was struck by a smaller object perhaps 20km wide, the researchers said.
It was the solar system's largest known break-up event in the past 2 billion years. Solar radiation reaching Earth's surface was reduced for at least 2 million years by the dust in space and in the planet's atmosphere, said study co-author Philipp Heck, an associate curator at the Field Museum in Chicago.
Another cooling mechanism was that the iron-rich meteoritic dust fertilised large parts of the ocean surface leading to increased plankton productivity and drawdown of atmospheric carbon dioxide, added Birger Schmitz, a geology professor at Lund University in Sweden and lead author of the research published in the journal Science Advances in September 2019.
"In the last few decades, researchers have begun to understand that evolution of life on Earth is dependent on astronomical events also," Schmitz said.
After noting the dinosaur-demise event caused by an asteroid perhaps 10km wide, Schmitz added, "For the first time, scientists can now present another example of how an extraterrestrial event formed life on Earth."
The researchers found traces of dust in sedimentary rocks formed at the time containing special helium isotopes and rare minerals that revealed its extraterrestrial origin.
Invertebrate groups that experienced diversification included horseshoe crablike trilobites, clams, clam-like brachiopods and a group called gastropods that included snails and slugs.
The cooling event unfolded gradually, enabling marine life during the Ordovician Period to adapt, unlike the sudden impact that erased the dinosaurs from the planet.
Earth's climate changed from being tropical to semi-tropical worldwide to becoming divided into climate zones as it is today with frozen poles and tropical conditions at the equator. | 0.828815 | 3.811503 |
The Almagest // is a 2nd-century Greek-language mathematical and astronomical treatise on the apparent motions of the stars and planetary paths, written by Claudius Ptolemy (c. AD 100 – c. 170). One of the most influential scientific texts of all time, it canonized a geocentric model of the Universe that was accepted for more than 1200 years from its origin in Hellenistic Alexandria, in the medieval Byzantine and Islamic worlds, and in Western Europe through the Middle Ages and early Renaissance until Copernicus. It is also a key source of information about ancient Greek astronomy.
Ptolemy set up a public inscription at Canopus, Egypt, in 147 or 148. N. T. Hamilton found that the version of Ptolemy's models set out in the Canopic Inscription was earlier than the version in the Almagest. Hence the Almagest could not have been completed before about 150, a quarter-century after Ptolemy began observing.[pages needed]
The work was originally titled "Μαθηματικὴ Σύνταξις" (Mathēmatikē Syntaxis) in Ancient Greek, and also called Syntaxis Mathematica in Latin. The treatise was later titled Hē Megalē Syntaxis (Ἡ Μεγάλη Σύνταξις, "The Great Treatise"; Latin: Magna Syntaxis), and the superlative form of this (Ancient Greek: μεγίστη, megiste, "greatest") lies behind the Arabic name al-majisṭī (المجسطي), from which the English name Almagest derives. The Arabic name is important due to the popularity of a Latin translation known as Almagestum made in the 12th century from an Arabic translation, which would endure until original Greek copies resurfaced in the 15th century.
The Syntaxis Mathematica consists of thirteen sections, called books. As with many medieval manuscripts that were handcopied or, particularly, printed in the early years of printing, there were considerable differences between various editions of the same text, as the process of transcription was highly personal. An example illustrating how the Syntaxis was organized is given below. It is a Latin edition printed in 1515 at Venice by Petrus Lichtenstein.
- Book I contains an outline of Aristotle's cosmology: on the spherical form of the heavens, with the spherical Earth lying motionless as the center, with the fixed stars and the various planets revolving around the Earth. Then follows an explanation of chords with table of chords; observations of the obliquity of the ecliptic (the apparent path of the Sun through the stars); and an introduction to spherical trigonometry.
- Book II covers problems associated with the daily motion attributed to the heavens, namely risings and settings of celestial objects, the length of daylight, the determination of latitude, the points at which the Sun is vertical, the shadows of the gnomon at the equinoxes and solstices, and other observations that change with the spectator's position. There is also a study of the angles made by the ecliptic with the vertical, with tables.
- Book III covers the length of the year, and the motion of the Sun. Ptolemy explains Hipparchus' discovery of the precession of the equinoxes and begins explaining the theory of epicycles.
- Books IV and V cover the motion of the Moon, lunar parallax, the motion of the lunar apogee, and the sizes and distances of the Sun and Moon relative to the Earth.
- Book VI covers solar and lunar eclipses.
- Books VII and VIII cover the motions of the fixed stars, including precession of the equinoxes. They also contain a star catalogue of 1022 stars, described by their positions in the constellations, together with ecliptic longitude and latitude. Ptolemy states that the longitudes (which increase due to precession) are for the beginning of the reign of Antoninus Pius (138 AD), whereas the latitudes do not change with time. (But see below, under The star catalog.) The constellations north of the zodiac and the northern zodiac constellations (Aries through Virgo) are in the table at the end of Book VII, while the rest are in the table at the beginning of Book VIII. The brightest stars were marked first magnitude (m = 1), while the faintest visible to the naked eye were sixth magnitude (m = 6). Each numerical magnitude was considered twice the brightness of the following one, which is a logarithmic scale. (The ratio was subjective as no photodetectors existed.) This system is believed to have originated with Hipparchus. The stellar positions too are of Hipparchan origin, despite Ptolemy's claim to the contrary.
- Ptolemy identified 48 constellations: The 12 of the zodiac, 21 to the north of the zodiac, and 15 to the south.
- Book IX addresses general issues associated with creating models for the five naked eye planets, and the motion of Mercury.
- Book X covers the motions of Venus and Mars.
- Book XI covers the motions of Jupiter and Saturn.
- Book XII covers stations and retrograde motion, which occurs when planets appear to pause, then briefly reverse their motion against the background of the zodiac. Ptolemy understood these terms to apply to Mercury and Venus as well as the outer planets.
- Book XIII covers motion in latitude, that is, the deviation of planets from the ecliptic.
The cosmology of the Syntaxis includes five main points, each of which is the subject of a chapter in Book I. What follows is a close paraphrase of Ptolemy's own words from Toomer's translation.
- The celestial realm is spherical, and moves as a sphere.
- The Earth is a sphere.
- The Earth is at the center of the cosmos.
- The Earth, in relation to the distance of the fixed stars, has no appreciable size and must be treated as a mathematical point.
- The Earth does not move.
The star catalogEdit
As mentioned, Ptolemy includes a star catalog containing 1022 stars. He says that he "observed as many stars as it was possible to perceive, even to the sixth magnitude", and that the ecliptic longitudes are for the beginning of the reign of Antoninus Pius (138 AD). But calculations show that his ecliptic longitudes correspond more closely to around 58 AD. He states that he found that the longitudes had increased by 2° 40′ since the time of Hipparchos. This is the amount of axial precession that occurred between the time of Hipparchos and 58 AD. It appears therefore that Ptolemy took a star catalog of Hipparchos and simply added 2° 40′ to the longitudes.. However, the figure he used seems to have been based on Hipparchos' own estimate for precession, which was 1° in 100 years, instead of the correct 1° in 72 years. Dating attempts through proper motion of the stars also appear to date the actual observation to Hipparchos' time instead of Ptolemy.
Many of the longitudes and latitudes have been corrupted in the various manuscripts. Most of these errors can be explained by similarities in the symbols used for different numbers. For example, the Greek letters Α and Δ were used to mean 1 and 4 respectively, but because these look similar copyists sometimes wrote the wrong one. In Arabic manuscripts, there was confusion between for example 3 and 8 (ج and ح). (At least one translator also introduced errors. Gerard of Cremona, who translated an Arabic manuscript into Latin around 1175, put 300° for the latitude of several stars. He had apparently learned from Moors, who used the letter "sin" for 300 (like the Hebrew "shin"), but the manuscript he was translating came from the East, where "sin" was used for 60, like the Hebrew "samech".)
Even without the errors introduced by copyists, and even accounting for the fact that the longitudes are more appropriate for 58 AD than for 137 AD, the latitudes and longitudes are not very accurate, with errors of large fractions of a degree. Some errors may be due to atmospheric refraction causing stars that are low in the sky to appear higher than where they really are. A series of stars in Centaurus are off by a couple degrees, including the star we call Alpha Centauri. These were probably measured by a different person or persons from the others, and in an inaccurate way.
Ptolemy's planetary modelEdit
Ptolemy assigned the following order to the planetary spheres, beginning with the innermost:
- Sphere of fixed stars
Other classical writers suggested different sequences. Plato (c. 427 – c. 347 BC) placed the Sun second in order after the Moon. Martianus Capella (5th century AD) put Mercury and Venus in motion around the Sun. Ptolemy's authority was preferred by most medieval Islamic and late medieval European astronomers.
Ptolemy inherited from his Greek predecessors a geometrical toolbox and a partial set of models for predicting where the planets would appear in the sky. Apollonius of Perga (c. 262 – c. 190 BC) had introduced the deferent and epicycle and the eccentric deferent to astronomy. Hipparchus (2nd century BC) had crafted mathematical models of the motion of the Sun and Moon. Hipparchus had some knowledge of Mesopotamian astronomy, and he felt that Greek models should match those of the Babylonians in accuracy. He was unable to create accurate models for the remaining five planets.
The Syntaxis adopted Hipparchus' solar model, which consisted of a simple eccentric deferent. For the Moon, Ptolemy began with Hipparchus' epicycle-on-deferent, then added a device that historians of astronomy refer to as a "crank mechanism": He succeeded in creating models for the other planets, where Hipparchus had failed, by introducing a third device called the equant.
Ptolemy wrote the Syntaxis as a textbook of mathematical astronomy. It explained geometrical models of the planets based on combinations of circles, which could be used to predict the motions of celestial objects. In a later book, the Planetary Hypotheses, Ptolemy explained how to transform his geometrical models into three-dimensional spheres or partial spheres. In contrast to the mathematical Syntaxis, the Planetary Hypotheses is sometimes described as a book of cosmology.
Ptolemy's comprehensive treatise of mathematical astronomy superseded most older texts of Greek astronomy. Some were more specialized and thus of less interest; others simply became outdated by the newer models. As a result, the older texts ceased to be copied and were gradually lost. Much of what we know about the work of astronomers like Hipparchus comes from references in the Syntaxis.
The first translations into Arabic were made in the 9th century, with two separate efforts, one sponsored by the caliph Al-Ma'mun. Sahl ibn Bishr is thought to be the first Arabic translator. By this time, the Syntaxis was lost in Western Europe, or only dimly remembered. Henry Aristippus made the first Latin translation directly from a Greek copy, but it was not as influential as a later translation into Latin made by Gerard of Cremona from the Arabic (finished in 1175). Gerard translated the Arabic text while working at the Toledo School of Translators, although he was unable to translate many technical terms such as the Arabic Abrachir for Hipparchus. In the 12th century a Spanish version was produced, which was later translated under the patronage of Alfonso X.
In the 15th century, a Greek version appeared in Western Europe. The German astronomer Johannes Müller (known, from his birthplace of Königsberg, as Regiomontanus) made an abridged Latin version at the instigation of the Greek churchman Johannes, Cardinal Bessarion. Around the same time, George of Trebizond made a full translation accompanied by a commentary that was as long as the original text. George's translation, done under the patronage of Pope Nicholas V, was intended to supplant the old translation. The new translation was a great improvement; the new commentary was not, and aroused criticism. The Pope declined the dedication of George's work, and Regiomontanus's translation had the upper hand for over 100 years.
During the 16th century, Guillaume Postel, who had been on an embassy to the Ottoman Empire, brought back Arabic disputations of the Almagest, such as the works of al-Kharaqī, Muntahā al-idrāk fī taqāsīm al-aflāk ("The Ultimate Grasp of the Divisions of Spheres", 1138/9).
The Almagest under the Latin title Syntaxis mathematica, was edited by J. L. Heiberg in Claudii Ptolemaei opera quae exstant omnia, vols. 1.1 and 1.2 (1898, 1903).
Three translations of the Almagest into English have been published. The first, by R. Catesby Taliaferro of St. John's College in Annapolis, Maryland, was included in volume 16 of the Great Books of the Western World in 1952. The second, by G. J. Toomer, Ptolemy's Almagest in 1984, with a second edition in 1998. The third was a partial translation by Bruce M. Perry in The Almagest: Introduction to the Mathematics of the Heavens in 2014.
A direct French translation from the Greek text was published in two volumes in 1813 and 1816 by Nicholas Halma, including detailed historical comments in a 69-page preface. The scanned books are available in full at the Gallica French national library.
- N. T. Hamilton, N. M. Swerdlow, G. J. Toomer. "The Canobic Inscription: Ptolemy's Earliest Work". In Berggren and Goldstein, eds., From Ancient Omens to Statistical Mechanics. Copenhagen: University Library, 1987.
- "Almagestum (1515)". Universität Wien. Retrieved 31 May 2014.
- Ley, Willy (December 1963). "The Names of the Constellations". For Your Information. Galaxy Science Fiction. pp. 90–99.
- Toomer, G. J. (1998), Ptolemy's Almagest (PDF), Princeton University Press, ISBN 0-691-00260-6
- Ptolemy. Almagest., Book I, Chapter 5.
- Christian Peters and Edward Knobel (1915). Ptolemy's Catalogue of the Stars – A Revision of the Almagest. p. 15.
- Dambis, A. K.; Efremov, Yu. N. (2000). "Dating Ptolemy's Star Catalogue through Proper Motions: The Hipparchan Epoch". Journal for the History of Astronomy. 31 (2): 115–134. doi:10.1177/002182860003100202.
- Peters and Knobel, pp. 9-14.
- Peters and Knobel, p. 14.
- Peters and Knobel, p. 112.
- Michael Hoskin. The Cambridge Concise History of Astronomy. Chapter 2, page 44.
- See p. 3 of Introduction of the Toomis translation.
- Islamic science and the making of European Renaissance, by George Saliba, p. 218 ISBN 978-0-262-19557-7
- Perry, Bruce M. (2014), The Almagest: Introduction to the Mathematics of the Heavens, Green Lion Press, ISBN 978-188800943-9
- Halma, Nicolas (1813). Composition mathématique de Claude Ptolémée, traduite pour la première fois du grec en français, sur les manuscrits originaux de la bibliothèque impériale de Paris, tome 1 (in French). Paris: J. Hermann. p. 608.
- Halma, Nicolas (1816). Composition mathématique de Claude Ptolémée, ou astronomie ancienne, traduite pour la première fois du grec en français sur les manuscrits de la bibliothèque du roi, tome 2 (in French). Paris: H. Grand. p. 524.
- James Evans (1998) The History and Practice of Ancient Astronomy, Oxford University Press ISBN 0-19-509539-1
- Michael Hoskin (1999) The Cambridge Concise History of Astronomy, Cambridge University Press ISBN 0-521-57291-6
- Olaf Pedersen (1974) A Survey of the Almagest, Odense University Press ISBN 87-7492-087-1.
- Alexander Jones & Olaf Pedersen (2011) A Survey of the Almagest, Springer ISBN 9780387848259
- Olaf Pedersen (1993) Early Physics and Astronomy: A Historical Introduction, 2nd edition, Cambridge University Press ISBN 0-521-40340-5
|Wikimedia Commons has media related to Almagest.|
- Syntaxis mathematica in J.L. Heiberg's edition (1898-1903)
- Ptolemy's De Analemmate. PDF scans of Heiberg's Greek edition, now in the public domain (Koine Greek)
- Toomer's English translation, 1984.
- Ptolemy. Almagest. Latin translation from the Arabic by Gerard of Cremona. Digitized version of manuscript made in Northern Italy c. 1200–1225 held by the State Library of Victoria.
- University of Vienna: Almagestum (1515) PDFs of different resolutions. Edition of Petrus Liechtenstein, Latin translation of Gerard of Cremona.
- Almagest Planetary Model Animations
- Online luni-solar and planetary ephemeris calculator based on the Almagest
- A podcast discussion by Prof. M Heath and Dr A. Chapman of a recent re-discovery of a 14th-century manuscript in the university of Leeds Library
- Star catalog in ASCII (Latin) | 0.88273 | 3.829315 |
Nebulae are one of the most abundant objects for amateur astronomical study and are very rewarding to photograph. A bright nebula can be counted amongst the most inspiring splendours nature has to offer. What’s more, they are generally very diverse with a wide range of dimensions, magnitudes, and availability to small telescopes. Nebulae are fascinating: what could be more wonderful than contemplating these celestial objects, contemplating a snapshot in time of stars being born, imagining the emergence of planetary systems, and even in some well developed areas, perhaps the bombardment of surfaces that may become conducive to life? Their ethereal nature, short lifetimes, and range of forms make observing them a truly pleasing study.
A Brief History of Nebulae
In the ancient world, the book that survived—and was used for almost one and a half millennia—was the Almagest by the Alexandrian astronomer Claudius Ptolemy. This text included seven nebulous objects, three of which were starry asterisms, but not physically related objects. Two were taken from Hipparchus’ existing catalogue of fixed stars, and two were new: one is now known colloquially as Ptolemy’s cluster and is the star cluster recorded as Messier 7; the other makes up most of the constellation of Coma Berenices, the star cluster Melotte 111. However, it must be emphasized that these are not nebulae in the true sense of the word; in pre-telescopic times these were unresolved clusters of stars, not collections of gas and dust.
The first person to recognize and discover a nebula in the true sense of a gaseous cloud was Nicholas de Peiresc, who saw the Orion nebula in 1610. It is notable that it is also the first deep sky object ever discovered with a telescope, though Galileo did note that the Beehive cluster in Cancer could be resolved into stars—not a true nebula in any sense. He did, however, observe the Orion nebula without noticing a gaseous component. That the true nature of nebulae were still a mystery and not identified as gaseous clouds can be seen from the claim of Simon Marius on his discovery of the Andromeda galaxy in 1612, the first person in the West to record the object.
Caption: NASA’s Spitzer and Hubble Space Telescopes teamed up to expose the chaos that baby stars are creating 1,500 light years away in a cosmic cloud called the Orion nebula
With the advent of spectroscopes and photography, large nebulous areas were revealed as clouds of hydrogen gas and silicate and carbonate dust within the Milky Way. It was John Herschel who made the supposition midway through the eighteenth century that nebulae and star clusters were intimately connected, and paraphrased the nebulae as being the “chaotic material of future suns,” a term that turned out to be very prescient.
It was the great American astronomer Edwin Hubble who finally made the connection between HII regions, dark nebulae, reflection nebulae, and the stars that illuminate them in a seminal paper entitled The Source of Luminosity in Galactic Nebulae, published in the Astrophysical Journal in August, 1922. Here he showed that the ionization from bright stars led to the emission lines of the nebulae, and supposed that dark nebulae and reflection nebulae were areas of sky where the illumination was coming from stars newly born or, in the case of dark nebulae, were as yet unilluminated, as stars were yet to form in them. Later studies in the late 1920s and into the 1930s by Otto Struve, Herman Zanstra, Phillip Keenan, and others showed the nature of reflection nebulae in such objects as the Pleiades and the nebulae in Orion, Messier 78.
Today we can understand the connection between the true nebulae and objects of many kinds such as star clusters, and individual stars, too.
There is nothing quite like the sight of a glowing patch of gas in the eyepiece to start the imagination on a train of thought that leads right down to the production of you and I here on Earth. Nebulae are usually taken to be emission regions of glowing gas illuminated by newly formed stars. However, there are other types, some of which are wonderful objects in their own right, such as Planetary nebulae, the death of stars with masses close to that of the sun. By definition, nebulae are patches of gas or “clouds” but that hides the distinctiveness of each type.
Nebulae can therefore be divided into emission nebulae, planetary nebulae, dark nebulae, and reflection nebulae. Although there are also special subsets, such as supernovae remnants, the main types here are recognized by professional and amateur astronomer alike. No matter what nebulae one may pick, they are all intimately tied to the stellar evolution process.
Stars experience stages of birth, growth, middle age, old age, and finally death. Astronomers talk of these stages as progressive stellar evolution. They begin with dark, emission, and reflection nebulae and generally end with a planetary nebula or the expanding mass of a supernova explosion. Stars are the only entities in our universe that follow the strict rule of evolution, slowly changing with time, but they always remain stars for the majority of their lives.
Before stars begin to form in emission nebulae, their materials are corralled together in large molecular clouds which are warm yet unlit collections of basic gas and dust. These molecular clouds can be enormous, stretching hundreds of light years across and having masses of millions of times that of our sun. Being so large, one would think that it would be easy to see such clouds, but by their very nature, anything that does not emit light in the blackness of space is going to be difficult to spot.
Most of the dark nebulae studied in our galaxy are known as “Barnard Objects” after Edward Emmerson Barnard, the man responsible for identifying them by means of photography at Mount Wilson. Approximately 80 of E. E. Barnard’s dark nebulae are half a degree or larger in size. To see them, they require contrast against the starry backdrop of the Milky Way, and so a large field of view or the naked eye is best for seeing many of them. Examples such as the coal sack in the southern hemisphere or the Cygnus rift in the northern hemisphere are ones that spring to most minds. In many cases a pair of binoculars will suffice for most dark nebulae, though photography brings them out beautifully against the starry canvas of our galactic home.
Some of the best examples of dark nebulae are B33, the Horsehead nebula in Orion, Le Gentil’s nebula in northern Cygnus, and the lovely B59, the Pipe nebula in Ophiuchus
As materials collapse and condense inside molecular clouds, local condensations lead to the production of protostars and eventually new stars. These newborns are highly energetic and their radiation energizes part of the molecular clouds until they begin to shine of their own accord. We see such areas as emission nebulae. Astronomers label emission nebulae as HII regions, or ionized hydrogen clouds, which really are the glowing nurseries of stars and planets and are full of the materials necessary for life. Although much of this chemistry is relatively simple, there is enough material in an average HII cloud to make several generations of stars, as can be attested to by examination of many of these wonderful regions. Star clusters are evident in their proximity, and the clouds themselves are lit either by radiant members newly born or are hidden by bars of dust giving hints of emergence into a new world around them.
The Pipe Nebula (composed by B77, B78 and B59) is one of the largest dark nebulas in the sky. In this field of view are also visible many other dark nebulae in the network that is the central Milky Way. Image courtesy of Yuri Beletsky (Las Campanas Observatory, Carnegie Institution for Science).
The pipe nebula (composed by B77, B78 and B59) is one of the largest dark nebulas in he sky (7°!). In this field of view are also well visible many other dark nebulas in that intricate network that is the central milky way.
Ionized hydrogen regions are very widespread across the Milky Way, and can even be seen in some external galaxies such as NGC 604 in the Pinwheel galaxy Messier 33. However, not all of them are bright and obvious for the visual observer, and some respond better to photographic efforts than to mere viewing. The subtle red colours of most nebulae are not seen visually as the eye does not discern red easily in the dark, and most objects are fainter than expected.
Excellent examples of HII regions are the winter glory of the Orion nebula M42/43 and the Rosette nebulae NGC 2237 in Monoceros. In summer skies, the wonderful M8 and M20 in Sagittarius or M16 and M17 in Serpens are visited regularly by amateurs.
Once stars are fully formed, converting hydrogen to helium, and generally in equilibrium, we see them as clusters of stars. The bright blue light from such stars or clusters is enough to give sufficient scattering to make the dust visible, and as the light is of short wavelengths, the frequency spectrum of many reflection nebulae is similar to that of the illuminating stars. Reflection nebulae are not particularly rare but their relatively low light profile in comparison to light-emitting nebulae, such as HII regions, make them a little harder to see, and the nebulae are generally well located close to the stars. This makes the starlight overwhelming on occasion and renders visual representation of such nebulae difficult.
Examples such as the Pleiades, or many of the Messier numbers such as M36 – M38 in Auriga, show us how stars born in HII regions stay together for long periods before interaction with the galaxy thins them out into individuals. It is when the stable relationship of hydrogen burning ends that stars begin the next process of nebulae formation—dying in a planetary nebulae or exploding as a supernova.
Stellar Death and Nebulae
This ending depends on the mass of the star. A star larger than 15 times the mass of our sun will become a supernova, whilst those under this limit will become planetary nebulae. Most stars convert hydrogen to helium for millions or even billions of years, but once the hydrogen begins to run out, the star is doomed.
Once there is sufficient helium build-up in the core to significantly interfere with the hydrogen reactions, the core shuts down and begins to contract. However, there is a lot of latent energy in the overlying layers from radiation attempting to escape the outer envelope. As a consequence of this radiation pressure, the star will begin to expand, as gravity works primarily upon the greater mass of the core and only has a relatively weak effect on the outer layers. At this point the core contracts, the outer layers expand, and the star begins to cool.
As it does this, the star changes colour and cools to become an orange K type sub-giant. The star then utilizes the energy of hydrogen-helium conversion, which now takes place in a shell around the inert hydrogen core rather than throughout the core as in its previous incarnation. Over time the star will continue to expand and cool until it becomes an M type red giant. It is now large, luminous, and has an extensive solar wind, which is driving the material of the outermost layers off the star. This expulsion of material is important in the development of a planetary nebula. Under such forces, a star can lose as much as 1/100,000th of a solar mass per year.
Eventually, gravity compresses the helium core until sufficient pressures and temperatures build up inside to fuse helium to carbon. Once a new source of energy has been established, the star has a short stay of execution. However, there is insufficient helium fuel to power the star, and as this fuel becomes exhausted, the outer layers expand again with latent energy from the radiation release and they are eventually pushed off the star, lost to space with an increase in the power of the stellar wind at this stage. Once the luminous outer envelope of the star is lost, the naked core is all that is left: a small, hot remnant with a fraction of the luminosity of the whole star, and the object dims appreciably and makes its way rapidly ending its days as a white dwarf. That is what planetary nebulae are—the thrusting away of the envelope and the exposing of the white dwarf remnant.
Observing planetary nebulae is not particularly difficult, as there are several good examples for amateur study. The Messier objects M27 and M57 in Vulpecula and Lyra are beautiful objects that stand out against the starry backdrop of the Milky Way, whilst M97 in Ursa Major, NGC 7662 in Andromeda, and NGC 6543 in Draco are lovely examples of their type.
Conversely, the death of a massive star is a relatively rare event. This is partly because such stars are rare in numbers within the galaxy. Nevertheless, there are enough of these rare but exciting objects to become worthy of study, and they generally give themselves away due to the expulsion of materials in shells or nebulous clouds. Stars such as Wolf-Rayet types have large UV excess or are termed Luminous Blue Variables (LBV) and are great candidates for supernova explosions. Massive stars which are ending their lives as red giants, such as Betelguese in Orion, are also appropriate candidates for spectacular explosions. Massive stars continue the fusion process from hydrogen to helium, through carbon, oxygen, nitrogen neon, aluminium, silicon, and others right up to the iron stage. Once the silicon is turned to iron in the core, the last (exothermic) process that holds the star up against gravity is over. To make iron fuse into the next generation of heavier elements it is necessary to inject energy in to the star, as the process is endothermic—it needs energy just to keep going.
No energy is available at this stage, and so the core falters and is squeezed by the overlying layers, and the materials break down allowing a huge implosion of the core. This implosion rebounds, and the outer layers falling in under gravity are met by an enormous shock wave which causes the formation of elements heavier than iron on the periodic table in a process known as explosive nucleosynthesis. The resultant explosion of the star spreads its outer layers into space at a very rapid acceleration—up to 60,000km a second—and the light from the explosion is so bright that it can outshine entire galaxies for a brief period.
The expanding gasses may be lit by radiation for a few months and by the conversion of Ni56 to Fe56 but the light fades eventually to leave an expanding patch of gasses. The core at this stage either becomes a black hole, dependent on how much mass has been shed by the core over the last gasps of its lifetime, or a neutron star like the one in the Crab nebula. The synchrotron radiation from the neutron star, which has now become a pulsar, is then responsible for the ionization of the expanding nebula.
By their brief and ethereal nature, there are very few supernova remnants available for amateur study. The best known examples are the Crab nebula in Taurus and the Veil nebula in Cygnus.
Nebulae come in all shapes and sizes and different brightness. Some will be right at the edge of your observing ability whilst others will be well within reach. The application of photography by many amateur astronomers today render images which would challenge those from a major observatory only 50 years ago. The life cycle from gas cloud to star back to gas cloud is a reminder that the universe is constantly recycling materials, and that the rubbish of yesteryear is actually the future of stars, planets, and possibly even life elsewhere. Getting to know and appreciate their beauty and their stories gives us a fresh perspective on our place in the cosmos and an endless vista of wonderful objects to observe.
Gallery of Author’s Images
About the Author
Martin Griffiths is an enthusiastic science communicator, writer and professional astronomer. He is a recipient of the Astrobiology Society of Britain’s Public Outreach Award (2008) and the Astronomical League’s Outreach Master Award (2010). He is currently an astronomer at the University of South Wales in the UK, and a consultant to the Welsh Government through his involvement with the Dark Sky Discovery initiative, enabling public access to dark sky sites in association with Dark Sky Wales, Dark Sky Scotland, and Natural England. He was also responsible for surveying the sky quality of the Brecon Beacons National Park in their successful bid to gain International Dark Sky Association Dark Sky Reserve status in 2013 and is a consultant to the Hay Tourism Board for their annual dark sky festivals. Griffiths is the Director of the Brecon Beacons Observatory, a public and education resource, fitted with a 30cm telescope situated in the Dark Sky Reserve. He is also a Fellow of the Royal Astronomical Society; a Fellow of the Higher Education Academy; a member of the Astrobiology Society of Britain; the European Society for the History of Science: the British Astronomical Association; the British Science Association; and the Webb Deep-Sky Society. | 0.911939 | 3.950867 |
Scientists ability to study the Sun, the star that sustains life o Earth, took a massive leap forward today with the launch of SOHO, a sophisticated state-of-the-art spacecraft built by the European Space Agency (ESA).
"Understanding how the Sun behaves is of crucial importance to all of us on Earth. It affects our everyday lives" said Roger Bonnet, Director of Science at ESA, who witnessed SOHO's spectacular nighttime launch from Cape Canaveral. "When SOHO begins work in four months time, scientists will, for the first time, be able to study this star 24 hours a day, 365 days a year".
The 12 instruments on SOHO will probe the Sun inside out, from the star's very centre to the solar wind that blasts its way through the solar system. It will even listen to sounds, like musical notes, deep within the star by recording their vibrations when they reach the surface.
SOHO was launched from Cape Canaveral Air Station, Florida, atop an Atlas IIAS rocket, at 09:08 CET on Saturday 2 December 1995. The 1.6 tonne observatory was released into its transfer orbit from the rocket's Centaur upper stage about two hours after launch. It will take four months for the satellite to reach its final position, a unique vantage point, located 1.5 million kilometres from Earth, where the gravitational pull of the Earth and Sun are equal. From here, the Lagrange point, SOHO will have an unobstructed view of the Sun all year round. SOHO's launch was delayed from 23 November because a flaw was discovered in a precision regulator, which throttles the power of the booster engine on the Atlas rocket. The system was replaced and retested before the launch.
SOHO is a project of international cooperation between ESA and NASA. The spacecraft was designed and built in Europe, NASA provided the launch and will operate the satellite from its Goddard Space Flight Center, Maryland. European scientists provided eight of the observatory's instruments and US scientists a further three. The spacecraft is part of the international Solar-Terrestrial Science Programme, the next member of which is Cluster, a flotilla of four spacecraft that will study how the Sun affects Earth and surrounding space. Cluster is scheduled for launch by Ariane 5 end of April 1996. | 0.867879 | 3.022023 |
At the American Astronomical Society (AAS) meeting now under way in Washington, DC, several teams of astronomers have announced new advances in understanding the giant black holes that inhabit the centers of nearly all large galaxies. And one group has announced the first evidence of a star being ripped apart by a medium-sized black hole, a variety that astronomers have not been sure exists.
In recent years, astronomers have found that every time they search the heart of a large galaxy that has a central bulge of old stars, they find a black hole with about a million to several billion times the mass of the Sun. But what happens when two large galaxies collide and merge, a scenario that has played out countless times in the universe’s history? Numerous studies suggest that the two black holes should go into orbit around each other and eventually spiral together and merge — but not for a long time. If this picture is correct, astronomers ought to find many galaxies with two supermassive holes.
This image, taken with Hubble's Advanced Camera for Surveys, clearly reveals that the faint, distant galaxy COSMOS J100043.15+020637.2 has two bright nuclei. The tidal tail of stars to the left shows that the galaxy recently merged with another, which apparently brought along its own supermassive black hole. Spectra of the two nuclei show that they have different radial velocities. They'll eventually spiral together and combine.
The problem is, astronomers have searched nearby galaxies for double black holes for many years and have only found a handful of convincing candidates. But at a press conference Monday at the AAS, a group led by Julia Comerford of the University of California at Berkeley announced 33 galaxies that have two. “We have discovered 33 pairs of these waltzing supermassive black holes,” she said. “This result is significant because it shows us that they are much more common than previously known from observations.”
All but one of the pairs come from an analysis of several thousand very distant galaxies observed in the DEEP2 Galaxy Redshift Survey (the other comes from the COSMOS galaxy survey). Many of these have supermassive holes that are actively swallowing gas, making their surroundings shine bright. Comerford and her colleagues identified 33 paired cases, in which one active nucleus is moving at high speed (a few hundred kilometers per second, or roughly 500,000 miles per hour) with respect to the host galaxy and its own nucleus.
The black holes in each pair are typically a few thousand light-years apart, meaning they are not yet close enough to each other to go into a tight orbit. For this reason, Comerford describes them as “dual black holes,” and not true binary black holes.
But as the interloper gravitationally stirs up the stars and gas that it passes, it loses momentum. So it should eventually sink to the center to form a true binary with the galaxy's native hole. Their inspiral and eventual merger should be a long, drawn-out process that will take hundreds of millions or billions of years.
Another group, led by Francesca Civano of the Harvard-Smithsonian Center for Astrophysics, studied X-ray and optical spectra of one of those 33 galaxies and found evidence that a black hole that already resulted from a merger 1 to 10 million years ago is shooting away from the galaxy’s center at the incredible speed of at least 1,300 km per second (3 million miles per hour). The simplest explanation is that it was born from the merger of two unequal black holes. Computer simulations indicate that gravitational radiation emitted asymmetrically as such holes merge can give the end product a huge kick, in some cases enough to eject it clear out of its galaxy. Civano says the measured radial velocity of this fast-moving hole is consistent with such a kick, but that further observations are needed to determine if this interpretation is correct.
A third group, led by Ruth Daly of Penn State University, studied 55 supermassive black holes that are producing powerful high-speed particle jets. Using a new method that she published last year, Daly estimated each hole’s spin from the jet’s power. She found a wide range of black-hole spins among her 55 objects. The most distant of them, up to 10 billion light-years away and seen when the universe was young, spin at the maximum speed theoretically possible. But closer black holes, some just a few tens of millions of light-years away in essentially the present-day universe, spin at only about 10% to 80% of their theoretical maximum speed.
A fourth group looked for unusual activity around suspected "intermediate- mass" black holes, those with perhaps a few thousand times the mass of the Sun. Astronomers have sought this variety for decades and found several very strong candidates. But conclusive proof does not yet exist, and the field remains rife with controversy. Some of the best candidates have been found in the centers of globular clusters, collections of several hundred thousand ancient stars.
An X-ray image from the Chandra X-ray Observatory, shown in blue, is overlaid on an optical image of the elliptical galaxy NGC 1399 (mostly hidden in the X-ray glare). The Chandra observations indicate that one object in the galaxy's fringe is a so-called ultraluminous X-ray source (ULX): one that emits more X-rays than any known stellar X-ray source, but less than the supermassive black holes in galaxy centers. This one shows spectral signs of having recently torn apart a heavy-element-rich white dwarf star.
X-ray: NASA / CXC / UA / J. Irwin. Optical: NASA / STScI
The team, led by Jimmy Irwin of the University of Alabama, studied a globular cluster in the fringes of elliptical galaxy NGC 1399, located about 65 million light-years away in Fornax. Unlike most globulars, this one shows strong X-ray emission. The strength and other characteristics of the X-ray blaze ("ULX" in the image at right) suggest that the hole has an intermediate mass — much greater than the stellar-mass black holes.
Visible-light spectra show large amounts of the relatively heavy elements oxygen and nitrogen in its hot stuff, but no hydrogen. Heavy elements aren't found in gaseous form in globular clusters — but they would be expected if an old white-dwarf star were torn to gaseous shreds by passing very close to a black hole.
Although other explanations remain very much in play, Irwin said this is the first evidence that an intermediate-mass black hole ripped apart a star. “If our assumptions are true,” he added, “we found the first stellar disruption event in a globular cluster, and that intermediate-mass black holes exist in the universe.”
As with most results presented at conferences, these results have yet to be fully vetted by the astronomical community and have not been independently confirmed. | 0.83514 | 4.061128 |
What would it look like to orbit a black hole? Many black holes are surrounded by swirling pools of gas known as accretion disks. These disks can be extremely hot, and much of the orbiting gas will eventually fall through the black hole’s event horizon — where it will never been seen again. The featured animation is an artist’s rendering of the curious disk spiraling around the supermassive black hole at the center of spiral galaxy NGC 3147. Gas at the inner edge of this disk is so close to the black hole that it moves unusually fast — at 10 percent of the speed of light. Gas this fast shows relativistic beaming, making the side of the disk heading toward us appear significantly brighter than the side moving away. The animation is based on images of NGC 3147 made recently with the Hubble Space Telescope.
You are a spaceship soaring through the universe. So is your dog. We all carry with us trillions of microorganisms as we go through life. These multitudes of bacteria, fungi, and archaea have different DNA than you. Collectively called your microbiome, your shipmates outnumber your own cells. Your crew members form communities, help digest food, engage in battles against intruders, and sometimes commute on a liquid superhighway from one end of your body to the other. Much of what your microbiome does, however, remains unknown. You are the captain, but being nice to your crew may allow you to explore more of your local cosmos.
By the turn of the 20th century advances in photography contributed an important tool for astronomers. Improving photographic materials, long exposures, and new telescope designs produced astronomical images with details not visible at the telescopic eyepiece alone. Remarkably recognizable to astrophotographers today, this stunning image of the star forming Orion Nebula was captured in 1901 by American astronomer and telescope designer George Ritchey. The original glass photographic plate, sensitive to green and blue wavelengths, has been digitized and light-to-dark inverted to produce a positive image. His hand written notes indicate a 50 minute long exposure that ended at dawn and a reflecting telescope aperture of 24 inches masked to 18 inches to improve the sharpness of the recorded image. Ritchey’s plates from over a hundred years ago preserve astronomical data and can still be used for exploring astrophysical processes.
Like an illustration in a galactic Just So Story, the Elephant’s Trunk Nebula winds through the emission nebula and young star cluster complex IC 1396, in the high and far off constellation of Cepheus. Also known as vdB 142, the cosmic elephant’s trunk is over 20 light-years long. This colorful close-up view was recorded through narrow band filters that transmit the light from ionized hydrogen, sulfur, and oxygen atoms in the region. The resulting composite highlights the bright swept-back ridges that outline pockets of cool interstellar dust and gas. Such embedded, dark, tendril-shaped clouds contain the raw material for star formation and hide protostars within. Nearly 3,000 light-years distant, the relatively faint IC 1396 complex covers a large region on the sky, spanning over 5 degrees. The dramatic scene spans a 1 degree wide field, about the size of 2 Full Moons.
Despite interfering moonlight, many denizens of planet Earth were able to watch this year’s Perseid meteor shower. This pastoral scene includes local skygazers admiring the shower’s brief, heavenly flashes in predawn hours near peak activity on August 13 from Nalati Grassland in Xinjiang, China. A composite, the image registers seven frames taken during a two hour span recording Perseid meteor streaks against a starry sky. Centered along the horizon is the Plough, the north’s most famous asterism, though some might see the familiar celestial kitchen utensil known as the Big Dipper. Perhaps the year’s most easily enjoyed meteor shower, Perseid meteors are produced as Earth itself sweeps through dust from periodic comet Swift-Tuttle. The dust particles are vaporized at altitudes of 100 kilometers or so as they plow through the atmosphere at 60 kilometers per second.
What could shoot out a neutron star like a cannon ball? A supernova. About 10,000 years ago, the supernova that created the nebular remnant CTB 1 not only destroyed a massive star but blasted its newly formed neutron star core — a pulsar — out into the Milky Way Galaxy. The pulsar, spinning 8.7 times a second, was discovered using downloadable software Einstein@Home searching through data taken by NASA’s orbiting Fermi Gamma-Ray Observatory. Traveling over 1,000 kilometers per second, the pulsar PSR J0002+6216 (J0002 for short) has already left the supernova remnant CTB 1, and is even fast enough to leave our Galaxy. Pictured, the trail of the pulsar is visible extending to the lower left of the supernova remnant. The featured image is a combination of radio images from the VLA and DRAO radio observatories, as well as data archived from NASA’s orbiting IRAS infrared observatory. It is well known that supernovas can act as cannons, and even that pulsars can act as cannonballs — what is not known is how supernovas do it.
Tonight is a good night to see meteors. Comet dust will rain down on planet Earth, streaking through dark skies during the peak of the annual Perseid Meteor Shower. The featured composite image was taken during last year’s Perseids from the Poloniny Dark Sky Park in Slovakia. The unusual building in the foreground is a planetarium on the grounds of Kolonica Observatory. Although the comet dust particles travel parallel to each other, the resulting shower meteors clearly seem to radiate from a single point on the sky in the eponymous constellation Perseus. The radiant effect is due to perspective, as the parallel tracks appear to converge at a distance, like train tracks. The Perseid Meteor Shower is expected to peak after midnight tonight, although unfortunately this year the sky will be brightened by a near full Moon. | 0.932942 | 3.831097 |
University of California, Los Angeles
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Researchers with the UCLA Team are investigating six broad frontiers of knowledge within the scope of astrobiology, using techniques and instruments that have not been widely applied before. These are:
- Prediction, detection, and characterization of extrasolar planetary systems that may be abodes for life. Investigation of the prevalence and properties of comets and small objects observationally and also theoretically, the latter in the context of modeling planetesimal accretion in the presence of one or more giant planets.
- Geobiology and biogeochemistry of the oldest record of life on Earth and Mars. Exploration of the undiscovered Hadean history of Earth and Mars as cradles for life using Earth’s oldest geological terrains (Australia, Canada, Greenland) plus Martian meteorites and returned samples
- Paleomicrobiology and the evolution of metabolic pathways in the Archean environment. Definition of the morphological attributes plus trace element and isotopic signatures of microbial biosynthetic pathways in living cells, and the application of this knowledge to interpret the microbial fossil record of the early Earth as a prelude to Mars.
- Genomic evolution , the tree of life, and the early fossil record of life on Earth. Reconstruction of the genomes, and hence the biochemistries, of crucial nodes in the tree of life and integration of that knowledge with the fossil record using key fossils, biogeochemical signatures, radioisotopic ages, and molecular clocks. This line of investigation includes both experimental and theoretical studies of evolutionary processes.
- Planetary science: Celestial influences on planetary environments. This emphasis examines the early Solar System environment as a potential habitat for life using naturally delivered and recovered extraterrestrial materials. Geophysical and geological exploration of an area in the Bellingshausen Sea, which is the only known site of an asteroid impact into a deep-ocean basin, is being used to understand the processes and environmental effects of an oceanic event of this scale. Additional insight into large impacts within the habitable zone is coming from long numerical integrations of Solar System dynamics. And, in a different study members of the UCLA Team have developed a mission-testable, end-member model for heat production within Europa that has important implications for the possibility of maintaining life in Europa’s subsurface ocean.
- Detection of life in the Solar System. Small spacecraft-mounted searches for evidence of biology and prebiology on Mars, Europa, and Titan based on laboratory and field experiences on Earth. Currently the UCLA Teams is working on the Artemis multi-Scout mission, which has been selected by NASA as one of ten potential payloads for launch in 2007. The plan for Artemis is to send an orbiter carrying three or more small landers which will be targeted to a wide range of latitudes, including the polar regions. | 0.899839 | 3.207359 |
Indian astrophysicists have discovered large ultraviolet lobes and jets that were hurled out from a dying star, using data from AstroSat – space observatory launched by the Indian Space Research Organisation (ISRO) in 2015.
The discovery has been featured as the AstroSat Picture of the Month (APOM) for October.
Professor Kameswara Rao of the Indian Institute of Astrophysics (IIA) and his collaborators used the Ultra-Violet Imaging Telescope (UVIT) on board AstroSat to stare at a planetary nebula called NGC 6302, popularly known as the Butterfly Nebula. A planetary nebula is formed when a star like our Sun, or a few times heavier, is in its dying days. The term, a misnomer now, was coined by astronomers in the 19th century since the nebula looked like planets through their telescopes.
“When hydrogen and helium fuel that kept the star shining gets exhausted, the star expands in size and becomes a red giant star. Such stars shed most of their outer layers which expands outwards, and the inner core, made of carbon and oxygen, shrinks further and becomes hotter. This hot core shines brightly in the ultraviolet, and ionizes the expanding gas. This glowing ionized gas is what is seen as a planetary nebula”, Prof Rao explained.
Sriram Krishna, a student of Rao, spent many hours analysing the data from the Butterfly Nebula. “Its central star is one of the hottest that we know, at 220000 degrees. The name itself comes from the shape of the two lobes of expanding gas that look like the wings of a butterfly”, he said. One might expect a Planetary Nebula to be spherical, but it actually exhibits a range of complicated structures. “We used the UVIT on AstroSat to make four images of the nebula, each in different ultraviolet ‘colours’, or filters. The image made with the filter centred at 160.8 nanometres, called F169M, had a surprise in store for us”, said Sriram.
Astronomers have studied the two lobes of the nebula for many years through visible light images. They expect that the more energetic ultraviolet light would be emitted closer to the central star, where the hot stellar wind hits the slowly expanding gas. “However, we discovered that the lobes imaged with the F169M filter in ultraviolet were about three times larger than the size of the lobes imaged in visible light”, said Sriram. After careful analysis, their study concluded that this ultraviolet emission must be due to cold molecular hydrogen gas outside the visible lobes which had gone undetected so far.
“Our discovery points to an unseen companion star in an orbit with the central star”, said Firoza Sutaria, one of the co-authors. In addition, researchers discovered two faint jets blasting out from the centre, at almost right angles to our new ultraviolet lobes. The team led by Prof Rao has recently discovered a large ultraviolet halo in yet another planetary nebula using AstroSat, and will be looking at many more such objects in the future. They hope that such discoveries may provide the answer to the age old puzzle of the ‘missing mass problem in planetary nebulae’.
This discovery was made possible because of the uniqueness of UVIT. “Of all the ultraviolet telescopes in space, UVIT is special in its ability to image a large field of view with a very high resolution, or detail”, said Dr V. Girish of ISRO. “This ability, coupled with a novel image analysis software that we had developed led us to this discovery”, explained Prof Jayant Murthy, a co-author of the paper, and Director of IIA.
These results have been published recently in the journal Astronomy and Astrophysics, co-authored by Kameswara Rao, Sriram Krishna, Jayant Murthy, Firoza Sutaria and Rekesh Mohan of IIA, Alak Ray of Homi Bhabha Centre for Science Education and De Marco of Macquarie University in Australia.
Article Courtesy: India Science Wire
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For NASA’s Kepler space telescope, the world will end in ice rather than fire.
Kepler, which is responsible for 70 percent of the roughly 3,800 confirmed exoplanet discoveries to date, has closed its powerful eyes. The prolific telescope is out of fuel and will be decommissioned in the next week or two, NASA officials announced yesterday (Oct. 30).
Kepler will not go out in a dramatic blaze of glory like NASA’s Saturn-orbiting Cassini spacecraft, which was intentionally deorbited into the ringed planet’s thick atmosphere in September 2017 when its fuel gauge began scraping “E.” [Kepler’s 7 Greatest Exoplanet Discoveries]
Rather, Kepler team members will beam a single, simple command to the sun-orbiting planet hunter, triggering a decommissioning sequence that’s already aboard the spacecraft. Kepler will shut down its radio transmitter and onboard fault-protection systems, becoming an inert chunk of metal that floats, silent and unresponding, through the cold, dark depths of space.
“Kepler is currently trailing the Earth by about 94 million miles, and will remain the same distance from the Earth for the foreseeable future,” Charlie Sobeck, project system engineer at NASA’s Ames Research Center in Moffett Field, California, said during a teleconference with reporters yesterday.
There will be some jostling over the decades. By 2060, for example, the faster-orbiting Earth will have almost caught up with Kepler, NASA officials explained in a new video. Our planet’s gravity will then nudge the space telescope toward the sun a bit, and Kepler will move ahead of Earth on a slightly shorter, faster orbit. But in 2117, Kepler will pop back onto its old path after another encounter with Earth. And the cycle will continue.
So a rescue or refueling mission would be nearly impossible, NASA officials have said. Astronauts repaired and upgraded the agency’s Hubble Space Telescope five separate times from 1993 to 2009, but Hubble resides in low-Earth orbit, a mere 353 miles (569 kilometers) above our planet.
Kepler launched in March 2009, tasked with determining how common Earth-like planets are around the Milky Way galaxy. The spacecraft hunted for alien worlds using the “transit method,” noting the tiny dips in stars’ brightness caused by orbiting planets crossing their faces.
Kepler initially stared at about 150,000 stars simultaneously. This original work came to an end in May 2013, when the spacecraft lost the second of its four orientation-maintaining reaction wheels. However, mission team members soon figured out that they could stabilize Kepler using the remaining wheels and sunlight pressure, and in 2014 the scope embarked on a new mission known as K2.
During K2, Kepler made a variety of observations over shifting 80-day campaigns, studying everything from asteroids and comets in our own solar system to distant supernova explosions.
But Kepler will forever be remembered for its exoplanet finds. The spacecraft’s current tally stands at 2,681 alien worlds, 354 of which were discovered during K2. Nearly 2,900 Kepler exoplanet “candidates” still await vetting by follow-up analysis or observation, and history suggests that most of them will end up being confirmed.
Kepler has long been about far more than just those raw numbers, however. The space telescope’s observations have revealed that planets outnumber stars in the galaxy; that Earth-like, potentially habitable worlds are common; and that planets, and planetary systems, are far more varied and diverse than the limited example provided by our own solar system.
Such discoveries are reshaping astronomers’ understanding of humanity’s place in the universe and better equipping astrobiologists to search for signs of our cosmic neighbors, mission team members said.
“Basically, Kepler opened the gate for mankind’s exploration of the cosmos,” Kepler mission founding principal investigator Bill Borucki, who retired in 2015 after many years at NASA Ames, said during yesterday’s telecon.
The total price tag for Kepler will end up being about $700 million, Sobeck and Borucki said. | 0.864287 | 3.055869 |
When photographic film and plates were used for astronomical imaging, it was common to produce a final image from a single exposure, which might last for hours. Digital sensors don't work as well for such long exposures, but make it easier to combine short exposures, which brings several benefits. I'll try to address both aspects below, though it is a large topic. I'll note that combining multiple exposures is a common technique in both astronomical research (for quantitative scientific analysis) and astrophotography (where an aesthetically pleasing rendering is the objective).
I'm going to focus only on multiple exposures of a single field (not "panorama"-type merging), and I'm going to focus on merging exposures to produce images that show faint detail and sharp stars, not star trails shots. (Star trails are also often photographed in multiple exposures, for the reasons I describe in my first section, but the benefits I describe in my second section don't really apply.)
Why don't digital sensors handle long exposures well?
Each pixel in an image produced by your camera corresponds to a photosite on the sensor. The photosite's job is to absorb photons (particles of light) and convert them to electrons. These electrons build up during the exposure in proportion to the number of photons hitting the photosite, and then they're read out (basically, counted) at the end of the exposure, to give the brightness of that pixel.
Each photosite has a maximum number of electrons that it can hold, called "full well." Once a photosite hits "full well", any additional photons that fall on that photosite will fail to be counted—the photosite or pixel is said to be "saturated". So one downside to a long exposure is that the brightest stars in the image may saturate early in the exposure and their full brightness compared to fainter objects may not be recorded. (They may also cause artifacts like spilling over into large, ugly "saturation trails" on some types of sensor.)
But another problem is that throughout the exposure, electrons are building up in all the photosites due to noise. One source of noise is "dark current", which arises from the temperature of the sensor. Sensors in research instruments at observatories are normally cryogenically cooled, for example with liquid nitrogen. This keeps dark current at a pretty negligible level in these instruments. Many amateur astronomical sensors are cooled with dry ice or a thermoelectric cooler, which isn't as cold, but still helpful. Ordinary DSLRs are not cooled at all, and in fact heat up during an exposure, so the dark current is significant. Besides dark current, the brightness of the sky, even at a dark site, causes electrons to build up in the photosites.
As these "background" counts from the sky and dark current are building up, the gap between the background and full well for the photosite narrows, reducing the "dynamic range" between the faintest and brightest objects you can record. Eventually, if your exposure were long enough, every photosite would be saturated from the background, and you wouldn't have any detail anywhere.
So, if long exposures are bad, what's the good news?
The good news is that with digital images, it's pretty easy to combine a bunch of short exposures into the equivalent of a long exposure, by adding or averaging a pixel's values in each exposure to produce the final image. But while we're doing that, we can take advantage of several benefits:
We can fix up tracking errors. As you know, the night sky appears to rotate overhead as the earth turns on its axis. This means that for a long exposure, your camera or telescope needs to follow this apparent motion, and it needs to do so very accurately, to keep the stars from appearing out-of-round on the image. For very brief exposures (~seconds) you might get away with a camera fixed on a tripod. For longer exposures (~minutes or possibly longer) you can use a clock drive that turns the camera at the same rate as the sky; this is called tracking. But the clock drive probably isn't exactly the right speed, and the polar alignment of the mount probably isn't quite right, so for longer exposures you need an autoguider (or a lot of patience to guide by hand). Guiding corrects for errors in tracking, by "watching" a star and keeping it in the same place during the exposure.
If you combine short exposures, your tracking or guiding only needs to be good enough to keep the stars sharp for the duration of your short exposures. Before combining the short exposures, you register the images to line everything up again. This can usually be done automatically with software.
We can throw out bad exposures. If an airplane, or a satellite, or a car's headlights, ruins a 30-second exposure, you can toss out that 30-second exposure and use the rest. This is way better than throwing out a 5-hour exposure because of the same defects.
We can avoid sensor defects and other bad pixels. As noted above, there's likely to be some tracking or guiding error that means we need to register the images before combining them. Because of these small errors, a particular star will probably fall on a different pixel in different exposures. So if our sensor has a bad pixel or bad column, we can average our exposures in a way that only uses the "good" values and not the "bad" values. (On telescopes that guide well, like observatory-class telescopes, the telescope may be deliberately offset slightly between exposures to achieve this benefit.) Also, cosmic rays often cause "hot pixel"-like effects in long exposures, so we can find those pixels and exclude them from the average.
Our exposure can be longer than a night! Thus far, astronomers' efforts to destroy the sun have been thwarted by the soulless minions of orthodoxy. As a result, each night is only something like 12 hours on average, and not all of that is completely dark, and whatever object we're trying to photograph may not be up the whole time, depending on the time of year and our location. So combining exposures lets us take exposures on multiple nights. This also means that we can plan our observing over multiple nights, to observe each object during the time of night that it's highest in the sky, so we're looking through less air than when it's near the horizon. | 0.815193 | 3.898275 |
The Earth once had two moons circling in the same orbit, say scientists, until a collision between the two created the moon we see today.
The big crash could explain why the moon is so lopsided, and more mountainous on its far side, say planetary scientists at the University of California, Santa Cruz.
This has always been a puzzle. The moon’s near side is relatively low and flat, while the topography of the far side is high and mountainous, with a much thicker crust.
It had already been surmised that our moon was created through a collision with a Mars-sized object, ejecting debris that coalesced to form the moon.
But the new study suggests that the impact also created another, smaller body, which eventually fell back onto the moon and coated one side with an extra layer of solid crust tens of kilometers thick.
“Our model works well with models of the moon-forming giant impact, which predict there should be massive debris left in orbit about the Earth, besides the moon itself. It agrees with what is known about the dynamical stability of such a system, the timing of the cooling of the moon, and the ages of lunar rocks,” says Erik Asphaug, professor of Earth and planetary sciences.
Asphaug’s team used computer simulations of an impact between the moon and a smaller companion (about one-thirtieth the mass of the moon) to study the dynamics of the collision and track the evolution and distribution of lunar material in its aftermath.
They found that in such a low-velocity collision, the impact wouldn’t form a crater or cause much melting. Instead, most of the colliding material would be piled onto the impacted hemisphere as a thick new layer of solid crust.
“The collision could have happened anywhere on the moon,” says postdoctoral researcher Martin Jutzi. “The final body is lopsided and would reorient so that one side faces Earth.”
Other models have been proposed to explain the formation of the highlands, including the suggestion that tidal forces were responsible. More data should help establish which, if either, is correct. | 0.851421 | 3.816045 |
Astronomers in Chile have used a special infrared telescope to capture an astounding nine billion pixel image of the center of our home galaxy. The 84 million star catalogue compiled by the ESO’s Visible Infrared Survey Telescope for Astronomy (VISTA) is not only the biggest image of the Milky Way ever produced, but is also one of the largest astronomical images of all time.
The image captures part of the center of our spiral galaxy, known as the Galactic Bulge. The bulge is notoriously difficult to photograph as a tremendous amount of dust obscures most images, but scientists were able to sidestep this issue by using VISTA’s infrared technology.
“By observing in detail the myriads of stars surrounding the centre of the Milky Way we can learn a lot more about the formation and evolution of not only our galaxy, but also spiral galaxies in general,” said Roberto Saito, astronomer at Pontificia Universidad Católica de Chile and lead author of the study.
Scientists were excited by the large number of red dwarf stars captured in the image, as they are ideal candidates for the use of the transit method in searching for small exoplanets like our own. The transit method observes partial blockages of a star’s light as a planet orbits in front of it. Red dwarfs are typically faint stars and therefore small interferences in their light are more easily discernible.
The VISTA image is so large that if the whole photo were rendered in the resolution of a normal book, the image would span nearly 30 feet (9 m). The ESO has made all the data from their study publically available, and what’s more they have also released the image equipped with a zoom function which makes for mind-boggling viewing.
Due to its almost non-existent humidity and clear skies, the Atacama is the planet’s premier location for astronomy. Chile is home to almost half the world’s telescope infrastructure, and this is set to increase to over two thirds by 2018.
Two more of Chile’s astronomy projects in particular have been tipped to generate groundbreaking findings. Currently under construction in the Atacama, the European Extremely Large Telescope is expected to enable astronomers to see further into the history of the universe than ever before. Meanwhile, the recently unveiled Dark Energy Camera in the Andes of Central Chile hopes to contribute to our understanding of dark matter and the makeup of the universe. | 0.862614 | 3.540672 |
Meteor showers result from the Earth’s orbital path intersecting areas of comet debris. Comets, as they orbit the Sun, leave behind pieces of their icy, dirty, selves. If these debris clouds happen to be along the Earth’s orbital path then the Earth will regularly pass through the comet debris cloud. As this happens the small comet pieces hit our outer atmosphere and vaporize from the friction generated heat. We then see these as the shooting stars that make up meteor showers.
There are, however, two exceptions to this. The January Quadrantid Meteors and the Geminids each come from their own respective asteroid rather than a comet. The source for the Geminids is Asteroid 3200 Phaethon
Looking toward the south to southwest and adding to viewing the Geminids is an un-named meteor shower with a radiant just below the bottom of the ‘Square of Pegasus’, between the ‘square’ and the ‘Circlet’ pattern of stars forming the head of the Western Fish of Pisces the Fishes. This meteor shower originates from Comet Wirtanen, a short-period comet orbiting the Sun every 5.5 years. The comet was discovered in 1948 and according to some predictions the Earth may pass through this comet’s debris cloud for the first time since the comet’s discovery. This part of the sky is over the south at sunset and as this graphic shows the radiant is over the southwest as the Geminids radiant is over the eastern horizon.
Click here to go to the Qué tal in the Current Skies web site for more observing information. | 0.801583 | 3.339324 |
Search for advanced civilizations beyond Earth finds nothing obvious in 100,000 galaxies
After searching 100,000 galaxies for signs of highly advanced extraterrestrial life, a team of scientists using observations from NASA’s WISE orbiting observatory has found no evidence of advanced civilizations in them.
“The idea behind our research is that, if an entire galaxy had been colonized by an advanced spacefaring civilization, the energy produced by that civilization’s technologies would be detectable in mid-infrared wavelengths — exactly the radiation that the WISE satellite was designed to detect for other astronomical purposes,” said Jason T. Wright, an assistant professor of astronomy and astrophysics at the Center for Exoplanets and Habitable Worlds at Penn State University, who conceived of and initiated the research.
The research team’s first paper about its Glimpsing Heat from Alien Technologies Survey (G-HAT), will be published in the Astrophysical Journal Supplement Series on April 15, 2015. Also among the team’s discoveries are some mysterious new phenomena in our own Milky Way galaxy.
“Whether an advanced spacefaring civilization uses the large amounts of energy from its galaxy’s stars to power computers, space flight, communication, or something we can’t yet imagine, fundamental thermodynamics tells us that this energy must be radiated away as heat in the mid-infrared wavelengths,” Wright said. “This same basic physics causes your computer to radiate heat while it is turned on.”
Theoretical physicist Freeman Dyson proposed in the 1960s that advanced alien civilizations beyond Earth could be detected by the telltale evidence of their mid-infrared emissions. It was not until space-based telescopes like the WISE satellite that it became possible to make sensitive measurements of this radiation emitted by objects in space.
Roger Griffith, a postbaccalaureate researcher at Penn State and the lead author of the paper, scoured almost the entire catalog of the WISE satellite’s detections — nearly 100 million entries — for objects consistent with galaxies emitting too much mid-infrared radiation. He then individually examined and categorized around 100,000 of the most promising galaxy images.
Wright reports, “We found about 50 galaxies that have unusually high levels of mid-infrared radiation. Our follow-up studies of those galaxies may reveal if the origin of their radiation results from natural astronomical processes, or if it could indicate the presence of a highly advanced civilization.”
In any case, Wright said, the team’s non-detection of any obvious alien-filled galaxies is an interesting and new scientific result. “Our results mean that, out of the 100,000 galaxies that WISE could see in sufficient detail, none of them is widely populated by an alien civilization using most of the starlight in its galaxy for its own purposes. That’s interesting because these galaxies are billions of years old, which should have been plenty of time for them to have been filled with alien civilizations, if they exist. Either they don’t exist, or they don’t yet use enough energy for us to recognize them,” Wright said.
“This research is a significant expansion of earlier work in this area,” said Brendan Mullan, director of the Buhl Planetarium at the Carnegie Science Center in Pittsburgh and a member of the G-HAT team. “The only previous study of civilizations in other galaxies looked at only 100 or so galaxies, and wasn’t looking for the heat they emit. This is new ground.”
Matthew Povich, an assistant professor of astronomy at Cal Poly Pomona, and a co-investigator on the project, said “Once we had identified the best candidates for alien-filled galaxies, we had to determine whether they were new discoveries that needed follow-up study, or well-known objects that had a lot of mid-infrared emission for some natural reason.” Jessica Maldonado, a Cal Poly Pomona undergraduate, searched the astronomical literature for the best of the objects detected as part of the study to see which were well known and which were new to science. “Ms. Maldonado discovered that about a half dozen of the objects are both unstudied and really interesting looking,” Povich said.
“When you’re looking for extreme phenomena with the newest, most sensitive technology, you expect to discover the unexpected, even if it’s not what you were looking for,” said Steinn Sigurdsson, professor of astronomy and astrophysics at Penn State’s Center for Exoplanets and Habitable Worlds and a co-investigator on the research team. “Sure enough, Roger and Jessica did find some puzzling new objects. They are almost certainly natural astronomical phenomena, but we need to study them more carefully before we can say for sure exactly what’s going on.”
Among the discoveries within our own Milky Way galaxy are a bright nebula around the nearby star 48 Librae, and a cluster of objects easily detected by WISE in a patch of sky that appears totally black when viewed with telescopes that detect only visible light. “This cluster is probably a group of very young stars forming inside a previously undiscovered molecular cloud, and the 48 Librae nebula apparently is due to a huge cloud of dust around the star, but both deserve much more careful study,” Povich said.
“As we look more carefully at the light from these galaxies,” said Wright, “we should be able to push our sensitivity to alien technology down to much lower levels, and to better distinguish heat resulting from natural astronomical sources from heat produced by advanced technologies. This pilot study is just the beginning.” | 0.864034 | 3.571206 |
The Galearthéan Institute Of Flat Earth Science & Technology
Read our Mission Statement
All Galearthéan lunar phases are predominantly the result of the three interacting phenomena, hereby known as SRG:
- Seasonal Sunlight
- Radioactive Recharge
- Gravitational Arches
Of all the wondrous phenomena which contradict the indoctrinated fallacy of a Spherical Earth, the most majestic of these have to be the miracle of the Galearthéan Daylight Moon Phenomena.
Witnessing the Moon during daylight is not a miracle in itself.
Yet, the miracle is beheld whence the Moon is high, the Sun is low and its topmost luminosity a hemispherical impossibility.
Yet before we can voyage deep into the Galearthéan Cosmological Explanation of this most spectacular event, it is necessary to explain the fundamental principles of Galearthéan Lunar Phases.
Whilst the most visibly obvious cause of the Moon’s glowing is its reflection of sunlight which travels above us whence the Earth is in darkness, the Moon is actually and nevertheless a self luminous planetoid.
As like a solitary Candle in a large Church does not illuminate the whole building, neither will the Sun illuminate the entire Earth as it orbits around. However, as like the Candle, a very mild glowing of light will travel unto further regions whence it is not blocked by variations in terrain. Herewith, it is this very soft surviving “mild glow” above our planar which reaches the surface of the Moon.
The reason the Moon shines so brightly even under such weak influence is due to the accumulation of ionizing radiation over millions of years. Whence this blanket of absorbed radiation becomes momentarily recharged by phases of sunlight, it will become excited and glow brightly across its surface.
It is only the Sun’s assistance which initiates the Moon’s own self generating luminosity.
Whilst the Moon is closer in orbit to the planar than the Sun is, both the Sun and Moon vary their heights throughout the year, as they orbit above and around our planar disc, causing a fluctuation of angular reflectivity and thus radioactive recharge upon the Moon’s surface.
Behold now, for it is actually this very beautiful self luminosity which causes anomalies such as an otherwise impossible Crescent Moon during bright daylight, whereby its luminous and darkened hemispheres contradict the clearly witnessable relative position of the Sun.
Its darkened hemisphere? A result of a gravitational anomaly.
This phenomena, known as a Szion Gravitational Arch, will now be discussed herein this article.
Meanwhile, for more information about the Galearthéan Moon and the Lunar Phases, visit our main page _*~ and select an item from the menu.
Of Szion & The Moon
Szion: The Galearthéan principle stating that neither the speed of light nor the nature of gravity is a constant. To elaborate, many observable phenomena are only apparitional in actuality, since founded subtleties of varying degrees prompt resigning observations unto a greater five dimensional science.
Gravitational Arches: Due to Szion, the five dimensional realm of influence, these are periodic patches in outer space of fluctuating gravity, forming in the shape of magnificent arches above our expansive plane. These cause various astronomical curiosities such as the bending of light and thus the ocular phases of the Moon, Venus and other objects.
“Szion Gravitational Arches” usually only manifest and reside about the close orbit of physical objects, whereby in outer space, an object’s relative density of plenum in conversation with the local antidensity of vacuum “fluctuates”, causing a change in the consequential gravity about that region of space.
Szion is a scientifically documentable fact, observable on two primary occasions:
- Whence a Crescent Moon and Sun are both visible in the daylight sky.
- Whence the Sun and Moon are both visible in the sky during a Total Lunar Eclipse.
1.) It is important to remember, that according to NASA, lunar phases are not caused by shadow of ANY kind, but by the mere direction of sunlight upon the Moon’s surface. Yet if this were true, then it would not only be impossible to witness a Crescent Moon whence the Sun is shining brightly, especially whence from the opposite horizon, but also there would be ZERO terminator line whatsoever dividing the Moon in half, since only a shadow or thus a Szion gravitational anomaly would cause such a visually sharp separation of its hemispheres.
Thus the illuminated half of the Moon during this event is a combination of reflection and self luminosity, while the darkened side is a result of a Szion Gravitational Arch bending the Moon’s own light around itself.
Furthermore, if you look closely, sometimes you will notice a very gentle glowing on its dark side and this is caused by an excessive charging of its radiated blanket, whilst conflicting gravitational influences affect the Szion Arch, allowing some light to reach or radiate out from its surface.
2.) Indoctrinated round Earth science teaches that a phenomena called “selenelion” is the explanation for this anomaly, whereby the planet’s atmosphere refracts light around its curve, causing the illusion of both objects being visible from the ground.
Yet this is a contradiction in terms! For they themselves state this event to be an “unusual” occurrence yet whilst at the same time acknowledging refraction to be a “regular” anomaly. Yet this nevertheless “regular” refraction would only in turn put all Solar and Lunar observations out of synchronisation, if we consider this Lunar Eclipse to be only unique.
In fact, if the Earth’s atmosphere is what causes their appearance in the sky through “bendy light”, then the Moon would seldom appear “eclipsed” by the Earth ever, for this very same refraction would often cause it to shine during most other eclipse events.
Furthermore if atmospheric refraction truly inflicted such a tremendous influence on the positions of objects in the sky, then many other necessary arial or astronomical observations would present very confusing results.
For example, aeroplanes would be observed approaching our locality whence they have not yet actually even reached the horizon! This would cause tremendous worry to many aeroplane pilots, especially during a time of war and battle.
Nay, all Galearthéan Lunar phases are purely cosmological mechanics of Szion.
A miracle then, it is true, for Szion is the direct astronomical explanation for the witnessing of Stars which shine brightly through the surface of the darkened Moon!
The phenomena of Lunar Transparency is a regularly documented observation throughout the history of the world, even to the extent that popular world religions incorporate such depictions into their culture of worship.
Szion Gravitational Arches are then effectively five dimensional bubbles which warp space, causing objects to appear transparent, satellites or planets to assume unusual orbits and even to slow down or speed up the passage of time.
In time to come, the human race will discover such anomalies of space and time to be more than common throughout the universe and that our Moon is but one piece of a much greater cosmological majesty. | 0.8865 | 3.530208 |
Another two white-dwarfs in Universe
Thanks to the Hubble Space Telescope, a team of astronomers found chemical signatures of debris of rocky planets around two white dwarfs, one constellation not far from us. So far it has been very difficult to observe planets within the clusters, but the same method could allow us to discover many more.
An Earth-like planet placed where we wouldn’t just expect: the atmosphere around a couple of old stars now reduced to white dwarfs in a cluster of stars in our vicinity. The Hubble Space Telescope has uncovered that there are at least debris, which suggests that the formation of rocky planets may be very common in star clusters. The two white dwarfs – the remains of stars that once were similar to the Sun – are located 150 light-years away in the cluster Hyades in the constellation of Taurus. The constellation is relatively young, born just 625 million years ago.
Astronomers believe that all stars are formed in clusters. However, so far the search for planets within the clusters did not go well – of the approximately 800 known extrasolar planets, only four are in orbit around stars that are part of clusters. This lack could be due to the nature of the stars within the clusters, young and active, its surrounding area being difficult to study in detail. A new study by Jay Farihi from University of Cambridge, published in the Monthly Notices of the Royal Astronomical Society has allowed observing stars that “retire” within the clusters, looking for signs of planet formation.
Spectroscopic observations conducted with Hubble identified silicon in the atmospheres of two white dwarfs, an important ingredient of the rock material that forms the Earth and other terrestrial planets of the Solar System. The silicon in question could have come from asteroids “crushed” by the gravity of white dwarfs. The rocky debris is likely to have formed a ring around the white dwarf, ending up being concentrated inwards. But if there were any asteroids, it most likely means that there were rocky planets around these stars formed early in their history.
“We have identified the chemical evidence of the presence of brick rocky planets,” says Farihi. “When these stars were born, they formed planets, and there is a good chance that currently retains some. The traces of rocky debris that we see are the proof. “In addition to finding silicon in the atmospheres of stars in the Hyades, Hubble also detected low levels of carbon, another sign of the rocky nature of the debris: in fact, astronomers know that the levels of carbon must be very low in rock materials of terrestrial nature. Find its weak chemical signature required the use of the powerful Hubble’s Cosmic Origins Spectrograph (COS): carbon footprints can only be detected in ultraviolet light, which cannot be studied by ground-based telescopes.
The team now plans to analyze other white dwarfs with the same technique to identify not only the composition of the rocks, but also the star around which they orbit. “The beauty of this technique is that no matter what the universe is doing, we will be able to measure it,” said Farihi. “So far we have used the solar system as a sort of map, but we do not know what happens in the rest of the Universe. We hope that with Hubble and his powerful spectrograph COS- ultraviolet light, and with the next ground-based telescopes from 30 – 40 meters, we will be able to tell other parts of the story.” | 0.883805 | 3.956004 |
These 210 images reflect Rosetta’s ever-changing view of Comet 67P/Churyumov–Gerasimenko between July 2014 and September 2016.
The sequence begins in the month leading up to Rosetta’s arrival on 6 August, when the comet was barely a few pixels in the field of view. Suddenly, the curious shape was revealed and Rosetta raced to image its surface, coming within 10 km, to find a suitable place for Philae to land just three months later.
Philae’s landing is featured with the ‘farewell’ images taken by both spacecraft of each other shortly after separation, and by Philae as it drew closer to the surface at its first touchdown point. An image taken at the final landing site is also shown.
The subsequent images, taken by Rosetta, reflect the varying distance from the comet as well as the comet’s rise and fall in activity as they orbited the Sun.
Before the comet reached its most active phase in August 2015, Rosetta was able to make some close flybys, including one in which the lighting geometry from the Sun was such that the spacecraft’s shadow could be seen on the surface.
Then, owing to the increase of dust in the local environment, Rosetta had to maintain a safer distance and carry out scientific observations from afar, but this also gave some impressive views of the comet’s global activity, including jets and outburst events.
Once the activity began to subside, Rosetta could come closer again and conduct science nearer to the nucleus, including capturing more high-resolution images of the surface, and looking out for changes after this active period.
Eventually, as the comet returned to the colder outer Solar System, so the available solar power to operate Rosetta fell. The mission concluded with Rosetta making its own dramatic descent to the surface on 30 September 2016. A selection of the final images taken are reflected in the last images shown in this montage. | 0.835095 | 3.392366 |
Climate science is complicated business, and understanding the extent to which climate change is man-made also requires an understanding of Earth's powerful natural cycles. One of those natural cycles involves Earth's orbit and its complicated dance with the sun.
The first thing you need to know about Earth's orbit and its effect on climate change is that orbital phases occur over tens of thousands of years, so the only climate trends that orbital patterns might help explain are long-term ones.
Even so, looking at Earth's orbital cycles can still offer some invaluable perspective on what is happening in the short term. Most notably, you might be surprised to learn that Earth's current warming trend is happening in spite of a relatively cool orbital phase. It's therefore possible to better appreciate the high degree that anthropogenic warming must be taking place in contrast.
Not as simple as you might think
Many people might be surprised to learn that Earth's orbit around the sun is much more complicated than the simple diagrams studied in childhood science classrooms. For instance, there are at least three major ways that Earth's orbit varies over the course of millennia: its eccentricity, its obliquity and its precession. Where the Earth is within each of these cycles has a significant effect on the amount of solar radiation — and thus, warmth — that the planet gets exposed to.
Check out this must-see educational video for a visual presentation on Earth's complicated orbit:
Earth's orbital eccentricity
Earth's orbit around the sun is more of an oval instead of a circle. The degree of a planet's orbital ellipse is referred to as its eccentricity. This image shows an orbit with an eccentricity of 0.5. (Photo: NASA)
Unlike what is portrayed in many diagrams of the solar system, Earth's orbit around the sun is elliptical, not perfectly circular. The degree of a planet's orbital ellipse is referred to as its eccentricity. What this means is that there are times of the year when the planet is closer to the sun than at other times. Obviously, when the planet is closer to the sun, it receives more solar radiation.
The point at which the Earth passes closest to the sun is called perihelion, and the point furthest from the sun is called aphelion.
It turns out that the shape of the Earth's orbital eccentricity varies over time from being nearly circular (low eccentricity of 0.0034) and mildly elliptical (high eccentricity of 0.058). It takes roughly 100,000 years for Earth to undergo a full cycle. In periods of high eccentricity, radiation exposure on Earth can accordingly fluctuate more wildly between periods of perihelion and aphelion. Those fluctuations are likewise far milder in times of low eccentricity. Currently, the Earth's orbital eccentricity is at about 0.0167, which means its orbit is closer to being at its most circular.
Earth's axial obliquity
Most people know that the planet's seasons are caused by the tilt of the Earth's axis. For instance, when it is summer in the Northern Hemisphere and winter in the Southern Hemisphere, the Earth's North Pole is tilted toward the sun. The seasons are likewise reversed when when the South Pole is tilted more toward the sun.
What many people don't realize, however, is that the angle at which the Earth tilts varies according to a 40,000 year cycle. These axial variations are referred to as a planet's obliquity.
For Earth, the tilt of the axis varies between 22.1 and 24.5 degrees. When the tilt is at a higher degree, the seasons can likewise be more severe. Currently the Earth's axial obliquity is at about 23.5 degrees — roughly in the middle of the cycle — and is in a decreasing phase.
Perhaps the most complicated of Earth's orbital variations is that of precession. Basically, because Earth wobbles on its axis, the particular season that occurs when Earth is at perihelion or aphelion varies over time. This can create a profound difference in the severity of the seasons, depending on whether you live in the Northern or Southern Hemisphere. For instance, if it is summer in the Northern Hemisphere when Earth is in perihelion, then that summer is likely to be more extreme. By comparison, when the Northern Hemisphere instead experiences summer in aphelion, the seasonal contrast will be less severe. The following image may help to visualize how this works:
(Photo: GregBenson [CC BY-SA 3.0]/Wikimedia Commons)
This cycle fluctuates on roughly a 21- to 26,000-year basis. Currently, summer solstice in the Northern Hemisphere happens near aphelion, so the Southern Hemisphere should experience more extreme seasonal contrasts than the Northern Hemisphere, all other factors being equal.
What's climate change got to do with it?
Quite simply, the more solar radiation bombarding Earth at any given time, the warmer the planet should get. So Earth's place in each of these cycles should have a measurable effect on long term climate trends — and it does. But that's not all. Another factor has to do with which hemisphere happens to be receiving the heaviest bombardment. This is because land warms faster than oceans do, and the Northern Hemisphere is covered by more land and less ocean than the Southern Hemisphere is.
It has also been shown that shifts between glacial and interglacial periods on Earth are most related to the severity of summers in the Northern Hemisphere. When summers are mild, enough snow and ice remains throughout the season, maintaining a glacial layer. When summers are too hot, however, more ice melts in the summer than can be replenished in the winter.
Given all of this, we might imagine a "perfect orbital storm" for global warming: when Earth's orbit is at its highest eccentricity, Earth's axial obliquity is at its highest degree, and the Northern Hemisphere is in perihelion at summer solstice.
But that's not what we see today. Instead, Earth's Northern Hemisphere currently experiences its summer in aphelion, the planet's obliquity is currently in the decreasing phase of its cycle, and Earth's orbit is fairly near its lowest phase of eccentricity. In other words, the current position of the Earth's orbit should result in cooler temperatures, but instead the average temperature of the planet is on the rise.
The immediate lesson in all of this is that there must be more to Earth's average temperature than can be explained through orbital phases. But a secondary lesson also lurks: Anthropogenic global warming, which climate scientists overwhelmingly believe is the prime culprit in our current warming trend, is at least powerful enough in the short term to counteract a relatively cool orbital phase. It's a fact that should at least give us pause to consider the profound effect that humans can have on the climate even against a backdrop of Earth's natural cycles. | 0.821775 | 3.598897 |
The sun is so far from Earth that its light takes eight minutes to reach the surface of our planet. Despite the distance, its magnetic field is having is having on our world is a huge influence. For example, a strong electromagnetic pulse can cause the light on the whole continent, so scientists it is extremely important to know the power of the magnetic field. Unfortunately, to obtain accurate data, they have not yet succeeded, but researchers from Queen’s University in Belfast claim to have done it.
To obtain an accurate measurement of the magnetic field scientists interfered with the Earth’s atmosphere — it weakens the field lines, so its capacity may be much higher than previously thought. The researchers claim that they received accurate data due to the good for the circumstances — they turned his telescope to the area of the surface of the Sun, which is considered the most volatile.
We have very few measurements of force and spatial characteristics of the magnetic field of the Sun. It’s a bit like trying to study the Earth’s climate, not being able to measure the temperature in different geographical locations.
David Kuridze, research fellow, Aberystwyth University
During the ten-day observation they recorded a powerful flash — analysis of its structure showed that the strength of the solar magnetic field 10 times greater than previously thought. If so, then the opening really means a lot. The magnetic field of the Sun determines the boundaries of the Solar system and protects us from cosmic rays. It also directly affects the climate of the Earth, and forms the Northern lights, and their changes are able to change the figures of compasses and GPS systems.
Discoveries concerning magnetic fields of the planets are still. In September 2018 the spacecraft “Juno” opened new features in Jupiter’s magnetic field. It turned out that it has a much complex structure — read about it in our material.
If you want to be aware of the news of science and technology, be sure to subscribe to our channel in Yandex.Zen. There you will find materials that have not got on the page! | 0.87492 | 3.207723 |
Planetary scientists using the Hubble Space Telescope have spotted a dark mini-moon orbiting the distant dwarf planet Makemake. The moon, nicknamed MK 2, is roughly 160 km (100 miles) wide and orbits about 20,000 km (13,000 miles) from Makemake. Makemake is 1,300 times brighter than its moon and is also much larger, at 1,400 km (870 miles) across, about 2/3rd the size of Pluto.
“Our discovery of the Makemakean moon means that every formally-designated Kuiper Belt dwarf planet has at least one moon!” said Alex Parker on Twitter. Parker, along with Mark Buie, both from the Southwest Research Institute, led the same team that found the small moons of Pluto in 2005, 2011, and 2012, and they used the same Hubble technique to find MK 2. NASA says Hubble’s Wide Field Camera 3 has the unique ability to see faint objects near bright ones, and together with its sharp resolution, allowed the scientists to pull the moon out from bright Makemake’s glare.
Previous searches for moons around Makemake came up empty, but Parker said their analysis shows the moon has a very dark surface and it is also in a nearly edge-on orbit, which made it very hard to find.
This moon might be able to provide more details about Makemake, such as its mass and density. For example, when Pluto’s moon Charon was discovered in 1978, astronomers were able to measure Charon’s orbit and then calculate the mass of Pluto, which showed Pluto’s mass was hundreds of times smaller than originally estimated.
“Makemake is in the class of rare Pluto-like objects, so finding a companion is important,” Parker said. “The discovery of this moon has given us an opportunity to study Makemake in far greater detail than we ever would have been able to without the companion.”
Parker also said the discovery of a moon for Makemake might solve a long-standing mystery about the dwarf planet. Thermal observations of Makemake by the Spitzer and Herschel space observatories seemed to show the bright world had some darker, warmer material on its surface, but other observations couldn’t confirm this.
Parker said perhaps the dark material isn’t on Makemake’s surface, but instead is in orbit. “I modeled the emission we expect from Makemake’s moon, and if the moon is very dark, it accounts for most previous thermal measurements,” he said on Twitter.
The researchers will need more Hubble observations to make accurate measurements to determine if the moon’s orbit is elliptical or circular, and this could help determine its origin. A tight circular orbit means that MK 2 probably formed from a collision between Makemake and another Kuiper Belt Object. If the moon is in a wide, elongated orbit, it is more likely to be a captured object from the Kuiper Belt. Many KBOs are covered with very dark material, so that might explain the dark surface of MK 2. | 0.830782 | 3.81657 |
Astrophysics: Frontiers and Controversies - Video
By Charles Bailyn
To listen to an audio podcast, mouse over the title and click Play. Open iTunes to download and subscribe to podcasts.
(ASTR 160) This course focuses on three particularly interesting areas of astronomy that are advancing very rapidly: Extra-Solar Planets, Black Holes, and Dark Energy. Particular attention is paid to current projects that promise to improve our understanding significantly over the next few years. The course explores not just what is known, but what is currently not known, and how astronomers are going about trying to find out. This course was recorded in Spring 2007.
|1||Video01 - Introduction||Professor Bailyn introduces the course and discusses the course material and requirements.||12/6/2011||Free||View in iTunes|
|2||Video02 - Planetary Orbits||Exoplanets are introduced and students learn how astronomers detect their presence as well as the challenges associated with it.||12/6/2011||Free||View in iTunes|
|3||Video03 - Our Solar System and the Pluto Problem||Class begins with a review of the first problem set. Newton's Third Law is applied in explaining how exoplanets are found.||12/6/2011||Free||View in iTunes|
|4||Video04 - Discovering Exoplanets: Hot Jupiters||The formation of planets is discussed with a special emphasis on the bodies in the Solar System. Planetary differences between the celestial bodies in the Inner and Outer Solar System are observed.||12/6/2011||Free||View in iTunes|
|5||Video05 - Planetary Transits||Professor Bailyn talks about student responses for a paper assignment on the controversy over Pluto. The central question is whether the popular debate is indeed a "scientific controversy."||12/6/2011||Free||View in iTunes|
|6||Video06 - Microlensing, Astrometry and Other Methods||The class begins with a discussion on transits – important astronomical events that help astronomers to find new planets. The event occurs when a celestial body moves across the face of the star it revolves around and blocks some of its light.||12/6/2011||Free||View in iTunes|
|7||Video07 - Direct Imaging of Exoplanets||Class begins with a problem on transits and learning what information astronomers obtain through observing them. For example, radii of stars can be estimated. Furthermore, applying the Doppler shift method, one can find the mass of a star.||12/6/2011||Free||View in iTunes|
|8||Video08 - Introduction to Black Holes||The second half of the course begins, focusing on black holes and relativity.||12/6/2011||Free||View in iTunes|
|9||Video09 - Special and General Relativity||The discussion of black holes continues with an introduction of the concept of event horizon. A number of problems are worked out to familiarize students with mathematics related to black hole event horizons.||12/6/2011||Free||View in iTunes|
|10||Video10 - Tests of Relativity||The lecture begins with the development of post-Newtonian approximations from Newtonian terms.||12/6/2011||Free||View in iTunes|
|11||Video11 - Special and General Relativity (cont.)||The lecture begins with a comprehensive overview of the historical conditions under which Einstein developed his theories. Of particular impact were the urgent need at the turn of the 19th century to synchronize clocks around the world...||12/6/2011||Free||View in iTunes|
|12||Video12 - Stellar Mass Black Holes||One last key concept in Special Relativity is introduced before discussion turns again to black celestial bodies (black holes in particular) that manifest the relativistic effects students have learned about in the previous lectures.||12/6/2011||Free||View in iTunes|
|13||Video13 - Stellar Mass Black Holes (cont.)||Class begins with clarification of equations from the previous lecture. Four post-Newtonian gravitational effects are introduced and discussed in detail.||12/6/2011||Free||View in iTunes|
|14||Video14 - Pulsars||Professor Bailyn begins with a summary of the four post-Newtonian effects of general relativity that were introduced and explained last time: precession of the perihelion, the deflection of light, the gravitational redshift, and gravitational waves.||12/6/2011||Free||View in iTunes|
|15||Video15 - Supermassive Black Holes||The lecture begins with a question-and-answer session about black holes. Topics include the extent to which we are sure black holes exist in the center of all galaxies, how massive they are, and how we can observe them.||12/6/2011||Free||View in iTunes|
|16||Video16 - Hubble's Law and the Big Bang||The third and final part of the course begins, consisting of a series of lectures on cosmology. A brief history of how cosmology developed into a scientific subject is offered.||12/6/2011||Free||View in iTunes|
|17||Video17 - Hubble's Law and the Big Bang (cont.)||Class begins with a review of magnitudes and the problem set involving magnitude equations. Implications of the Hubble Law and Hubble Diagram are discussed.||12/6/2011||Free||View in iTunes|
|18||Video18 - Hubble's Law and the Big Bang (cont.)||Professor Bailyn returns to the subject of the expansion of the universe to offer explanations that do not require belief in the Big Bang theory.||12/6/2011||Free||View in iTunes|
|19||Video19 - Omega and the End of the Universe||Class begins with a review of the issues previously addressed about the origin and fate of the universe.||12/6/2011||Free||View in iTunes|
|20||Video20 - Dark Matter||This lecture introduces an important concept related to the past and future of the universe: the Scale factor, which is a function of time.||12/6/2011||Free||View in iTunes|
|21||Video21 - Dark Energy and the Accelerating Universe and the Big Rip||Class begins with a review of the mysterious nature of dark matter, which accounts for three quarters of the universe. Different models of the universe are graphed. The nature, frequency, and duration of supernovae are then addressed.||12/6/2011||Free||View in iTunes|
|22||Video22 - Supernovae||Professor Bailyn offers a review of what is known so far about the expansion of the universe from observing galaxies, supernovae, and other celestial phenomena.||12/6/2011||Free||View in iTunes|
|23||Video23 - Other Constraints: The Cosmic Microwave Background||Reasons for the expansion of the universe are addressed at the start of this lecture, focusing especially on the acceleration of dark energy. Supernovae were the first evidence for the existence of dark energy. Two other proofs are presented||12/6/2011||Free||View in iTunes|
|24||Video24 - The Multiverse and Theories of Everything||Professor Bailyn begins the class with a discussion of a recent New York Times article about the discovery of a new, earth-like planet.||12/6/2011||Free||View in iTunes|
Astrophysics for poets but with production problems
On the whole, a thorough and well taught introduction for those with limited mathematics. Others have commented on content but a few words about production are in order. First, the professor uses an overhead projector which severely restricts the volume of information the student can see at any time compared to the (more normal) use of a blackboard. Second, while the professor patiently and fully answers questions from students in the classroom we, the listeners, cannot hear these questions and are left to deduce what he is responding to. And, finally, on the rare occasions when the professor displays slides the camera remains on the professor and, frustratingly, does not show us the slide material.
I am a high school physics teacher, and my students are absolutely fascinated with these topics. I have also been inspired by his method of simplifying the calculations. The “fables” are fantastic. I love it.
The way the professor teaches and carry the subject is simply amazing! He can keep your attention for the entire class and thats hard to see nowadays. The course is easy to understand without knowing too much of math,so for all those who thinks this class is difficult,you can simply go through it without a problem.
Anyway, fascinating subject and a fantastic course for sure. | 0.906501 | 3.298707 |
Kepler laws of planetary motion are expressed as:(1) All the planets move around the Sun in the elliptical orbits, having the Sun as one of the foci. (2) A radius vector joining any planet to Sun sweeps out equal areas in equal intervals of time.(3) The square of the period of any planet about the sun is proportional to the cube of the planet’s mean distance from the sun.
Three laws of planetary motion
Using newton’s laws of motion and law of universal gravitation, we can understand and analyze the behavior of all the bodies in the solar system: the orbits of the planets and comets about the sun and of natural and artificial satellites about their planets. We make two assumptions that simplify the analysis:
- We consider the gravitational force only between the orbiting body and the central body (the sun) , ignoring the perturbing effect of the gravitational force of other bodies (such as other planets).
- We assume that the central body is so much more massive than the orbiting body that we can ignore its motion under their mutual interaction. In reality, both objects orbit around their common center of mass, but if one object is very much more massive than the other, the center of mass is approximately at the center of the more massive body. Exceptions to this second assumption will be noted.
The empirical basis for understanding the motions of the planets is Kepler’s three laws, and we now show how these laws are related to the analytical results of newton’s laws.
Kepler’s first law of planetary motion
“All planets move in elliptical orbits, with the sun at one focus.”
Consider a planet of mass ‘m’ moving in such an orbit around the sun, whose mass is M.We assume that M>>m so that the center of mass of the planet sun system is approximately at the center of mass of the planet sun system is approximately at the center of the sun. The orbit is described by two parameters: the semi-major axis ‘a’ and the eccentricity ‘e’.The distance from the center of the ellipse to either focus is ‘ea’.The maximum distance Ra of the planet from the sun is called aphelion,similarly, the closest distance RP is called perihelion.
Fro the figure we see that:
Ra=a +ea =a(1+e) ———-(1)
A circular orbit is a special case of an elliptical orbit with e=0.
For a circular orbit, from equation (1) and (2) we get,
Kepler’s second law of planetary motion
“A line joining any planet to the sun sweeps out equal areas in equal times.”
“Areal velocity of the planet around the sun is constant.”
Kepler’s 2nd law equation
Consider a planet of mass is moving in an elliptical orbit around the sun. The sun and the planet are separated by distance r. Consider the small area ∆A covered in a time interval ∆t, as shown in the figure. The area of the wedge is approximately the area of a triangle with base ‘rΔθ‘ and height ‘r’.Since the area of a triangle is one-half of the base times the height.
Where dA/dt is called areal velocity.Since angular momentum ‘L’ and mass of the planet is constant.
Kepler’s third law of planetary motion
“The square of the period of any planet about the sun is proportional to the cube of the planet’s mean distance from the sun.”
Kepler’s 3rd law equation
Let us prove this result for circular orbits. Consider a planet of mass ‘m’ is moving around the sun of mass ‘M’ in a circular orbit of radius ‘r’ as shown in the figure. The gravitational force provides the necessary centripetal force to the planet for circular motion. Hence
T2 ∝ r3
A similar result is obtained for elliptical orbits with radius ‘r’ replaced by semi-major axis ‘a’ given by the relation:
T2 ∝ a3 | 0.888439 | 4.066325 |
It’s time to update your desktop wallpaper, folks. The Hubble Space Telescope has captured some of the most remarkable images ever seen of the faintest and earliest known galaxies in the Universe.
Using a technique called gravitational lensing — a phenomenon whereby intense gravitational forces can be leveraged as a kind of cosmic-scale magnifying glass — an international team of astronomers has catalogued over 250 “dwarf” galaxies that popped into existence a mere 600 to 900 million years after the Big Bang. It’s considered one of the largest samples of primordial galaxies yet to be discovered.
The light beams from these galaxies have been wafting through space for the past 12 billion years. It’s a unique opportunity for astronomers to peer back in time to when the Universe was still very young.
As a release from the Hubble site explains, the light emitted by these galaxies likely played a major role during the formative reionization epoch:
Reionisation started when the thick fog of hydrogen gas that cloaked the early Universe began to clear. Ultraviolet light was now able to travel over larger distances without being blocked and the Universe became transparent to ultraviolet light.
By observing the ultraviolet light from the galaxies found in this study the astronomers were able to calculate whether these were in fact some of the galaxies involved in the process. The team determined, for the first time with some confidence, that the smallest and most abundant of the galaxies in the study could be the major actors in keeping the Universe transparent. By doing so, they have established that the epoch of reionisation — which ends at the point when the Universe is fully transparent — came to a close about 700 million years after the Big Bang.
If you think these images are impressive, just wait until the space-based James Webb Telescope comes online sometime around 2018-19.
All these images are available in wallpaper size, which you can find here. | 0.823994 | 3.518498 |
There’s a race among the astrophysics community to determine the mass of the entire Milky Way galaxy. That figure takes into account the collection of stellar matter, gases, rocks, dust, and other natural junk flying around through the vacuum of space. But it misses a precise measurement of one very critical yet very elusive substance important to the Milky Way (and every other galaxy, for that matter): dark matter, which comprises about 85 percent of all matter in the universe.
The short answer is that it’s about the mass of the sun times 700 billion. The sun has a mass of two nonillion — that’s a 2 followed by 30 zeros — kilograms, which is 330,000 times the mass of Earth.
In the race to pinpoint what the mass of the Milky Way is when it includes dark mater is Gwendolyn Eadie, a Ph.D. candidate in physics and astronomer at McMaster University in Ontario, Canada.
In a study submitted to The Astrophysical Journal and presented at the Canadian Astronomical Society’s conference today in Winnipeg, Eadie demonstrates a new method of calculating the galaxy’s total mass by adding the velocities, positions, and orbits of globular star clusters to better determine where the galaxy’s major gravitational forces are centered, and how powerful they are.
See, dark matter is important to scientists because, while we’ve never actually observed it directly, we’ve observed its effect on other objects in space. We see the orbits and movements of other objects zipping around the universe and have watched them behave in unusual ways that can only be explained by a massive clump of matter sitting nearby and creating a powerful gravitational effect.
To that effect, Eadie and her colleagues focused on measuring and observing what are called globular clusters — spherical collections of stars that themselves orbit a galactic core. If you follow how a globular cluster moves and orbits the center of a galaxy, you can perhaps locate where those dark matter agglomerations lie — and their size.
Unfortunately, scientists so far only have a partial notion of the velocities and motions of those globular clusters.
Eadie decided to work around this problem by taking these partially-known velocities, and merging them with velocities of GCs that are fully known — then estimating the mass of the entire galaxy based on those numbers.
The result? An estimated Milky Way mass that comes out to about 7 x 10^11 solar masses — so about 700 billion times the mass of the sun.
So if we haven’t found dark matter yet, at least we’re getting better at predicting exactly what kind of role it plays in our own galaxy — and the universe as a whole. | 0.841218 | 4.121066 |
Miguel de Cervantes, the great Spanish author, tried to go to the Americas in more than one occasion. I wonder whether he would have been a Fulbright scholar if he would have lived in the modern times. In the end he remained in Spain and he is buried in the convent Trinitarians nuns in Madrid, where there is a search now underway for his tomb. As well as his monumental work Don Quixote, which he himself considered the first modern novel, his extensive literary production included poetry and theater. It also appears that his scientific culture must have been considerable, as he kept in touch with the advances that were made at the start of the 17th century following the invention of the telescope. It is even possible that he made a significant scientific contribution, naming the satellites of the planet Jupiter, which were identified when Galileo Galilei, the revolutionary astronomer-physicist-mathematician from Pisa, pointed the new instrument to the sky.
Galileo discovered the jovian satellites in 1610, among several other key discoveries. As a good courtesan, he called them with the generic name of the Medicean Stars, after his master, Cossimo II of Medici, Duke of Tuscany, and only provided roman numerals for each of them. Nowadays they are called Ganymede (the biggest and brightest), Calixto, Io and Europa, but at the beginning of the XVII a strong argument appeared between several important scientists and theologians regarding the nature and significance. These moons also played a key role in other aspects: from cartography to the determination of the speed of light.
But it seems that it was Cervantes, in a curious poem included in the short novel “La Gitanilla” (The little gypsy), one belonging to the twelve “Novelas Ejemplares” (Exemplary novels) who actually named them. The key part is:
Junto a la casa del Sol
va Júpiter; que no hay cosa
difícil a la privanza
fundada en prudentes obras.
Va la Luna en las mejillas
de una y otra humana diosa;
Venus casta, en la belleza
de las que este cielo forman.
cruzan, van, vuelven y tornan
por el cinto tachonado
de esta esfera milagrosa.
The four final lines have an explicit meaning: the words “cruzan, van, vuelven y tornan” (“they cross, go, come back and do it again”) leaves little room for one’s imagination, and would refer to a relatively concise description of orbiting around Jupiter; while the last two lines, “por el cinto tachonado / de esta esfera milagrosa” (“by the gilded belt / of this miraculous sphere”) refers to the Ecliptic, the imaginary circle about which the planets move, and apparently the Sun, and the celestial sphere. Hence, it is written from an astronomical perspective, and not only from a mythological one.
Remarkably, Cervantes refers to the Jupiter’s satellites shortly after they were discovered, given that The Exemplary novels were published in 1613. Therefore, Cervantes, who had a very strong influence in the European literature and specially in the English plays, would not only the first person to write a novel – and an extraordinary one – in Spanish. Through his poetry, which was not always highly regarded, he would also have given a name to these four objects, the faint jovian moons that have helped to construct the picture of the world as we know it today.
But the story does not end here. Galileo accused the German astronomer Simon Marius of plagiarism, since Marius claimed co-discovery (he did it quite late, in 1614, and he is credited with the naming of these four satellites). Marius’ name was only cleaned three hundred years after the event. More about this amazing plot here…
David Barrado Navascués
Centro de Astrobiología (CAB), INTA-CSIC
European Space Astronomy Center (ESAC, Madrid) | 0.819344 | 3.309709 |
Let’s discover the idea. Distance is defined by two definitions.
The initial could be the length and the second is length/distance. If we define the length because the distance between two points, then we would possess the second definition, which is also known as in essence the light cone or angle of incidence. So, how do we come up having a definition with the weight in physics?
write an essay online
For those that are not acquainted with everyday term, let me clarify. The speed of light is a concept that has various applications. In Newtonian Physics, this speed is measured in units referred to as meters per second. It describes the price at which an object moves relative to some physical source like the earth or maybe a bigger light supply. It’s also known as the time interval more than which a phenomenon occurs or changes.
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It would be the same speed of light that we practical experience as we move via our every day planet, the speed of sound. It is actually also known as the speed of light in space, which signifies it truly is traveling more rapidly than the speed of light in the infinite space about us.
In terms of physics, this is the time interval in which an object is in a given place when its velocity is equal for the speed of light in the empty space surrounding the write my paper for me cheap earth’s orbit plus the sun. What’s the definition from the weight in physics?
Weight is defined as the force that is required to turn an object to accelerate it forward, and also the difference involving this force plus the force of gravity is known as its weight. To calculate the acceleration of an object, you simply must multiply the mass instances the acceleration. How do we arrive in the definition of weightin physics? As a additional refinement, it turns out that mass is defined because the sum of each of the particles that make up the body.
When an object is added to the system, it takes on a smaller sized role, which is inversely proportional to the mass that is definitely made use of in the calculation. So, as the addition for the method goes away, the mass becomes somewhat extra important. The equation is often rewritten in order that the acceleration is defined by the mass from custom writing the object divided by the square on the velocity of the object (this really is the second definition with the weight in physics).
This is often a very tiny piece from the story of ways to discover distance. Now, the following query is what does the direction on the angle of incidence mean? Properly, this depends on the path from the source in the light (that is the earth), nevertheless it is apparent that the place of the source is where the light is reflected back from.
To illustrate, let’s look at a straight line passing straight in front from the sun and light getting into from above. At this point, the angle of incidence could be optimistic mainly because the light was reflected off the surface from the sun.
Another approach to express the principle of distance is to use a graphic representation. The term distance and the word to define distance are derived in the reality that the distance within a circle must be expressed in meters along with the distance in an ellipse must be expressed in meters squared. The geometric point of view in the partnership among a point and also a line must be place into a method of equations, referred to as the metric.
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We can visualize this as a method of equations which has a continual E, which can be the gravitational continual. In physics, the constant E is called the acceleration, the difference amongst the force of gravity as well as the acceleration.
How to discover Distance Physics
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There are two basic theories on planet formation. One is thatAnd Stars would not split in half, it would likely shoot out a streamer of "core material" that is of a different charge than its surface material. This material (mass ejection) would pile up at a certain altitude and be pinched into a sphere... Likely many other "globules" would also harden into planetlike objects and would begin to orbit the old or new sun.
stars get too much electrical stress and split in halves, forming
the binary systems that are so common. During this process
the core of the star may be elongated and break up forming
a planet or many planets which are held between the stars by
electrical forces, or possibly by the rotation of the binary system
balancing either electrical or gravitational forces. This sort of
planet could be hollow.
The other theory is that gas giants or brown dwarfs or stars
eject material which become planets like Venus. One theorises
that a plasma current enters the surface of Saturn, say, and
pulls on the planet extracting this material that forms a planet.
If so, then this current could go through the centre of this
material and a hollow planet could again eventuate. Another
intriguing possibility is that this material comes not from the
core of Saturn, but from the surface. Thus Saturn would be a
hollow planet with a solid surface that was fairly thin. Then it
would be fairly easy to remove a chunk of this surface material.
Just maybe the 'heavy' elements, formed by the electrical
discharges on the surface of a star or brown dwarf or gas
giant, don't fall to the core, but rather congeal at the surface.
It's a wonderful world of theory here ! | 0.822768 | 3.059308 |
Astronomers have directly measured a blazing-bright object on the opposite side of the Milky Way, almost doubling the record for the most distant object measured in our own galaxy.
The researchers used a system of 10 radio telescopes in New Mexico called the Very Long Baseline Array (VLBA) to pinpoint the distance to the glowing, star-forming region.
Humans have detected and measured objects 13.3 billion light-years away, at the very edge of the observable universe. (One light-year is the distance light travels in year, about 6 trillion miles, or 10 trillion kilometers.) So why is it so difficult to measure objects across the Milky Way, which is a mere 100,000 light-years wide? [Astronomically Far Away: How to Measure the Universe]
The answer has to do with location. Our solar system is positioned about halfway out on one of the galaxy's massive spiral arms, so the only view we get of the Milky Way is side-on. It's like trying to map a forest you're standing in by measuring the distances between the trees around you. Except, you can't walk around in these "woods," because the Earth isn't moving fast enough to give Earthlings much of a different perspective on a human timescale. This is why the constellations look the same today as they did thousands of years ago.
Dust, gas and stars in the galactic disk obscure our view of objects farther away, just as the trees obscure a person's view in the analogy, researchers said in a statementabout the new study from the National Radio Astronomy Observatory (NRAO). But we can twist and turn to get a better look at the woods around us and see how the features appear to move as we change our perspective, the researchers said. This phenomenon, called parallax, is what makes your finger seem to jump when you hold it in front of your nose and alternate which eye you use to look at it.
Most distances in astronomy are extrapolated from data about the brightness of different objects, said Tom Dame, a researcher at the Harvard-Smithsonian Center for Astrophysics in Massachusetts and co-author on the new work. And often, scientists have to use one distance to calibrate for that of an object located farther out, and repeat that process multiple times. But using parallax cuts out that reliance on knowledge about other objects.
"The thing about parallax is it's just beautifully direct. It's just based on trigonometry," Dame told Space.com.
Dame's group used that technique to measure the distance to a star-forming region called G007.47+00.05 on the opposite side of the Milky Way. Researchers used the VLBA to measure the region's apparent shift in the sky when viewed from opposite points in Earth's orbit around the sun.
The resultant jump was roughly the angle that a baseball on the moon would take up in your field of vision, as viewed from Earth, according to the statement. This corresponds to a distance of more than 66,500 light-years. The previous record for a parallax measurement stood at about 36,000 light-years, researchers said in the statement.
"Most of the stars and gas in our galaxy are within this newly measured distance from the sun," Alberto Sanna, the study's lead author and a researcher at the Max Planck Institute for Radio Astronomy in Germany, said in the statement. "With the VLBA, we now have the capability to measure enough distances to accurately trace the galaxy's spiral arms and learn their true shapes."
G007.47+00.05 is a powerful source of microwaves, which pass through dust and gas relatively undiminished, Dame said. The region's incredible brightness confused scientists until they determined that molecules in the region resonate with and amplify the light of a young, massive star located nearby. The system functions like a microwave laser, called a maser. In this case, "we happen to be right along the beam," said Dame.
The measurement was part of a larger, five-year project called the Bar and Spiral Structure Legacy Survey (BeSSeL), which aims to map the far side of the Milky Way using parallax measurements of these maser sources, said Dame. This measurement came in the last year of the survey, when the team spent more time on a few objects of particular interest, Dame said. The BeSSeL survey measured about 200 maser sources in total.
"Within the next 10 years, we should have a fairly complete picture," Mark Reid, who heads the BeSSeL team from the Harvard-Smithsonian Center for Astrophysics, said in the NRAO statement.
The new work was detailed today (Oct. 12) in the journal Science. | 0.906943 | 3.942539 |
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