Astronaut Alex Gerst recently captured this glorious photo from the International Space Station. It shows a series of towering thunderstorms rising up from a Saharan dust storm. The ISS was over Libya at the time as Gerst watched the anvil-like structures protrude above the dusty layer. (Credit: NASA/JSC/Gerst)
If there was a tsunami warning in your area, could you escape on foot? That's the question a new tool released by the USGS takes on. The Pedestrian Evacuation Analyst takes into account not just foot-speed but terrain, and also highlights the areas of high-ground that would likely be the safest points.
Astrobiologists can now add a new term to their lexicon: The Venus Zone. It describes the area around a star in which a planet is likely to exhibit the inhospitable hell-like conditions found on the planet Venus. The concept will help astronomers determine which exoplanets are more analogous to Earth, and thus friendlier to alien life.
Around 12,800 years ago, a sudden, catastrophic event plunged much of the Earth into a period of cold climatic conditions and drought. This drastic climate change—the Younger Dryas—coincided with the extinction of Pleistocene megafauna, such as the saber-tooth cats and the mastodon, and resulted in major declines in prehistoric human populations, including the termination of the Clovis culture. A new study published in The Journal of Geology provides support for the theory that a cosmic impact event over North America some 13,000 years ago caused a major period of climate change known as the Younger Dryas stadial, or “Big Freeze.”
Researchers from 21 universities in 6 countries believe the key to the mystery of the Big Freeze lies in nanodiamonds scattered across Europe, North America, and portions of South America, in a 50-million-square-kilometer area known as the Younger Dryas Boundary (YDB) field.
Microscopic nanodiamonds, melt-glass, carbon spherules, and other high-temperature materials are found in abundance throughout the YDB field, in a thin layer located only meters from the Earth’s surface. Because these materials formed at temperatures in excess of 2200 degrees Celsius, the fact they are present together so near to the surface suggests they were likely created by a major extraterrestrial impact event.
In addition to providing support for the cosmic impact event hypothesis, the study also offers evidence to reject alternate hypotheses for the formation of the YDB nanodiamonds, such as by wildfires, volcanism, or meteoric flux.
The team’s findings serve to settle the debate about the presence of nanodiamonds in the YDB field and challenge existing paradigms across multiple disciplines, including impact dynamics, archaeology, paleontology, limnology, and palynology.
C. R. Kinzie, et al., “Nanodiamond-Rich Layer across Three Continents Consistent with Major Cosmic Impact at 12,800 Cal BP,” The Journal of Geology 2014, 122(5). http://ift.tt/1ll1fHM
The Daily Galaxy via University of Chicago
Planet Venus, with its thick atmosphere made of carbon dioxide, its parched surface, and pressures so high that landers are crushed within a few hours, offers scientists a chance to study a planet very foreign to our own. These mysterious holes provide additional clues to understanding Venus's atmosphere, how the planet interacts with the constant onslaught of solar wind from the sun, and perhaps even what's lurking deep in its core.
Until now. Collinson set out to search for signatures of these holes in data from the European Space Agency's Venus Express. Venus Express, launched in 2006, is currently in a 24-hour orbit around the poles of Venus. This orbit places it in much higher altitudes than that of the Pioneer Venus Orbiter, so Collinson wasn't sure whether he'd spot any markers of these mysterious holes. But even at those heights the same holes were spotted, thus showing that the holes extended much further into the atmosphere than had been previously known.
The observations also suggested the holes are more common than realized. Pioneer Venus Orbiter only saw the holes at a time of great solar activity, known as solar maximum. The Venus Express data, however, shows the holes can form during solar minimum as well.
Interpreting what is happening in Venus's ionosphere requires understanding how Venus interacts with its environment in space. This environment is dominated by a stream of electrons and protons – a charged, heated gas called plasma -- which zoom out from the sun. As this solar wind travels it carries along embedded magnetic fields, which can affect charged particles and other magnetic fields they encounter along the way. Earth is largely protected from this radiation by its own strong magnetic field, but Venus has no such protection.
What Venus does have, however, is an ionosphere, a layer of the atmosphere filled with charged particles. The Venusian ionosphere is bombarded on the sun-side of the planet by the solar wind. Consequently, the ionosphere, like air flowing past a golf ball in flight, is shaped to be a thin boundary in front of the planet and to extend into a long comet-like tail behind. As the solar wind plows into the ionosphere, it piles up like a big plasma traffic jam, creating a thin magnetosphere around Venus – a much smaller magnetic environment than the one around Earth.
Venus Express is equipped to measure this slight magnetic field. As it flew through the ionospheric holes it recorded a jump in the field strength, while also spotting very cold particles flowing in and out of the holes, though at a much lower density than generally seen in the ionosphere. The Venus Express observations suggest that instead of two holes behind Venus, there are in fact two long, fat cylinders of lower density material stretching from the planet's surface to way out in space. Collinson said that some magnetic structure probably causes the charged particles to be squeezed out of these areas, like toothpaste squeezed out of a tube.
The next question is what magnetic structure can create this effect? Imagine Venus standing in the middle of the constant solar wind like a lighthouse erected in the water just off shore. Magnetic field lines from the sun move toward Venus like waves of water approaching the lighthouse. The far sides of these lines then wrap around the planet leading to two long straight magnetic field lines trailing out directly behind Venus. These lines could create the magnetic forces to squeeze the plasma out of the holes.
But such a scenario would place the bottom of these tubes on the sides of the planet, not as if they were coming straight up out of the surface. What could cause magnetic fields to go directly in and out of the planet? Without additional data, it's hard to know for sure, but Collinson's team devised two possible models that can match these observations.
In one scenario, the magnetic fields do not stop at the edge of the ionosphere to wrap around the outside of the planet, but instead continue further.
“We think some of these field lines can sink right through the ionosphere, cutting through it like cheese wire,” said Collinson. "The ionosphere can conduct electricity, which makes it basically transparent to the field lines. The lines go right through down to the planet's surface and some ways into the planet."
In this scenario, the magnetic field travels unhindered directly into the upper layers of Venus. Eventually, the magnetic field hits Venus’ rocky mantle – assuming, of course, that the inside of Venus is like the inside of Earth. A reasonable assumption given that the two planets are the same mass, size and density, but by no means a proven fact.
A similar phenomenon does happen on the moon, said Collinson. The moon is mostly made up of mantle and has little to no atmosphere. The magnetic field lines from the sun go through the moon's mantle and then hit what is thought to be an iron core.
In the second scenario, the magnetic fields from the solar system do drape themselves around the ionosphere, but they collide with a pile up of plasma already at the back of the planet. As the two sets of charged material jostle for place, it causes the required magnetic squeeze in the perfect spot.
Either way, areas of increased magnetism would stream out on either side of the tail, pointing directly in and out of the sides of the planet. Those areas of increased magnetic force could be what squeezes out the plasma and creates these long ionospheric holes.
Scientists will continue to explore just what causes these holes. Confirming one theory or the other will, in turn, help us understand this planet, so similar and yet so different from our own.
The Daily Galaxy via Goddard Space Flight Center
Astronomers searching the atmospheres of alien worlds for gases that might be produced by life can't rely on the detection of just one type, such as oxygen, ozone, or methane, because in some cases these gases can be produced non-biologically, according to extensive simulations by researchers in the NASA Astrobiology Institute’s Virtual Planetary Laboratory.
The researchers carefully simulated the atmospheric chemistry of alien worlds devoid of life thousands of times over a period of more than four years, varying the atmospheric compositions and star types. "When we ran these calculations, we found that in some cases, there was a significant amount of ozone that built up in the atmosphere, despite there not being any oxygen flowing into the atmosphere," said Shawn Domagal-Goldman of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "This has important implications for our future plans to look for life beyond Earth."
Methane is a carbon atom bound to four hydrogen atoms. On Earth, much of it is produced biologically (flatulent cows are a classic example), but it can also be made inorganically; for example, volcanoes at the bottom of the ocean can release the gas after it is produced by reactions of rocks with seawater.
Ozone and oxygen were previously thought to be stronger biosignatures on their own. Ozone is three atoms of oxygen bound together. On Earth, it is produced when molecular oxygen (two oxygen atoms) and atomic oxygen (a single oxygen atom) combine, after the atomic oxygen is created by other reactions powered by sunlight or lightning. Life is the dominant source of the molecular oxygen on our planet, as the gas is produced by photosynthesis in plants and microscopic, single-cell organisms.
Because life dominates the production of oxygen, and oxygen is needed for ozone, both gases were thought to be relatively strong biosignatures. But this study demonstrated that both molecular oxygen and ozone can be made without life when ultraviolet light breaks apart carbon dioxide (a carbon atom bound to two oxygen atoms). Their research suggests this non-biological process could create enough ozone for it to be detectable across space, so the detection of ozone by itself would not be a definitive sign of life.
"However, our research strengthens the argument that methane and oxygen together, or methane and ozone together, are still strong signatures of life," said Domagal-Goldman. "We tried really, really hard to make false-positive signals for life, and we did find some, but only for oxygen, ozone, or methane by themselves." Domagal-Goldman and AntÃgona Segura from the Universidad Nacional Autónoma de México in Mexico City are lead authors of a paper about this research, along with astronomer Victoria Meadows, geologist Mark Claire, and Tyler Robison, an expert on what Earth would look like as an extrasolar planet. The paper appeared in the Astrophysical Journal Sept. 10, and is available online.
Methane and oxygen molecules together are a reliable sign of biological activity because methane doesn't last long in an atmosphere containing oxygen-bearing molecules. "It's like college students and pizza," says Domagal-Goldman. "If you see pizza in a room, and there are also college students in that room, chances are the pizza was freshly delivered, because the students will quickly eat the pizza. The same goes for methane and oxygen. If both are seen together in an atmosphere, the methane was freshly delivered because the oxygen will be part of a network of reactions that will consume the methane. You know the methane is being replenished. The best way to replenish methane in the presence of oxygen is with life. The opposite is true, as well. In order to keep the oxygen around in an atmosphere that has a lot of methane, you have to replenish the oxygen, and the best way to do that is with life."
Scientists have used computer models to simulate the atmospheric chemistry on planets beyond our solar system (exoplanets) before, and the team used a similar model in its research. However, the researchers also developed a program to automatically compute the calculations thousands of times, so they could see the results with a wider range of atmospheric compositions and star types.
In doing these simulations, the team made sure they balanced the reactions that could put oxygen molecules in the atmosphere with the reactions that might remove them from the atmosphere. For example, oxygen can react with iron on the surface of a planet to make iron oxides; this is what gives most red rocks their color. A similar process has colored the dust on Mars, giving the Red Planet its distinctive hue. Calculating the appearance of a balanced atmosphere is important because this balance would allow the atmosphere to persist for geological time scales. Given that planetary lifetimes are measured in billions of years, it's unlikely astronomers will happen by chance to be observing a planet during a temporary surge of oxygen or methane lasting just thousands or even millions of years.
It was important to make the calculations for a wide variety of cases, because the non-biological production of oxygen is subject to both the atmospheric and stellar environment of the planet. If there are a lot of gases that consume oxygen, such as methane or hydrogen, then any oxygen or ozone produced will be destroyed in the atmosphere. However, if the amount of oxygen-consuming gases is vanishingly small, the oxygen and the ozone might stick around for a while. Likewise, the production and destruction of oxygen, ozone, and methane is driven by chemical reactions powered by light, making the type of star important to consider as well. Different types of stars produce the majority of their light at specific colors. For example, massive, hot stars or stars with frequent explosive activity produce more ultraviolet light.
"If there is more ultraviolet light hitting the atmosphere, it will drive these photochemical reactions more efficiently," said Domagal-Goldman. "More specifically, different colors (or wavelengths) of ultraviolet light can affect oxygen and ozone production and destruction in different ways."
Astronomers detect molecules in exoplanet atmospheres by measuring the colors of light from the star the exoplanet is orbiting. As this light passes through the exoplanet's atmosphere, some of it is absorbed by atmospheric molecules. Different molecules absorb different colors of light, so astronomers use these absorption features as unique "signatures" of the type and quantity of molecules present.
“One of the main challenges in identifying life signatures is to distinguish between the products of life and those compounds generated by geological processes or chemical reactions in the atmosphere. For that we need to understand not only how life may change a planet but how planets work and the characteristics of the stars that host such worlds”, said Segura.
The team plans to use this research to make recommendations about the requirements for future space telescopes designed to search exoplanet atmospheres for signs of alien life.
"Context is key – we can't just look for oxygen, ozone, or methane alone," says Domagal-Goldman. "To confirm life is making oxygen or ozone, you need to expand your wavelength range to include methane absorption features. Ideally, you’d also measure other gases like carbon dioxide and carbon monoxide [a molecule with one carbon atom and one oxygen atom]. So we're thinking very carefully about the issues that could trip us up and give a false-positive signal, and the good news is by identifying them, we can create a good path to avoid the issues false positives could cause. We now know which measurements we need to make. The next step is figuring out what we need to build and how to build it."
The research was funded in part by the NASA Astrobiology Institute's (NAI) Virtual Planetary Laboratory (VPL). The NAI is administered by NASA's Ames Research Center in Mountain View, California, and funded as part of the NASA Astrobiology Program at NASA Headquarters, Washington. The VPL is based at the University of Washington, and comprises researchers at 20 institutions working to understand how telescopic observations and modeling studies can determine if exoplanets are able to support life, or had life in the past. Additional support for the research was provided by the NASA Postdoctoral Program, managed by Oak Ridge Associated Universities.
The team represented an international collaboration that included researchers from NASA Goddard, NASA Ames, the NAI/VPL, the Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Mexico; the University of St. Andrews, St. Andrews, Scotland; and the University of Washington, Seattle.
The Daily Galaxy via http://ift.tt/XeLLnF
Kepler researchers want to understand how terrestrial planets like Venus, Earth and Mars and gas giant planets like Jupiter are distributed in planetary systems around other stars. Understanding how planetary systems form and where different types of planets form can shed light on whether our solar system is unique, or more likely, is a "standard" form of planetary system formation.
Identification of planets orbiting distant stars is spurring the search for an Earth-like planet. Now a team of researchers has developed a way to distinguish a distant Venus-like planet from an Earth-like one. While the Earth has oceans of water and relatively moderate temperatures, Venus has no liquid water and exists in a runaway greenhouse scenario where the levels of carbon dioxide are so high that the atmosphere traps all the heat and the planet is torrid. Venus is 95 percent the size of Earth so size is not a distinguishing characteristic when sorting Earth- and Venus-like planets. Distance from a star, however, is what potentially makes a planet Earth-like or Venus-like.
NASA's Kepler space telescope can identify planets close to their suns by recording the shadow that a planet makes when crossing in front of its star. Multiple views over time not only sort out the errant sunspot from a potential planet, but also provide the planet's orbit -- the all-important distance from the star.
"Just as stars have habitable zones -- the orbital belt where planets have water that can remain liquid -- stars have Venus zones," said Kopparapu, working with Stephen Kane, assistant professor of physics and astronomy, San Francisco State University and Shawn Domagal-Goldman, research assistant, planetary studies, NASA Goddard Space Flight Center.
The researchers looked at potential Venus-like planets located in the Kepler database. They searched for planets that were between half Earth's size and almost one and a half times the size of Earth that fell within the Venus zone, locating 43 potential Venus-like planets. Their findings will be posted on ArXiv on Sept. 9 and will appear in an upcoming issue of Astrophysical Journal Letters.
These are only potential Venus-like planets because while they are the correct size and fall in the Venus zone, the Kepler space telescope cannot determine if these planets have an atmosphere, which is necessary for a Venus analog.
"We would need to use something like the planned James Webb Space Telescope to see if planets have an atmosphere," said Kopparapu. "If a planet has an atmosphere dominated by a greenhouse gas such as carbon dioxide, is the right size and has the correct amount of light falling on it, then it might be a Venus-like planet."
Some planets with the proper size and location will be devoid of atmosphere, some planets in the Venus zone will be gas giants, not Venus-like at all, but some will mimic the atmospheric scenario that currently exists on Venus.
Not all stars are the same as the sun, so both the Venus zone and habitable zone shift depending on the energy output of individual star types. Also, the Kepler Space Telescope's method of identifying planets is biased toward planets closer to their stars -- more Venus zone planets will be identified than Earth-like planets. And not all of the planets identified by Kepler have been determined to be actual planets.
This past December, a team of European astrophysicists discovered the most extensive planetary system to date, orbiting star KOI-351. The star system has seven planets, more than in other known planetary systems arranged in a similar fashion to the eight planets in the Solar System, with small rocky planets close to the parent star and gas giant planets at greater distances.
Although the planetary system around KOI-351 is packed together more tightly, “We cannot stress just how important this discovery is. It is a big step in the search for a ‘twin’ to the Solar System, and thus also in finding a second Earth,” said Juan Cabrera, an astrophysicist at the DLR Institute of Planetary Research in Berlin-Adlershof.
KOI is the abbreviation for ‘Kepler Object of Interest’, which means the star was observed by NASA’s Kepler space telescope, between 2008 and 2013, and classified as a candidate for the existence of exoplanets. At present, KOI-351 is the star with the most extrasolar planets, or exoplanets for short. The star is 2500 light years away from Earth.
Astrophysicists around the world have been searching for a star system similar to our own for a long time. Now, the team led by Cabrera has taken a major step in this direction. Three of the seven planets in orbit around the star KOI-351 were discovered in recent years, and have periods of 331, 211 and 60 days, similar to those of Earth, Venus and Mercury.
The Daily Galaxy via Penn State University
Image at top of page credit: http://ift.tt/NtSlAB
Quasars are supermassive black holes that live at the center of distant massive galaxies. They shine as the most luminous beacons in the sky across the entire electromagnetic spectrum by rapidly accreting matter into their gravitationally inescapable centers. New work from Carnegie’s Hubble Fellow Yue Shen and Luis Ho of the Kavli Institute for Astronomy and Astrophysics (KIAA) at Peking University solves a quasar mystery that astronomers have been puzzling over for 20 years. Their work, published in the September 11 issue of Nature, shows that most observed quasar phenomena can be unified with two simple quantities: one that describes how efficiently the hole is being fed, and the other that reflects the viewing orientation of the astronomer.
Using the largest and most-homogeneous sample to date of over 20,000 quasars from the Sloan Digital Sky Survey, combined with several novel statistical tests, Shen and Ho were able to demonstrate that one particular property related to the accretion of the hole, called the Eddington ratio, is the driving force behind the so-called main sequence. The Eddington ratio describes the efficiency of matter fueling the black hole, the competition between the gravitational force pulling matter inward and the luminosity driving radiation outward. This push and pull between gravity and luminosity has long been suspected to be the primary driver behind the so-called main sequence, and their work at long last confirms this hypothesis.
The graph above shows the distribution of the 20,000 luminous Sloan Digital Sky Survey quasars in the two-dimensional space of broad line width versus FeII strength, color-coded by the strength of the narrow line emission. The strong horizontal trend is the main sequence of quasars driven by the efficiency of the black hole accretion, while the vertical spread of broad line width is largely due to our viewing angle to the inner region of the quasar. A larger version is available here.
Of additional importance, they found that the orientation of an astronomer’s line-of-sight when looking down into the black hole’s inner region plays a significant role in the observation of the fast-moving gas innermost to the hole, which produces the broad emission lines in quasar spectra. This changes scientists’ understanding of the geometry of the line-emitting region closest to the black hole, a place called the broad-line region: the gas is distributed in a flattened, pancake-like configuration. Going forward, this will help astronomers improve their measurements of black hole masses for quasars.
“Our findings have profound implications for quasar research. This simple unification scheme presents a pathway to better understand how supermassive black holes accrete matter and interplay with their environments,” Shen said.
“And better black hole mass measurements will benefit a variety of applications in understanding the cosmic growth of supermassive black holes and their place in galaxy formation,” Ho added.
The Chandra X-Ray image at the top of the page is the first x-ray picture of the Andromeda Galaxy (M31) on October 13, 1999. The blue dot in the center of the image is a "cool" million-degree x-ray source where a supermassive black hole with the mass of 30-million suns is located. The x-rays are produced by matter funneling toward the black hole. Numerous other hotter x-ray sources are also apparent. Most of these are probably due to x-ray binary systems, in which a quasar or black hole is in close orbit around a normal star.
The Daily Galaxy via Carnegie Institute
The Chandra X-Ray image at the top of the page is the first x-ray picture of the Andromeda Galaxy (M31) on October 13, 1999. The blue dot in the center of the image is a "cool" million-degree x-ray source where a supermassive black hole with the mass of 30-million suns is located. The x-rays are produced by matter funneling toward the black hole. Numerous other hotter x-ray sources are also apparent. Most of these are probably due to x-ray binary systems, in which a quasar or black hole is in close orbit around a normal star.
Image Credit: NASA/UMass/D.Wang et al., IR: NASA/STScI
The question of how massive stars spend their short lives until they become supernovae is of great interest for astrophysicists. According to the standard theory, which is only applicable to isolated stars, only cool and extended (red supergiants) or hot and blue (Wolf-Rayet stars) are able to become supernovae. However, growing evidence suggests that most massive stars are not lonely singles but they belong to close binary systems with profuse interactions. Episodes of mass transfer between the members of binary star systems affect the way the stars evolve, meaning that there are a great many more potential scenarios for the final stages of supernova progenitors.
However, the team led by Melina C. Bersten at Kavli IPMU and Omar Benvenuto at the University of La Plata, Argentina, showed that the exploding star must have been extended, like a yellow supergiant, and that it must have belonged to a binary system (see web release on September 28 2012: http://ift.tt/1wj1KpC). "We produced detailed models that self-consistently explained every property of SN 2011dh through the explosion of a yellow supergiant star in a binary system," remarked Melina C. Bersten.
In March 2013, the proposal of Benvenuto, Bersten and collaborators was given substantial support when the disappearance of the yellow supergiant was observed, indicating that it and not a bright blue star was the exploding object (see web release on Apr. 5 2013: http://ift.tt/1wj1Hu8). "At that time there was just one piece of the puzzle missing to confirm our model: we had to find the companion star that, according to our calculations, was a hot, compact object," said Omar Benvenuto.
With that goal, the group set out to obtain HST observing time, which was granted in 2013 and recently executed on August 7, 2014. Images were obtained in the ultraviolet regime, where the companion star was expected to be most clearly visible. A point source was clearly detected in the new images at the exact location of the supernova (see announcement in http://ift.tt/1mqgHgL).
"One of the most exciting moments in my career as an astronomer was when I displayed the newly arrived HST images and saw the object right there, where we had anticipated it to be all along" said Gastón Folatelli , who led the efforts to obtain the new Hubble Space Telescope (HST) observations.
"To our excitement, the object had the properties predicted by the models," explained Schuyler Van Dyk, of Caltech, who was in charge of the image analysis. Folatelli and collaborators judged it unlikely that the detection was due to some other contaminating source.
Further HST observations were recently obtained in the optical range by another European team. "When available, such data will not only serve to definitely validate the existence of the companion star, but also they will provide critical information to refine the binary model originally proposed by our team", said Ken'ichi Nomoto from Kavli IPMU. This is a unique opportunity to make such a detailed study of the progenitor of a supernova. The results will have important implications for our knowledge of stellar evolution and its connection with supernova properties.
The case of SN 2011dh beautifully illustrates the advantages of an active feedback between theory and observation. "As a scientist, for me it is like a dream come true to make a prediction and have it confirmed step by step as the supernova evolves and facts are revealed. It is a rare case for astronomy, where events usually take much longer to develop. We are very happy with how the story of SN 2011dh proceeded," concluded Melina C. Bersten.
The Daily Galaxy via University of Tokyo
Image credit: Artist's conception of the progenitor system of SN 2011dh. The system consists of a blue compact star and a yellow supergiant. Kavli IPMU/Aya Tsuboi
A new survey of galaxies by NASA's Spitzer Space Telescope is taking a plunge into the deep and uncharted waters of our cosmos. In one of the longest surveys the telescope will have ever performed, astronomers have begun a three-month expedition trawling for faint galaxies billions of light-years away. The results are already yielding big surprises.
These early results from the SPLASH project, an international effort officially called the Spitzer Large Area Survey with Hyper-Suprime-Cam, build on previous evidence from Spitzer and other telescopes showing that the universe's earliest galaxies are more massive than expected. The project is turning up hundreds of hefty galaxies 100 times the mass of our own Milky Way, dating back to a time when our universe was less than one billion years old. (Our universe is 13.8 billion years old.)
The findings cast doubt on current models of galaxy formation, which struggle to explain how these remote and young galaxies grew so big so fast.
"Galaxies were being assembled faster than we thought, and we can only see this by finding large numbers of them with a survey like SPLASH," said Peter Capak, also of IPAC, and principal investigator of SPLASH.
While astronomers have seen such massive galaxies before, SPLASH is unique in finding large numbers of them. Now that Spitzer is in the "warm" phase of its mission, it dedicates more time to long-term projects such as this one. The telescope ran out of the coolant needed to chill some of its instruments in 2009, but two of its infrared channels work at the slightly warmer temperature. With fewer instruments, the telescope spends more time surveying large patches of sky.
By the end of the SPLASH survey, Spitzer will have spent 2,475 hours staring at two sky fields known as the Cosmic Evolution Survey (COSMOS) and Subaru/XMM-Newton deep field (SXDS), equivalent in size to about eight full moons. These are two of the darkest patches of sky, away from the plane of our Milky Way galaxy's flat spiral disk and its bright starlight. Many telescopes have studied these regions extensively at multiple wavelengths of light, spying the faint glow of millions of galaxies beyond our own. Spitzer's infrared vision helps weigh the galaxies, revealing their masses.
Astronomers are surprised by the early SPLASH results and its catch of "big fish." Current theories of star formation hold that the very first galaxies collided and merged, bulking up in size. In these models, the stars formed in bursts as these smaller galaxies smashed into each other. But this process takes time. Spitzer's finding of massive galaxies in an era between 800 and 1,600 million years after the birth of our universe barely leaves enough time for the galaxies' roughly one hundred billion stars to have formed.
The researchers in the image below are from left to right are: Peter Capak and Charles Steinhardt of NASA's Infrared Processing and Analysis Center (IPAC) at the California Institute of Technology in Pasadena, and Josh Speagle from Harvard University, Cambridge, Massachusetts.
"It's really hard to form something so massive so quickly," said Josh Speagle, co-author of the study from Harvard University. "So it's entirely possible that these galaxies have been forming stars continuously since the moment they were born."
Another explanation is that the first-ever galaxies got their foothold in the universe sooner than thought. Astronomers think the first galaxies formed around 500 million years after the Big Bang. If galaxies started forming earlier than this, by about 400 million years after the Big Bang, then they might have had the time needed to merge with other galaxies and ultimately grow into the behemoths found by Spitzer.
Follow-up observations with a host of telescopes are now being planned to figure out exactly how these galaxies got so big. Japan's Subaru telescope atop Mauna Kea in Hawaii will collect deep optical images of the galaxies over the course of several years.
The technical Astrophysical Journal Letters paper is online at http://ift.tt/YxcYcn
The image at the top of the page is the latest Hubble Ultra Deep Field, built up from years worth of long exposures of a tiny spot in the Southern Hemisphere sky showing about 10,000 galaxies ranging in distance. The image is augmented by including the ultraviolet part of the spectrum that NASA's photo team artificially colored a bright blue to go along with the exaggerated colors assigned to the optical (greens) and infrared (reds). The UV is strongest - due to Doppler shifts - from hot, star-forming regions ranging in distance between 5 and 10 billion light years.
The Daily Galaxy via http://ift.tt/VbRnRM and http://ift.tt/VbRqwS
The Milky Way galaxy is orbited by more than 150 globular star clusters, which are balls of hundreds of thousands of old stars dating back to the formation of the galaxy. One of these, along with several others in the constellation of Sagittarius (The Archer), was found in the late eighteenth century by the French comet hunter Charles Messier and given the designation Messier 54.
Astronomers have now observed Messier 54 using the VLT as a test case to try to solve one of the mysteries of modern astronomy — the lithium problem.
Most of the light chemical element lithium now present in the Universe was produced during the Big Bang, along with hydrogen and helium, but in much smaller quantities. Astronomers can calculate quite accurately how much lithium they expect to find in the early Universe, and from this work out how much they should see in old stars. But the numbers don't match — there is about three times less lithium in stars than expected. This mystery remains, despite several decades of work.
There are several possible proposed solutions to the riddle. The first is that the calculations of the amounts of lithium produced in the Big Bang are wrong — but very recent tests suggest that this is not the case. The second is that the lithium was somehow destroyed in the earliest stars, before the formation of the Milky Way. The third is that some process in the stars has gradually destroyed lithium during their lives.
Up to now it has only been possible to measure lithium in stars in the Milky Way. But now a team of astronomers led by Alessio Mucciarelli (University of Bologna, Italy) has used the VLT to measure how much lithium there is in a selection of stars in Messier 54. They find that the levels are close to those in the Milky Way. So, whatever it is that got rid of the lithium seems not to be specific to the Milky Way.
This new image of the cluster was created from data taken with the VLT Survey Telescope (VST) at the Paranal Observatory. As well as showing the cluster itself it reveals the extraordinarily dense forest of much closer Milky Way stars that lie in the foreground.
The Daily Galaxy via ESO
A team of scientists At the Las Campanas Observatory in Chile has discovered the first evidence of water ice clouds on an object outside of our own Solar System. Water ice clouds exist on our own gas giant planets -- Jupiter, Saturn (above), Uranus, and Neptune -- but have not been seen outside of the planets orbiting our Sun until now.
W0855 is the fourth-closest system to our own Sun, practically a next-door neighbor in astronomical distances. A comparison of the team's near-infrared images of W0855 with models for predicting the atmospheric content of brown dwarfs showed evidence of frozen clouds of sulfide and water. Atrist depiction of W0855 below.
"This was a battle at the telescope to get the detection," said Carnegie Institute's Jacqueline Faherty Faherty.
Chris Tinney, an Astronomer at the Australian Centre for Astrobiology, UNSW Australia and co-author on the result stated: "This is a great result. This object is so faint and it's exciting to be the first people to detect it with a telescope on the ground."
Brown dwarfs aren't quite very small stars, but they aren't quite giant planets either. They are too small to sustain the hydrogen fusion process that fuels stars. Their temperatures can range from nearly as hot as a star to as cool as a planet, and their masses also range between star-like and giant planet-like. They are of particular interest to scientists because they offer clues to star-formation processes. They also overlap with the temperatures of planets, but are much easier to study since they are commonly found in isolation.
"Ice clouds are predicted to be very important in the atmospheres of planets beyond our Solar System, but they've never been observed outside of it before now," Faherty said.
This work was supported by the Australian Research Council. It made use of data from the NASA WISE mission, which was a joint project of the University of California Los Angeles and the Jet Propulsion Laboratory and Caltech, funded by NASA. It also made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory and Caltech, under contract with NASA.
Journal Reference: Jacqueline K. Faherty, C. G. Tinney, Andrew Skemer, Andrew J. Monson. Indications of Water Clouds in the Coldest Known Brown Dwarf. The Astrophysical Journal, 2014; 793 (1): L16 DOI: 10.1088/2041-8205/793/1/L16
The Daily Galaxy via Carnegie Institute
Image Credit: Courtesy of NASA/JPL-Caltech/Penn State University
"Sunspots have been the perennial marker for understanding the mechanisms that rule the sun's interior," said Scott McIntosh, a space scientist at the National Center for Atmospheric Research in Boulder, Colorado. "But the processes that make sunspots are not well understood, and far less, those that govern their migration and what drives their movement. Now we can see there are bright points in the solar atmosphere, which act like buoys anchored to what's going on much deeper down. They help us develop a different picture of the interior of the sun."
These markers provide a new way to watch the way the magnetic fields evolve and move through our closest star. They also show that a substantial adjustment to established theories about what drives this mysterious cycle may be needed.
Historically, theories about what's going on inside the sun to drive the solar cycle have relied on only one set of observations: the detection of sunspots, a data record that goes back centuries. Over the past few decades, realizing that sunspots are areas of intense magnetic fields, researchers have also been able to include observations of magnetic measurements of the sun from more than 90 million miles away.
Over the course of a solar cycle, the sunspots tend to migrate progressively lower in latitude, moving toward the equator. The prevailing theory is that two symmetrical, grand loops of material in each solar hemisphere, like huge conveyor belts, sweep from the poles to the equator where they sink deeper down into the sun and then make their way steadily back to the poles. These conveyor belts also move the magnetic field through the churning solar atmosphere. The theory suggests that sunspots move in synch with this flow – tracking sunspots has allowed a study of that flow and theories about the solar cycle have developed based on that progression. But there is much that remains unknown: Why do the sunspots only appear lower than about 30 degrees? What causes the sunspots of consecutive cycles to abruptly flip magnetic polarity from positive to negative, or vice versa? Why is the timing of the cycle so variable?
Beginning in 2010, McIntosh and his colleagues began tracking the size of different magnetically balanced areas on the sun, that is, areas where there are an equal number of magnetic fields pointing down into the sun as pointing out. The team found magnetic parcels in sizes that had been seen before, but also spotted much larger parcels than those previously noted -- about the diameter of Jupiter. The researchers also looked at these regions in imagery of the sun's atmosphere, the corona, captured by NASA’s Solar Dynamics Observatory, or SDO. They noticed that ubiquitous spots of extreme ultraviolet and X-ray light, known as brightpoints, prefer to hover around the vertices of these large areas, dubbed “g-nodes” because of their giant scale.
These brightpoints and g-nodes, therefore, open up a whole new way to track how material flows inside the sun. McIntosh and his colleagues then collected information about the movement of these features over the past 18 years of available observations from the joint European Space Agency and NASA Solar and Heliospheric Observatory and SDO to monitor how the last solar cycle progressed and the current one started. They found that bands of these markers – and therefore the corresponding large magnetic fields underneath – also moved steadily toward the equator over time, along the same path as sunspots, but beginning at a latitude of about 55 degrees. In addition, each hemisphere of the sun usually has more than one of these bands present.
Bands of magnetized solar material – with alternating south and north polarity – march toward the sun's equator. Comparing the evolution of the bands with the sunspot number in each hemisphere over time may change the way we think about what's driving the sun's 11-year sunspot cycle.
McIntosh explains that a complex interaction of magnetic field lines may take place in the sun’s interior that is largely hidden from view. The recent observations suggest that the sun is populated with bands of differently polarized magnetic material that, once they form, steadily move toward the equator from high latitudes. These bands will either have a northern or southern magnetic polarity and their sign alternates in each hemisphere such that the polarities always cancel. For example, looking at the sun’s northern hemisphere, the band closest to the equator – perhaps of northern polarity – would have magnetic field lines that connect it to another band, at higher latitudes, of southern polarity. Across the equator, in the bottom half of the sun, a similar process occurs, but the bands would be an almost mirror image of those across the equator, southern polarity near the equator and northern at higher latitudes. Magnetic field lines would connect the four bands; inside each hemisphere and across the equator as well.
While the field lines remain relatively short like this, the sun's magnetic system is calmer, producing fewer sunspots and fewer eruptions. This is solar minimum. But once the two low-latitude marching bands reach the equator their polarities essentially cancel each other out. Abruptly they disappear. This process, from migratory start to finish at the equator takes 19 years on average, but is seen to vary from 16 to about 21 years.
Following the equatorial battle and cancellation, the sun is left with just two large bands that have migrated to about 30 degrees latitude. The magnetic field lines from these bands are much longer and so the bands in each hemisphere feel less of each other. At this point, the sunspots begin to grow rapidly on the bands, beginning the ramp-up to solar max. The growth only lasts so long, however, because the process of generating a new band of opposite polarity has already begun at high latitudes. When that new band begins to appear, the complex four-band connection starts over and the number of sunspots starts to decrease on the low-latitude bands.
In this scenario, it is the magnetic band’s cycle – the lifetime of each band as it marches toward the equator – that truly defines the entire solar cycle. “Thus, the 11-year solar cycle can be viewed as the overlap between two much longer cycles,” said Robert Leamon, co-author along with Scott McIntosh, first author of a paper on these results that appears in the September 1, 2014, issue of the Astrophysical Journal, at Montana State University in Bozeman and NASA Headquarters in Washington.
The new conceptual model also provides an explanation of why sunspots are trapped below 30 degrees and abruptly change sign. However, the model creates a question about a different latitude line: Why do the magnetic markers, the brightpoints and g-nodes, start appearing at 55 degrees?
"Above that latitude, the solar atmosphere appears to be disconnected from the rotation beneath it," said McIntosh. "So there is reason to believe that, inside the sun, there's a very different internal motion and evolution at high latitudes compared to the region near the equator. 55-degrees seems to be a critical latitude for the sun and something we need to explore further."
Solar cycles theories are best tested by making predictions as to when we will see the next solar minimum and the next solar maximum. This research paper forecasts that the sun will enter solar minimum somewhere in the last half of 2017, with the sunspots of the next cycle appearing near the end of 2019.
"People make their predictions for when this solar cycle will end and the next one will start," said Leamon. "Sometime in 2019 or 2020, some people will be proved right and others wrong."
In the meantime, regardless of whether the new hypothesis provided by McIntosh and his colleagues is correct, this long term set of bright points and g-node locations offers a new set of observations to explore the drivers of solar activity beyond only sunspots. Inserting this information into solar models will provide an opportunity to improve simulations of our star. Such advanced models tell us more about other stars too, leading to a better understanding of similar magnetic activity on more exotic, distant celestial counterparts.
The image at the top of the page is a composite of 25 separate images from NASA's SDO, spanning one year from April 2012 to April 2013. The image reveals the migration tracks of active regions towards the equator during that period.
Image Credit: NASA/SDO/Goddard
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The Eta Carinae star system does not lack for superlatives. Not only does it contain one of the biggest and brightest stars in our galaxy, weighing at least 90 times the mass of the sun, it is also extremely volatile and is expected to have at least one supernova explosion in the future.
Astronomers reported extremely volatile behavior from Eta Carinae in the 19th century, when it became very bright for two decades, outshining nearly every star in the entire sky. This event became known as the “Great Eruption.” Data from modern telescopes reveal that Eta Carinae threw off about ten times the sun’s mass during that time. Surprisingly, the star survived this tumultuous expulsion of material, adding “extremely hardy” to its list of attributes.
Today, astronomers are trying to learn more about the two stars in the Eta Carinae system and how they interact with each other. The heavier of the two stars is quickly losing mass through wind streaming away from its surface at over a million miles per hour. While not the giant purge of the Great Eruption, this star is still losing mass at a very high rate that will add up to the sun’s mass in about a millennium.
Though smaller than its partner, the companion star in Eta Carinae is also massive, weighing in at about 30 times the mass of the sun. It is losing matter at a rate that is about a hundred times lower than its partner, but still a prodigious weight loss compared to most other stars. The companion star beats the bigger star in wind speed, with its wind clocking in almost ten times faster.
When these two speedy and powerful winds collide, they form a bow shock – similar to the sonic boom from a supersonic airplane – that then heats the gas between the stars. The temperature of the gas reaches about ten million degrees, producing X-rays that Chandra detects.
The Chandra image of Eta Carinae shows low energy X-rays in red, medium energy X-rays in green, and high energy X-rays in blue. Most of the emission comes from low and high energy X-rays. The blue point source is generated by the colliding winds, and the diffuse blue emission is produced when the material that was purged during the Great Eruption reflects these X-rays. The low energy X-rays further out show where the winds from the two stars, or perhaps material from the Great Eruption, are striking surrounding material. This surrounding material might consist of gas that was ejected before the Great Eruption.
An interesting feature of the Eta Carinae system is that the two stars travel around each other along highly elliptical paths during their five-and-a-half-year long orbit. Depending on where each star is on its oval-shaped trajectory, the distance between the two stars changes by a factor of twenty. These oval-shaped trajectories give astronomers a chance to study what happens to the winds from these stars when they collide at different distances from one another.
Throughout most of the system's orbit, the X-rays are stronger at the apex, the region where the winds collide head-on. However, when the two stars are at their closest during their orbit (a point that astronomers call “periastron”), the X-ray emission dips unexpectedly.
To understand the cause of this dip, astronomers observed Eta Carinae with Chandra at periastron in early 2009. The results provided the first detailed picture of X-ray emission from the colliding winds in Eta Carinae. The study suggests that part of the reason for the dip at periastron is that X-rays from the apex are blocked by the dense wind from the more massive star in Eta Carinae, or perhaps by the surface of the star itself.
Another factor responsible for the X-ray dip is that the shock wave appears to be disrupted near periastron, possibly because of faster cooling of the gas due to increased density, and/or a decrease in the strength of the companion star’s wind because of extra ultraviolet radiation from the massive star reaching it. Researchers are hoping that Chandra observations of the latest periastron in August 2014 will help them determine the true explanation.
These results were published in the April 1, 2014 issue of The Astrophysical Journal and are available online.
Image credit: NASA/CXC/GSFC/K.Hamaguchi, et al.
The 2020 Mars rover has the overarching goal of seeking the signs of life, following up on the Curiosity rover's discovery at the Gale Crater landing site (above) that Mars could have been habitable billions of years ago. So the focus of the NASA science community is: Where would be the best place on Mars where evidence of life might have been preserved, according to Michael Meyer, NASA's lead scientist for the Mars program. NASA officials have identified more than 50 potential landing spots requested by the scientific community during a workshop held in May. Now, NASA officials working with the rover are going to start investigating those suggestions to see which will be the best fit for the spacecraft and its mission, specifically an area that isn't too rocky or high in altitude.
The 2020 mission will be based on the design of the highly successful Mars Science Laboratory rover, Curiosity, which landed almost two years ago, and currently is operating on Mars. The new rover will carry more sophisticated, upgraded hardware and new instruments to conduct geological assessments of the rover's landing site, determine the potential habitability of the environment, and directly search for signs of ancient Martian life.
Scientists will use the Mars 2020 rover to identify and select a collection of rock and soil samples that will be stored for potential return to Earth by a future mission.
The Mars 2020 rover also will help advance our knowledge of how future human explorers could use natural resources available on the surface of the Red Planet. An ability to live off the Martian land would transform future exploration of the planet. Designers of future human expeditions can use this mission to understand the hazards posed by Martian dust and demonstrate technology to process carbon dioxide from the atmosphere to produce oxygen. These experiments will help engineers learn how to use Martian resources to produce oxygen for human respiration and potentially for use as an oxidizer for rocket fuel.
"The 2020 rover will help answer questions about the Martian environment that astronauts will face and test technologies they need before landing on, exploring and returning from the Red Planet," said William Gerstenmaier, associate administrator for the Human Exploration and Operations Mission Directorate at NASA Headquarters in Washington. "Mars has resources needed to help sustain life, which can reduce the amount of supplies that human missions will need to carry. Better understanding the Martian dust and weather will be valuable data for planning human Mars missions. Testing ways to extract these resources and understand the environment will help make the pioneering of Mars feasible."
The rover 2020 will carry seven carefully-selected instruments to conduct unprecedented science and exploration technology investigations on the Red Planet. The payload proposals are:
Mastcam-Z, an advanced camera system with panoramic and stereoscopic imaging capability with the ability to zoom. The instrument also will determine mineralogy of the Martian surface and assist with rover operations. The principal investigator is James Bell, Arizona State University in Tempe.
SuperCam, an instrument that can provide imaging, chemical composition analysis, and mineralogy. The instrument will also be able to detect the presence of organic compounds in rocks and regolith from a distance.
Planetary Instrument for X-ray Lithochemistry (PIXL), an X-ray fluorescence spectrometer that will also contain an imager with high resolution to determine the fine scale elemental composition of Martian surface materials. PIXL will provide capabilities that permit more detailed detection and analysis of chemical elements than ever before.
Scanning Habitable Environments with Raman & Luminescence for Organics and Chemicals (SHERLOC), a spectrom
eter that will provide fine-scale imaging and uses an ultraviolet (UV) laser to determine fine-scale mineralogy and detect organic compounds. SHERLOC will be the first UV Raman spectrometer to fly to the surface of Mars and will provide complementary measurements with other instruments in the payload.
The Mars Oxygen ISRU Experiment (MOXIE), an exploration technology investigation that will produce oxygen from Martian atmospheric carbon dioxide.
Mars Environmental Dynamics Analyzer (MEDA), a set of sensors that will provide measurements of temperature, wind speed and direction, pressure, relative humidity and dust size and shape.
The Radar Imager for Mars' Subsurface Exploration (RIMFAX), a ground-penetrating radar that will provide centimeter-scale resolution of the geologic structure of the subsurface.
Instruments developed from the selected proposals will be placed on a rover similar to Curiosity, which has been exploring Mars since 2012. Using a proven landing system and rover chassis design to deliver these new experiments to Mars will ensure mission costs and risks are minimized as much as possible, while still delivering a highly capable rover.
Curiosity recently completed a Martian year on the surface -- 687 Earth days -- having accomplished the mission's main goal of determining whether Mars once offered environmental conditions favorable for microbial life.
In 2016, a Mars lander mission called InSight will launch to take the first look into the deep interior of Mars. The agency also is participating in the European Space Agency's (ESA's) 2016 and 2018 ExoMars missions, including providing "Electra" telecommunication radios to ESA's 2016 orbiter and a critical element of the astrobiology instrument on the 2018 ExoMars rover.
NASA's Mars Exploration Program views Mars as a dynamic system, including its present and past environment, climate cycles, geology and biological potential. In parallel, NASA is developing the human spaceflight capabilities needed for future round-trip missions to Mars.
NASA's Jet Propulsion Laboratory will build and manage operations of the Mars 2020 rover for the NASA Science Mission Directorate at the agency's headquarters in Washington.
The Daily Galaxy via NASA/JPL
An international team that has discovered what they believe is evidence of a planet forming around a star about 335 light years from Earth. The team members initially set out to study the protoplanetary disk around a star known as HD 100546, and as sometimes happens in scientific inquiry, it was by "chance" that they stumbled upon the formation of the planet orbiting this star. A protoplanetary disk, or circumstellar disk, is a very large disk of material orbiting a newly formed star out of which a planetary system may form. The team was studying the warm gas in this disk using a technique called spectro-astrometry, which allows astronomers to detect small changes in the position of moving gas.
The astronomers were able to investigate the extra emission as it orbited the star, and concluded that a likely explanation for the observations is a small circumplanetary disk of hot gas orbiting a forming planet. The candidate planet would be a gas giant at least three times the mass of Jupiter. The theory is that material from the large protoplanetary disk feeds into the circumplanetary disk, which then feeds onto the growing planet. Hence, a circumplanetary disk plays a mediating role in the growth of the planet. The remnants of a circumplanetary disk could also give birth to moons, such as those seen around Jupiter in our solar system. As Carr explains, a novel aspect of this new evidence for planet formation is the possible detection of a circumplanetary disk.
The team's study is based on four sets of observations gathered in 2003, 2006, 2010, and 2013. They used the Gemini Observatory and the Very Large Telescope at the European Southern Observatory, both located in Chile. The Gemini Observatory consists of twin 8.1-meter diameter optical/infrared telescopes located on mountains in Hawaii and Chile. The VLT is not just one telescope, but an array of four, each with a main mirror of 8.2 meters in diameter. The data were collected using high-resolution infrared spectrographs that allowed precise measurements of the motions of molecular gas surrounding the star.
A planet forming in the disk has cleared the disk within 13AU of the star, a distance comparable to that of Saturn from the sun. As gas and dust flows from the circumstellar disk to the planet, this material surrounds the planet as a circumplanetary disk (inset). These rotating disks are believed to be the birthplaces of planetary moons, such as the Galilean moons that orbit Jupiter. While they are theoretically predicted to surround giant planets at birth, there has been little observational evidence to date for circumplanetary disks outside the solar system. Brittain et al. (2014) report evidence for an orbiting source of carbon monoxide emission whose size is consistent with theoretical predictions for a circumplanetary disk. Observations over 10 years trace the orbit of the forming planet from behind the near side of the circumstellar disk in 2003 to the far side of the disk in 2013. These observations provide a new way to study how planets form.
"These results provide a rare opportunity," says Naval Research Laboratory scientist Dr. John Carr, "to study planet formation in action. Our analysis strongly suggests we are observing a disk of hot gas that surrounds a forming giant planet in orbit around the star. While such circumplanetary disks have been theorized to surround giant planets at birth and to control the flow of gas onto the growing planet, these findings are the first observational evidence for their existence. If our interpretation is correct, we are essentially seeing a planet caught in the act of formation."
Looking ahead, the team would like to continue to monitor the motion of the planet and obtain additional data to better define the properties of the circumplanetary disk. They predict that the planet and its disk will disappear from view in about two years time when they become hidden by the inner edge of the circumstellar disk. So, if the team's model is correct, the signature of the orbiting planet will not be seen for another 15 years until its orbit brings it back into view.
The research team consisted of Dr. Sean Brittain, Clemson University; Dr. John S. Carr, Naval Research Laboratory, Remote Sensing Division; Dr. Joan R. Najita, National Optical Astronomy Observatory in Tucson, Arizona; and Dr. Sascha P. Quanz and Dr. Michael R. Meyer, both of ETH Zurich, Institute for Astronomy.
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Image credit: With thanks to http://ift.tt/1q7evBg
In 2013, huge active plumes containing water vapour being released from the surface of Jupiter’s moon Europa have been discovered. This sensational find was made using the NASA/ESA Hubble Space Telescope. Europa has been a focus of extraterrestrial research for some time now as there were clear indications that it harbours a liquid ocean beneath its icy crust. Now, it appears, the geysers have vanished.
But new Hubble observations in January and February of this year showed no signs of the massive plumes. "It could be just the way that we use the auroral emissions coming from those plumes at the UV [ultraviolet] wavelengths of light that we use with Hubble," discovery team member Kurt Retherford, of the Southwest Research Institute in San Antonio, told Space.com. "These things depend on Jupiter's plasma environment," Retherford added. "Maybe there were just a lot of particles, atoms, getting excited by electrons and ions in Europa's atmosphere, more so than at other times, and [they] just lit up the plumes more than they usually do."
Retherford added that the plumes may sometimes simply be too small to see by the scientists who are relying on the Earth-orbiting Hubble to study the features on Europa, Retherford said. Another possibility Retherford noted is that the geysers don't exist, that the detection by Hubble, which was based primarily on observations the telescope made in December 2012, was an artifact or misinterpretation of some sort. "The best explanation still is plumes for that dataset, no doubt about it," he said
The existence of the plumes "is the kind of thing that could have a profound impact on how we explore Europa," Curt Niebur, outer planets program scientist at NASA headquarters, said during a NASA planetary sciences subcommittee meeting Wednesday held on Sept. 3."With an ocean that is tens of kilometers below the ice, most likely, if you can have a plume that's possibly bringing material from that ocean up to orbit, well, that's going to affect how you explore," Niebur added.
“Water is generally considered a basic prerequisite for life – at least as we know it on earth,” said Lorenz Roth, who was in charge of analysing the 2013 Hubble observations and who has been working at the Southwest Research Institute in America. “For this reason, the discovery of a water vapour plumes on the moon Europa has increasingly become a focus of extraterrestrial research.” The plumes eject material from the surface which will make further investigations of the moon Jupiter much easier in the future.
“We have been advancing the search for water and water plumes with multiple Hubble campaigns,” says Joachim Saur. “However, it was only after a camera on the Hubble Space Telescope in one of the last Space Shuttle Missions was repaired that we were able to achieve enough sensitivity to observe the fountains.”
The water plumes could only be seen in the observations when Europe was in a position in its orbit where the moon was furthest away from Jupiter. That means that the activity of the fountain varies temporally. Europa’s orbit is not quite circular but slightly elliptical. When Europa is furthest away from Jupiter in its orbit, the tidal forces cause the huge fractures in Europa’s ice surface to widen from which presumably the vapour is released.
Similar plumes of water vapour were discovered by the Cassini spacecraft on the Saturnian moon Enceladus. The activities there are similar to those on Europa during its orbit around its mother planet.
The Daily Galaxy via uni-koeln.de and space.com
Image Credit: K. Retherford, Southwest Research Institute, NASA/ESA/K.
Our galactic supercluster is 100 times bigger in volume and mass than previously thought . Using an innovative mapping technique, astronomers have charted an enormous region they're now calling Laniakea. The new study, which better defines the dividing line between superclusters, offers a completely new look at our galaxy's surroundings.
Astronomers have determined that our own Milky Way galaxy is part of a newly identified ginormous supercluster of galaxies, which they have dubbed "Laniakea," which means "immense heaven" in Hawaiian. This discovery clarifies the boundaries of our galactic neighborhood and establishes previously unrecognized linkages among various galaxy clusters in the local Universe.The Milky Way resides in the outskirts of the supercluster, whose extent has for the first time been carefully mapped using these new techniques. This so-called Laniakea Supercluster is 500 million light-years in diameter and contains the mass of one hundred million billion Suns spread across 100,000 galaxies.
Within the boundaries of the Laniakea Supercluster, galaxy motions are directed inward, in the same way that water streams follow descending paths toward a valley. The Great Attractor region is a large flat bottom gravitational valley with a sphere of attraction that extends across the Laniakea Supercluster.
"We have finally established the contours that define the supercluster of galaxies we can call home," said lead researcher R. Brent Tully, an astronomer at the University of Hawaii at Manoa. "This is not unlike finding out for the first time that your hometown is actually part of much larger country that borders other nations."
Superclusters are among the largest structures in the known Universe. They are made up of groups, like our own Local Group, that contain dozens of galaxies, and massive clusters that contain hundreds of galaxies, all interconnected in a web of filaments. Though these structures are interconnected, they have poorly defined boundaries.
To better refine cosmic mapmaking, the researchers are proposing a new way to evaluate these large-scale galaxy structures by examining their impact on the motions of galaxies. A galaxy between structures will be caught in a gravitational tug-of-war in which the balance of the gravitational forces from the surrounding large-scale structures determines the galaxy's motion.
By using the GBT and other radio telescopes to map the velocities of galaxies throughout our local Universe, the team was able to define the region of space where each supercluster dominates. "Green Bank Telescope observations have played a significant role in the research leading to this new understanding of the limits and relationships among a number of superclusters," said Tully.
The name Laniakea was suggested by Nawa'a Napoleon, an associate professor of Hawaiian Language and chair of the Department of Languages, Linguistics, and Literature at Kapiolani Community College, a part of the University of Hawaii system. The name honors Polynesian navigators who used knowledge of the heavens to voyage across the immensity of the Pacific Ocean.
The GBT is the world's largest fully steerable radio telescope. Its location in the National Radio Quiet Zone and the West Virginia Radio Astronomy Zone protects the incredibly sensitive telescope from unwanted radio interference.
The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.
A short video about Laniakea that gives the viewer a general sense of the structure of our home supercluster and of galaxy motions in the nearby universe is available at http://ift.tt/1lzLNI3
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