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  • Radio Search for Artificial Emissions from 'Oumuamua
    Donnerstag, 06.12.2018, 00:18:11 Uhr
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    Radio Search for Artificial Emissions from 'Oumuamua Mountain View CA (SPX) Dec 05, 2018 -
    It's the first time a visitor from another star system has been seen nearby. But what is it? An asteroid, a comet ... or an alien artifact?Scientists at the SETI Institute have attempted to address this question by using the Allen Telescope Array (ATA) to observe 'Oumuamua when it was about 170 million miles away, or slightly less than the diameter of Earth's orbit.The intention was to measure artificial radio transmissions which, if found, would be strong evidence that this object is not simply a rock tossed into space by a random gravitational slingshot interaction that occurred in its home star system."We were looking for a signal that would prove that this object incorporates some technology - that it was of artificial origin," says Gerry Harp, lead author of a paper to be published in the February 2019 issue of Acta Astronautica."We didn't find any such emissions, despite a quite sensitive search. While our observations don't conclusively rule out a non-natural origin for 'Oumuamua, they constitute important data in accessing its likely makeup."Following its discovery in October 2017, 'Oumuamua was the subject of popular speculation about a possible non-natural origin largely because it brought to mind the interstellar spaceship in Arthur C. Clarke's novel Rendezvous with Rama. Its highly elongated shape and the fact that no coma was observed strengthened this hypothesis for some, as these are uncharacteristic of asteroids and comets.A recent paper published in Astrophysical Journal Letters by researchers at Harvard has also suggested the possibility that 'Oumuamua is a deliberate construction. The Harvard researchers argue that the slight, unexpected acceleration observed for this object could be caused by pressure from sunlight as 'Oumuamua swung around the Sun.Their hypothesis is that the object might be a light sail, either deliberately or accidentally sent our way. A deliberate origin is considered somewhat more likely because our solar system is a very small target for any object that is not being aimed.Such arguments strengthen the importance of observations such as those conducted on the ATA that can constrain the true nature of 'Oumuamua.Observations were made between November 23 and December 5, 2017, using the wide-band correlator of the ATA at frequencies between 1 and 10 GHz and with a frequency resolution of 100 kHz. No signals were found at a level that would be produced by an omnidirectional transmitter on-board the object of power 30 to 300 milliwatts.In portions of the radio spectrum that are routinely cluttered by artificial satellite telemetry, the threshold for detection was as high as 10 watts. In all cases, these limits to the powers that could be detected are quite modest - comparable to that of cell phones or citizen band radios.While no signals were found coming from 'Oumuamua, the types of observations reported by SETI Institute scientists may have utility in constraining the nature of any interstellar objects detected in the future, or even the small, well-known objects in our own solar system.It has been long-hypothesized that some of the latter could be interstellar probes, and radio observations offer a way to address this imaginative, but by no means impossible, idea.Research Report: "Radio SETI Observations of the Interstellar Object 'Oumuamua," G. R. Harp et al., 2019 Feb., Acta Astronautica
  • Telescopes Reveal More Than 100 Exoplanets
    Donnerstag, 06.12.2018, 00:18:11 Uhr
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    Telescopes Reveal More Than 100 Exoplanets Tokyo, Japan (SPX) Dec 03, 2018 -
    An international team of astronomers using a combination of ground and space based telescopes have reported more than 100 extrasolar planets (here after, exoplanets) in only three months. These planets are quite diverse and expected to play a large role in developing the research field of exoplanets and life in the universe.Exoplanets, planets that revolve around stars other than the Sun, have been actively researched in recent years. One of the reasons is the success of the Kepler Space Telescope, which launched in 2009 to search for exoplanets. If a planet crosses (transits) in front of its parent star, then the observed brightness of the star drops by a small amount.The Kepler Space Telescope detected many exoplanets using this method. However, such dimming phenomena could be caused by other reasons. Therefore, confirmation that the phenomena are really caused by exoplanets is very important. The Kepler space telescope experienced mechanical trouble in 2013, which led to a successor mission called K2. Astronomers around the world are competing to confirm exoplanets suggested by the K2 data.An international research team involving researchers at the University of Tokyo and Astrobiology Center of the National Institutes of Natural Sciences investigated 227 K2 exoplanet candidates using other space telescopes and ground-based telescopes. They confirmed that 104 of them are really exoplanets.Seven of the confirmed exoplanets have ultra-short orbital periods less than 24 hours. The formation process of exoplanets with such short orbital periods is still unclear. Further study of these ultra-short period planets will help to advance research into the processes behind their formation. They also confirmed many low-mass rocky exoplanets with masses less than twice that of the Earth as well as some planetary systems with multiple exoplanets.Mr. John Livingston, a Ph.D. student at the University of Tokyo and lead author of the papers reporting the exoplanets, explains, "Although the Kepler Space Telescope has been officially retired by NASA, its successor space telescope, called TESS, has already started collecting data. In just the first month of operations, TESS has already found many new exoplanets, and it will continue to discover many more. We can look forward to many new exciting discoveries in the coming years."Research Reports: "Sixty Validated Planets from K2 Campaigns 5-8," John H. Livingston et al., 2018 Nov. 26, Astronomical Journal and "44 Validated Planets from K2 Campaign 10," John H. Livingston et al., 2018 Aug. 2, Astronomical Journal
  • Exoplanet mission launch slot announced
    Donnerstag, 06.12.2018, 00:18:11 Uhr
    Exoplanet mission launch slot announced Paris (ESA) Nov 26, 2018 -
    The Characterising Exoplanet Satellite, Cheops, will target 15 October to 14 November 2019 for launch.Cheops will lift off on a Soyuz rocket operated by Arianespace from Europe's spaceport in Kourou, sharing the ride into space with a satellite that is part of the Italian Cosmo-SkyMed constellation. The two satellites will separate in turn into their own orbits soon after ascent, with Cheops operating in a low-Earth orbit at an altitude of 700 km.The satellite will observe individual bright stars that are known to host exoplanets, in particular those in the Earth-to-Neptune size range. By targeting known planets, Cheops will know exactly when and where to point to catch the exoplanet as it transits across the disk of its host star.Its ability to observe multiple transits of each planet will enable scientists to achieve the high-precision transit signatures that are needed to measure the sizes of small planets.The combination of the accurate and precise sizes determined by Cheops with masses determined from other measurements will be used to establish the bulk density of the planets, placing constraints on their composition; these, together with information on the host stars and the planet orbits, will provide key insight into the formation and evolutionary history of planets in the super-Earth to Neptune size range.The satellite, which recently completed its environmental test campaign at ESA's technical centre in the Netherlands, is currently at Airbus Defence and Space, Spain to perform final tests, ahead of being declared fit for launch in early 2019.To engage and inspire different audiences with this exciting mission, Cheops will carry two plaques etched with thousands of miniaturised drawings made by school children, while the rocket fairing will feature a colourful design that was selected in a public competition aimed at graphic artists earlier this year.
  • Oxygen could have been available to life as early as 3.5 billion years ago
    Donnerstag, 06.12.2018, 00:18:11 Uhr
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    Oxygen could have been available to life as early as 3.5 billion years ago London, UK (SPX) Nov 28, 2018 -
    Microbes could have performed oxygen-producing photosynthesis at least one billion years earlier in the history of the Earth than previously thought.The finding could change ideas of how and when complex life evolved on Earth, and how likely it is that it could evolve on other planets.Oxygen in the Earth's atmosphere is necessary for complex forms of life, which use it during aerobic respiration to make energy.The levels of oxygen dramatically rose in the atmosphere around 2.4 billion years ago, but why it happened then has been debated. Some scientists think that 2.4 billion years ago is when organisms called cyanobacteria first evolved, which could perform oxygen-producing (oxygenic) photosynthesis.Other scientist think that cyanobacteria evolved long before 2.4 billion years ago but something prevented oxygen from accumulating in the air.Cyanobacteria perform a relatively sophisticated form of oxygenic photosynthesis - the same type of photosynthesis that all plants do today. It has therefore been suggested that simpler forms of oxygenic photosynthesis could have existed earlier, before cyanobacteria, leading to low levels of oxygen being available to life.Now, a research team led by Imperial College London have found that oxygenic photosynthesis arose at least one billion years before cyanobacteria evolved. Their results, published in the journal Geobiology, show that oxygenic photosynthesis could have evolved very early in Earth's 4.5-billion-year history.Lead author Dr Tanai Cardona, from the Department of Life Sciences at Imperial, said: "We know cyanobacteria are very ancient, but we don't know exactly how ancient. If cyanobacteria are, for example, 2.5 billion years old that would mean oxygenic photosynthesis could have started as early as 3.5 billion years ago. It suggests that it might not take billions of years for a process like oxygenic photosynthesis to start after the origin of life."If oxygenic photosynthesis evolved early, it could mean it is a relatively simple process to evolve. The probability of complex life emerging in a distant exoplanet may then be quite high.It is difficult for scientists to figure out when the first oxygen-producers evolved using the rock record on Earth. The older the rocks, the rarer they are, and the harder it is to prove conclusively that any fossil microbes found in these ancient rocks used or produced any amount of oxygen.Instead, the team investigated the evolution of two of the main proteins involved in oxygenic photosynthesis.In the first stage of photosynthesis, cyanobacteria use light energy to split water into protons, electrons and oxygen with the help of a protein complex called Photosystem II.Photosystem II is made up of two proteins called D1 and D2. Originally, the two proteins were the same, but although they have very similar structures, their underlying genetic sequences are now different.This shows that D1 and D2 have been evolving separately - in cyanobacteria and plants they only share 30 percent of their genetic sequence. Even in their original form, D1 and D2 would have been able to perform oxygenic photosynthesis, so knowing how long ago they were identical could reveal when this ability first evolved.To find out the difference in time between D1 and D2 being 100 percent identical, and them being only 30 percent the same in cyanobacteria and plants, the team determined how fast the proteins were changing - their rate of evolution.Using powerful statistics methods and known events in the evolution of photosynthesis, they determined that the D1 and D2 proteins in Photosystem II evolved extremely slowly - even slower than some of the oldest proteins in biology that are believed to be found in the earliest forms of life.From this, they calculated that the time between the identical D1 and D2 proteins and the 30 percent similar versions in cyanobacteria and plants is at least a billion years, and could be more than that.Dr Cardona said: "Usually, the appearance of oxygenic photosynthesis and cyanobacteria are considered to be the same thing. So, to find out when oxygen was being produced for the first time researchers have tried to find when cyanobacteria first evolved."Our study instead shows that oxygenic photosynthesis likely got started long before the most recent ancestor of cyanobacteria arose. This is in agreement with current geological data that suggests that whiffs of oxygen or localized accumulations of oxygen were possible before three billion years ago."Therefore, the origin of oxygenic photosynthesis and the ancestor of cyanobacteria do not represent the same thing. There could be a very large gap in time between one and the other. It is a massive change in perspective."Now, the team are trying to recreate what the photosystem looked like before D1 and D2 evolved in the first place. Using the known variation in photosystem genetic codes across all species alive today, they are trying to piece together the ancestral photosystem genetic code.Research paper
  • Bacteria Likely to Soon Infect ISS Crew Found to Be Antibiotic-Resistant
    Donnerstag, 06.12.2018, 00:18:11 Uhr
    Bacteria Likely to Soon Infect ISS Crew Found to Be Antibiotic-Resistant Houston TX (Sputnik) Nov 27, 2018 -
    Although the newly researched strains bear a striking similarity to ones typically found on Earth, specifically in intensive care units in hospitals, the discovery is a wake-up call given the no-gravity conditions of their habitat and the fact that these microorganisms are unresponsive to conventional antimicrobial agents.JPL-NASA scientists have identified a highly unwelcome guest thriving on board the International Space station - strains of Enterobacter, and what's most worrying is that these bacteria are highly resistant to antibiotics, a research paper published in the journal BMC Microbiology has it.For the time being, the strains of Enterobacter found on the ISS have luckily been found to be not pathogenic to humans, but the mere fact of them having been spotted on the station, in the unique conditions of microgravity, at least a tad of space radiation and intensely increased carbon dioxide levels, could carry worrisome implications.Meanwhile, human bodies have long been known to be teeming with healthy and beneficial microbes, which cannot and should not be totally eradicated since they are an effective firewall against those which pose danger.It took three years to describe and characterise the genomes of the strains collected back in 2015. The ISS bacterial strains have notably been identified to be similar to three types found recently on Earth, potentially causing disease in newly-born children and patients with a compromised immune system, according to microbiologist Kasthuri Venkateswaran.No imminent danger with regard to the astronauts has been revealed, since no Enterobacter-related medical conditions have been registered in orbit since the samples were collected. However, the scientists asserted that there could potentially be a hazard, since they compared their antibiotic resistance to the three clinical strains from Earth and found that they are entirely unaffected by such wide-spread antibiotics as cefazolin, cefoxitin, oxacillin, penicillin and rifampin and some others. Computer modelling suggested there is 79 percent probability that they will evolve into a human pathogen, given certain conditions."Whether or not an opportunistic pathogen like E. bugandensis causes disease and how much of a threat it is, depends on a variety of factors, including environmental ones," Venkateswaran noted, adding that it is no less crucial to depict how various spacecraft-related conditions and factors may affect pathogenicity and virulence in the long run.Source: Sputnik News
  • Jumping genes shed light on how advanced life may have emerged
    Donnerstag, 06.12.2018, 00:18:11 Uhr
    Jumping genes shed light on how advanced life may have emerged Urbana IL (SPX) Nov 20, 2018 -
    A previously unappreciated interaction in the genome turns out to have possibly been one of the driving forces in the emergence of advanced life, billions of years ago.?This discovery began with a curiosity for retrotransposons, known as "jumping genes," which are DNA sequences that copy and paste themselves within the genome, multiplying rapidly. Nearly half of the human genome is made up of retrotransposons, but bacteria hardly have them at all.Nigel Goldenfeld, Swanlund Endowed Chair of Physics at the University of Illinois and Carl R. Woese Institute for Genomic Biology, and Thomas Kuhlman, a former physics professor at Illinois who is now at University of California, Riverside, wondered why this is."We thought a really simple thing to try was to just take one (retrotransposon) out of my genome and put it into the bacteria just to see what would happen," Kuhlman said. "And it turned out to be really quite interesting."Their results, published in the Proceedings of the National Academy of Sciences, give more depth to the history of how advanced life may have emerged billions of years ago - and could also help determine the possibility and nature of life on other planets.Along the way to explaining life, the researchers first encountered death - bacterial death, that is. When they put retrotransposons in bacteria, the outcome was fatal."As they jump around and make copies of themselves, they jump into genes that the bacteria need to survive," Kuhlman said. "It's incredibly lethal to them."When retrotransposons copy themselves within the genome, they first find a spot in the DNA and cut it open. To survive, the organism then has to repair this cut. Some bacteria, like E. coli, only have one way to perform this repair, which usually ends up removing the new retrotransposon. But advanced organisms (eukaryotes) have an additional "trick" called nonhomologous end-joining, or NHEJ, that gives them another way to repair cuts in their DNA.Goldenfeld and Kuhlman decided to see what would happen if they gave bacteria the ability to do NHEJ, thinking that it would help them tolerate the damage to their DNA. But it just made the retrotransposons better at multiplying, causing even more damage than before."It just completely killed everything," Kuhlman said. "At the time, I thought I was just doing something wrong."They realized that the interaction between NHEJ and retrotransposons may be more important than they previously thought.Eukaryotes typically have many retrotransposons in their genome, along with a lot of other "junk" DNA, which doesn't have a well-understood function. Within the genome, there must be a constant interplay between NHEJ and retrotransposons, as NHEJ tries to control how rapidly the retrotransposons multiply. This gives the organism more power over their genome, and the presence of "junk" DNA is important."As you get more and more junk in your DNA, you can start taking these pieces and combining them together in different ways, more ways than you could without all the junk in there," Kuhlman said.These conditions - the accumulation of "junk" DNA, the presence of retrotransposons and their interactions with NHEJ - make the genome more complex. This is one feature that may distinguish advanced organisms, like humans, from simpler ones, like bacteria.Advanced organisms can also manage their genome by using their spliceosome, a molecular machine that sorts through the "junk" DNA and reconstructs the genes back to normal.Some parts of the spliceosome are similar to group II introns, bacteria's primitive version of retrotransposons. Introns are also found in eukaryotes, and along with the spliceosome are evolutionarily derived from group II introns. Goldenfeld said this poses an evolutionary question."What came first, the spliceosome or the group II introns? Clearly the group II introns," he said. "So then you can ask: where did the eukaryotic cell first get those group II introns in order to build up the spliceosome early on?"This study suggests that group II introns, the ancestors of introns in the spliceosome and retrotransposons in eukaryotes, somehow invaded early eukaryotic cells. Then, their interactions with NHEJ created a "selection pressure" that helped lead to the emergence of the spliceosome, which helped life become advanced billions of years ago.The spliceosome helped life become advanced by enabling eukaryotes to do more with their DNA. For example, even though humans have roughly the same number of genes as C. elegans, a worm, humans can do more with those genes."There's not much difference between this very simple worm and humans, which is obviously insane," Goldenfeld said. "What's happening is that humans are able to take these genes and mix and match them in many combinations to do much more complicated functions than C. elegans does."Not only did NHEJ and retrotransposons help with the creation of the spliceosome; this study suggests that they may also have assisted in making chromosomes - DNA molecules that contain genetic material - more advanced. Interactions between NHEJ and retrotransposons may have aided in the transition from circular chromosomes (which bacteria generally have) to linear ones (which more advanced organisms have), another indicator of advanced life.Goldenfeld said that before this research, many researchers studied the role of retrotransposons, but the importance of NHEJ was not fully appreciated. This research proves that it played a part, billions of years ago, in eukaryotes becoming the advanced organisms we know today."This certainly was not the only thing that was going on," Goldenfeld said. "But if it hadn't happened, it's hard to see how you could have complex life."This study contributes to the larger questions that the Institute for Universal Biology, a NASA Astrobiology Institute that Goldenfeld directs, seeks to answer - questions like: what had to happen in order for life to become advanced?Answering this question in greater detail could help scientists determine the possibility of life on other planets."If life exists on other planets, presumably one would expect it to be microbial. Could it ever have made this transition to complex life?" Goldenfeld said. "It's not that you're inevitably going to get advanced life, because there are a bunch of things that have to happen."The physics perspective of this study helps to quantify these theoretical questions. This quantification comes from simply taking measurements in a laboratory and using those measurements to make models of evolution, as was done in this study.In doing so, basic measurements in a laboratory become a time machine to the past."We're doing laboratory evolution," Goldenfeld said. "We're looking at what evolutionary processes must have happened billions of years ago."
  • New Climate Models of TRAPPIST-1's Seven Intriguing Worlds
    Donnerstag, 06.12.2018, 00:18:11 Uhr
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    New Climate Models of TRAPPIST-1's Seven Intriguing Worlds Seattle WA (SPX) Nov 26, 2018 -
    Not all stars are like the Sun, so not all planetary systems can be studied with the same expectations. New research from a University of Washington-led team of astronomers gives updated climate models for the seven planets around the star TRAPPIST-1.The work also could help astronomers more effectively study planets around stars unlike our Sun, and better use the limited, expensive resources of the James Webb Space Telescope, now expected to launch in 2021."We are modeling unfamiliar atmospheres, not just assuming that the things we see in the solar system will look the same way around another star," said Andrew Lincowski, UW doctoral student and lead author of a paper published Nov. 1 in Astrophysical Journal. "We conducted this research to show what these different types of atmospheres could look like."The team found, briefly put, that due to an extremely hot, bright early stellar phase, all seven of the star's worlds may have evolved like Venus, with any early oceans they may have had evaporating and leaving dense, uninhabitable atmospheres. However, one planet, TRAPPIST-1 e, could be an Earthlike ocean world worth further study, as previous research also has indicated.TRAPPIST-1, 39 light-years or about 235 trillion miles away, is about as small as a star can be and still be a star. A relatively cool "M dwarf" star - the most common type in the universe - it has about 9 percent the mass of the Sun and about 12 percent its radius. TRAPPIST-1 has a radius only a little bigger than the planet Jupiter, though it is much greater in mass.All seven of TRAPPIST-1's planets are about the size of Earth and three of them - planets labeled e, f and g - are believed to be in its habitable zone, that swath of space around a star where a rocky planet could have liquid water on its surface, thus giving life a chance. TRAPPIST-1 d rides the inner edge of the habitable zone, while farther out, TRAPPIST-1 h orbits just past that zone's outer edge."This is a whole sequence of planets that can give us insight into the evolution of planets, in particular around a star that's very different from ours, with different light coming off of it," said Lincowski. "It's just a gold mine."Previous papers have modeled TRAPPIST-1 worlds, Lincowski said, but he and this research team "tried to do the most rigorous physical modeling that we could in terms of radiation and chemistry - trying to get the physics and chemistry as right as possible."The team's radiation and chemistry models create spectral, or wavelength, signatures for each possible atmospheric gas, enabling observers to better predict where to look for such gases in exoplanet atmospheres. Lincowski said when traces of gases are actually detected by the Webb telescope, or others, some day, "astronomers will use the observed bumps and wiggles in the spectra to infer which gases are present - and compare that to work like ours to say something about the planet's composition, environment and perhaps its evolutionary history."He said people are used to thinking about the habitability of a planet around stars similar to the Sun. "But M dwarf stars are very different, so you really have to think about the chemical effects on the atmosphere(s) and how that chemistry affects the climate."Combining terrestrial climate modeling with photochemistry models, the researchers simulated environmental states for each of TRAPPIST-1's worlds.Their modeling indicates that:
    * TRAPPIST-1 b, the closest to the star, is a blazing world too hot even for clouds of sulfuric acid, as on Venus, to form.* Planets c and d receive slightly more energy from their star than Venus and Earth do from the Sun and could be Venus-like, with a dense, uninhabitable atmosphere.* TRAPPIST-1 e is the most likely of the seven to host liquid water on a temperate surface, and would be an excellent choice for further study with habitability in mind.* The outer planets f, g and h could be Venus-like or could be frozen, depending on how much water formed on the planet during its evolution.Lincowski said that in actuality, any or all of TRAPPIST-1's planets could be Venus-like, with any water or oceans long burned away. He explained that when water evaporates from a planet's surface, ultraviolet light from the star breaks apart the water molecules, releasing hydrogen, which is the lightest element and can escape a planet's gravity.This could leave behind a lot of oxygen, which could remain in the atmosphere and irreversibly remove water from the planet. Such a planet may have a thick oxygen atmosphere - but not one generated by life, and different from anything yet observed."This may be possible if these planets had more water initially than Earth, Venus or Mars," he said. "If planet TRAPPIST-1 e did not lose all of its water during this phase, today it could be a water world, completely covered by a global ocean. In this case, it could have a climate similar to Earth."Lincowski said this research was done more with an eye on climate evolution than to judge the planets' habitability. He plans future research focusing more directly on modeling water planets and their chances for life."Before we knew of this planetary system, estimates for the detectability of atmospheres for Earth-sized planets were looking much more difficult," said co-author Jacob Lustig-Yaeger, a UW astronomy doctoral student.The star being so small, he said, will make the signatures of gases (like carbon dioxide) in the planet's atmospheres more pronounced in telescope data."Our work informs the scientific community of what we might expect to see for the TRAPPIST-1 planets with the upcoming James Webb Space Telescope."Lincowski's other UW co-author is Victoria Meadows, professor of astronomy and director of the UW's Astrobiology Program. Meadows is also principal investigator for the NASA Astrobiology Institute's Virtual Planetary Laboratory, based at the UW. All of the authors were affiliates of that research laboratory."The processes that shape the evolution of a terrestrial planet are critical to whether or not it can be habitable, as well as our ability to interpret possible signs of life," Meadows said. "This paper suggests that we may soon be able to search for potentially detectable signs of these processes on alien worlds."TRAPPIST-1, in the Aquarius constellation, is named after the ground-based Transiting Planets and Planetesimals Small Telescope, the facility that first found evidence of planets around it in 2015.Research Report: "Evolved Climates and Observational Discriminants for the TRAPPIST-1 Planetary System," Andrew P. Lincowski et al., 2018 Nov. 1, Astrophysical Journal
  • Researchers Are Perfecting Technology to Look for Signs of Alien Life
    Donnerstag, 06.12.2018, 00:18:11 Uhr
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    Researchers Are Perfecting Technology to Look for Signs of Alien Life Kamuela HI (SPX) Nov 21, 2018 -
    Astronomers have gleaned some of the best data yet on the composition of a planet known as HR 8799c - a young giant gas planet about 7 times the mass of Jupiter that orbits its star every 200 years.The team used state-of-the art instrumentation at the W. M. Keck Observatory on Maunakea, Hawaii to confirm the existence of water in the planet's atmosphere, as well as a lack of methane.While other researchers had previously made similar measurements of this planet, these new, more robust data demonstrate the power of combining high-resolution spectroscopy with a technique known as adaptive optics, which corrects for the blurring effect of Earth's atmosphere."This type of technology is exactly what we want to use in the future to look for signs of life on an Earth-like planet. We aren't there yet but we are marching ahead," says Dimitri Mawet, an associate professor of astronomy at Caltech and a research scientist at JPL, which Caltech manages for NASA.Mawet is co-author of a new paper on the findings published in The Astronomical Journal.The lead author is Ji Wang, formerly a postdoctoral scholar at Caltech and now an assistant professor at Ohio State University.Taking pictures of planets that orbit other stars - exoplanets - is a formidable task. Light from the host stars far outshines the planets, making them difficult to see.More than a dozen exoplanets have been directly imaged so far, including HR 8799c and three of its planetary companions. In fact, HR 8799 is the only multiple-planet system to have its picture taken. Discovered using adaptive optics on the Keck II telescope, the direct images of HR8799 are the first-ever of a planetary system orbiting a star other than our Sun.Once an image is obtained, astronomers can use instruments, called spectrometers, to break apart the planet's light, like a prism turning sunlight into a rainbow, thereby revealing the fingerprints of chemicals. So far, this strategy has been used to learn about the atmospheres of several giant exoplanets.The next step is to do the same thing only for smaller planets that are closer to their stars (the closer a planet is to its star and the smaller its size, the harder is it to see).The ultimate goal is to look for chemicals in the atmospheres of Earth-like planets that orbit in the star's "habitable zone" - including any biosignatures that might indicate life, such as water, oxygen, and methane.Mawet's group hopes to do just this with an instrument on the upcoming Thirty Meter Telescope, a giant telescope being planned for the late 2020s by several national and international partners, including Caltech.But for now, the scientists are perfecting their technique using Keck Observatory - and, in the process, learning about the compositions and dynamics of giant planets."Right now, with Keck, we can already learn about the physics and dynamics of these giant exotic planets, which are nothing like our own solar system planets," says Wang.In the new study, the researchers used an instrument on the Keck II telescope called NIRSPEC (near-infrared cryogenic echelle spectrograph), a high-resolution spectrometer that works in infrared light.They coupled the instrument with Keck Observatory's powerful adaptive optics, a method for creating crisper pictures using a guide star in the sky as a means to measure and correct the blurring turbulence of Earth's atmosphere.This is the first time the technique has been demonstrated on directly imaged planets using what's known as the L-band, a type of infrared light with a wavelength of around 3.5 micrometers, and a region of the spectrum with many detailed chemical fingerprints."The L-band has gone largely overlooked before because the sky is brighter at this wavelength," says Mawet. "If you were an alien with eyes tuned to the L-band, you'd see an extremely bright sky. It's hard to see exoplanets through this veil."The researchers say that the addition of adaptive optics made the L-band more accessible for the study of the planet HR 8799c. In their study, they made the most precise measurements yet of the atmospheric constituents of the planet, confirming it has water and lacks methane as previously thought."We are now more certain about the lack of methane in this planet," says Wang. "This may be due to mixing in the planet's atmosphere. The methane, which we would expect to be there on the surface, could be diluted if the process of convection is bringing up deeper layers of the planet that don't have methane."The L-band is also good for making measurements of a planet's carbon-to-oxygen ratio - a tracer of where and how a planet forms. Planets form out of swirling disks of material around stars, specifically from a mix of hydrogen, oxygen, and carbon-rich molecules, such as water, carbon monoxide, and methane.These molecules freeze out of the planet-forming disks at different distances from the star - at boundaries called snowlines. By measuring a planet's carbon-to-oxygen ratio, astronomers can thus learn about its origins.Mawet's team is now gearing up to turn on their newest instrument at Keck Observatory, called the Keck Planet Imager and Characterizer (KPIC). It will also use adaptive optics-aided high-resolution spectroscopy but can see planets that are fainter than HR 8799c and closer to their stars."KPIC is a springboard to our future Thirty Meter Telescope instrument," says Mawet. "For now, we are learning a great deal about the myriad ways in which planets in our universe form."Research Report: "Detecting Water in the Atmosphere of HR 8799 c with L-band High Dispersion Spectroscopy Aided By Adaptive Optics," Ji Wang et al., 2018 Nov. 20, Astronomical Journal
  • Study reveals one of universe's secret ingredients for life
    Donnerstag, 06.12.2018, 00:18:11 Uhr
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    Study reveals one of universe's secret ingredients for life Canberra, Australia (SPX) Nov 23, 2018 -
    A new study led by The Australian National University (ANU) has investigated the nature of a cosmic phenomenon that slows down star formation, which helps to ensure the universe is a place where life can emerge.Lead researcher Dr. Roland Crocker from the ANU Research School of Astronomy and Astrophysics said the research team studied a particular way stars provide a counter-pressure to gravity that slows down the star-formation process."If star formation happened rapidly, all stars would be bound together in massive clusters, where the intense radiation and supernova explosions would likely sterilize all the planetary systems, preventing the emergence of life," he said."The conditions in these massive star clusters would possibly even prevent planets from forming in the first place."The study found that ultraviolet and optical light from young and massive stars spreads out into the gas from which the stars have recently formed and hits cosmic dust, which then scatters infrared light that acts effectively as a kind of pressure that pushes against gravity."The phenomenon we studied occurs in galaxies and star clusters where there's a lot of dusty gas that is forming heaps of stars relatively quickly," Dr. Crocker said."In galaxies forming stars more slowly - such as the Milky Way - other processes are slowing things down. The Milky Way forms two new stars every year, on average."Other galaxies in our vicinity and elsewhere in the universe continuously form new stars at a relatively slow and steady rate.Dr. Crocker said the study's mathematical findings indicated the phenomenon set an upper limit on how quickly stars can form in a galaxy or giant gas cloud."This and other forms of feedback help to keep the universe alive and vibrant," he said."We are investigating other ways stars might feed back into their environment to slow down the overall rate of star formation."Professor Mark Krumholz and Dr. Dougal Mackey from the ANU Research School of Astronomy and Astrophysics, Professor Todd Thompson from Ohio State University in the United States and Associate Professor Holger Baumgardt at the University of Queensland contributed to the study, which was published in the Monthly Notices of the Royal Astronomical Society.Research Report: "Radiation Pressure Limits on the Star Formation Efficiency and Surface Density of Compact Stellar Systems," Roland M. Crocker et al., 2018 Oct. 1, Monthly Notices of the Royal Astronomical Society
  • What magnetic fields can tell us about life on other planets
    Donnerstag, 06.12.2018, 00:18:11 Uhr
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    What magnetic fields can tell us about life on other planets Berkeley CA (SPX) Nov 23, 2018 -
    Every school kid knows that Earth has a magnetic field - it's what makes compasses align north-south and lets us navigate the oceans. It also protects the atmosphere, and thus life, from the Sun's powerful wind.But what about other Earth-like planets in the galaxy? Do they also have magnetic fields to protect emerging life?A new analysis looks at one type of exoplanet - super-Earths up to five times the size of our own planet - and concludes that they probably do have a magnetic field, but one generated in a totally novel way: by the planets' magma oceans.The surprising discovery that slowly churning melted rock at or under the surface can generate a strong magnetic field also suggests that in Earth's early years, when it was largely a lump of melted rock, it also had a magma-generated magnetic field. This was in addition to its present-day field, which is generated in the liquid-iron outer core."This is a new regime for the generation of planetary magnetic fields," said Burkhard Militzer, a UC Berkeley professor of earth and planetary science. "Our magnetic field on Earth is generated in the liquid outer iron core. On Jupiter, it arises from the convection of liquid metallic hydrogen. On Uranus and Neptune, it is assumed to be generated in the ice layers. Now we have added molten rocks to this diverse list of field-generating materials."The link between a planet's interior and its magnetic field also provides a way for astronomers to learn about the makeup and ages of exoplanets too far away to visit."This is far in the future, but if someone makes an observation of an exoplanet and they find a magnetic field, that may be an indication that there is a magma ocean, even if they cannot see this directly," Militzer said.The conclusions also have implications for chances for life on other planets. As magma oceans cool from the top, a surface hospitable to life could appear while the melted mantle continues to churn."A magnetic field is helpful in protecting a planetary atmosphere from being blown away by the stellar winds," said former UC Berkeley postdoctoral fellow Francois Soubiran, now at the Ecole Normale Superieure in Lyon, France. "Most of the super-Earths we are detecting now are very close to their host stars and exposed to very strong stellar winds. Thus, the possibility for a magnetic field to exist is definitely a key component in the evolution of the planet and its habitability."Soubiran and Militzer published their findings Sept. 24 in the journal Nature Communications.Earth's Internal Dynamo
    The magnetic field of Earth today is generated in the molten-iron outer core, where rising and sinking masses of electrically conducting liquid iron, combined with the planet's spin, create a dynamo and a persistent magnetic field.But the rocky Earth was molten after its initial formation 4.5 billion years ago, and some layers may have remained molten and convecting - like boiling water, only slower - for millions of years after its birth. Could the slowly convecting magma ocean have generated a magnetic field akin to the one generated in the iron core today?The same question arose after super-Earths were discovered around other stars. Super-Earths are so massive that their interior, the mantle, should remain liquid and convecting for a few billion years after formation.In both cases, the slowly boiling magma on a spinning planet can generate a strong magnetic field only if the liquid rock conducts electricity.No one knew if this was true
    Experiments on silicates - a term referring to the thousands of silicon-based minerals that make up Earth's rocky interior - at the high temperatures and pressures inside a super-Earth are difficult. Even establishing whether a rock remains solid or becomes liquid is not straightforward at the conditions typical of planetary interiors: temperatures of 10,000 C and pressures 10 million times that of the air around us."At standard temperatures and pressures, silicates are completely insulating; the electrons are either tightly bound to the nuclei or they are in molecular bonds and not able to freely move and create macroscopic electric currents," Soubiran said. "Even if the high internal pressure helps reduce the barriers for the electrons to move, it was not necessarily obvious silicates would be conducting in super-Earths."But Soubiran and Militzer had access to atomic-scale computer models of minerals that allowed them to calculate the conductivity of, in this case, quartz (silicon dioxide), magnesia (magnesium oxide) and a silicon-magnesium-oxide (post-perovskite), all of which are common in rocks on Earth, the moon and probably all of our solar system's planets.After performing lengthy calculations for each of the three, they discovered that these silicates become modestly conducting when they change from solid to liquid at high temperatures and pressures. When they plugged the conductivities into models of Earth's interior, they discovered that the rocks were sufficiently conducting to sustain a dynamo and thus a magnetic field."Our calculations showed that the disorganized structure of the liquid helped the electrons become conducting," Soubiran said. Liquid silicates at 10,000 C and 10 million atmospheres of pressure have only about one-hundredth the conductivity of liquid iron, for example.Soubiran noted that planets rotating with a period of two days or more would generate an Earth-like magnetic field: a dipole field with a clear north and south. Slower rotation, however, could create a more disorganized field that would be harder to detect from afar.Bruce Buffett, a UC Berkeley expert on the dynamics of Earth's interior who was not involved in the research, said that planets can generate magnetic fields only if they have the right balance of electrical conductivity and fluid velocity to create the feedback necessary to sustain a magnetic field."The expectation of many geophysicists was that, at least under Earth conditions, the conductivity of liquid silicates would fall more into the category of, well, if you had really, really large fluid motions to compensate for a low conductivity, you might have a magnetic field," said Buffett, a professor of earth and planetary science."This is the first detailed calculation for higher temperature and pressure conditions, and it finds that the conductivities appear to be a little bit higher, so the fluid motions you would need to make this all work are maybe a little bit less extreme."Research Report: "Electrical Conductivity and Magnetic Dynamos in Magma Oceans of Super-Earths," Francois Soubiran and Burkhard Militzer, 2018 Sep. 24, Nature Communications
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