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  • NASA study shows disk patterns can self-generate
    17.01.2018 03:02:53
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    NASA study shows disk patterns can self-generate Greenbelt MD (SPX) Jan 17, 2018 -
    When exoplanet scientists first spotted patterns in disks of dust and gas around young stars, they thought newly formed planets might be the cause. But a recent NASA study cautions that there may be another explanation - one that doesn't involve planets at all.Exoplanet hunters watch stars for a few telltale signs that there might be planets in orbit, like changes in the color and brightness of the starlight. For young stars, which are often surrounded by disks of dust and gas, scientists look for patterns in the debris - such as rings, arcs and spirals - that might be caused by an orbiting world."We're exploring what we think is the leading alternative contender to the planet hypothesis, which is that the dust and gas in the disk form the patterns when they get hit by ultraviolet light," said Marc Kuchner, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.Kuchner presented the findings of the new study on Thursday, Jan. 11, at the American Astronomical Society meeting in Washington. A paper describing the results has been submitted to The Astrophysical Journal.When high-energy UV starlight hits dust grains, it strips away electrons. Those electrons collide with and heat nearby gas. As the gas warms, its pressure increases and it traps more dust, which in turn heats more gas. The resulting cycle, called the photoelectric instability (PeI), can work in tandem with other forces to create some of the features astronomers have previously associated with planets in debris disks.Kuchner and his colleagues designed computer simulations to better understand these effects. The research was led by Alexander Richert, a doctoral student at Penn State in University Park, Pennsylvania, and includes Wladimir Lyra, a professor of astronomy at California State University, Northridge and research associate at NASA's Jet Propulsion Laboratory in Pasadena, California. The simulations were run on the Discover supercomputing cluster at the NASA Center for Climate Simulation at Goddard.In 2013, Lyra and Kuchner suggested that PeI could explain the narrow rings seen in some disks. Their model also predicted that some disks would have arcs, or incomplete rings, which were first directly observed in 2016."People very often model these systems with planets, but if you want to know what a disk with a planet looks like, you first have to know what a disk looks like without a planet," Richert said.Richert is lead author on the new study, which builds on Lyra and Kuchner's previous simulations by including an additional new factor: radiation pressure, a force caused by starlight striking dust grains.Light exerts a minute physical force on everything it encounters. This radiation pressure propels solar sails and helps direct comet tails so they always point away from the Sun. The same force can push dust into highly eccentric orbits, and even blow some of the smaller grains out of the disk entirely.The researchers modeled how radiation pressure and PeI work together to affect the movement of dust and gas. They also found that the two forces manifest different patterns depending on the physical properties of the dust and gas.The 2013 simulations of PeI revealed how dust and gas interact to create rings and arcs, like those observed around the real star HD 141569A. With the inclusion of radiation pressure, the 2017 models show how these two factors can create spirals like those also observed around the same star. While planets can also cause these patterns, the new models show scientists should avoid jumping to conclusions."Carl Sagan used to say extraordinary claims require extraordinary evidence," Lyra said."I feel we are sometimes too quick to jump to the idea that the structures we see are caused by planets. That is what I consider an extraordinary claim. We need to rule out everything else before we claim that."Kuchner and his colleagues said they would continue to factor other parameters into their simulations, like turbulence and different types of dust and gas. They also intend to model how these factors might contribute to pattern formation around different types of stars.A NASA-funded citizen science project spearheaded by Kuchner, called Disk Detective, aims to discover more stars with debris disks. So far, participants have contributed more than 2.5 million classifications of potential disks. The data has already helped break new ground in this research.Research Report: "The Interplay Between Radiation Pressure and the Photoelectric Instability in Optically Thin Disks of Gas And Dust," Alexander J. W. Richert, Wladimir Lyra, and Marc Kuchner, 2018, submitted to the Astrophysical Journal
  • Hubble finds substellar objects in the Orion Nebula
    17.01.2018 03:02:53
    Hubble finds substellar objects in the Orion Nebula Baltimore MD (SPX) Jan 15, 2018 -
    In an unprecedented deep survey for small, faint objects in the Orion Nebula, astronomers using NASA's Hubble Space Telescope (http://www.nasa.gov/hubble) have uncovered the largest known population of brown dwarfs sprinkled among newborn stars. Looking in the vicinity of the survey stars, researchers not only found several very-low-mass brown dwarf companions, but also three giant planets. They even found an example of binary planets where two planets orbit each other in the absence of a parent star.Brown dwarfs are a strange class of celestial object that have masses so low that their cores never become hot enough to sustain nuclear fusion, which powers stars. Instead, brown dwarfs cool and fade as they age. Despite their low mass, brown dwarfs provide important clues to understanding how stars and planets form, and may be among the most common objects in our Milky Way galaxy.Located 1,350 light-years away, the Orion Nebula is a relatively nearby laboratory for studying the star formation process across a wide range, from opulent giant stars to diminutive red dwarf stars and elusive, faint brown dwarfs.This survey could only be done with Hubble's exceptional resolution and infrared sensitivity.Because brown dwarfs are colder than stars, astronomers used Hubble to identify them by the presence of water in their atmospheres."These are so cold that water vapor forms," explained team lead Massimo Robberto of the Space Telescope Institute in Baltimore, Maryland."Water is a signature of substellar objects. It's an amazing and very clear mark. As the masses get smaller, the stars become redder and fainter, and you need to view them in the infrared. And in infrared light, the most prominent feature is water."But hot water vapor in the atmosphere of brown dwarfs cannot be easily seen from Earth's surface, due to the absorbing effects of water vapor in our own atmosphere. Fortunately, Hubble is up above the atmosphere and has near-infrared vision that can easily spot water on distant worlds.The Hubble team identified 1,200 candidate reddish stars. They found that the stars split into two distinct populations: those with water, and those without. The bright ones with water were confirmed to be faint red dwarfs. The multitude of fainter water-rich, free-floating brown dwarfs and planets within the Orion nebula are all new discoveries. Many stars without water were also detected, and these are background stars in the Milky Way. Their light was reddened by passing through interstellar dust, and therefore not relevant to the team's study.The team also looked for fainter, binary companions to these 1,200 reddish stars. Because they are so close to their primary stars, these companions are nearly impossible to discover using standard observing methods. But by using a unique, high-contrast imaging technique developed by Laurent Pueyo at the Space Telescope Science Institute, astronomers were able to resolve faint images of a large number of candidate companions.This first analysis did not allow Hubble astronomers to determine whether these objects orbit the brighter star or if their proximity in the Hubble image is a result of chance alignment. As a consequence, they are classified as candidates for now. However, the presence of water in their atmospheres indicates that most of them cannot be misaligned stars in the galactic background, and thus must be brown dwarfs or exoplanet companions.In all, the team found 17 candidate brown dwarf companions to red dwarf stars, one brown dwarf pair, and one brown dwarf with a planetary companion. The study also identified three potential planetary mass companions: one associated to a red dwarf, one to a brown dwarf, and one to another planet."We experimented with a method, high-contrast imaging post processing, that astronomers have been relying on for years. We usually use it to look for very faint planets in the close vicinity of nearby stars, by painstakingly observing them one by one," said Pueyo."This time around, we decided to combine our algorithms with the ultra-stability of Hubble to inspect the vicinity of hundreds of very young stars in every single exposure obtained by the Orion survey. It turns out that even if we do not reach the deepest sensitivity for a single star, the sheer volume of our sample allowed us to obtain an unprecedented statistical snapshot of young exoplanets and brown dwarf companions in Orion."Combining the two unique techniques, imaging in the water filters and high-contrast image processing, the survey provided an unbiased sample of newly formed low-mass sources, both dispersed in the field and companions of other low-mass objects."We could reprocess the entire Hubble archive and try to find jewels there," Robberto said.The team presented their results at the 231st meeting of the American Astronomical Society in Washington, D.C.Finding the signatures of low-mass stars and their companions will become much more efficient with the launch of NASA's infrared-sensitive James Webb Space Telescope in 2019.
  • Citizen scientists discover five-planet system
    17.01.2018 03:02:53
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    Citizen scientists discover five-planet system Pasadena CA (SPX) Jan 12, 2018 -
    In its search for exoplanets - planets outside of our solar system - NASA's Kepler telescope trails behind Earth, measuring the brightness of stars that may potentially host planets. The instrument identifies potential planets around other stars by looking for dips in the brightness of the stars that occur when planets cross in front of, or transit, them. Typically, computer programs flag the stars with these brightness dips, then astronomers look at each one and decide whether or not they truly could host a planet candidate.Over the three years of the K2 mission, 287,309 stars have been observed, and tens of thousands more roll in every few months. So how do astronomers sift through all that data?Enter the Exoplanet Explorers citizen scientist project, developed by UC Santa Cruz astronomer Ian Crossfield and Caltech staff scientist Jessie Christiansen. Exoplanet Explorers is hosted on Zooniverse, an online platform for crowdsourcing research."People anywhere can log on and learn what real signals from exoplanets look like, and then look through actual data collected from the Kepler telescope to vote on whether or not to classify a given signal as a transit, or just noise," says Christiansen."We have each potential transit signal looked at by a minimum of 10 people, and each needs a minimum of 90 percent of 'yes' votes to be considered for further characterization."In early April, just two weeks after the initial prototype of Exoplanet Explorers was set up on Zooniverse, it was featured in a three-day event on the ABC Australia television series Stargazing Live.In the first 48 hours after the project was introduced, Exoplanet Explorers received over 2 million classifications from more than 10,000 users. Included in that search was a brand-new dataset from the K2 mission - the reincarnation of the primary Kepler mission, ended three years ago. K2 has a whole new field of view and crop of stars around which to search for planets. No professional astronomer had yet looked through this dataset, called C12.Back in California, Crossfield and Christiansen joined NASA astronomer Geert Barentsen, who was in Australia, in examining results as they came in. Using the depth of the transit curve and the periodicity with which it appears, they made estimates for how large the potential planet is and how close it orbits to its star.On the second night of the show, the researchers discussed the demographics of the planet candidates found so far - 44 Jupiter-sized planets, 72 Neptune-sized, 44 Earth-sized, and 53 so-called Super Earth's, which are larger than Earth but smaller than Neptune."We wanted to find a new classification that would be exciting to announce on the final night, so we were originally combing through the planet candidates to find a planet in the habitable zone - the region around a star where liquid water could exist," says Christiansen."But those can take a while to validate, to make sure that it really is a real planet and not a false alarm. So, we decided to look for a multi-planet system because it's very hard to get an accidental false signal of several planets."After this decision, Barentsen left to get a cup of tea. By the time he returned, Christiansen had sorted the crowdsourced data to find a star with multiple transits and discovered a star with four planets orbiting it. Three of the four planets had 100 percent "yes" votes from over 10 people, and the remaining one had 92 percent "yes" votes. This is the first multi-planet system of exoplanets discovered entirely by crowdsourcing.After the discovery was announced on Stargazing Live, Christiansen and her colleagues continued to study and characterize the system, dubbed K2-138. They statistically validated the set of planet signals as being "extremely likely," according to Christiansen, to be signals from true planets.They also found that the planets are orbiting in an interesting mathematical relationship called a resonance, in which each planet takes almost exactly 50 percent longer to orbit the star than the next planet further in.The researchers also found a fifth planet on the same chain of resonances, and hints of a sixth planet as well. A paper describing the system has been accepted for publication in The Astronomical Journal, and Christiansen is speaking about K2-138 at this week's 231st meeting of the American Astronomical Society in Washington, DC.This is the only system with a chain of unbroken resonances in this configuration, and may provide clues to theorists looking to unlock the mysteries of planet formation and migration."The clockwork-like orbital architecture of this planetary system is keenly reminiscent of the Galilean satellites of Jupiter," says Konstantin Batygin, assistant professor of planetary science and Van Nuys Page Scholar, who was not involved with the study."Orbital commensurabilities among planets are fundamentally fragile, so the present-day configuration of the K2-138 planets clearly points to a rather gentle and laminar formation environment of these distant worlds.""Some current theories suggest that planets form by a chaotic scattering of rock and gas and other material in the early stages of the planetary system's life. However, these theories are unlikely to result in such a closely packed, orderly system as K2-138," says Christiansen."What's exciting is that we found this unusual system with the help of the general public."Research Report: "The K2-138 System: A Near-Resonant Chain of Five Sub-Neptune Planets Discovered by Citizen Scientists," Jessie L. Christiansen et al., 2018 February, Astronomical Journal
  • Ingredients for life revealed in meteorites that fell to Earth
    17.01.2018 03:02:53
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    Ingredients for life revealed in meteorites that fell to Earth Berkeley CA (SPX) Jan 11, 2018 -
    Two wayward space rocks, which separately crashed to Earth in 1998 after circulating in our solar system's asteroid belt for billions of years, share something else in common: the ingredients for life. They are the first meteorites found to contain both liquid water and a mix of complex organic compounds such as hydrocarbons and amino acids.A detailed study of the chemical makeup within tiny blue and purple salt crystals sampled from these meteorites, which included results from X-ray experiments at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), also found evidence for the pair's past intermingling and likely parents. These include Ceres, a brown dwarf planet that is the largest object in the asteroid belt, and the asteroid Hebe, a major source of meteorites that fall on Earth.The study, published Jan. 10 in the journal Science Advances, provides the first comprehensive chemical exploration of organic matter and liquid water in salt crystals found in Earth-impacting meteorites. The study treads new ground in the narrative of our solar system's early history and asteroid geology while surfacing exciting possibilities for the existence of life elsewhere in Earth's neighborhood."It's like a fly in amber," said David Kilcoyne, a scientist at Berkeley Lab's Advanced Light Source (ALS), which provided X-rays that were used to scan the samples' organic chemical components, including carbon, oxygen, and nitrogen. Kilcoyne was part of the international research team that prepared the study.While the rich deposits of organic remnants recovered from the meteorites don't provide any proof of life outside of Earth, Kilcoyne said the meteorites' encapsulation of rich chemistry is analogous to the preservation of prehistoric insects in solidified sap droplets.Queenie Chan, a planetary scientist and postdoctoral research associate at The Open University in the U.K. who was the study's lead author, said, "This is really the first time we have found abundant organic matter also associated with liquid water that is really crucial to the origin of life and the origin of complex organic compounds in space."She added, "We're looking at the organic ingredients that can lead to the origin of life," including the amino acids needed to form proteins.If life did exist in some form in the early solar system, the study notes that these salt crystal-containing meteorites raise the "possibility of trapping life and/or biomolecules" within their salt crystals. The crystals carried microscopic traces of water that is believed to date back to the infancy of our solar system - about 4.5 billion years ago.Chan said the similarity of the crystals found in the meteorites - one of which smashed into the ground near a children's basketball game in Texas in March 1998 and the other which hit near Morocco in August 1998 - suggest that their asteroid hosts may have crossed paths and mixed materials.There are also structural clues of an impact - perhaps by a small asteroid fragment impacting a larger asteroid, Chan said.This opens up many possibilities for how organic matter may be passed from one host to another in space, and scientists may need to rethink the processes that led to the complex suite of organic compounds on these meteorites."Things are not as simple as we thought they were," Chan said.There are also clues, based on the organic chemistry and space observations, that the crystals may have originally been seeded by ice- or water-spewing volcanic activity on Ceres, she said."Everything leads to the conclusion that the origin of life is really possible elsewhere," Chan said."There is a great range of organic compounds within these meteorites, including a very primitive type of organics that likely represent the early solar system's organic composition."Chan said the two meteorites that yielded the 2-millimeter-sized salt crystals were carefully preserved at NASA's Johnson Space Center in Texas, and the tiny crystals containing organic solids and water traces measure just a fraction of the width of a human hair. Chan meticulously collected these crystals in a dust-controlled room, splitting off tiny sample fragments with metal instruments resembling dental picks."What makes our analysis so special is that we combined a lot of different state-of-the-art techniques to comprehensively study the organic components of these tiny salt crystals," Chan said.Yoko Kebukawa, an associate professor of engineering at Yokohama National University in Japan, carried out experiments for the study at Berkeley Lab's ALS in May 2016 with Aiko Nakato, a postdoctoral researcher at Kyoto University in Japan. Kilcoyne helped to train the researchers to use the ALS X-ray beamline and microscope.The beamline equipped with this X-ray microscope (a scanning transmission X-ray microscope, or STXM) is used in combination with a technique known as XANES (X-ray absorption near edge structure spectroscopy) to measure the presence of specific elements with a precision of tens of nanometers (tens of billionths of a meter)."We revealed that the organic matter was somewhat similar to that found in primitive meteorites, but contained more oxygen-bearing chemistry," Kebukawa said."Combined with other evidence, the results support the idea that the organic matter originated from a water-rich, or previously water-rich parent body - an ocean world in the early solar system, possibly Ceres."Kebukawa also used the same STXM technique to study samples at the Photon Factory, a research site in Japan. And the research team enlisted a variety of other chemical experimental techniques to explore the samples' makeup in different ways and at different scales.Chan noted that there are some other well-preserved crystals from the meteorites that haven't yet been studied, and there are plans for follow-up studies to identify if any of those crystals may also contain water and complex organic molecules.Kebukawa said she looks forward to continuing studies of these samples at the ALS and other sites: "We may find more variations in organic chemistry.""Organic Matter in Extraterrestrial Water-Bearing Salt Crystals Indicates Ceres as an Organic-Rich Body," Queenie H.S. Chan, Michael E. Zolensky, et al., 2018 Jan. 10, Science Advance
  • Iron-Rich Stars Host Shorter-Period Planets
    17.01.2018 03:02:53
    Iron-Rich Stars Host Shorter-Period Planets Baltimore MD (SPX) Jan 10, 2018 -
    Astronomers with the Sloan Digital Sky Survey (SDSS) have learned that the chemical composition of a star can exert unexpected influence on its planetary system - a discovery made possible by an ongoing SDSS survey of stars seen by NASA's Kepler spacecraft, and one that promises to expand our understanding of how extrasolar planets form and evolve."Without these detailed and accurate measurements of the iron content of stars, we could have never made this measurement," says Robert Wilson, a graduate student in astronomy at the University of Virginia and lead author of the paper announcing the results.The team presented their results at the American Astronomical Society (AAS) meeting in National Harbor, Maryland. Using SDSS data, they found that stars with higher concentrations of iron tend to host planets that orbit quite close to their host star - often with orbital periods of less than about eight days - while stars with less iron tend to host planets with longer periods that are more distant from their host star. Further investigation of this effect may help us understand the full variety of extrasolar planetary systems in our galaxy, and shed light on why planets are found where they are.The story of planets around Sun-like stars began in 1995, when a team of astronomers discovered a single planet orbiting a Sun-like star 50 light-years from Earth. The pace of discovery accelerated in 2009, when NASA launched the Kepler spacecraft, a space telescope designed to look for extrasolar planets.During its four-year primary mission, Kepler monitored thousands of stars at a time, watching for the tiny dimming of starlight that indicates a planet passing in front its host star. And because Kepler looked at the same stars for years, it saw their planets over and over again, and was thus able to measure the time the planet takes to orbit its star.This information reveals the distance to from star to planet, with closer planets orbiting faster than farther ones. Thanks to Kepler's tireless monitoring, the number of exoplanets with known orbital periods increased dramatically, from about 400 in 2009 to more than 3,000 today.Although Kepler was perfectly designed to spot extrasolar planets, it was not designed to learn about the chemical compositions of the stars around which those planets orbit. That knowledge comes from the SDSS's Apache Point Observatory Galactic Evolution Experiment (APOGEE), which has studied hundreds of thousands of stars all over the Milky Way Galaxy. APOGEE works by collecting a spectrum for each star - a measurement of how much light the star gives off at different wavelengths (colors) of light.Because atoms of each chemical element interact with light in their own characteristic way, a spectrum allows astronomers to determine not only which elements a star contains, but also how much - for all elements including the key element iron."All Sun-like stars are mostly hydrogen, but some contain more iron than others," says Johanna Teske of the Carnegie Institution for Science, a member of the research team."The amount of iron a star contains is an important clue to how it formed and how it will evolve over its lifetime."By combining data from these two sources - planetary orbits from Kepler and stellar chemistry from APOGEE - astronomers have learned about the relationships between these "iron-enriched" stars and the planetary systems they hold."We knew that the element enrichment of a star would matter for its own evolution," says Teske, "But we were surprised to learn that it matters for the evolution of its planetary system as well."The work presented today builds on previous work, led by Gijs Mulders of the University of Arizona, using a larger but less precise sample of spectra from the LAMOST-Kepler project. (LAMOST, the Large-Area Multi-Object fiber Spectroscopic Telescope, is a Chinese sky survey.) Mulders and collaborators found a similar trend - closer-in planets orbiting more iron-rich stars - but did not pin down the critical period of eight days."It is encouraging to see an independent confirmation of the trend we found in 2016," says Mulders."The identification of the critical period really shows that Kepler is the gift that keeps on giving."What is particularly surprising about the new result, Wilson explained, is that the iron-enriched stars have only about 25 percent more iron than the others in the sample."That's like adding five-eighths of a teaspoon of salt into a cupcake recipe that calls for half a teaspoon of salt, among all its other ingredients. I'd still eat that cupcake," he says."That really shows us how even small differences in stellar composition can have profound impacts on planetary systems."But even with this new discovery, astronomers are left with many unanswered questions about how extrasolar planets form and evolve, especially planets Earth-sized or slightly larger ("super-Earths"). Do iron-rich stars intrinsically form planets with shorter orbits? Or are planets orbiting iron-rich stars more likely to form farther out and then migrate to shorter period, closer-in orbits? Wilson and collaborators hope to work with other astronomers to create new models of protoplanetary disks to test both of these explanations."I'm excited that we still have much to learn about how the chemical compositions of stars impact their planets, particularly about how small planets form," Teske says."Plus, APOGEE provides many more stellar chemical abundances besides iron, so there are likely other trends buried within this rich dataset that we have yet to explore."
  • SETI project homes in on strange 'fast radio bursts'
    17.01.2018 03:02:53
    SETI project homes in on strange 'fast radio bursts' Berkeley CA (SPX) Jan 11, 2018 -
    Recent observations of a mysterious and distant object that emits intermittent bursts of radio waves so bright that they're visible across the universe provide new data about the source but fail to clear up the mystery of what causes them.The observations by the Breakthrough Listen team at UC Berkeley using the Robert C. Byrd Green Bank Telescope in West Virginia show that the fast radio bursts from this object, called FRB 121102, are nearly 100 percent linearly polarized, an indication that the source of the bursts is embedded in strong magnetic fields like those around a massive black hole.The measurements confirm observations by another team of astronomers from the Netherlands, which detected the polarized bursts using the William E. Gordon Telescope at the Arecibo Observatory in Puerto Rico.Both teams will report their findings during a media briefing on Jan. 10 at a meeting of the American Astronomical Society in Washington, D.C. The results are detailed in a combined paper to be published online the same day by the journal Nature.Fast radio bursts are brief, bright pulses of radio emission from distant but so far unknown sources, and FRB 121102 is the only one known to repeat: more than 200 high-energy bursts have been observed coming from this source, which is located in a dwarf galaxy about 3 billion light years from Earth.The nearly 100 percent polarization of the radio bursts is unusual, and has only been seen in radio emissions from the extreme magnetic environments around massive black holes, such as those at the centers of galaxies.The Dutch and Breakthrough Listen teams suggest that the fast radio bursts may come from a highly magnetized rotating neutron star - a magnetar - in the vicinity of a massive black hole that is still growing as gas and dust fall into it.The short bursts, which range from 30 microseconds to 9 milliseconds in duration, indicate that the source could be as small as 10 kilometers across - the typical size of a neutron star.Other possible sources are a magnetar interacting with the nebula of material shed when the original star exploded to produce the magnetar; or interactions with the highly magnetized wind from a rotating neutron star, or pulsar."At this point, we don't really know the mechanism. There are many questions, such as, how can a rotating neutron star produce the high amount of energy typical of an FRB?" said UC Berkeley postdoctoral fellow Vishal Gajjar of Breakthrough Listen and the Berkeley SETI Research Center.Gajjar will participate in the media briefing with three members of the Dutch ASTRON team: Daniele Michilli and Jason Hessels of the University of Amsterdam and Betsey Adams of the Kapteyn Astronomical Institute."This result is an excellent demonstration of the capabilities of the Breakthrough Listen instrumentation and the synergies between SETI and other types of astronomy," said Andrew Siemion, director of the Berkeley SETI Research Center and of the Breakthrough Listen program."We look forward to working with the international scientific community to learn more about these enigmatic and dynamic sources."Are FRBs signals from advanced civilizations?
    Another possibility, though remote, is that the FRB is a high-powered signal from an advanced civilization. Hence the interest of Breakthrough Listen, which looks for signs of intelligent life in the universe, funded by $100 million over 10 years from internet investor Yuri Milner."We can not rule out completely the ET hypothesis for the FRBs in general," Gajjar said.Breakthrough Listen has to date recorded data from a dozen FRBs, including FRB 121102, and plans eventually to sample all 30-some known sources of fast radio bursts."We want a complete sample so that we can conduct our standard SETI analysis in search of modulation patterns or narrow-band signals - any kind of information-bearing signal emitted from their direction that we don't expect from nature," he said.Breakthrough Listen allotted tens of hours of observational time on the Green Bank Telescope to recording radio emissions from FRB 121102, and last August 26 detected 15 bursts over a relatively short period of five hours. They analyzed the two brightest of these and found that the radio waves were nearly 100 percent linearly polarized.The team plans a few more observations of FRB 121102 before moving on to other FRB sources. Gajjar said that they want to observe at higher frequencies - up to 12 gigahertz, versus the present Green Bank observations in the 4-8 GHz range - to see if the energy drops off at higher frequencies. This could help narrow the range of possible sources, he said.
  • Extraterrestrial Hypatia stone rattles solar system status quo
    17.01.2018 03:02:53
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    Extraterrestrial Hypatia stone rattles solar system status quo Johannesburg, South Africa (SPX) Jan 10, 2018 -
    In 2013, researchers announced that a pebble found in south-west Egypt, was definitely not from Earth. By 2015, other research teams had announced that the 'Hypatia' stone was not part of any known types of meteorite or comet, based on noble gas and nuclear probe analyses.(The stone was named Hypatia after Hypatia of Alexandria, the first Western woman mathematician and astronomer).However, if the pebble was not from Earth, what was its origin and could the minerals in it provide clues on where it came from? Micro-mineral analyses of the pebble by the original research team at the University of Johannesburg have now provided unsettling answers that spiral away from conventional views of the material our solar system was formed from.The internal structure of the Hypatia pebble is somewhat like a fruitcake that has fallen off a shelf into some flour and cracked on impact, says Prof Jan Kramers, lead researcher of the study published in Geochimica et Cosmochimica Acta on 28 Dec 2017."We can think of the badly mixed dough of a fruit cake representing the bulk of the Hypatia pebble, what we called two mixed 'matrices' in geology terms. The glace cherries and nuts in the cake represent the mineral grains found in Hypatia 'inclusions'. And the flour dusting the cracks of the fallen cake represent the 'secondary materials' we found in the fractures in Hypatia, which are from Earth," he says.The original extraterrestrial rock that fell to Earth must have been at least several meters in diameter, but disintegrated into small fragments of which the Hypatia stone is one.Weird matrix
    Straight away, the Hypatia mineral matrix (represented by fruitcake dough), looks nothing like that of any known meteorites, the rocks that fall from space onto Earth every now and then."If it were possible to grind up the entire planet Earth to dust in a huge mortar and pestle, we would get dust with on average a similar chemical composition as chondritic meteorites," says Kramers."In chondritic meteorites, we expect to see a small amount of carbon{C} and a good amount of silicon (Si). But Hypatia's matrix has a massive amount of carbon and an unusually small amount of silicon.""Even more unusual, the matrix contains a high amount of very specific carbon compounds, called polyaromatic hydrocarbons, or PAH, a major component of interstellar dust, which existed even before our solar system was formed. Interstellar dust is also found in comets and meteorites that have not been heated up for a prolonged period in their history," adds Kramers.In another twist, most (but not all) of the PAH in the Hypatia matrix has been transformed into diamonds smaller than one micrometer, which are thought to have been formed in the shock of impact with the Earth's atmosphere or surface. These diamonds made Hypatia resistant to weathering so that it is preserved for analysis from the time it arrived on Earth.Weirder grains never found before
    When researcher Georgy Belyanin analyzed the mineral grains in the inclusions in Hypatia, (represented by the nuts and cherries of a fruitcake), a number of most surprising chemical elements showed up."The aluminum occurs in pure metallic form, on its own, not in a chemical compound with other elements. As a comparison, gold occurs in nuggets, but aluminum never does. This occurrence is extremely rare on Earth and the rest of our solar system, as far as is known in science," says Belyanin."We also found silver iodine phosphide and moissanite (silicon carbide) grains, again in highly unexpected forms. The grains are the first documented to be found in situ (as is) without having to first dissolve the surrounding rock with acid," adds Belyanin."There are also grains of a compound consisting of mainly nickel and phosphorus, with very little iron; a mineral composition never observed before on Earth or in meteorites," he adds.Dr Marco Andreoli, a Research Fellow at the School of Geosciences at the University of the Witwatersrand, and a member of the Hypatia research team says, "When Hypatia was first found to be extraterrestrial, it was a sensation, but these latest results are opening up even bigger questions about its origins".Unique minerals in our solar system
    Taken together, the ancient unheated PAH carbon as well as the phosphides, the metallic aluminum, and the moissanite suggest that Hypatia is an assembly of unchanged pre-solar material. That means, matter that existed in space before our Sun, the Earth and the other planets in our solar system were formed.Supporting the pre-solar concept is the weird composition of the nickel-phosphorus-iron grains found in the Hypatia inclusions. These three chemical elements are interesting because they belong to the subset of chemical elements heavier than carbon and nitrogen which form the bulk of all the rocky planets."In the grains within Hypatia the ratios of these three elements to each other are completely different from that calculated for the planet Earth or measured in known types of meteorites. As such these inclusions are unique within our solar system," adds Belyanin."We think the nickel-phosphorus-iron grains formed pre-solar, because they are inside the matrix, and are unlikely to have been modified by shock such as collision with the Earth's atmosphere or surface, and also because their composition is so alien to our solar system", he adds."Was the bulk of Hypatia, the matrix, also formed before our solar system? Probably not, because you need a dense dust cloud like the solar nebula to coagulate large bodies" he says.A different kind of dust
    Generally, science says that our solar system's planets ultimately formed from a huge, ancient cloud of interstellar dust (the solar nebula) in space. The first part of that process would be much like dust bunnies coagulating in an unswept room. Science also holds that the solar nebula was homogenous, that is, the same kind of dust everywhere.But Hypatia's chemistry tugs at this view."For starters, there are no silicate minerals in Hypatia's matrix, in contrast to chondritic meteorites (and planets like the Earth, Mars and Venus), where silicates are dominant. Then there are the exotic mineral inclusions. If Hypatia itself is not presolar, both features indicate that the solar nebula wasn't the same kind of dust everywhere - which starts tugging at the generally accepted view of the formation of our solar system", says Kramers.Into the future
    "What we do know is that Hypatia was formed in a cold environment, probably at temperatures below that of liquid nitrogen on Earth (-196 Celsius). In our solar system it would have been way further out than the asteroid belt between Mars and Jupiter, where most meteorites come from."Comets come mainly from the Kuiper Belt, beyond the orbit of Neptune and about 40 times as far away from the sun as we are. Some come from the Oort Cloud, even further out. We know very little about the chemical compositions of space objects out there. So our next question will dig further into where Hypatia came from," says Kramers.The little pebble from the Libyan Desert Glass strewn field in south-west Egypt presents a tantalizing piece for an extraterrestrial puzzle that is getting ever more complex.Research paper
  • Chemists discover plausible recipe for early life on Earth
    17.01.2018 03:02:53
    Chemists discover plausible recipe for early life on Earth La Jolla, CA (SPX) Jan 09, 2018 -
    Chemists at The Scripps Research Institute (TSRI) have developed a fascinating new theory for how life on Earth may have begun.Their experiments, described in the journal Nature Communications, demonstrate that key chemical reactions that support life today could have been carried out with ingredients likely present on the planet four billion years ago."This was a black box for us," said Ramanarayanan Krishnamurthy, PhD, associate professor of chemistry at TSRI and senior author of the new study."But if you focus on the chemistry, the questions of origins of life become less daunting."For the new study, Krishnamurthy and his coauthors, who are all members of the National Science Foundation/National Aeronautics and Space Administration Center for Chemical Evolution, focused on a series of chemical reactions that make up what researchers refer to as the citric acid cycle.Every aerobic organism, from flamingoes to fungi, relies on the citric acid cycle to release stored energy in cells. In previous studies, researchers imagined early life using the same molecules for the citric acid cycle as life uses today.The problem with that approach, Krishnamurthy explai20ns, is that these biological molecules are fragile and the chemical reactions used in the cycle would not have existed in the first billion years of Earth - the ingredients simply didn't exist yet.Leaders of the new study started with the chemical reactions first. They wrote the recipe and then determined which molecules present on early Earth could have worked as ingredients.The new study outlines how two non-biological cycles - called the HKG cycle and the malonate cycle - could have come together to kick-start a crude version of the citric acid cycle. The two cycles use reactions that perform the same fundamental chemistry of a-ketoacids and b-ketoacids as in the citric acid cycle.These shared reactions include aldol additions, which bring new source molecules into the cycles, as well as beta and oxidative decarboxylations, which release the molecules as carbon dioxide (CO2).As they ran these reactions, the researchers found they could produce amino acids in addition to CO2, which are also the end products of the citric acid cycle. The researchers think that as biological molecules like enzymes became available, they could have led to the replacement of non-biological molecules in these fundamental reactions to make them more elaborate and efficient."The chemistry could have stayed the same over time, it was just the nature of the molecules that changed," says Krishnamurthy."The molecules evolved to be more complicated over time based on what biology needed.""Modern metabolism has a precursor, a template, that was non-biological," adds Greg Springsteen, PhD, first author of the new study and associate professor of chemistry at Furman University.Making these reactions even more plausible is the fact that at the center of these reactions is a molecule called glyoxylate, which studies show could have been available on early Earth and is part of the citric acid cycle today (called the "Glyoxylate shunt or cycle").Krishnamurthy says more research needs to be done to see how these chemical reactions could have become as sustainable as the citric acid cycle is today.
  • Planets around other stars are like peas in a pod
    17.01.2018 03:02:53
    Planets around other stars are like peas in a pod Montreal, Canada (SPX) Jan 10, 2018 -
    An international research team led by Universite de Montreal astrophysicist Lauren Weiss has discovered that exoplanets orbiting the same star tend to have similar sizes and a regular orbital spacing. This pattern, revealed by new W. M. Keck Observatory observations of planetary systems discovered by the Kepler Telescope, could suggest that most planetary systems have a different formation history than the solar system.Thanks in large part to the NASA Kepler Telescope, launched in 2009, many thousands of exoplanets are now known. This large sample allows researchers to not only study individual systems, but also to draw conclusions on planetary systems in general. Dr. Weiss is part of the California Kepler Survey team, which used the W. M. Keck Observatory on Maunakea in Hawaii, to obtain high-resolution spectra of 1305 stars hosting 2025 transiting planets originally discovered by Kepler. From these spectra, they measured precise sizes of the stars and their planets.In this new analysis led by Weiss and published in The Astronomical Journal, the team focused on 909 planets belonging to 355 multi-planet systems. These planets are mostly located between 1,000 and 4,000 light-years away from Earth. Using a statistical analysis, the team found two surprising patterns.They found that exoplanets tend to be the same sizes as their neighbors. If one planet is small, the next planet around that same star is very likely to be small as well, and if one planet is big, the next is likely to be big. They also found that planets orbiting the same star tend to have a regular orbital spacing."The planets in a system tend to be the same size and regularly spaced, like peas in a pod. These patterns would not occur if the planet sizes or spacings were drawn at random." explains Weiss.The similar sizes and orbital spacing of planets have implications for how most planetary systems form. In classic planet formation theory, planets form in the protoplanetary disk that surrounds a newly formed star. The planets might form in compact configurations with similar sizes and a regular orbital spacing, in a manner similar to the newly observed pattern in exoplanetary systems.However, in our solar system, the inner planets have surprisingly large spacing and diverse sizes. Abundant evidence in the solar system suggests that Jupiter and Saturn disrupted our system's early structure, resulting in the four widely-spaced terrestrial planets we have today. That planets in most systems are still similarly sized and regularly spaced suggests that perhaps they have been mostly undisturbed since their formation.To test that hypothesis, Weiss is conducting a new study at the Keck Observatory to search for Jupiter analogs around Kepler's multi-planet systems. The planetary systems studied by Weiss and her team have multiple planets quite close to their star. Because of the limited duration of the Kepler Mission, little is known about what kind of planets, if any, exist at larger orbital distances around these systems. They hope to test how the presence or absence of Jupiter-like planets at large orbital distances relate to patterns in the inner planetary systems.Regardless of their outer populations, the similarity of planets in the inner regions of extrasolar systems requires an explanation. If the deciding factor for planet sizes can be identified, it might help determine which stars are likely to have terrestrial planets that are suitable for life.The article "The California-Kepler Survey V. Peas in a Pod: Planets in a Kepler Multi-planet System are Similar in Size and Regularly Spaced" is published in The Astronomical Journal. It was funded by the Trottier Family Foundation. In addition to Lauren M. Weiss (Institute for research on exoplanets iREx, Universite de Montreal), the team includes Benjamin J. Fulton (Caltech, University of Hawaii), Erik A. Petigura (Caltech), Andrew W. Howard (Caltech), Howard Isaacson (UC Berkeley), Geoffrey W. Marcy (UC Berkeley), Phillip A. Cargile (Harvard), Leslie Hebb (Hobart and William Smith Colleges), Timothy D. Morton (Princeton), Evan Sinukoff (University of Hawaii, Caltech), Ian J. M. Crossfield (University of California, Santa Cruz) and Lea A. Hirsch (Caltech).The Institute for research on exoplanets (iREx) of Universite de Montreal brings together top researchers and their students so as to benefit as much as possible from major current and upcoming observation projects, with the ultimate goal of finding life elsewhere. The Institute is devoted to exploring new worlds and seeking life on other planets.Some of the data presented herein were obtained at W. M. Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.Ames manages the Kepler and K2 missions for NASA's Science Mission Directorate. NASA's Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace and Technologies Corp. operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.
  • Discovering the structure of RNA
    17.01.2018 03:02:53
    Weitere Links:
    Discovering the structure of RNA Trieste, Italy (SPX) Jan 05, 2018 -
    It is the less known member of the nucleic acid family, superseded in popularity by its cousin DNA. And yet RNA, or ribonucleic acid, plays an essential role in many biological processes: not only as messenger molecule with the task of transmitting genetic information from the nucleus to the cytoplasm for protein production, but also as protagonist of different and significantly important cellular mechanisms.In many of these, its structure plays a crucial role. Structure is different and characteristic for each RNA depending on the sequence of specific units, known as nucleotides, which compose it like the links of a chain.A research team at SISSA, led by Professor Giovanni Bussi, has developed a computerised simulation model which can effectively predict the three-dimensional conformation of the RNA filament starting from a sequence of nucleotides.The lead author of the study, just published in the journal Nucleic Acids Research, is SISSA researcher Simon Poblete. The work promises to have a significant impact in the research and application field."RNA structure is a crucial factor for many of its functions", explains Giovanni Bussi."The experimental determination of RNA structures may take years, which is why there is great interest in developing methods to predict its structure. Until today, predictive models have concentrated primarily on the study of RNA parts which form double helices."However, the RNA filament can take specific and complex conformations governed by the so-called "non-canonical" interactions, which are very different from those predicted by Watson-Crick's double helix model for DNA".Current simulation models, says Bussi, "work very well: starting from one sequence they are able to envisage a variety of possible structures. The problem is that they are unable to tell which is the right structure among many. Our model, which uses a simplified representation of RNA and has been designed explicitly to correctly predict non-canonical interactions, has proven very efficient in this regard".To test its quality, researchers have used it to predict the structure of RNA molecules whose three-dimensional conformation is known, starting from the knowledge of the sequence alone."Comparing our predictions with known structures, we have understood that our approach really works" confirms Giovanni Bussi.This can have an important impact on basic research, to help shed light on the relationship between structure and function of these molecules, but also on application realms, above all in the medical and therapeutic sector.Bussi adds: "RNA is particularly interesting for its practical implications; once a RNA molecule has been identified, as many molecules as desired can be obtained with little effort and identical to the first one by means of a fast and low-cost replication process."If, for example, we were able to find the RNA molecule able to trigger precise processes within the organism with important therapeutic effects due to its specific structure, this would open up truly unheard-of prospects".Research paper
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