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Now, a team of astronomers, including UC Santa Barbara physicist Joseph Hennawi, have made the first measurements of small-scale ripples in this primeval hydrogen gas using rare double quasars. Although the regions of cosmic web they studied lie nearly 11 billion light years away, they were able to measure variations in its structure on scales 100,000 times smaller, comparable to the size of a single galaxy. The results appear in the journal Science. Intergalactic gas is so tenuous that it emits no light of its own. Instead astronomers study it indirectly by observing how it selectively absorbs the light coming from faraway sources known as quasars. Quasars constitute a brief hyperluminous phase of the galactic life cycle powered by matter falling into a galaxy's central supermassive black hole. Acting like cosmic lighthouses, they are bright, distant beacons that allow astronomers to study intergalactic atoms residing between the location of the quasar and the Earth. But because these hyperluminous episodes last only a tiny fraction of a galaxy's lifetime, quasars are correspondingly rare and are typically separated from each other by hundreds of millions of light years. In order to probe the cosmic web on much smaller length scales, the astronomers exploited a fortuitous cosmic coincidence: They identified exceedingly rare pairs of quasars and measured subtle differences in the absorption of intergalactic atoms along the two sightlines. "Pairs of quasars are like needles in a haystack," explained Hennawi, associate professor in UCSB's Department of Physics. Hennawi pioneered the application of algorithms from "machine learning"—a brand of artificial intelligence—to efficiently locate quasar pairs in the massive amounts of data produced by digital imaging surveys of the night sky. "In order to find them, we combed through images of billions of celestial objects millions of times fainter than what the naked eye can see." Once identified, the quasar pairs were observed with the largest telescopes in the world, including the 10-meter Keck telescopes at the W.M. Keck Observatory on Mauna Kea, Hawaii, of which the University of California is a founding partner. "One of the biggest challenges was developing the mathematical and statistical tools to quantify the tiny differences we measured in this new kind of data," said lead author Alberto Rorai, Hennawi's former Ph.D. student who is now a postdoctoral researcher at Cambridge University. Rorai developed these tools as part of the research for his doctoral degree and applied them to spectra of quasars with Hennawi and other colleagues. The astronomers compared their measurements to supercomputer models that simulate the formation of cosmic structures from the Big Bang to the present. On a single laptop, these complex calculations would require almost 1,000 years to complete, but modern supercomputers enabled the researchers to carry them out in just a few weeks. "The input to our simulations are the laws of physics and the output is an artificial universe, which can be directly compared to astronomical data," said co-author Jose Oñorbe, a postdoctoral researcher at the Max Planck Institute for Astronomy in Heidelberg, Germany, who led the supercomputer simulation effort. "I was delighted to see that these new measurements agree with the well-established paradigm for how cosmic structures form." "One reason why these small-scale fluctuations are so interesting is that they encode information about the temperature of gas in the cosmic web just a few billion years after the Big Bang," explained Hennawi. Astronomers believe that the matter in the universe went through phase transitions billions of years ago, which dramatically changed its temperature. Known as cosmic re-ionization, these transitions occurred when the collective ultraviolet glow of all stars and quasars in the universe became intense enough to strip electrons off atoms in intergalactic space. How and when re-ionization occurred is one of the biggest open questions in the field of cosmology, and these new measurements provide important clues that will help narrate this chapter of cosmic history. Explore further: Discovery nearly doubles known quasars from the ancient universe More information: "Measurement of the small-scale structure of the intergalactic medium using close quasar pairs" Science, science.sciencemag.org/cgi/doi/10.1126/science.aaf9346


News Article | April 20, 2017
Site: www.latimes.com

For the first time, astronomers have caught a type Ia supernova being magnified by more than 50 times and split into four images in the night sky thanks to gravitational lensing. The discovery, described in the journal Science, could help scientists get a better handle on the rate of expansion of the universe and shed light on the mysterious, invisible mass in the universe known as dark matter. “Once this grows into a larger sample, then certainly you can use this to constrain gravitational lensing and dark matter and Einstein’s general theory of relativity — all of these,” said study co-author Mansi Kasliwal, an astronomer at Caltech. As it travels through the universe, light is squeezed, stretched, bent, scattered and filtered before it reaches our telescopes. These alterations allow us to suss out the nature of the contents of the universe. But oftentimes, this complex mix of changes makes it devilishly difficult to sort out what’s really happening to a given star, supernova or other astrophysical object. For example, a star that seems dim could be bright and faraway, or dim and nearby. This is where Type Ia supernovae come in. These stellar deaths — which happen when a white dwarf in a binary system picks up too much mass from its companion star — always peak at the same luminosity. So if astronomers see a dim type Ia, they know it’s far; if they see a bright one, they know it’s nearby. But far enough away, these “standard candles” become increasingly difficult to see and study. So scientists have been looking for a type Ia whose light has been gravitationally lensed — magnified by a massive object, such as a galaxy, sitting between the supernova and Earth’s telescopes. The artificial brightening caused by gravitational lensing would allow researchers to study far more distant type Ia explosions in order to learn more about the faraway universe. After all, type Ia supernovae have actually helped scientists to understand and measure the accelerating expansion of the cosmos — which earned the Nobel Prize in physics in 2011. That’s because the astronomers were able to compare the actual distance as measured by the supernovae’s brightness to their redshift, the stretching of starlight that signals how fast a distant object is moving, largely because of the expanding universe. Ever since the phenomenon of gravitational lensing was predicted by Albert Einstein, plenty of lensed objects have been discovered. In that time, there also have been a decent number of type Ia supernovae spotted in the heavens. Finding a gravitationally lensed type Ia, however, has proved elusive. But on Sept. 5, the intermediate Palomar Transient Factory at the Palomar Observatory in San Diego spotted a strangely bright object appear in the night sky; the Global Relay of Observatories Watching Transients Happen, which calls on an international network of telescopes, followed up soon after. The object also was studied using NASA’s Hubble Space Telescope and the W.M. Keck Observatory in Hawaii. “It just made no sense because the spectroscopic redshift was so high that that would make this event intrinsically over-bright — just too bright to be a type Ia supernova even though the spectrum looked just like a type Ia supernova,” Kasliwal said. “When I saw that spectrum I was completely baffled. I just didn’t know how to make sense of it. And then [lead author] Ariel Goobar, my colleague, said, ‘Well, what if this was lensed?’ ” The supernova, iPTF16geu, turned out to be magnified and split into four distinct images by a galaxy with the mass of 10 billion suns and a radius of close to 3,000 light-years. The stellar explosion lies about 4.4 billion light-years from us; the galaxy, in the same line of sight, is about 2 billion light-years away. The light coming from this lensed supernova, and others like it, should give astronomers fresh insight into dark matter and Einstein’s general theory of relativity. The differences in arrival times of the four different images could help researchers perform high-precision measurements of the universe’s expansion rate. “It took a thousand tries to find one, but we are hopeful,” Kasliwal said. “It’s the first but should definitely not be the last.” The search is soon to get a major upgrade. Scientists are in the process of putting a new, larger camera at the Palomar Observatory, which should make the search process go about 10 times faster. Follow @aminawrite on Twitter for more science news and "like" Los Angeles Times Science & Health on Facebook.


News Article | April 17, 2017
Site: news.yahoo.com

In the last decade, the Keck Observatory in Hawaii, one of the world’s most powerful telescopes, has spent hours staring at the night sky in search of exoplanets and accumulating huge amounts of data about potential new worlds elsewhere in the Milky Way. But maybe, Nate Tellis wondered, Keck might have picked up something else along the way. Somewhere in all that data, could there be a signal from an intelligent civilization trying to reach Earth? Tellis is a scientist at the University of California at Berkeley, where, as his LinkedIn biography puts it, he spends his days “trawling” astronomy datasets for statistical deviations, trying to figure out whether they’re actually extraterrestrial pings. He searches particularly for laser light, powerful pulses of photons that could be as short as a nanosecond. Tellis, along with astronomer Geoff Marcy, recently dug into the Keck archives for data from 5,600 stars, observed between 2004 and 2016. Tellis and Marcy built a laser-detecting computer algorithm to comb through all that recorded starlight—and the result, detailed in a recent study in the Astronomical Journal, is the largest survey of its kind in the field of optical-based searches for extraterrestrial life. Recommended: America Can’t Do Much About North Korea It didn’t find anything. So far, this has been par for the course when it comes to the search for extraterrestrial life, better known by the shorthand SETI. Astronomers first began using telescopes to look for potential alien communication in 1960, and they have been met with silence ever since. “I think when you’re doing a SETI project, it’s very important not to get discouraged by a null detection,” Tellis said. “SETI has been in process for about 60 years, and it’s been non-detection after non-detection after non-detection.” Astronomers and engineers have spent that time developing more powerful technology to conduct SETI surveys. The majority of SETI searches have relied on radio telescopes, which scour the skies for signals in the radio and microwave parts of the light spectrum. In the 1960s, “lasers were new, tricky, low-power devices; by contrast, radio technology had been developing for decades and was relatively mature,” according to a history from the SETI group at Harvard. These days, lasers can outshine the sun, albeit in tiny pulses. But a tiny pulse—preferably more than one, to prove it’s not a fluke—is all it would take for a distant, advanced civilization to tell Earth “hey, we’re here!” If humans can get really good at sending radio and laser signals, the reasoning goes, maybe intelligent civilizations beyond Earth can, too—and then send them our way. Unlike radio SETI, optical SETI looks for signals in the visible portion of the light spectrum. Lasers travel well over galactic distances. The light, concentrated into a narrow beam that can be 10 times as bright as the sun, would experience less interference from interstellar dust and gas than radio waves might. Laser emissions are also capable of carrying massive amounts of information. The network of cables at the bottom of the ocean is a collection of pulses of light, firing at high frequencies to transmit digital data and bring us the internet. The dataset Tellis used for his study contained thousands of observations of stars as young as 200 million years and stars as old as nearly 10 billion years. Keck’s instruments collected millions of photons of light from these stars. What Tellis and his algorithm looked for were brief surges in photons. The first run of the data reported 5,000 potential candidates for mysterious laser beams, but they were eventually ruled out, explained away as emissions from stars’ outer layers, cosmic rays from our sun, or internal reflections from telescope instruments. Tellis got some firsthand Keck time to observe at least one target, KIC 8462852, a star about 1,500 light-years from Earth. In 2015, astronomers announced the Kepler space telescope had observed an unusual dimming of its light, which some believe could be caused by structures built by an advanced civilization around the star. The light emission observed from KIC 8462852 was the best candidate for an alien laser beam in the survey before it was ruled out. The results may not have been surprising, but the method is noteworthy, says Jason Wright, an astronomer at Penn State University who contributed to some of the software code Tellis and Marcy used in the study. Recycling astronomical datasets that were produced for another purpose is pretty unusual, but it makes sense. There is strong competition among astronomers for observation time on the world’s best telescopes, and SETI proposals are usually low on the priority list. “If you proposed to do a laser SETI study on Keck with thousands of hours, there’s nobody that will let you do it,” Wright said. Meanwhile, there’s plenty of astronomical datasets sitting around, waiting for a second look. One man’s trash is another man’s treasure, even in the search for life in the universe. Tellis, Wright said, “was digging through all the trash in case someone threw out a diamond.” Tellis’s survey, like all SETI surveys, has its limitations. The data examined only some types of stars, in a specific wavelength range, and in Earth’s cosmic neighborhood. The telescope may not have been able to detect signals that were too faint or too bright, and too far away. Optical SETI also depends on something beyond our control: a laser beam must first be aimed at Earth for it to be detected. Imagine another life-form on a distant world conducting the same kind of search, Tellis said. “If we had pointed our telescope at Earth at sort of the distance that we’ve been doing here, we wouldn’t have seen us,” he said, because Earth is not firing a laser beam into the universe as a beacon of its existence. Other worlds may not be, either. “Every single one of those stars could have a New York City, a Paris, a London, and we would have no idea,” Tellis said. Read more from The Atlantic: The Easter Egg Roll and the Bygone Era of White House Openness Will Tesla Do to Cars What Apple Did to Smartphones? This article was originally published on The Atlantic.


News Article | April 10, 2017
Site: www.scientificcomputing.com

Recently, astronomers announced the discovery that a star called TRAPPIST-1 is orbited by seven Earth-size planets. Three of the planets reside in the "habitable zone," the region around a star where liquid water is most likely to exist on the surface of a rocky planet. Other potentially habitable worlds have also been discovered in recent years, leaving many people wondering: How do we find out if these planets actually host life? At Caltech, in the Exoplanet Technology Laboratory, or ET Lab, of Associate Professor of Astronomy Dimitri Mawet, researchers have been busy developing a new strategy for scanning exoplanets for biosignatures—signs of life such as oxygen molecules and methane. These chemicals—which don't naturally stick around for long because they bind with other chemicals—are abundant on Earth largely thanks to the living creatures that expel them. Finding both of these chemicals around another planet would be a strong indicator of the presence of life. In two new papers to be published in The Astrophysical Journal and The Astronomical Journal, Mawet's team demonstrates how this new technique, called high-dispersion coronagraphy, could be used to look for extraterrestrial biosignatures with the planned Thirty Meter Telescope (TMT), which, when completed by the late 2020s, will be the world's largest optical telescope. Using theoretical and laboratory models, the researchers show that this technique could detect biosignatures on Earth-like planets around M-dwarf stars, which are smaller and cooler than our sun and the most common type of star in the galaxy. The strategy could also be used on stars like our own sun, using future space telescopes such as NASA's proposed Habitable Exoplanet Imaging Mission (HabEx) and Large UV/Optical/IR Surveyor (LUVOIR). "We've shown this technique works in theory and in the lab, so our next step is to show it works on the sky," says Ji Wang, one of the lead authors on the two new papers and a postdoctoral scholar in the Mawet lab. The team will test the instrumentation on the W. M. Keck Observatory in Hawaii this year or next. The new technique involves three main components: a coronagraph, a set of optical fibers, and a high-resolution spectrometer. Coronagraphs are devices used in telescopes to block or remove starlight so that planets can be imaged. Stars outshine their planets by a few thousand to a few billion times, making the planets difficult to see. Many different types of coronagraphs are in development; for example, Mawet's group recently installed and took initial images with its new vortex coronagraph on the Keck Observatory. Once an image of a planet has been obtained, the next step is to study the planet's atmosphere using a spectrometer, an instrument that breaks apart the planet's light to reveal "fingerprints" of chemicals, such as oxygen and methane. Most coronagraphs work in conjunction with low-resolution spectrometers. Mawet's new technique incorporates a high-resolution spectrometer, which has several advantages. One main advantage is in helping to further sift out the unwanted starlight. With high-resolution spectrometers, the spectral features of a planet are more detailed, making it easier to distinguish and separate the planet's light from the lurking starlight. What this means is that, in Mawet's method, the coronagraph does not have to be as good at sifting out starlight as was thought necessary to characterize Earth-like worlds. "This new technique doesn't require the coronagraph to work as hard, and that's important because we can use current technologies that are already available," says Mawet, who is also a research scientist at the Jet Propulsion Laboratory (JPL), which is managed by Caltech for NASA. "With a high-resolution spectrometer, we can improve the sensitivity of our system by a factor of 100 to 1,000 over current ground-based methods." Another advantage of using high-resolution spectrometers lies in the richness of the data. In addition to providing more detail about the molecular constituents of a planet's atmosphere, these instruments should be able to reveal a planet's rotation rate and provide rough maps of surface features and weather patterns. "It's a long shot, but we might even have the ability to look for continents on candidate Earth-like planets," says Mawet. In the team's design, the coronagraph is connected to the high-resolution spectrometer using a set of optical fibers. Surprisingly, laboratory experiments revealed that the fibers also filter out starlight. "This was completely serendipitous," says Garreth Ruane, co-author on the two new papers and a National Science Foundation postdoctoral fellow in Mawet's group. "It's icing on the cake." Next, the researchers will demonstrate their technique at the Keck Observatory. Although the instrumentation cannot yet study potential Earth-like planets—that will require the larger Thirty Meter Telescope—the system should be able to reveal new details about the atmospheres of larger gas exoplanets, including exotic varieties that are nothing like those in our own solar system. "This new innovation of combining the coronagraph with a high-res spectrometer gives us a clear pathway to ultimately search for life beyond Earth." The first study, titled "Observing Exoplanets with High-Dispersion Coronagraphy. I. The Scientific Potential of Current and Next-Generation Large Ground and Space Telescopes," led by Wang and appearing in The Astronomical Journal, includes Caltech co-authors Mawet, Ruane visiting associate Renyu Hu, and postdoctoral scholar Bjoern Benneke. The second study, titled, "Observing Exoplanets with High-Dispersion Coronagraphy. II. Demonstration of an Active Single-Mode Fiber Injection Unit," led by Mawet and appearing in The Astrophysical Journal, includes Caltech co-authors Ruane and Wang; Caltech summer students Wenhao Xuan, Daniel Echeverri, and Michael Randolph; graduate student Nikita Klimovich; postdoctoral scholar Jacques-Robert Delorme; assistant research engineer Jason Fucik; and Associate Director for Development of Caltech Optical Observatories


News Article | April 10, 2017
Site: www.scientificcomputing.com

Recently, astronomers announced the discovery that a star called TRAPPIST-1 is orbited by seven Earth-size planets. Three of the planets reside in the "habitable zone," the region around a star where liquid water is most likely to exist on the surface of a rocky planet. Other potentially habitable worlds have also been discovered in recent years, leaving many people wondering: How do we find out if these planets actually host life? At Caltech, in the Exoplanet Technology Laboratory, or ET Lab, of Associate Professor of Astronomy Dimitri Mawet, researchers have been busy developing a new strategy for scanning exoplanets for biosignatures—signs of life such as oxygen molecules and methane. These chemicals—which don't naturally stick around for long because they bind with other chemicals—are abundant on Earth largely thanks to the living creatures that expel them. Finding both of these chemicals around another planet would be a strong indicator of the presence of life. In two new papers to be published in The Astrophysical Journal and The Astronomical Journal, Mawet's team demonstrates how this new technique, called high-dispersion coronagraphy, could be used to look for extraterrestrial biosignatures with the planned Thirty Meter Telescope (TMT), which, when completed by the late 2020s, will be the world's largest optical telescope. Using theoretical and laboratory models, the researchers show that this technique could detect biosignatures on Earth-like planets around M-dwarf stars, which are smaller and cooler than our sun and the most common type of star in the galaxy. The strategy could also be used on stars like our own sun, using future space telescopes such as NASA's proposed Habitable Exoplanet Imaging Mission (HabEx) and Large UV/Optical/IR Surveyor (LUVOIR). "We've shown this technique works in theory and in the lab, so our next step is to show it works on the sky," says Ji Wang, one of the lead authors on the two new papers and a postdoctoral scholar in the Mawet lab. The team will test the instrumentation on the W. M. Keck Observatory in Hawaii this year or next. The new technique involves three main components: a coronagraph, a set of optical fibers, and a high-resolution spectrometer. Coronagraphs are devices used in telescopes to block or remove starlight so that planets can be imaged. Stars outshine their planets by a few thousand to a few billion times, making the planets difficult to see. Many different types of coronagraphs are in development; for example, Mawet's group recently installed and took initial images with its new vortex coronagraph on the Keck Observatory. Once an image of a planet has been obtained, the next step is to study the planet's atmosphere using a spectrometer, an instrument that breaks apart the planet's light to reveal "fingerprints" of chemicals, such as oxygen and methane. Most coronagraphs work in conjunction with low-resolution spectrometers. Mawet's new technique incorporates a high-resolution spectrometer, which has several advantages. One main advantage is in helping to further sift out the unwanted starlight. With high-resolution spectrometers, the spectral features of a planet are more detailed, making it easier to distinguish and separate the planet's light from the lurking starlight. What this means is that, in Mawet's method, the coronagraph does not have to be as good at sifting out starlight as was thought necessary to characterize Earth-like worlds. "This new technique doesn't require the coronagraph to work as hard, and that's important because we can use current technologies that are already available," says Mawet, who is also a research scientist at the Jet Propulsion Laboratory (JPL), which is managed by Caltech for NASA. "With a high-resolution spectrometer, we can improve the sensitivity of our system by a factor of 100 to 1,000 over current ground-based methods." Another advantage of using high-resolution spectrometers lies in the richness of the data. In addition to providing more detail about the molecular constituents of a planet's atmosphere, these instruments should be able to reveal a planet's rotation rate and provide rough maps of surface features and weather patterns. "It's a long shot, but we might even have the ability to look for continents on candidate Earth-like planets," says Mawet. In the team's design, the coronagraph is connected to the high-resolution spectrometer using a set of optical fibers. Surprisingly, laboratory experiments revealed that the fibers also filter out starlight. "This was completely serendipitous," says Garreth Ruane, co-author on the two new papers and a National Science Foundation postdoctoral fellow in Mawet's group. "It's icing on the cake." Next, the researchers will demonstrate their technique at the Keck Observatory. Although the instrumentation cannot yet study potential Earth-like planets—that will require the larger Thirty Meter Telescope—the system should be able to reveal new details about the atmospheres of larger gas exoplanets, including exotic varieties that are nothing like those in our own solar system. "This new innovation of combining the coronagraph with a high-res spectrometer gives us a clear pathway to ultimately search for life beyond Earth." The first study, titled "Observing Exoplanets with High-Dispersion Coronagraphy. I. The Scientific Potential of Current and Next-Generation Large Ground and Space Telescopes," led by Wang and appearing in The Astronomical Journal, includes Caltech co-authors Mawet, Ruane visiting associate Renyu Hu, and postdoctoral scholar Bjoern Benneke. The second study, titled, "Observing Exoplanets with High-Dispersion Coronagraphy. II. Demonstration of an Active Single-Mode Fiber Injection Unit," led by Mawet and appearing in The Astrophysical Journal, includes Caltech co-authors Ruane and Wang; Caltech summer students Wenhao Xuan, Daniel Echeverri, and Michael Randolph; graduate student Nikita Klimovich; postdoctoral scholar Jacques-Robert Delorme; assistant research engineer Jason Fucik; and Associate Director for Development of Caltech Optical Observatories


News Article | May 20, 2017
Site: www.scientificamerican.com

The star often called the most mysterious in the galaxy has begun darkening again. Scientists are now rushing to watch the event with as many telescopes as they can muster to attempt to understand what is causing its bewildering fluctuations of light. The star, called KIC 8462852 and nicknamed “Tabby's Star” after Yale University astronomer Tabetha “Tabby” Boyajian, first made news in 2015 when researchers discovered something odd about its light, whose strange brightenings and dimmings have even caused some to speculate it might host alien megastructures around it. The star is an otherwise-normal F type star—slightly larger and hotter than our sun—located about 1,480 light-years away from Earth in the constellation Cygnus, the Swan. When Boyajian and her colleagues analyzed data from NASA's Kepler space telescope, however, they found dozens of strange instances of KIC 8462852 darkening up to 22 percent. These dimming events are far too substantial to be caused by planets crossing the face of the star, so scientists looked for other explanations. Some have even suggested that it might host signs of intelligent alien life—specifically, a Dyson sphere, a hypothetical megastructure built around a star to capture as much of its energy as possible to power an advanced civilization. In order to solve this mystery astronomers have been planning to analyze the full spectrum of light from Tabby's Star as it darkens via spectral measurements that split light into its constituent wavelengths. Because different materials absorb different wavelengths of light, spectra from the star could reveal what is causing its light fluctuations. “We’ve been waiting to catch another dip in light,” Jason Wright, an astronomer at The Pennsylvania State University, said in an online chat May 19. Now scientists have discovered Tabby's Star is dimming again, and are racing to get as many telescopes as they can to watch it in as many wavelengths of light as possible, Wright said. “All week there's been some indication that something might be up,” he said. “Sure enough, at about 4 A.M. this morning [Pacific time], I got a phone call from Tabby [Boyajian] saying that Fairborn Observatory in Arizona had confirmed the star as 3 percent dimmer than it normally is. That's enough to say that it’s absolutely no statistical fluke, and we’ve now confirmed it with multiple observatories.” Astronomers have proposed several possible reason’s for Tabby’s Star’s strange behavior, and each would create a different spectral signature. If clouds of dust are causing the dimming, they usually absorb bluer wavelengths of light, making stars look redder whereas comets passing close to a star would heat up and emit infrared light, Wright said. If interstellar clouds of gas are responsible, those are usually rich in sodium, hydrogen and calcium. And if the dimming is a phenomenon intrinsic to Tabby's Star itself, the spectra will show no signs that anything is absorbing the star's light. If an alien megastructure is the cause, it is difficult to predict what it might look like—if it is solid, “we might see the star getting dimmer overall,” Wright said. In 2015 Boyajian and her colleagues predicted a dimming event might happen in May 2017. Based on the Kepler data, they suggested dimming of Tabby's Star might follow a roughly 750-day cycle. “It’s right on schedule,” Wright said. Boyajian herself demurred as to the accuracy of the estimate, noting “the prediction was a long shot—we cast a net of several hundred days.” Among the telescopes Wright said researchers now hope to use to catch this dimming event in the act: —Both telescopes at the Keck Observatory in Hawaii, which operate in optical and near-infrared wavelengths —NASA's Swift Gamma-Ray Burst Mission, which operates in gamma ray, x-ray, ultraviolet and optical wavelengths —Fairborn Observatory in Arizona, which operates in optical wavelengths —The Large Binocular Telescope in Arizona, which operates in optical and near-infrared wavelengths “Our plan is to observe the star in as many wavelengths as we can,” Wright said. “This could be the weekend that we take the data that solves the puzzle.” Even more telescopes may also join in. “It's been a crazy 18 hours, and it’s going to be a really exciting weekend,” he said. It remains unknown how long this dimming might last. “Most dips in the Kepler data take two to seven days,” Wright said. “So if this is a deep dip, it might be going on for a week. If it’s a shallow dip, it could be gone soon. Hopefully it’s a deep dip.” The data from Kepler does suggest such dimming events happen in clusters. “This could just be the beginning,” Wright added.


There are four known forces in the universe: electromagnetic force, strong nuclear force, weak nuclear force, and gravitational force. Physicists know how to make the first three work together, but gravity is the odd one out. For decades, there have been theories that a fifth force ties gravity to the others, but no one has been able to prove it thus far. "This is really exciting. It's taken us 20 years to get here, but now our work on studying stars at the center of our galaxy is opening up a new method of looking at how gravity works," said Andrea Ghez, Director of the UCLA Galactic Center Group and co-author of the study. The research is published in the current issue of Physical Review Letters. Ghez and her co-workers analyzed extremely sharp images of the center of our galaxy taken with Keck Observatory's adaptive optics (AO). Ghez used this cutting-edge system to track the orbits of stars near the supermassive black hole located at the center of the Milky Way. Their stellar path, driven by gravity created from the supermassive black hole, could give clues to the fifth force. "By watching the stars move over 20 years using very precise measurements taken from Keck Observatory data, you can see and put constraints on how gravity works. If gravitation is driven by something other than Einstein's theory of General Relativity, you'll see small variations in the orbital paths of the stars," said Ghez. This is the first time the fifth force theory has been tested in a strong gravitational field such as the one created by the supermassive black hole at the center of the Milky Way. Historically, measurements of our solar system's gravity created by our sun have been used to try and detect the fifth force, but that has proven difficult because its gravitational field is relatively weak. "It's exciting that we can do this because we can ask a very fundamental question – how does gravity work?" said Ghez. "Einstein's theory describes it beautifully well, but there's lots of evidence showing the theory has holes. The mere existence of supermassive black holes tells us that our current theories of how the universe works are inadequate to explain what a black hole is." Ghez and her team, including lead author Aurelien Hees and co-author Tuan Do, both of UCLA, are looking forward to summer of 2018. That is when the star S0-2 will be at its closest distance to our galaxy's supermassive black hole. This will allow the team to witness the star being pulled at maximum gravitational strength – a point where any deviations to Einstein's theory is expected to be the greatest. Explore further: Astronomers solve puzzle about bizarre object at the center of our galaxy More information: A. Hees et al. Testing General Relativity with Stellar Orbits around the Supermassive Black Hole in Our Galactic Center, Physical Review Letters (2017). DOI: 10.1103/PhysRevLett.118.211101


News Article | May 11, 2017
Site: www.futurity.org

In the vast expanses between galaxies, only atoms—a haze of hydrogen gas left over from the Big Bang—occupy solitary cubes one meter on a side. On the largest scale, this diffuse material forms a network of filamentary structures known as the “cosmic web,” its tangled strands spanning billions of light years and accounting for the majority of atoms in the universe. Now, a team of astronomers has made the first measurements of small-scale ripples in this primeval hydrogen gas using rare double quasars. Although the regions of cosmic web they studied lie nearly 11 billion light years away, they were able to measure variations in its structure on scales 100,000 times smaller, comparable to the size of a single galaxy. The results appear in the journal Science. Intergalactic gas is so tenuous that it emits no light of its own. Instead astronomers study it indirectly by observing how it selectively absorbs the light coming from faraway sources known as quasars. Quasars constitute a brief hyperluminous phase of the galactic life cycle powered by matter falling into a galaxy’s central supermassive black hole. Acting like cosmic lighthouses, they are bright, distant beacons that allow astronomers to study intergalactic atoms residing between the location of the quasar and the Earth. But because these hyperluminous episodes last only a tiny fraction of a galaxy’s lifetime, quasars are correspondingly rare and are typically separated from each other by hundreds of millions of light years. In order to probe the cosmic web on much smaller length scales, the astronomers exploited a fortuitous cosmic coincidence: They identified exceedingly rare pairs of quasars and measured subtle differences in the absorption of intergalactic atoms along the two sightlines. “Pairs of quasars are like needles in a haystack,” explains Joseph Hennawi, an associate professor in the University of California, Santa Barbara’s physics department who pioneered the application of algorithms from machine learning to efficiently locate quasar pairs in the massive amounts of data produced by digital imaging surveys of the night sky. “In order to find them, we combed through images of billions of celestial objects millions of times fainter than what the naked eye can see,” he says. Once identified, researchers observed the quasar pairs with the largest telescopes in the world, including the 10-meter Keck telescopes at the W.M. Keck Observatory on Mauna Kea, Hawaii. “One of the biggest challenges was developing the mathematical and statistical tools to quantify the tiny differences we measured in this new kind of data,” says lead author Alberto Rorai, Hennawi’s former PhD student who is now a postdoctoral researcher at Cambridge University. Rorai developed these tools as part of the research for his doctoral degree and applied them to spectra of quasars with Hennawi and other colleagues. The astronomers compared their measurements to supercomputer models that simulate the formation of cosmic structures from the Big Bang to the present. On a single laptop, these complex calculations would require almost 1,000 years to complete, but modern supercomputers enabled the researchers to carry them out in just a few weeks. “The input to our simulations are the laws of physics and the output is an artificial universe, which can be directly compared to astronomical data,” says coauthor Jose Oñorbe, a postdoctoral researcher at the Max Planck Institute for Astronomy in Heidelberg, Germany, who led the supercomputer simulation effort. “I was delighted to see that these new measurements agree with the well-established paradigm for how cosmic structures form.” “One reason why these small-scale fluctuations are so interesting is that they encode information about the temperature of gas in the cosmic web just a few billion years after the Big Bang,” explains Hennawi. Astronomers believe that the matter in the universe went through phase transitions billions of years ago, which dramatically changed its temperature. Known as cosmic re-ionization, these transitions occurred when the collective ultraviolet glow of all stars and quasars in the universe became intense enough to strip electrons off atoms in intergalactic space. How and when re-ionization occurred is one of the biggest open questions in the field of cosmology, and these new measurements provide important clues that will help narrate this chapter of cosmic history.


News Article | February 16, 2017
Site: www.techtimes.com

Astronomers have found 60 new planets, including a super-Earth, orbiting stars near the solar system. For two decades, scientists observed 1,600 stars using the W.M. Keck Observatory in Hawaii and discovered 60 new planets outside of the solar system. Through the project called the Lick-Carnegie Exoplanet Survey, which started in 1996 and aims to search for exoplanets, scientists were also able to find evidence of 54 planets, bringing the total number of potential new worlds to 114. Mikko Tuomi, from the University of Hertfordshire, and colleagues were able to detect the presence of the planets using a technique called radial velocity, which measures the tiny changes in the color and location of target stars. The method, which is one of the most successful technique for finding and confirming planets, takes advantage of the fact that planets are not just influenced by the gravity of the star that it orbits but the gravity of the planet itself also affects the star. Scientists used tools to detect the tiny wobble that the planet's gravity induces on the star. Using these signals, researchers were able to detect the presence of new extraterrestrial worlds. "Of these signals, 225 have already been published as planet claims, 60 are classified as significant unpublished planet candidates that await photometric follow-up to rule out activity-related causes, and 54 are also unpublished, but are classified as "significant" signals that require confirmation by additional data before rising to classification as planet candidates." the researchers reported. One of these newly discovered exoplanets is the super Earth called GJ 411b. Scientists described the planet as a hot super-Earth with rocky surface orbits the star GJ 411. The star, also known as Lalande 21185, is the fourth nearest star to the sun and is about 40 percent of the solar mass. The planet has a short orbital period of under 10 days and its discovery continues a trend astronomers have observed in the overall population of exoplanets discovered so far, which is that the smallest planets are likely to be found around the smallest stars. The discovery challenges conventional wisdom about planets. Scientists historically assumed that only a few stars had planets but there appears to be a nearly infinite number of planets beyond the solar system based on recent surveys of the sky. Tuomi said that when they look at the nearest stars, all of them seems to have planets orbiting them, something that astronomers were not convinced about a few years ago. He said that the newly found worlds also shed light on the evolution of planetary systems. "Over the recent years it has been established as a scientific fact that there are more planets in the Universe than there are stars. This means that virtually every star has a planet, or several of them, orbiting it," Tuomi said. "Our discovery of dozens of new nearby planets highlights this fact. But it also does more. We are now moving on from simply discovering these worlds." © 2017 Tech Times, All rights reserved. Do not reproduce without permission.


News Article | February 28, 2017
Site: www.eurekalert.org

A trip past the sun may have selectively altered the production of one form of water in a comet - an effect not seen by astronomers before, a new NASA study suggests. Astronomers from NASA's Goddard Space Flight Center in Greenbelt, Maryland, observed the Oort cloud comet C/2014 Q2, also called Lovejoy, when it passed near Earth in early 2015. Through NASA's partnership in the W. M. Keck Observatory on Mauna Kea, Hawaii, the team observed the comet at infrared wavelengths a few days after Lovejoy passed its perihelion - or closest point to the sun. The team focused on Lovejoy's water, simultaneously measuring the release of H2O along with production of a heavier form of water, HDO. Water molecules consist of two hydrogen atoms and one oxygen atom. A hydrogen atom has one proton, but when it also includes a neutron, that heavier hydrogen isotope is called deuterium, or the "D" in HDO. From these measurements, the researchers calculated the D-to-H ratio - a chemical fingerprint that provides clues about exactly where comets (or asteroids) formed within the cloud of material that surrounded the young sun in the early days of the solar system. Researchers also use the D-to-H value to try to understand how much of Earth's water may have come from comets versus asteroids. The scientists compared their findings from the Keck observations with another team's observations made before the comet reached perihelion, using both space- and ground-based telescopes, and found an unexpected difference: After perihelion, the output of HDO was two to three times higher, while the output of H2O remained essentially constant. This meant that the D-to-H ratio was two to three times higher than the values reported earlier. "The change we saw with this comet is surprising, and highlights the need for repeated measurements of D-to-H in comets at different positions in their orbits to understand all the implications," said Lucas Paganini, a researcher with the Goddard Center for Astrobiology and lead author of the study, available online in the Astrophysical Journal Letters. Changes in the water production are expected as comets approach the sun, but previous understanding suggested that the release of these different forms of water normally rise or fall more-or-less together, maintaining a consistent D-to-H value. The new findings suggest this may not be the case. "If the D-to-H value changes with time, it would be misleading to assume that comets contributed only a small fraction of Earth's water compared to asteroids," Paganini said, "especially, if these are based on a single measurement of the D-to-H value in cometary water." The production of HDO in comets has historically been difficult to measure, because HDO is a much less abundant form of water. Lovejoy, for example, released on the order of 1,500 times more H2O than HDO. Lovejoy's brightness made it possible to measure HDO when the comet passed near Earth, and the improved detectors that are being installed in some ground-based telescopes will permit similar measurements in fainter comets in the future. The apparent change in Lovejoy's D-to-H may be caused by the higher levels of energetic processes - such as radiation near the sun - that might have altered the characteristics of water in surface layers of the comet. In this case, a different D-to-H value might indicate that the comet has "aged" into a different stage of its lifecycle. Alternatively, prior results might have ignored possible chemical alteration occurring in the comet's tenuous atmosphere. "Comets can be quite active and sometimes quite dynamic, especially when they are in the inner solar system, closer to the sun," said Michael Mumma, director of the Goddard Center for Astrobiology and a co-author of the study. "The infrared technique provides a snapshot of the comet's output by measuring the production of H2O and HDO simultaneously. This is especially important because it eliminates many sources of systematic uncertainty."

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