Association of Universities for Research in Astronomy
Association of Universities for Research in Astronomy
News Article | May 11, 2017
A study combining observations from NASA's Hubble and Spitzer space telescopes reveals that the distant planet HAT-P-26b has a primitive atmosphere composed almost entirely of hydrogen and helium. Located about 437 light years away, HAT-P-26b orbits a star roughly twice as old as the sun. The analysis is one of the most detailed studies to date of a "warm Neptune," or a planet that is Neptune-sized and close to its star. The researchers determined that HAT-P-26b's atmosphere is relatively clear of clouds and has a strong water signature, although the planet is not a water world. This is the best measurement of water to date on an exoplanet of this size. The discovery of an atmosphere with this composition on this exoplanet has implications for how scientists think about the birth and development of planetary systems. Compared to Neptune and Uranus, the planets in our solar system with about the same mass, HAT-P-26b likely formed either closer to its host star or later in the development of its planetary system, or both. "Astronomers have just begun to investigate the atmospheres of these distant Neptune-mass planets, and almost right away, we found an example that goes against the trend in our solar system," said Hannah Wakeford, a postdoctoral researcher at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study published in the May 12, 2017, issue of Science. "This kind of unexpected result is why I really love exploring the atmospheres of alien planets." To study HAT-P-26b's atmosphere, the researchers used data from transits-- occasions when the planet passed in front of its host star. During a transit, a fraction of the starlight gets filtered through the planet's atmosphere, which absorbs some wavelengths of light but not others. By looking at how the signatures of the starlight change as a result of this filtering, researchers can work backward to figure out the chemical composition of the atmosphere. In this case, the team pooled data from four transits measured by Hubble and two seen by Spitzer. Together, those observations covered a wide range of wavelengths from yellow light through the near-infrared region. "To have so much information about a warm Neptune is still rare, so analyzing these data sets simultaneously is an achievement in and of itself," said co-author Tiffany Kataria of the Jet Propulsion Laboratory in Pasadena, California. Because the study provided a precise measurement of water, the researchers were able to use the water signature to estimate HAT-P-26b's metallicity. Astronomers calculate the metallicity, an indication of how rich the planet is in all elements heavier than hydrogen and helium, because it gives them clues about how a planet formed. To compare planets by their metallicities, scientists use the sun as a point of reference, almost like describing how much caffeine beverages have by comparing them to a cup of coffee. Jupiter has a metallicity about 2 to 5 times that of the sun. For Saturn, it's about 10 times as much as the sun. These relatively low values mean that the two gas giants are made almost entirely of hydrogen and helium. The ice giants Neptune and Uranus are smaller than the gas giants but richer in the heavier elements, with metallicities of about 100 times that of the sun. So, for the four outer planets in our solar system, the trend is that the metallicities are lower for the bigger planets. Scientists think this happened because, as the solar system was taking shape, Neptune and Uranus formed in a region toward the outskirts of the enormous disk of dust, gas and debris that swirled around the immature sun. Summing up the complicated process of planetary formation in a nutshell: Neptune and Uranus would have been bombarded with a lot of icy debris that was rich in heavier elements. Jupiter and Saturn, which formed in a warmer part of the disk, would have encountered less of the icy debris. Two planets beyond our solar system also fit this trend. One is the Neptune-mass planet HAT-P-11b. The other is WASP-43b, a gas giant twice as massive as Jupiter. But Wakeford and her colleagues found that HAT-P-26b bucks the trend. They determined its metallicity is only about 4.8 times that of the sun, much closer to the value for Jupiter than for Neptune. "This analysis shows that there is a lot more diversity in the atmospheres of these exoplanets than we were expecting, which is providing insight into how planets can form and evolve differently than in our solar system," said David K. Sing of the University of Exeter and the second author of the paper. "I would say that has been a theme in the studies of exoplanets: Researchers keep finding surprising diversity." The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington. NASA's Jet Propulsion Laboratory in Pasadena, California, manages the Spitzer Space Telescope for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA. For more information about Spitzer, visit: For images and more information about Hubble, visit:
News Article | May 11, 2017
Astronomers have produced a highly detailed image of the Crab Nebula They did so by combining data from telescopes spanning nearly the entire breadth of the electromagnetic spectrum, from radio waves seen by the Karl G. Jansky Very Large Array (VLA) to the powerful X-ray glow as seen by the orbiting Chandra X-ray Observatory. And, in between that range of wavelengths, the Hubble Space Telescope's crisp visible-light view, and the infrared perspective of the Spitzer Space Telescope. The Crab Nebula, the result of a bright supernova explosion seen by Chinese and other astronomers in the year 1054, is 6,500 light-years from Earth. At its center is a super-dense neutron star, rotating once every 33 milliseconds, shooting out rotating lighthouse-like beams of radio waves and light -- a pulsar (the bright dot at image center). The nebula's intricate shape is caused by a complex interplay of the pulsar, a fast-moving wind of particles coming from the pulsar, and material originally ejected by the supernova explosion and by the star itself before the explosion. This image combines data from five different telescopes: the VLA (radio) in red; Spitzer Space Telescope (infrared) in yellow; Hubble Space Telescope (visible) in green; XMM-Newton (ultraviolet) in blue; and Chandra X-ray Observatory (X-ray) in purple. The new VLA, Hubble, and Chandra observations all were made at nearly the same time in November of 2012. A team of scientists led by Gloria Dubner of the Institute of Astronomy and Physics (IAFE), the National Council of Scientific Research (CONICET), and the University of Buenos Aires in Argentina then made a thorough analysis of the newly revealed details in a quest to gain new insights into the complex physics of the object. They are reporting their findings in the Astrophysical Journal. "Comparing these new images, made at different wavelengths, is providing us with a wealth of new detail about the Crab Nebula. Though the Crab has been studied extensively for years, we still have much to learn about it," Dubner said. The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington. NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations. NASA's Jet Propulsion Laboratory in Pasadena, California, manages the Spitzer Space Telescope for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. Please follow SpaceRef on Twitter and Like us on Facebook.
News Article | May 18, 2017
With this discovery, most of the known dwarf planets in the Kuiper Belt larger than 600 miles across have companions. These bodies provide insight into how moons formed in the young solar system. "The discovery of satellites around all of the known large dwarf planets - except for Sedna - means that at the time these bodies formed billions of years ago, collisions must have been more frequent, and that's a constraint on the formation models," said Csaba Kiss of the Konkoly Observatory in Budapest, Hungary. He is the lead author of the science paper announcing the moon's discovery. "If there were frequent collisions, then it was quite easy to form these satellites." The objects most likely slammed into each other more often because they inhabited a crowded region. "There must have been a fairly high density of objects, and some of them were massive bodies that were perturbing the orbits of smaller bodies," said team member John Stansberry of the Space Telescope Science Institute in Baltimore, Maryland. "This gravitational stirring may have nudged the bodies out of their orbits and increased their relative velocities, which may have resulted in collisions." But the speed of the colliding objects could not have been too fast or too slow, according to the astronomers. If the impact velocity was too fast, the smash-up would have created lots of debris that could have escaped from the system; too slow and the collision would have produced only an impact crater. Collisions in the asteroid belt, for example, are destructive because objects are traveling fast when they smash together. The asteroid belt is a region of rocky debris between the orbits of Mars and the gas giant Jupiter. Jupiter's powerful gravity speeds up the orbits of asteroids, generating violent impacts. The team uncovered the moon in archival images of 2007 OR10 taken by Hubble's Wide Field Camera 3. Observations taken of the dwarf planet by NASA's Kepler Space Telescope first tipped off the astronomers of the possibility of a moon circling it. Kepler revealed that 2007 OR10 has a slow rotation period of 45 hours. "Typical rotation periods for Kuiper Belt Objects are under 24 hours," Kiss said. "We looked in the Hubble archive because the slower rotation period could have been caused by the gravitational tug of a moon. The initial investigator missed the moon in the Hubble images because it is very faint." The astronomers spotted the moon in two separate Hubble observations spaced a year apart. The images show that the moon is gravitationally bound to 2007 OR10 because it moves with the dwarf planet, as seen against a background of stars. However, the two observations did not provide enough information for the astronomers to determine an orbit. "Ironically, because we don't know the orbit, the link between the satellite and the slow rotation rate is unclear," Stansberry said. The astronomers calculated the diameters of both objects based on observations in far-infrared light by the Herschel Space Observatory, which measured the thermal emission of the distant worlds. The dwarf planet is about 950 miles across, and the moon is estimated to be 150 miles to 250 miles in diameter. 2007 OR10, like Pluto, follows an eccentric orbit, but it is currently three times farther than Pluto is from the sun. 2007 OR10 is a member of an exclusive club of nine dwarf planets. Of those bodies, only Pluto and Eris are larger than 2007 OR10. It was discovered in 2007 by astronomers Meg Schwamb, Mike Brown, and David Rabinowitz as part of a survey to search for distant solar system bodies using the Samuel Oschin Telescope at the Palomar Observatory in California. The team's results appeared in The Astrophysical Journal Letters. The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C. Explore further: 2007 OR10 is the largest unnamed dwarf planet in the solar system More information: "Discovery of a Satellite of the Large Trans-Neptunian Object (225088) 2007 OR10," Csaba Kiss et al., 2017 Mar. 20, Astrophysical Journal Letters iopscience.iop.org/article/10.3847/2041-8213/aa6484 , arxiv.org/abs/1703.01407
Agency: European Commission | Branch: FP7 | Program: CP-CSA-Infra | Phase: INFRA-2012-1.1.26. | Award Amount: 8.20M | Year: 2013
This project aims at integrating the major European infrastructures in the field of high-resolution solar physics. The following actions will be taken: (i) realise Trans-national Access to external European users; (ii) enhance and spread data acquisition and processing expertise to the Europe-wide community; (iii) increase the impact of high-resolution data by offering science-ready data and facilitating their retrieval and usage; (iv) encourage combination of space and ground-based data by providing unified access to pertinent data repositories; (v) foster synergies between different research communities by organising meetings where each presents state-of-the-art methodologies; (vi) train a new generation of solar researchers through setting up schools and an ambitious mobility programme; (vii) develop prototypes for new-generation post-focus instruments; (vii) study local and non-local atmospheric turbulence, their impact on image quality, and ways to negate their effects; (viii) improve the performance of existing telescopes; (ix) improve designs of future large European ground-and space-based solar telescopes; (x) lay foundations for combined use of facilities around the world and in space; (xi) reinforce partnership with industry to promote technology transfer through existing networks; and (xii) dissemination activities towards society. The project involves all pertinent European research institutions, infrastructures, and data repositories. Together, these represent first-class facilities. The additional participation by private companies and non-European research institutions maximizes the impact on the world-wide scale. In particular, the project achievements will be of principal importance in defining the exploitation of the future 4-meter European Solar Telescope.
News Article | April 19, 2016
Our galaxy is teeming with planets. Over the last 25 years, astronomers have cataloged about 2,000 worlds in 1,300 systems scattered around our stellar neighborhood. While most of these exoplanets look nothing like Earth (and in some cases, like nothing that orbits our sun), the bonanza of alien worlds implies a tantalizing possibility: There is a lot of real estate out there suitable for life. We haven’t explored every corner of our solar system. Life might be lurking beneath the surface of some icy satellites or in the soil of Mars. For such locales, we could conceivably visit and look for anything wriggling or replicating. But we can’t travel (yet) to worlds orbiting remote suns dozens of light-years away. An advanced alien civilization might transmit detectable radio signals, but primitive life would not be able to announce its presence to the cosmos. At least not intentionally. On Earth, life alters the atmosphere. If plants and critters weren’t around to keep churning out oxygen and methane, those gases would quickly vanish. Water, carbon dioxide, methane, oxygen and ozone are examples of “biosignatures,” key markers of a planet crawling with life as we know it. Setting aside questions about how recognizable alien life might be, detecting biosignatures in the atmosphere of an exoplanet would give astronomers the first strong clue that we are not alone. Biosignatures aren’t proof of thriving ecosystems. Ultraviolet light from a planet’s sun can zap water molecules and create a stockpile of oxygen; seawater filtering through rocks can produce methane. “We’ll never be able to say 100 percent that a planet has life,” says Sarah Rugheimer, an astrophysicist at the University of St. Andrews in Scotland. But astronomers hope that, given enough information about an exoplanet and the star it orbits, they can build a case for a world where sunlight and geology aren’t enough to explain its chemistry — one where life is a viable possibility. Finding a planet similar to Earth is probably still decades away, but thanks to a couple of upcoming telescopes, astronomers might be on the verge of spying on habitable worlds around nearby stars. NASA’s Transiting Exoplanet Survey Satellite, or TESS, will launch in 2017 on a quest to detect many of the exoplanets that orbit the stars closest to us. One year later, the James Webb Space Telescope will launch and peek inside some of these newfound atmospheres. With their powers combined, TESS and James Webb could identify nearby planets that are good candidates for life. These worlds will probably be quite different from Earth — they’ll be a bit larger and orbit faint, red suns — but some researchers hope that a few will offer hints of alien biology. Over the next decade, several telescopes will join existing observatories in the hunt for exoplanets and hints of alien life. Exoplanets don’t give up their secrets easily; they are distant, tiny and snuggled up to blazing stars. With some exceptions, current telescopes can’t directly see exoplanets, so astronomers use other means to infer their existence. In rare cases, a remote solar system is oriented so that its planets pass between their sun and Earth, an event known as a transit. During a transit, the star temporarily dims as a planet blocks some of its light. Transits are powerful tools; not only can they help reveal a planet’s density — a way to distinguish gas planets from solid ones — but they also can allow astronomers to inventory the molecules floating in an exoplanet’s atmosphere. During a transit, molecules in the planet’s atmosphere absorb certain wavelengths of the star’s light, leaving a chemical fingerprint. By deciphering that fingerprint, researchers can deduce the chemical makeup of an alien world. Astronomers so far have used the transit technique primarily with space-based telescopes such as the Hubble Space Telescope to investigate the atmospheres of more than 50 exoplanets, most of them worlds the size of Jupiter and Neptune (SN: 11/15/14, p. 4). The puffy atmospheres of giant planets are easier to detect than the relatively slim atmospheres of small rocky worlds. As tools have improved, researchers have started to check out super-Earths, planets that are smaller than Neptune but larger than ours. Though no such planets exist in our solar system, they appear to be one of the most common types in the galaxy. Only three super-Earths have come under telescope scrutiny so far: GJ 1214b, HD 97658b and 55 Cancri e. These worlds are nothing like Earth. Two of them orbit dim, red suns, all of them whip around their stars in a few days (or even hours) and none are in the coveted habitable zone — the region around a star where a planet’s temperatures are just right for liquid water. Around GJ 1214b and HD 97658b, astronomers found no signs of molecules absorbing starlight, leading researchers to conclude that both worlds are blanketed in clouds or haze (SN Online: 1/2/14). In February, researchers reported signs of hydrogen cyanide on 55 Cancri e. If confirmed, it would be the first detection of any molecule in the atmosphere of a super-Earth. “These are very challenging measurements, at the limit of [the Hubble Space Telescope’s] capabilities,” cautions Heather Knutson, an astrophysicist at Caltech. “We’re still learning about the performance of the telescope at this level of precision.” Astronomers will undoubtedly try to squeeze more information out of similar worlds. But, says Kevin France, an astrophysicist at the University of Colorado Boulder, “we’ve pushed Hubble about as far as we can.” And Hubble won’t be around forever (SN: 4/18/15, p. 18). To continue sniffing around in exoplanet atmospheres, researchers are looking toward Hubble’s successor, the James Webb Space Telescope. James Webb “is going to be a revolution in astronomy,” says Jonathan Lunine, an astrophysicist at Cornell University. The infrared observatory boasts a mirror 2.7 times as wide as Hubble’s. James Webb will seek out the first generation of stars, track how galaxies grow and — most relevant to the search for life — poke around in planetary atmospheres. Analyzing the atmospheres of planets the size of Neptune and Jupiter should be a breeze for James Webb. These large planets block enough light to make transits readily detectable, and the fluffy atmospheres are easier to measure. Super-Earths, which are smaller with thin atmospheres, are more challenging, but James Webb should be able to investigate a few. Although replicas of Earth are beyond even James Webb’s capabilities, there will be plenty for the observatory to do. “Even if we can’t get biosignatures on planets the size of Earth, we’re going to find out so much about the nature of exoplanets,” Lunine says. “It’s going to open up a huge number of doors.” The trouble with an Earth-like world is that it doesn’t transit often and both the planet and its atmosphere are tiny. It’s the same kind of problem an alien group would experience trying to detect us. When viewed from afar, Earth blocks less than 0.01 percent of the sun’s light, and only a few percent of that is due to the atmosphere. To an alien astronomer, Earth crosses the sun once a year for, at most, 13 hours. And that’s assuming the aliens live in the right part of the galaxy to witness an Earth transit. Telescopes operated by the bulk of the Milky Way’s citizens will never line up with both the sun and Earth. The odds of finding life improve if astronomers focus their efforts on M dwarfs, which make up about three-quarters of the stars in the galaxy. The dim red orbs are small, so a transiting planet blocks a relatively large fraction of the star’s light, making transits easier to detect. Habitable worlds also transit more frequently. To sustain liquid water, a planet must huddle close to one of these cool stars to stay warm. An orbit in the habitable zone of an M dwarf is much shorter than a comparable trip around the sun. Rather than wait for a year between transits, astronomers might have to wait for only a few weeks or months. Plus, a planet on a cozy orbit is more forgiving when it comes to getting the viewing geometry just right to see a transit. There are potential downsides to M dwarfs. Most of the light they radiate is infrared, so photosynthesis on orbiting planets would be very different compared with photosynthesis on Earth. There’s no guarantee that biosignatures from vegetation that thrives on infrared light would look anything like those from local varieties. Many M dwarfs also emit occasional blasts of ultraviolet radiation — blasts made even more dangerous because any habitable planet sits close to the star. Habitable worlds need to be so close, in fact, that the star’s gravity might prevent the planet from rotating, which could give rise to extreme climate differences between day and night. Recent research, though, indicates that none of these issues are necessarily deal breakers (SN: 2/7/15, p. 7). “There’s no reason why a planet around an M star couldn’t be like Earth,” says Lisa Kaltenegger, an astrophysicist at Cornell. James Webb should be able to poke around in the atmospheres of a few habitable super-Earths around M dwarfs, though it’s going to need some targets first (SN: 5/17/14, p. 6). NASA’s premier planet hunter, the Kepler space telescope, (SN: 12/27/14, p. 20) found 1,039 exoplanets during its four-year primary mission, with 4,706 additional candidates awaiting confirmation. But most of Kepler’s finds are too distant for James Webb. That’s where TESS comes in. It will catalog all the short-period transiting worlds around the sun’s nearest neighbors. “Those are the ones that astronomers even decades from now are going to want to focus on,” says George Ricker, an MIT astrophysicist and principal investigator for the TESS mission. Unlike Kepler, which gazed in one direction at 150,000 stars, TESS will spend two years monitoring 200,000 stars all around the sky. To cover that much ground, TESS will stare at one spot for about 27 days before moving onto a new patch. That’s not great for finding Earth twins on year-long orbits, but it’s good for finding worlds in the habitable zones of M dwarfs. Based on Kepler’s results, astrophysicist Peter Sullivan, then at MIT, and colleagues calculated in 2015 that TESS should discover about 1,700 exoplanets. Of these, more than 500 could be less than twice the size of Earth, of which about 50 would lie in the habitable zones of their host stars. But picking biosignatures, or any signatures, out of those atmospheres is going to be difficult. Estimates vary, but James Webb will need roughly 200 hours to study one super-Earth around a nearby M dwarf, and those hours count only when the planet is passing in front of its star. There’s a debate happening right now over how hard to chase that dream, Caltech’s Knutson says. Given its sluggish pace, James Webb might get to look at only a couple of habitable super-Earths. Astronomers could lavish large amounts of time on one or two systems that might not even pan out. Or they could focus telescope resources on Neptunes, Jupiters or hot super-Earths, where researchers can amass a lot of other data about a wide variety of worlds. While James Webb might get lucky and spy some biosignatures, the dream of finding another planet like Earth will probably have to wait a few decades for a larger observatory to come along. The transit technique is powerful but inefficient. From our vantage point, most planets don’t transit their suns, and those that do transit only once every orbit. “To really give us the best probability of detecting life, we need to build a telescope that can do direct detection,” Rugheimer says. Direct detection requires snapping a picture of an exoplanet and looking for biosignatures such as oxygen and methane imprinted on light reflecting off its surface. Since this technique doesn’t require alignments between planets and suns, it can, in principle, work for any world around any star. But to catch an Earth 2.0, astronomers are going to need a bigger telescope. Consider again those aliens who are looking for us. They would struggle to see Earth even if they set up camp 4.2 light-years away at the star next door, Proxima Centauri (an M dwarf, by the way). It’s like trying to see the head of a quilting pin 28 meters to the right of a basketball while standing about 7,500 kilo-meters away — roughly the distance from Honolulu to Pittsburgh. And the basketball is 10 billion times as bright as the pin. No observatories come close to being able to capture an image of an Earth-like planet around a sunlike star. But astronomers are thinking about what it would take. One idea is to put a gigantic mirror in space equipped with a device that can block the light of the star, such as the High-Definition Space Telescope proposed by the Association of Universities for Research in Astronomy. To see a few dozen Earth twins and characterize their atmospheres, that telescope would need a mirror 12 meters across. That’s bigger than any optical telescope currently on the ground and has 25 times the light-collecting area of Hubble. Such an observatory “would be a huge undertaking relative to what we’ve done in space before,” Lunine says. “But relative to other programs this country has undertaken, it’s not.” One of the keys to success with the high-definition telescope is a coronagraph, a disk that blocks the light from any star the telescope points at. Many telescopes already use coronagraphs, especially spacecraft designed to look at the sun. James Webb will be outfitted with a coronagraph, though not one designed to search for other Earths. The downside to a coronagraph is that it requires exceptional control of light that enters the telescope, which complicates the design. Other proposals to detect Earth-like planets, such as the NASA-commissioned Exo-S concept, use a starshade, a separate spacecraft shaped, appropriately, like the petals of a sunflower. The starshade flies tens of thousands of kilometers away from the telescope and maintains perfect alignment to prevent starlight from hitting the mirror (SN: 7/12/14, p. 11). Since a starshade is free-floating and does all the lightsuppression work, it should be able to partner up with any telescope, even a relatively small one already in use. But no one has attempted formation flying in space at this scale. And every time astronomers want to look at a new star, the starshade would have to move around the telescope to maintain alignment, which could take days or weeks. All that movement will require fuel, which limits how many stars astronomers can search. Today these missions and others like them exist only in papers and PowerPoint slides posted online. The concepts, the fruits of a community-wide brainstorming session on how to allocate funding in the 2030s and beyond, will require massive financial and logistical resources, but some astronomers think it will be worth it once TESS and James Webb can point to where the nearest habitable locales might be. “Once we know where the potential habitable worlds are in our sky, I hope that will change a lot of people’s curiosity,” Kaltenegger says. “I would want to know if there are other habitable worlds. I wouldn’t want to just guess.” Everyone agrees that finding a world teeming with life elsewhere in the galaxy is going to be exceptionally difficult. “Maybe nature needs to be on our side,” says Mark Clampin, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “But it won’t stop people from trying very hard. And we’ll probably make a lot of discoveries along the way.” This article appears in the April 30, 2016, Science News with the headline, "Putting eyes on exoplanets: Finding signs of life is hard, but new telescopes will soon begin searching."
News Article | February 24, 2017
Three decades ago, astronomers spotted one of the brightest exploding stars in more than 400 years. The titanic supernova, called Supernova 1987A (SN 1987A), blazed with the power of 100 million suns for several months following its discovery on Feb. 23, 1987. Since that first sighting, SN 1987A has continued to fascinate astronomers with its spectacular light show. Located in the nearby Large Magellanic Cloud, it is the nearest supernova explosion observed in hundreds of years and the best opportunity yet for astronomers to study the phases before, during, and after the death of a star. To commemorate the 30th anniversary of SN 1987A, new images, time-lapse movies, a data-based animation based on work led by Salvatore Orlando at INAF-Osservatorio Astronomico di Palermo, Italy, and a three-dimensional model are being released. By combining data from NASA's Hubble Space Telescope and Chandra X-ray Observatory, as well as the international Atacama Large Millimeter/submillimeter Array (ALMA), astronomers -- and the public -- can explore SN 1987A like never before. Hubble has repeatedly observed SN 1987A since 1990, accumulating hundreds of images, and Chandra began observing SN 1987A shortly after its deployment in 1999. ALMA, a powerful array of 66 antennas, has been gathering high-resolution millimeter and submillimeter data on SN 1987A since its inception. "The 30 years' worth of observations of SN 1987A are important because they provide insight into the last stages of stellar evolution," said Robert Kirshner of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and the Gordon and Betty Moore Foundation in Palo Alto, California. The latest data from these powerful telescopes indicate that SN 1987A has passed an important threshold. The supernova shock wave is moving beyond the dense ring of gas produced late in the life of the pre-supernova star when a fast outflow or wind from the star collided with a slower wind generated in an earlier red giant phase of the star's evolution. What lies beyond the ring is poorly known at present, and depends on the details of the evolution of the star when it was a red giant. "The details of this transition will give astronomers a better understanding of the life of the doomed star, and how it ended," said Kari Frank of Penn State University who led the latest Chandra study of SN 1987A. Supernovas such as SN 1987A can stir up the surrounding gas and trigger the formation of new stars and planets. The gas from which these stars and planets form will be enriched with elements such as carbon, nitrogen, oxygen and iron, which are the basic components of all known life. These elements are forged inside the pre-supernova star and during the supernova explosion itself, and then dispersed into their host galaxy by expanding supernova remnants. Continued studies of SN 1987A should give unique insight into the early stages of this dispersal. Some highlights from studies involving these telescopes include: Hubble studies have revealed that the dense ring of gas around the supernova is glowing in optical light, and has a diameter of about a light-year. The ring was there at least 20,000 years before the star exploded. A flash of ultraviolet light from the explosion energized the gas in the ring, making it glow for decades. The central structure visible inside the ring in the Hubble image has now grown to roughly half a light-year across. Most noticeable are two blobs of debris in the center of the supernova remnant racing away from each other at roughly 20 million miles an hour. From 1999 until 2013, Chandra data showed an expanding ring of X-ray emission that had been steadily getting brighter. The blast wave from the original explosion has been bursting through and heating the ring of gas surrounding the supernova, producing X-ray emission. In the past few years, the ring has stopped getting brighter in X-rays. From about February 2013 until the last Chandra observation analyzed in September 2015 the total amount of low-energy X-rays has remained constant. Also, the bottom left part of the ring has started to fade. These changes provide evidence that the explosion's blast wave has moved beyond the ring into a region with less dense gas. This represents the end of an era for SN 1987A. Beginning in 2012, astronomers used ALMA to observe the glowing remains of the supernova, studying how the remnant is actually forging vast amounts of new dust from the new elements created in the progenitor star. A portion of this dust will make its way into interstellar space and may become the building blocks of future stars and planets in another system. These observations also suggest that dust in the early universe likely formed from similar supernova explosions. Astronomers also are still looking for evidence of a black hole or a neutron star left behind by the blast. They observed a flash of neutrinos from the star just as it erupted. This detection makes astronomers quite certain a compact object formed as the center of the star collapsed -- either a neutron star or a black hole -- but no telescope has uncovered any evidence for one yet. These latest visuals were made possible by combining several sources of information including simulations by Salvatore Orlando and collaborators that appear in this paper: https:/ . The Chandra study by Frank et al. can be found online at http://lanl. . Recent ALMA results on SN 87A are available at https:/ . The Chandra program is managed by NASA's Marshall Space Flight Center in Huntsville, Alabama, for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations. The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of South Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.
News Article | October 26, 2016
Great balls of fire! NASA's Hubble Space Telescope has detected superhot blobs of gas, each twice as massive as the planet Mars, being ejected near a dying star. The plasma balls are zooming so fast through space it would take only 30 minutes for them to travel from Earth to the moon. This stellar "cannon fire" has continued once every 8.5 years for at least the past 400 years, astronomers estimate. The fireballs present a puzzle to astronomers, because the ejected material could not have been shot out by the host star, called V Hydrae. The star is a bloated red giant, residing 1,200 light-years away, which has probably shed at least half of its mass into space during its death throes. Red giants are dying stars in the late stages of life that are exhausting their nuclear fuel that makes them shine. They have expanded in size and are shedding their outer layers into space. The current best explanation suggests the plasma balls were launched by an unseen companion star. According to this theory, the companion would have to be in an elliptical orbit that carries it close to the red giant's puffed-up atmosphere every 8.5 years. As the companion enters the bloated star's outer atmosphere, it gobbles up material. This material then settles into a disk around the companion, and serves as the launching pad for blobs of plasma, which travel at roughly a half-million miles per hour. This star system could be the archetype to explain a dazzling variety of glowing shapes uncovered by Hubble that are seen around dying stars, called planetary nebulae, researchers say. A planetary nebula is an expanding shell of glowing gas expelled by a star late in its life. "We knew this object had a high-speed outflow from previous data, but this is the first time we are seeing this process in action," said Raghvendra Sahai of NASA's Jet Propulsion Laboratory in Pasadena, California, lead author of the study. "We suggest that these gaseous blobs produced during this late phase of a star's life help make the structures seen in planetary nebulae." Hubble observations over the past two decades have revealed an enormous complexity and diversity of structure in planetary nebulae. The telescope's high resolution captured knots of material in the glowing gas clouds surrounding the dying stars. Astronomers speculated that these knots were actually jets ejected by disks of material around companion stars that were not visible in the Hubble images. Most stars in our Milky Way galaxy are members of binary systems. But the details of how these jets were produced remained a mystery. "We want to identify the process that causes these amazing transformations from a puffed-up red giant to a beautiful, glowing planetary nebula," Sahai said. "These dramatic changes occur over roughly 200 to 1,000 years, which is the blink of an eye in cosmic time." Sahai's team used Hubble's Space Telescope Imaging Spectrograph (STIS) to conduct observations of V Hydrae and its surrounding region over an 11-year period, first from 2002 to 2004, and then from 2011 to 2013. Spectroscopy decodes light from an object, revealing information on its velocity, temperature, location, and motion. The data showed a string of monstrous, super-hot blobs, each with a temperature of more than 17,000 degrees Fahrenheit - almost twice as hot as the surface of the sun. The researchers compiled a detailed map of the blobs' location, allowing them to trace the first behemoth clumps back to 1986. "The observations show the blobs moving over time," Sahai said. "The STIS data show blobs that have just been ejected, blobs that have moved a little farther away, and blobs that are even farther away." STIS detected the giant structures as far away as 37 billion miles away from V Hydrae, more than eight times farther away than the Kuiper Belt of icy debris at the edge of our solar system is from the sun. The blobs expand and cool as they move farther away, and are then not detectable in visible light. But observations taken at longer sub-millimeter wavelengths in 2004, by the Submillimeter Array in Hawaii, revealed fuzzy, knotty structures that may be blobs launched 400 years ago, the researchers said. Based on the observations, Sahai and his colleagues Mark Morris of the University of California, Los Angeles, and Samantha Scibelli of the State University of New York at Stony Brook developed a model of a companion star with an accretion disk to explain the ejection process. "This model provides the most plausible explanation because we know that the engines that produce jets are accretion disks," Sahai explained. "Red giants don't have accretion disks, but many most likely have companion stars, which presumably have lower masses because they are evolving more slowly. The model we propose can help explain the presence of bipolar planetary nebulae, the presence of knotty jet-like structures in many of these objects, and even multipolar planetary nebulae. We think this model has very wide applicability." A surprise from the STIS observation was that the disk does not fire the monster clumps in exactly the same direction every 8.5 years. The direction flip-flops slightly from side-to-side to back-and-forth due to a possible wobble in the accretion disk. "This discovery was quite surprising, but it is very pleasing as well because it helped explain some other mysterious things that had been observed about this star by others," Sahai said. Astronomers have noted that V Hydrae is obscured every 17 years, as if something is blocking its light. Sahai and his colleagues suggest that due to the back-and-forth wobble of the jet direction, the blobs alternate between passing behind and in front of V Hydrae. When a blob passes in front of V Hydrae, it shields the red giant from view. "This accretion disk engine is very stable because it has been able to launch these structures for hundreds of years without falling apart," Sahai said. "In many of these systems, the gravitational attraction can cause the companion to actually spiral into the core of the red giant star. Eventually, though, the orbit of V Hydrae's companion will continue to decay because it is losing energy in this frictional interaction. However, we do not know the ultimate fate of this companion." The team hopes to use Hubble to conduct further observations of the V Hydrae system, including the most recent blob ejected in 2011. The astronomers also plan to use the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to study blobs launched over the past few hundred years that are now too cool to be detected with Hubble. The team's results appeared in the August 20, 2016, issue of The Astrophysical Journal. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C. Please follow SpaceRef on Twitter and Like us on Facebook.
Agency: European Commission | Branch: FP7 | Program: CP-FP | Phase: SPA.2012.2.1-01 | Award Amount: 3.22M | Year: 2013
Observations of oscillations on the solar and stellar surfaces have emerged as a unique and extremely powerful tool to gain information on, and understanding of, the processes in the Sun and stars, and the origin of the variability in the solar and stellar output. Through helio- and asteroseismology detailed inferences of the internal structure and rotation of the Sun, and extensive information on the properties of a broad range of stars can be obtained. Space-based observations play a leading role in helio- and asteroseismology, in close synergy with ground-based observations as well as theoretical modelling. Long observing sequences are essential for measuring the oscillation frequencies with the precision required, and to extract the lowest mode frequencies involved. The enormous value of long-term space-based observations has been demonstrated in the solar case by the joint ESA/NASA SOHO mission (Solar and Heliospheric Observatory. This is now being followed by instruments on the NASA Solar Dynamics Observatory (SDO) mission.Large volumes of exquisite data on stellar oscillations of stars with a broad range of masses and ages are being collected by the CNES space mission CoRoT (Convection, Rotation and Transit) and the NASA Kepler mission. Extensive Earth-based observations of solar oscillations have been undertaken with the GONG network (Global Oscillations Network Group) and the Birmingham Oscillation Network (BiSON) to ensure continuous monitoring. A asteroseismic network, SONG (Stellar Observations Network Group) is being established under Danish leadership. Equally important for asteroseismology is the availability of supplementary data on the stars from more traditional observations, to determine their surface temperature, composition, radius, etc. Only through a coordinated use of the space- and ground-based data can the full potential of helio- and asteroseismology be realized.
News Article | April 21, 2016
"As Hubble makes its 26th revolution around our home star, the sun, we celebrate the event with a spectacular image of a dynamic and exciting interaction of a young star with its environment. The view of the Bubble Nebula, crafted from WFC-3 images, reminds us that Hubble gives us a front row seat to the awe inspiring Universe we live in," said John Grunsfeld, Hubble astronaut and associate administrator of NASA's Science Mission Directorate at NASA Headquarters, in Washington, D.C. The Bubble Nebula is 7 light-years across—about one-and-a-half times the distance from our sun to its nearest stellar neighbor, Alpha Centauri, and resides 7,100 light-years from Earth in the constellation Cassiopeia. The seething star forming this nebula is 45 times more massive than our sun. Gas on the star gets so hot that it escapes away into space as a "stellar wind" moving at over 4 million miles per hour. This outflow sweeps up the cold, interstellar gas in front of it, forming the outer edge of the bubble much like a snowplow piles up snow in front of it as it moves forward. As the surface of the bubble's shell expands outward, it slams into dense regions of cold gas on one side of the bubble. This asymmetry makes the star appear dramatically off-center from the bubble, with its location in the 10 o'clock position in the Hubble view. Dense pillars of cool hydrogen gas laced with dust appear at the upper left of the picture, and more "fingers" can be seen nearly face-on, behind the translucent bubble. The gases heated to varying temperatures emit different colors: oxygen is hot enough to emit blue light in the bubble near the star, while the cooler pillars are yellow from the combined light of hydrogen and nitrogen. The pillars are similar to the iconic columns in the "Pillars of Creation" Eagle Nebula. As seen with the structures in the Eagle Nebula, the Bubble Nebula pillars are being illuminated by the strong ultraviolet radiation from the brilliant star inside the bubble. The Bubble Nebula was discovered in 1787 by William Herschel, a prominent British astronomer. It is being formed by a proto-typical Wolf-Rayet star, BD +60º2522, an extremely bright, massive, and short-lived star that has lost most of its outer hydrogen and is now fusing helium into heavier elements. The star is about 4 million years old, and in 10 million to 20 million years, it will likely detonate as a supernova. Hubble's Wide Field Camera 3 imaged the nebula in visible light with unprecedented clarity in February 2016. The colors correspond to blue for oxygen, green for hydrogen, and red for nitrogen. This information will help astronomers understand the geometry and dynamics of this complex system. The Bubble Nebula is one of only a handful of astronomical objects that have been observed with several different instruments onboard Hubble. Hubble also imaged it with the Wide Field Planetary Camera (WFPC) in September of 1992, and with Wide Field Planetary Camera 2 (WFPC2) in April of 1999. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.
News Article | October 26, 2016
The universe suddenly looks a lot more crowded, thanks to a deep-sky census assembled from surveys taken by NASA's Hubble Space Telescope and other observatories. Astronomers came to the surprising conclusion that there are at least 10 times more galaxies in the observable universe than previously thought. This places the universe's estimated population at, minimally, 2 trillion galaxies. The results have clear implications for galaxy formation, and also helps shed light on an ancient astronomical paradox -- why is the sky dark at night? In analyzing the data, a team led by Christopher Conselice of the University of Nottingham, U.K., found that 10 times as many galaxies were packed into a given volume of space in the early universe than found today. Most of these galaxies were relatively small and faint, with masses similar to those of the satellite galaxies surrounding the Milky Way. As they merged to form larger galaxies the population density of galaxies in space dwindled. This means that galaxies are not evenly distributed throughout the universe's history, the research team reports in a paper to be published in The Astrophysical Journal. "These results are powerful evidence that a significant galaxy evolution has taken place throughout the universe's history, which dramatically reduced the number of galaxies through mergers between them -- thus reducing their total number. This gives us a verification of the so-called top-down formation of structure in the universe," explained Conselice. One of the most fundamental questions in astronomy is that of just how many galaxies the universe contains. The landmark Hubble Deep Field, taken in the mid-1990s, gave the first real insight into the universe's galaxy population. Subsequent sensitive observations such as Hubble's Ultra Deep Field revealed a myriad of faint galaxies. This led to an estimate that the observable universe contained about 100 billion galaxies. The new research shows that this estimate is at least 10 times too low. Conselice and his team reached this conclusion using deep-space images from Hubble and the already published data from other teams. They painstakingly converted the images into 3-D, in order to make accurate measurements of the number of galaxies at different epochs in the universe's history. In addition, they used new mathematical models, which allowed them to infer the existence of galaxies that the current generation of telescopes cannot observe. This led to the surprising conclusion that in order for the numbers of galaxies we now see and their masses to add up, there must be a further 90 percent of galaxies in the observable universe that are too faint and too far away to be seen with present-day telescopes. These myriad small faint galaxies from the early universe merged over time into the larger galaxies we can now observe. "It boggles the mind that over 90 percent of the galaxies in the universe have yet to be studied. Who knows what interesting properties we will find when we discover these galaxies with future generations of telescopes? In the near future, the James Webb Space Telescope will be able to study these ultra-faint galaxies," said Conselice. The decreasing number of galaxies as time progresses also contributes to the solution for Olbers' paradox (first formulated in the early 1800s by German astronomer Heinrich Wilhelm Olbers): Why is the sky dark at night if the universe contains an infinity of stars? The team came to the conclusion that indeed there actually is such an abundance of galaxies that, in principle, every patch in the sky contains part of a galaxy. However, starlight from the galaxies is invisible to the human eye and most modern telescopes due to the other known factors that reduce visible and ultraviolet light in the universe. Those factors are the reddening of light due to the expansion of space, the universe's dynamic nature, and the absorption of light by intergalactic dust and gas. All combined, this keeps the night sky dark to our vision. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C. Please follow SpaceRef on Twitter and Like us on Facebook.