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  • richardmitnick 10:03 am on June 16, 2015 Permalink | Reply
    Tags: , Astrophysics, ,   

    From MIT: “Small thunderstorms may add up to massive cyclones on Saturn” 


    MIT News

    June 15, 2015
    Jennifer Chu | MIT News Office

    1
    Saturn’s north polar vortex.m Image courtesy of Caltech/Space Science Institute

    New model may predict cyclone activity on other planets.

    For the last decade, astronomers have observed curious “hotspots” on Saturn’s poles. In 2008, NASA’s Cassini spacecraft beamed back close-up images of these hotspots, revealing them to be immense cyclones, each as wide as the Earth.

    NASA Cassini Spacecraft
    Cassini

    Scientists estimate that Saturn’s cyclones may whip up 300 mph winds, and likely have been churning for years.

    While cyclones on Earth are fueled by the heat and moisture of the oceans, no such bodies of water exist on Saturn. What, then, could be causing such powerful, long-lasting storms?

    In a paper published today in the journal Nature Geoscience, atmospheric scientists at MIT propose a possible mechanism for Saturn’s polar cyclones: Over time, small, short-lived thunderstorms across the planet may build up angular momentum, or spin, within the atmosphere — ultimately stirring up a massive and long-lasting vortex at the poles.

    The researchers developed a simple model of Saturn’s atmosphere, and simulated the effect of multiple small thunderstorms forming across the planet over time. Eventually, they observed that each thunderstorm essentially pulls air towards the poles — and together, these many small, isolated thunderstorms can accumulate enough atmospheric energy at the poles to generate a much larger and long-lived cyclone.

    The team found that whether a cyclone develops depends on two parameters: the size of the planet relative to the size of an average thunderstorm on it, and how much storm-induced energy is in its atmosphere. Given these two parameters, the researchers predicted that Neptune, which bears similar polar hotspots, should generate transient polar cyclones that come and go, while Jupiter should have none.

    Morgan O’Neill, the paper’s lead author and a former PhD student in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS), says the team’s model may eventually be used to gauge atmospheric conditions on planets outside the solar system. For instance, if scientists detect a cyclone-like hotspot on a far-off exoplanet, they may be able to estimate storm activity and general atmospheric conditions across the entire planet.

    “Before it was observed, we never considered the possibility of a cyclone on a pole,” says O’Neill, who is now a postdoc at the Weizmann Institute of Science in Israel.

    “Only recently did Cassini give us this huge wealth of observations that made it possible, and only recently have we had to think about why [polar cyclones] occur.”

    O’Neill’s co-authors are Kerry Emanuel, the Cecil and Ida Green Professor of Earth, Atmospheric and Planetary Sciences, and Glenn Flierl, a professor of oceanography in EAPS.

    Beta-drifting toward a cyclone

    Polar cyclones on Saturn are a puzzling phenomenon, since the planet, known as a gas giant, lacks an essential ingredient for brewing up such storms: water on its surface.

    “There’s no surface at all — it just gets denser as you get deeper,” O’Neill says. “If you lack choppy waters or a frictional surface that allows wind to converge, which is how hurricanes form on Earth, how can you possibly get something that looks similar on a gas giant?”

    The answer, she found, may be something called “beta drift” — a phenomenon by which a planet’s spin causes small thunderstorms to drift toward the poles. Beta drift drives the motion of hurricanes on Earth, without requiring the presence of water. When a storm forms, it spins in one direction at the surface, and the opposite direction toward the upper atmosphere, creating a “dipole of vorticity.” (In fact, videos of hurricanes taken from space actually depict the storm’s spin as opposite to what’s observed on the ground.)

    “The whole atmosphere is kind of being dragged by the planet as the planet rotates, so all this air has some ambient angular momentum,” O’Neill explains. “If you converge a bunch of that air at the base of a thunderstorm, you’re going to get a small cyclone.”

    The combination of a planet’s rotation and a circulating storm generates secondary features called beta gyres that wrap around a storm and essentially split its dipole in half, tugging the top half toward the equator, and the bottom half toward the pole.

    The team developed a model of Saturn’s atmosphere and ran hundreds of simulations for hundreds of days each, allowing small thunderstorms to pop up across the planet. The researchers observed that multiple thunderstorms experienced beta drift over time, and eventually accumulated enough atmospheric circulation to create a much larger cyclone at the poles.

    “Each of these storms is beta-drifting a little bit before they sputter out and die,” O’Neill says. “This mechanism means that little thunderstorms — fast, abundant, but not very strong thunderstorms — over a long period of time can actually accumulate so much angular momentum right on the pole, that you get a permanent, wildly strong cyclone.”

    Next stop: Jupiter

    The team also explored conditions in which planets would not form polar cyclones, even though they may experience thunderstorms. The researchers found that whether a polar cyclone forms depends on two parameters: the energy within a planet’s atmosphere, or the total intensity of its thunderstorms; and the average size of its thunderstorms, relative to the size of the planet itself. Specifically, the larger an average thunderstorm compared to a planet’s size, the more likely a polar cyclone is to develop.

    O’Neill applied this relationship to Saturn, Jupiter, and Neptune. In the case of Saturn, the planet’s atmospheric conditions and storm activity are within the range that would generate a large polar cyclone. In contrast, Jupiter is unlikely to host any polar cyclones, as the ratio of any storm to its overall size would be extremely small. The dimensions of Neptune suggest that polar cyclones may exist there, albeit on a fleeting basis.

    “Saturn has an intense cyclone at each pole,” says Andrew Ingersoll, professor of planetary science at Caltech, who was not involved in the study. “The model successfully accounts for that. Jupiter doesn’t seem to have polar cyclones like Saturn’s, but Jupiter isn’t tipped over as much as Saturn, so we don’t get a good view of the poles. Thus the apparent absence of polar cyclones on Jupiter is still a mystery.”

    The researchers are eager to see whether their predictions, particularly for Jupiter, bear out. Next summer, NASA’s Juno spacecraft is scheduled to enter into an orbit around Jupiter, kicking off a one-year mission to map and explore Jupiter’s atmosphere.

    “If what we know about Jupiter currently is correct, we predict that we won’t see these wildly strong cyclones,” O’Neill says. “We’ll find out next year if our predictions are true.”

    This research was funded in part by the National Science Foundation.

    See the full article here.

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  • richardmitnick 12:48 pm on April 13, 2015 Permalink | Reply
    Tags: Astrophysics, , ,   

    From New Scientist: “Looking into the voids could help explain dark energy” 

    NewScientist

    New Scientist

    10 April 2015
    Anil Ananthaswamy

    1
    A complex web (Image: Volker Springle/Max Planck Institute for Astrophysics/SP)

    HOLES in the universe could help explain why it’s ripping apart. The number and size of cosmic voids could shed light on the mysterious dark energy that is causing the universe to grow at an ever-increasing pace.

    In the late 1990s, astronomers realised that the expansion of the universe was accelerating and attributed this to the inherent “dark energy” of space-time.

    But we understand little about dark energy. Each unit of space-time contains some, but if this energy density changes with time, it implies different fates for our universe. If it is constant, as current observations suggest, then the universe will expand forever. But if it changes, we could be heading for a more dramatic end, like a big rip or a big crunch.

    One way to understand whether dark energy changes with time is to observe its effect on the large-scale structure of the universe. Just instants after the big bang, quantum fluctuations in the fabric of space-time led to regions that had more matter than their neighbours. As the universe expanded, the denser regions evolved to form clusters of galaxies. The less dense regions became voids – regions of space-time almost empty of matter, which can stretch from 30 million to 150 million light years across.

    While most efforts at deciphering dark energy involve studying its effect on clusters of galaxies, Alice Pisani and colleagues at the Paris Institute of Astrophysics decided to see if dark energy influenced the number of voids in the universe. “Voids are just an unavoidable part of the distribution of matter in the universe,” says team member Benjamin Wandelt.

    It turns out that there was a time in the evolution of the universe when the effects of dark energy kicked in and stopped the formation of new large-scale structures, whether clusters or voids. The properties of dark energy influenced when this happened and therefore the distribution of these structures.

    Pisani and colleagues considered three scenarios, all of which can explain the observed rate of expansion today. One was that dark energy is a cosmological constant [Λ]; in the other scenarios, dark energy changed with time. The second caused the expansion to accelerate later but faster than the cosmological constant would have, and in the third, it was earlier but slower.

    “Depending exactly on when the universe started accelerating, you have more or less voids of various sizes,” says Wandelt. The team’s analysis shows that with later but faster acceleration, there should be more big voids but fewer smaller ones compared with the cosmological constant. The opposite would be the case for acceleration that began earlier but was slower (arxiv.org/abs/1503.07690).

    Observations are not yet good enough to differentiate between the three scenarios but the European Space Agency’s Euclid mission, due for launch in 2020, will study more voids than ever before. The Paris team says its analysis could be applied to the Euclid data to elucidate dark energy, alongside studies investigating clusters.

    ESA Euclid spacecraft
    ESA/Euclid

    See the full article here.

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  • richardmitnick 6:47 pm on January 8, 2015 Permalink | Reply
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    From Caltech: “Unusual Light Signal Yields Clues About Elusive Black Hole Merger” 

    Caltech Logo
    Caltech

    01/07/2015
    Ker Than

    The central regions of many glittering galaxies, our own Milky Way included, harbor cores of impenetrable darkness—black holes with masses equivalent to millions, or even billions, of suns. What is more, these supermassive black holes and their host galaxies appear to develop together, or “co-evolve.” Theory predicts that as galaxies collide and merge, growing ever more massive, so too do their dark hearts.

    bh
    Simulation of gravitational lensing by a black hole, which distorts the image of a galaxy in the background


    ESOCast
    Astronomers using ESO’s Very Large Telescope have discovered a gas cloud with several times the mass of the Earth accelerating towards the black hole at the centre of the Milky Way. This is the first time ever that the approach of such a doomed cloud to a supermassive black hole has been observed. This ESOcast explains the new results and includes spectacular simulations of how the cloud will break up over the next few years.
    Credit: ESO.

    ESO VLT Interferometer
    ESO VLT Interior
    ESO/VLT

    Black holes by themselves are impossible to see, but their gravity can pull in surrounding gas to form a swirling band of material called an accretion disk. The spinning particles are accelerated to tremendous speeds and release vast amounts of energy in the form of heat and powerful X-rays and gamma rays. When this process happens to a supermassive black hole, the result is a quasar—an extremely luminous object that outshines all of the stars in its host galaxy and that is visible from across the universe. “Quasars are valuable probes of the evolution of galaxies and their central black holes,” says George Djorgovski, professor of astronomy and director of the Center for Data-Driven Discovery at Caltech.

    In the January 7 issue of the journal Nature, Djorgovski and his collaborators report on an unusual repeating light signal from a distant quasar that they say is most likely the result of two supermassive black holes in the final phases of a merger—something that is predicted from theory but which has never been observed before. The discovery could help shed light on a long-standing conundrum in astrophysics called the “final parsec problem,” which refers to the failure of theoretical models to predict what the final stages of a black hole merger look like or even how long the process might take. “The end stages of the merger of these supermassive black hole systems are very poorly understood,” says the study’s first author, Matthew Graham, a senior computational scientist at Caltech. “The discovery of a system that seems to be at this late stage of its evolution means we now have an observational handle on what is going on.”

    Djorgovski and his team discovered the unusual light signal emanating from quasar PG 1302-102 after analyzing results from the Catalina Real-Time Transient Survey (CRTS), which uses three ground telescopes in the United States and Australia to continuously monitor some 500 million celestial light sources strewn across about 80 percent of the night sky. “There has never been a data set on quasar variability that approaches this scope before,” says Djorgovski, who directs the CRTS. “In the past, scientists who study the variability of quasars might only be able to follow some tens, or at most hundreds, of objects with a limited number of measurements. In this case, we looked at a quarter million quasars and were able to gather a few hundred data points for each one.”

    “Until now, the only known examples of supermassive black holes on their way to a merger have been separated by tens or hundreds of thousands of light years,” says study coauthor Daniel Stern, a scientist at NASA’s Jet Propulsion Laboratory. “At such vast distances, it would take many millions, or even billions, of years for a collision and merger to occur. In contrast, the black holes in PG 1302-102 are, at most, a few hundredths of a light year apart and could merge in about a million years or less.”

    Djorgovski and his team did not set out to find a black hole merger. Rather, they initially embarked on a systematic study of quasar brightness variability in the hopes of finding new clues about their physics. But after screening the data using a pattern-seeking algorithm that Graham developed, the team found 20 quasars that seemed to be emitting periodic optical signals. This was surprising, because the light curves of most quasars are chaotic—a reflection of the random nature by which material from the accretion disk spirals into a black hole. “You just don’t expect to see a periodic signal from a quasar,” Graham says. “When you do, it stands out.”

    Of the 20 periodic quasars that CRTS identified, PG 1302-102 was the best example. It had a strong, clean signal that appeared to repeat every five years or so. “It has a really nice smooth up-and-down signal, similar to a sine wave, and that just hasn’t been seen before in a quasar,” Graham says.

    The team was cautious about jumping to conclusions. “We approached it with skepticism but excitement as well,” says study coauthor Eilat Glikman, an assistant professor of physics at Middlebury College in Vermont. After all, it was possible that the periodicity the scientists were seeing was just a temporary ordered blip in an otherwise chaotic signal. To help rule out this possibility, the scientists pulled in data about the quasar from previous surveys to include in their analysis. After factoring in the historical observations (the scientists had nearly 20 years’ worth of data about quasar PG 1302-102), the repeating signal was, encouragingly, still there.

    The team’s confidence increased further after Glikman analyzed the quasar’s light spectrum. The black holes that scientists believe are powering quasars do not emit light, but the gases swirling around them in the accretion disks are traveling so quickly that they become heated into glowing plasma. “When you look at the emission lines in a spectrum from an object, what you’re really seeing is information about speed—whether something is moving toward you or away from you and how fast. It’s the Doppler effect,” Glikman says. “With quasars, you typically have one emission line, and that line is a symmetric curve. But with this quasar, it was necessary to add a second emission line with a slightly different speed than the first one in order to fit the data. That suggests something else, such as a second black hole, is perturbing this system.”

    Avi Loeb, who chairs the astronomy department at Harvard University, agreed with the team’s assessment that a “tight” supermassive black hole binary is the most likely explanation for the periodic signal they are seeing. “The evidence suggests that the emission originates from a very compact region around the black hole and that the speed of the emitting material in that region is at least a tenth of the speed of light,” says Loeb, who did not participate in the research. “A secondary black hole would be the simplest way to induce a periodic variation in the emission from that region, because a less dense object, such as a star cluster, would be disrupted by the strong gravity of the primary black hole.”

    In addition to providing an unprecedented glimpse into the final stages of a black hole merger, the discovery is also a testament to the power of “big data” science, where the challenge lies not only in collecting high-quality information but also devising ways to mine it for useful information. “We’re basically moving from having a few pictures of the whole sky or repeated observations of tiny patches of the sky to having a movie of the entire sky all the time,” says Sterl Phinney, a professor of theoretical physics at Caltech, who was also not involved in the study. “Many of the objects in the movie will not be doing anything very exciting, but there will also be a lot of interesting ones that we missed before.”

    It is still unclear what physical mechanism is responsible for the quasar’s repeating light signal. One possibility, Graham says, is that the quasar is funneling material from its accretion disk into luminous twin plasma jets that are rotating like beams from a lighthouse. “If the glowing jets are sweeping around in a regular fashion, then we would only see them when they’re pointed directly at us. The end result is a regularly repeating signal,” Graham says.

    Another possibility is that the accretion disk that encircles both black holes is distorted. “If one region is thicker than the rest, then as the warped section travels around the accretion disk, it could be blocking light from the quasar at regular intervals. This would explain the periodicity of the signal that we’re seeing,” Graham says. Yet another possibility is that something is happening to the accretion disk that is causing it to dump material onto the black holes in a regular fashion, resulting in periodic bursts of energy.

    “Even though there are a number of viable physical mechanisms behind the periodicity we’re seeing—either the precessing jet, warped accretion disk or periodic dumping—these are all still fundamentally caused by a close binary system,” Graham says.

    Along with Djorgovski, Graham, Stern, and Glikman, additional authors on the paper, A possible close supermassive black hole binary in a quasar with optical periodicity, include Andrew Drake, a computational scientist and co-principal investigator of the CRTS sky survey at Caltech; Ashish Mahabal, a staff scientist in computational astronomy at Caltech; Ciro Donalek, a computational staff scientist at Caltech; Steve Larson, a senior staff scientist at the University of Arizona; and Eric Christensen, an associate staff scientist at the University of Arizona. Funding for the study was provided by the National Science Foundation.

    See the full article here.

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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”
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  • richardmitnick 4:52 pm on January 8, 2015 Permalink | Reply
    Tags: , Astrophysics, , , ,   

    From Gemini Observatory: “THE GEMINI PLANET IMAGER PRODUCES STUNNING OBSERVATIONS IN ITS FIRST YEAR” 

    NOAO

    Gemini Observatory
    Gemini Observatory

    January 6, 2015
    Media Contacts:

    Peter Michaud
    Public Information and Outreach Manager
    Gemini Observatory, Hilo, HI
    Email: pmichaud”at”gemini.edu
    Cell: (808) 936-6643
    Desk: (808) 974-2510

    Science Contacts:

    Marshall Perrin
    STScI
    Email: mperrin”at”stsci.edu
    Phone: (410) 507-5483

    James R. Graham
    University of California Berkeley
    Email: jrg”at”berkeley.edu
    Cell: (510) 926-9820

    Stunning exoplanet images and spectra from the first year of science operations with the Gemini Planet Imager (GPI) were featured today in a press conference at the 225th meeting of the American Astronomical Society (AAS) in Seattle, Washington. The Gemini Planet Imager GPI is an advanced instrument designed to observe the environments close to bright stars to detect and study Jupiter-like exoplanets (planets around other stars) and see protostellar material (disk, rings) that might be lurking next to the star.

    1
    Figure 1. GPI imaging of the planetary system HR 8799 in K band, showing 3 of the 4 planets. (Planet b is outside the field of view shown here, off to the left.) These data were obtained on November 17, 2013 during the first week of operation of GPI and in relatively challenging weather conditions, but with GPI’s advanced adaptive optics system and coronagraph the planets can still be clearly seen and their spectra measured (see Figure 2). Image credit: Christian Marois (NRC Canada), Patrick Ingraham (Stanford University) and the GPI Team.

    2
    Figure 2. GPI spectroscopy of planets c and d in the HR 8799 system. While earlier work showed that the planets have similar overall brightness and colors, these newly-measured spectra show surprisingly large differences. The spectrum of planet d increases smoothly from 1.9-2.2 microns while planet c’s spectrum shows a sharper kink upwards just beyond 2 microns. These new GPI results indicate that these similar-mass and equal-age planets nonetheless have significant differences in atmospheric properties, for in-stance more open spaces between patchy cloud cover on planet c versus uniform cloud cover on planet d, or perhaps differences in atmospheric chemistry. These data are helping refine and improve a new generation of atmospheric models to explain these effects. Image credit: Patrick Ingraham (Stanford University), Mark Marley (NASA Ames), Didier Saumon (Los Alamos National Laboratory) and the GPI Team.

    Marshall Perrin (Space Telescope Science Institute), one of the instrument’s team leaders, presented a pair of recent and promising results at the press conference. He revealed some of the most detailed images and spectra ever of the multiple planet system HR 8799. His presentation also included never-seen details in the dusty ring of the young star HR 4796A. “GPI’s advanced imaging capabilities have delivered exquisite images and data,” said Perrin. “These improved views are helping us piece together what’s going on around these stars, yet also posing many new questions.”

    The GPI spectra obtained for two of the planetary members of the HR 8799 system presents a challenge for astronomers. GPI team member Patrick Ingraham (Stanford University), lead the paper on HR 8799. Ingraham reports that the shape of the spectra for the two planets differ more profoundly than expected based on their similar colors, indicating significant differences between the companions. “Current atmospheric models of exoplanets cannot fully explain the subtle differences in color that GPI has revealed. We infer that it may be differences in the coverage of the clouds or their composition.” Ingraham adds, “The fact that GPI was able to extract new knowledge from these planets on the first commissioning run in such a short amount of time, and in conditions that it was not even designed to work, is a real testament to how revolutionary GPI will be to the field of exoplanets.”

    Perrin, who is working to understand the dusty ring around the young star HR 4796A, said that the new GPI data present an unprecedented level of detail in studies of the ring’s polarized light. “GPI not only sees the disk more clearly than previous instruments, it can also measure how polarized its light appears, which has proven crucial in under-standing its physical properties.” Specifically, the GPI measurements of the ring show it must be partially opaque, implying it is far denser and more tightly compressed than similar dust found in the outskirts of our own Solar System, which is more diffuse. The ring circling HR 4796A is about twice the diameter of the planetary orbits in our Solar System and its star about twice our Sun’s mass. “These data taken during GPI commissioning show how exquisitely well its polarization mode works for studying disks. Such observations are critical in advancing our understanding of all types and sizes of planetary systems – and ultimately how unique our own solar system might be,” said Perrin.

    3
    Figure 3. GPI imaging polarimetry of the circumstellar disk around HR 4796A, a ring of dust and planetesimals similar in some ways to a scaled up version of the solar system’s Kuiper Belt.

    Kuiper Belt
    Kuiper Belt, for illustration of the discussion

    These GPI observations reveal a complex pattern of variations in brightness and polarization around the HR 4796A disk. The western side (tilted closer to the Earth) appears brighter in polarized light, while in total intensity the eastern side appears slightly brighter, particularly just to the east of the widest apparent separation points of the disk. Reconciling this complex and apparently-contradictory pattern of brighter and darker regions required a major overhaul of our understanding of this circumstellar disk. Image credit: Marshall Perrin (Space Telescope Science Institute), Gaspard Duchene (UC Berkeley), Max Millar-Blanchaer (University of Toronto), and the GPI Team.

    4
    Figure 4. Diagram depicting the GPI team’s revised model for the orientation and composition of the HR 4796A ring. To explain the observed polarization levels, the disk must consist of relatively large (> 5 µm) silicate dust particles, which scatter light most strongly and polarize it more for forward scattering. To explain the relative faintness of the east side in total intensity, the disk must be dense enough to be slightly opaque, comparable to Saturn’s optically thick rings, such that on the near side of the disk our view of its brightly illuminated inner portion is partially obscured. This revised model requires the disk to be much narrower and flatter than expected, and poses a new challenge for theories of disk dynamics to explain. GPI’s high contrast imaging and polarimetry capabilities together were essential for this new synthesis. Image credit: Marshall Perrin (Space Telescope Science Institute).

    During the commissioning phase, the GPI team observed a variety of targets, ranging from asteroids in our solar system, to an old star near its death. Other teams of scientists have been using GPI as well and already astronomers around the world have published eight papers in peer-reviewed journals using GPI data. “This might be the most productive new instrument Gemini has ever had,” said Professor James Graham of the University of California, who leads the GPI science team and who will describe the GPI exoplanet survey in a talk scheduled at the AAS meeting on Thursday, January 8th.

    The Gemini Observatory staff integrated the complex instrument into the telescope’s software and helped to characterize GPI’s performance. “Even though it’s so complicated, GPI now operates almost automatically,” said Gemini’s instrument scientist for GPI Fredrik Rantakyro. “This allows us to start routine science operations.” The instrument is now available to astronomers and their proposals are scheduled to start ob-serving in early 2015. In addition, “shared risk” observations are already underway, starting in November 2014.

    The one thing GPI hasn’t done yet is discovered a new planet. “For the early tests, we concentrated on known planets or disks” said GPI PI Bruce Macintosh. Now that GPI is fully operational, the search for new planets has begun. In addition to observations by astronomers world-wide, the Gemini Planet Imager Exoplanet Survey (GPIES) will look at 600 carefully selected stars over the next few years. GPI ‘sees’ planets through the infrared light they emit when they’re young, so the GPIES team has assembled a list of the youngest and closest stars. So far the team has observed 50 stars, and analysis of the data is ongoing. Discovering a planet requires confirmation observations to distinguish a true planet orbiting the target star from a distant star that happens to sneak into GPI’s field of view – a process that could take years with previous instruments. The GPIES team found one such object in their first survey run, but GPI observations were sensitive enough to almost immediately rule it out. Macintosh said, “With GPI, we can tell almost instantly that something isn’t a planet – rather than months of uncertainty, we can get over our disappointment almost immediately. Now it’s time to find some real planets!”

    About GPI/GPIES

    The Gemini Planet Imager (GPI) instrument was constructed by an international collaboration led by Lawrence Livermore National Laboratory under Gemini’s supervision. The GPI Exoplanet Survey (GPIES) is the core science program to be carried out with it. GPIES is led by Bruce Macintosh, now a professor at Stanford University and James Graham, professor at the University of California at Berkeley and is designed to find young, Jupiter-like exoplanets. They survey will observe 600 young nearby stars in 890 hours over three years. Targets have been carefully selected by team members at Arizona State University, the University of Georgia, and UCLA. The core of the data processing architecture is led by Marshall Perrin of the Space Telescope Science Institute, with the core software originally written by University of Montreal, data management infrastructure from UC Berkeley and Cornell University, and contributions from all the other team institutions. The SETI institute located in California manages GPIES’s communications and public out-reach. Several teams located at the Dunlap Institute, the University of Western Ontario, the University of Chicago, the Lowell Observatory, NASA Ames, the American Museum of Natural History, University of Arizona and the University of California at San Diego and at Santa Cruz also contribute to the survey. The GPI Exoplanet Survey is supported by the NASA Origins Program NNX14AG80, the NSF AAG pro-gram, and grants from other institutions including the University of California Office of the President. Dropbox Inc. has generously provided storage space for the entire survey’s archive.

    See the full article here.

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    Gemini North
    Gemini North, Hawai’i

    Gemini South
    Gemini South, Chile
    AURA Icon

    The Gemini Observatory consists of twin 8.1-meter diameter optical/infrared telescopes located on two of the best observing sites on the planet. From their locations on mountains in Hawai‘i and Chile, Gemini Observatory’s telescopes can collectively access the entire sky.
    Gemini was built and is operated by a partnership of six countries including the United States, Canada, Chile, Australia, Brazil and Argentina. Any astronomer in these countries can apply for time on Gemini, which is allocated in proportion to each partner’s financial stake.

     
  • richardmitnick 4:31 am on January 8, 2015 Permalink | Reply
    Tags: , Astrophysics, , , ,   

    From NASA Science: “Hubble: Pillars of Creation are also Pillars of Destruction” 

    NASA Science Science News

    Jan. 7, 2015
    Dr. Tony Phillips

    Although NASA’s Hubble Space Telescope has taken many breathtaking images of the universe, one snapshot stands out from the rest: the iconic view of the so-called “Pillars of Creation.” The jaw-dropping photo, taken in 1995, revealed never-before-seen details of three giant columns of cold gas bathed in the scorching ultraviolet light from a cluster of young, massive stars in a small region of the Eagle Nebula, or M16.

    e
    Overview of some famous sights in the Eagle Nebula

    NASA Hubble Telescope
    Hubble

    In celebration of its upcoming 25th anniversary in April, Hubble has revisited the famous pillars, providing astronomers with a sharper and wider view. Although the original image was dubbed the Pillars of Creation, the new image hints that they are also “pillars of destruction.”

    p
    Astronomers using NASA’s Hubble Space Telescope have assembled a bigger and sharper photograph of the iconic Eagle Nebula’s “Pillars of Creation”. Credit: NASA/ESA/Hubble Heritage Team (STScI/AURA)/J. Hester, P. Scowen (Arizona State U.)

    “I’m impressed by how transitory these structures are,” explains Paul Scowen of Arizona State University in Tempe. “They are actively being ablated away before our very eyes. The ghostly bluish haze around the dense edges of the pillars is material getting heated up and evaporating away into space. We have caught these pillars at a very unique and short-lived moment in their evolution.” Scowen and astronomer Jeff Hester, formerly of Arizona State University, led the original Hubble observations of the Eagle Nebula.


    HUBBLECast 82

    The original 1995 images were taken in visible light. The new image includes near-infrared light as well. The infrared view transforms the pillars into eerie, wispy silhouettes seen against a background of myriad stars. That’s because the infrared light penetrates much of the gas and dust, except for the densest regions of the pillars. Newborn stars can be seen hidden away inside the pillars.

    The infrared image shows that the very ends of the pillars are dense knots of dust and gas. They shadow the gas below them, keeping the gas cool and creating the long, column-like structures. The material in between the pillars has long since been evaporated away by the ionizing radiation from the central star cluster located above the pillars.

    At the top edge of the left-hand pillar, a gaseous fragment has been heated up and is flying away from the structure, underscoring the violent nature of star-forming regions. “These pillars represent a very dynamic, active process,” Scowen said. “The gas is not being passively heated up and gently wafting away into space. The gaseous pillars are actually getting ionized, a process by which electrons are stripped off of atoms, and heated up by radiation from the massive stars. And then they are being eroded by the stars’ strong winds and barrage of charged particles, which are literally sandblasting away the tops of these pillars.”

    When Scowen and Hester used Hubble to make the initial observations of the Eagle Nebula in 1995, astronomers had seen the pillar-like structures in ground-based images, but not in detail. They knew that the physical processes are not unique to the Eagle Nebula because star birth takes place across the universe. But at a distance of just 6,500 light-years, M16 is the most dramatic nearby example – as the team soon realized.

    As Scowen was piecing together the Hubble exposures of the Eagle, he was amazed at what he saw. “I called Jeff Hester on his phone and said, ‘You need to get here now,’” Scowen recalled. “We laid the pictures out on the table, and we were just gushing because of all the incredible detail that we were seeing for the very first time.”

    The first features that jumped out at the team in 1995 were the streamers of gas seemingly floating away from the columns. Astronomers had previously debated what effect nearby massive stars would have on the surrounding gas in stellar nurseries. “There is the only one thing that can light up a neighborhood like this: massive stars kicking out enough horsepower in ultraviolet light to ionize the gas clouds and make them glow,” Scowen said. “Nebulous star-forming regions like M16 are the interstellar neon signs that say, ‘We just made a bunch of massive stars here.’ This was the first time we had directly seen observational evidence that the erosionary process, not only the radiation but the mechanical stripping away of the gas from the columns, was actually being seen.”

    o
    The original 1995 image was beautiful.

    By comparing the 1995 and 2014 pictures, astronomers also noticed a lengthening of a narrow jet-like feature that may have been ejected from a newly forming star. The jet looks like a stream of water from a garden hose. Over the intervening 19 years, this jet has stretched farther into space, across an additional 60 billion miles, at an estimated speed of about 450,000 miles per hour.

    Our sun probably formed in a similar turbulent star-forming region. There is evidence that the forming solar system was seasoned with radioactive shrapnel from a nearby supernova. That means that our sun was formed as part of a cluster that included stars massive enough to produce powerful ionizing radiation, such as is seen in the Eagle Nebula. “That’s the only way the nebula from which the sun was born could have been exposed to a supernova that quickly, in the short period of time that represents, because supernovae only come from massive stars, and those stars only live a few tens of millions of years,” Scowen explained. “What that means is when you look at the environment of the Eagle Nebula or other star-forming regions, you’re looking at exactly the kind of nascent environment that our sun formed in.”

    See the full article here.

    Pillars in Near Infrared from ESO’s VLT
    3

    The 8.2-meter VLT’s ANTU telescope imaged the famous “Pillars of Creation” region and its surroundings in near-infrared using the ISAAC instrument. This enabled astronomers to penetrate the obscuring dust in their search to detect newly formed stars. The near-infrared results showed that 11 of the Pillars’ 73 evaporating gaseous globules (or EGGs) possibly contained stars, and that the tips of the pillars contain stars and nebulosity not seen in the Hubble image.

    ESA Video showing the Pillars in a variety of wavelengths.

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    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

    NASA leads the nation on a great journey of discovery, seeking new knowledge and understanding of our planet Earth, our Sun and solar system, and the universe out to its farthest reaches and back to its earliest moments of existence. NASA’s Science Mission Directorate (SMD) and the nation’s science community use space observatories to conduct scientific studies of the Earth from space to visit and return samples from other bodies in the solar system, and to peer out into our Galaxy and beyond. NASA’s science program seeks answers to profound questions that touch us all:

    This is NASA’s science vision: using the vantage point of space to achieve with the science community and our partners a deep scientific understanding of our planet, other planets and solar system bodies, the interplanetary environment, the Sun and its effects on the solar system, and the universe beyond. In so doing, we lay the intellectual foundation for the robotic and human expeditions of the future while meeting today’s needs for scientific information to address national concerns, such as climate change and space weather. At every step we share the journey of scientific exploration with the public and partner with others to substantially improve science, technology, engineering and mathematics (STEM) education nationwide.

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  • richardmitnick 8:10 pm on January 7, 2015 Permalink | Reply
    Tags: , Astrophysics, , ,   

    From NOAO: “Smashing Results About Our Nearby Galactic Neighbors” 

    NOAO Banner

    January 5, 2015
    Dr. Katy Garmany
    Deputy Press Officer
    National Optical Astronomy Observatory
    950 N Cherry Ave
    Tucson AZ 85719 USA
    +1 520-318-8526
    E-mail: kgarmany@noao.edu

    The Magellanic Clouds are the two brightest nearby satellite galaxies to our own Milky Way galaxy. From a new study it appears that not only are they much bigger than astronomers calculated, but also have non-uniform structure at their outer edge, hinting at a rich and complex field of debris left over from their formation and interaction. This is an early result from a survey called SMASH, for “Survey of the MAgellanic Stellar History”, carried out by an international team of astronomers using telescopes that include the Blanco 4-meter at Cerro Tololo Inter-American Observatory (CTIO) in Chile and presented today at the 225th meeting of the American Astronomical Society in Seattle, Washington.

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M. Blanco 4 meter Telescope

    The Large and Small Magellanic Clouds are dominant features in the Southern hemisphere sky. Although named after explorer Ferdinand Magellan who brought them to the attention of Europeans, they were already known to every early culture in the Southern hemisphere. The Large Cloud (LMC), covering about 5 degrees in angular size (10 lunar diameters), appears to the naked eye like a detached piece of the Milky Way. At a distance from us of about 160 thousand light years, even the brightest stars in these galaxies can’t be seen without a telescope.

    lmc
    The Large Magellanic Cloud

    s
    Small Magellanic Cloud

    As principal investigator Dr. David Nidever (University of Michigan) says, “We have a decent understanding of how large galaxies like the Milky Way form, but most galaxies in the universe are faint, distant, dwarf galaxies. The Magellanic Clouds are two of the few nearby dwarf galaxies, and SMASH is able to map out and study the structures in them like no other survey has been able to do before.”

    “We knew from the earlier work of SMASH team members that the LMC was larger than we thought, but those observations probed only 1 percent of the area that we need to explore. SMASH is probing an area 20 times larger, and is confirming beyond doubt that the LMC is really large while also giving us a chance to map its structure in detail.” said Dr. Knut Olsen (National Optical Astronomy Observatory) one of the leaders of the SMASH team. The team has identified stars belonging to the LMC at angular distances up to 20 degrees away, corresponding to 55 thousand light years. This was done using a new camera, dubbed DECam, mounted on the CTIO Blanco 4-meter telescope, which allows the SMASH team to identify faint stars over a much larger area than ever before.

    DECam
    DECam, built at FNAL

    With the Blanco telescope, SMASH can detect exceptionally diffuse stellar structures – up to 400,000 times fainter than the appearance of the faint band of the Milky Way in the night sky. This is possible because DECam can distinguish individual faint Magellanic stars over a huge area. (In astronomical parlance, the survey can reach a surface brightness limit of ~35 magnitudes per square arc second). That allows the team to detect stellar structures that were previously much too faint to see.

    The team is also exploring the Magellanic Stream, a gaseous structure that connects the two Clouds and extends in front and behind them. The existence of the Magellanic Stream, first detected with radio telescopes over 30 years ago, clearly indicates that the two galaxies are interacting with each other and with our Milky Way. Astronomers have long expected to also find stars in the Stream but so far none have been detected. It’s likely this is because the stellar component of the Stream is too faint to have been detected until the availability of the new camera. As Dr. Nidever said, “SMASH’s ability to reveal super-faint stellar structures should not only allow us to finally detect the stellar component of the Magellanic Stream but also map out its structure which will give us a much better understanding of the Magellanic Clouds’ interaction history.”

    See the full article here.

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    NOAO News
    NOAO is the US national research & development center for ground-based night time astronomy. In particular, NOAO is enabling the development of the US optical-infrared (O/IR) System, an alliance of public and private observatories allied for excellence in scientific research, education and public outreach.

    Our core mission is to provide public access to qualified professional researchers via peer-review to forefront scientific capabilities on telescopes operated by NOAO as well as other telescopes throughout the O/IR System. Today, these telescopes range in aperture size from 2-m to 10-m. NOAO is participating in the development of telescopes with aperture sizes of 20-m and larger as well as a unique 8-m telescope that will make a 10-year movie of the Southern sky.

    In support of this mission, NOAO is engaged in programs to develop the next generation of telescopes, instruments, and software tools necessary to enable exploration and investigation through the observable Universe, from planets orbiting other stars to the most distant galaxies in the Universe.

    To communicate the excitement of such world-class scientific research and technology development, NOAO has developed a nationally recognized Education and Public Outreach program. The main goals of the NOAO EPO program are to inspire young people to become explorers in science and research-based technology, and to reach out to groups and individuals who have been historically under-represented in the physics and astronomy science enterprise.

    About Our Observatories:
    Kitt Peak National Observatory (KPNO)

    Kitt Peak

    Kitt Peak National Observatory (KPNO) has its headquarters in Tucson and operates the Mayall 4-meter, the 3.5-meter WIYN , the 2.1-meter and Coudé Feed, and the 0.9-meter telescopes on Kitt Peak Mountain, about 55 miles southwest of the city.

    Cerro Tololo Inter-American Observatory (CTIO)

    NOAO Cerro Tolo

    The Cerro Tololo Inter-American Observatory (CTIO) is located in northern Chile. CTIO operates the 4-meter, 1.5-meter, 0.9-meter, and Curtis Schmidt telescopes at this site.

    The NOAO System Science Center (NSSC)

    Gemini North
    Gemini North

    Gemini South telescope
    Gemini South

    The NOAO System Science Center (NSSC) at NOAO is the gateway for the U.S. astronomical community to the International Gemini Project: twin 8.1 meter telescopes in Hawaii and Chile that provide unprecendented coverage (northern and southern skies) and details of our universe.

    NOAO is managed by the Association of Universities for Research in Astronomy under a Cooperative Agreement with the National Science Foundation.

     
  • richardmitnick 10:42 am on January 7, 2015 Permalink | Reply
    Tags: , , Astrophysics, ,   

    From Astronomy: “Making dreams reality” 

    Astronomy magazine

    Astronomy Magazine

    January 07, 2015
    Korey Haynes

    One of the coolest things about being at the American Astronomical Society (AAS) meeting is hearing about the future of space science straight from the source. Last night I got to hear about the far future of space observatories — what comes after the James Webb Space Telescope (JWST), set to launch in 2018. The next, next big project, currently dubbed the High Definition Space Telescope (if you don’t like it, the name will almost certainly change before launch), imagines the world’s leading ground-based telescopes of today, but in space.

    NASA Webb Telescope
    Webb

    The idea is for a 10- to 12-meter segmented mirror, which is similar to the currently existing Keck telescopes. It would fly, like JWST, at an Earth-Sun Lagranian point, and it would have capabilities from the ultraviolet to the infrared. In most ways, it would represent at least an order of magnitude improvement over JWST’s abilities.

    Keck Observatory
    Keck Observatory Interior
    Keck

    Why do we need an order of magnitude improvement over the most cutting-edge telescope we’re currently able to produce? Think of it this way: There only will be a handful of rocky planets close enough and bright enough for JWST to search for signs of life. It’s just not precise enough to study the farther, dimmer candidates satisfactorily. If the odds are only 1 in 10 that an Earth “twin” actually supports life (a reasonable fraction), do you want to take your chances and only able to study five planets? Better by far to study 50. That’s one of the many drivers to keep pushing for bigger, better telescopes for the future.

    While it may seem a bit premature to start thinking beyond JWST, it takes decades to walk a giant project like this from first concept to first light. JWST began its planning just after the launch of Hubble, so we’re actually right on track to start thinking about the succeeding generation, which would launch in the mid 2030s. By then, perhaps we even could fly servicing missions to such an observatory.

    Tuesday morning, we heard updates from the European Space Agency (ESA) on the Gaia mission, whose slogan is “a billion pixels for a billion stars.”

    ESA Gaia satellite
    Gaia

    Gaia is a space telescope with a gigapixel detector and two mirrors that fly in close formation. Its main purpose is astrometry, or measuring the positional change of stars on the sky, which Gaia accomplishes by observing them repeatedly as the spacecraft orbits. It can measure positions to such an accuracy that from Astronomy’s offices near Milwaukee, Wisconsin, it could measure the width of a human hair in Washington, D.C.

    Gaia is the successor to a mission called Hipparcos that operated between 1989 and 1993. Hipparcos was a revolutionary project, and its catalog consists of 120,000 stars. Gaia will measure more than one thousand million stars when its survey is complete. With a catalog that enormous and precise, it will find thousands of exoplanets through radial velocity searches. It will tell us unprecedented detail about stellar populations and even deliver detailed information about near-Earth objects.

    ESA Hipparcus spacecraft
    Hipparcos

    Gaia was launched back in 2013 and started collecting data in July. It will take almost two more years before it returns its first big results in astrometry, but it’s already found its first supernova and is working just as expected.

    Gaia will return the data set of a lifetime. It’s the manifestation of a dream when astronomers looked at Hipparcos and said, “Yes, but we can do even better.” Now astronomers right here, right now, are looking at JWST, the pinnacle of space observatories, and thinking the same thing. Imagine what we’ll be imagining in twenty more years.

    See the full article here.

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  • richardmitnick 10:08 am on January 7, 2015 Permalink | Reply
    Tags: , Astrophysics, , , Dennis Overbye - New York Times   

    From NYT: Dennis Overbye “So Many Earth-Like Planets, So Few Telescopes” 

    New York Times

    The New York Times

    JAN. 6, 2015

    NYT Dennis Overbye
    DENNIS OVERBYE

    It’s a big universe, but it’s full of small planets.

    Astronomers announced on Tuesday that they had found eight new planets orbiting their stars at distances compatible with liquid water, bringing the total number of potentially habitable planets in the just-right “Goldilocks” zone to a dozen or two, depending on how the habitable zone of a star is defined.

    NASA’s Kepler spacecraft, now in its fifth year of seeking out the shadows of planets circling other stars, has spotted hundreds, and more and more of these other worlds look a lot like Earth — rocky balls only slightly larger than our own home, that with the right doses of starlight and water could turn out to be veritable gardens of microbial Eden.

    NASA Kepler Telescope
    Kepler

    As the ranks of these planets grow, astronomers are planning the next step in the quest to end cosmic loneliness: gauging which hold the greatest promise for life and what tools will be needed to learn about them.
    Continue reading the main story

    The planets unveiled on Tuesday were detected by a group led by Guillermo Torres of the Harvard-Smithsonian Center for Astrophysics.

    On Monday, another group of astronomers said they had managed to weigh precisely a set of small planets and found that their densities and compositions almost exactly matched those of Earth.

    Courtney Dressing, also of the Harvard-Smithsonian Center for Astrophysics, said at a news conference, “I’m going to give you the recipe for a rocky planet.”

    She began, “Take one cup of magnesium …”

    Both groups announced their findings at a meeting of the American Astronomical Society in Seattle.

    Reviewing the history of exoplanets, Debra Fischer, a Yale astronomer, recalled that the first discovery of a planet orbiting another normal star, a Jupiter-like giant, was 20 years ago. Before that, she said, astronomers worried that “maybe the ‘Star Trek’ picture of the universe was not right, and there is no life anywhere else.”

    Dr. Fischer called the progress in the last two decades “incredibly moving.”

    And yet we still do not have a clue that we are not alone.

    And yet, I can’t help but feel a certain measure of bittersweetness, because without a dramatic paradigm shift in propulsion technology, even a nearby Earth 2.0 will be forever beyond our reach.

    So far, Kepler has discovered 4,175 potential planets, and 1,004 of them have been confirmed as real, according to Michele Johnson, a spokeswoman for NASA’s Ames Research Center, which operates Kepler.

    Most of them, however, including those announced Tuesday, are hundreds of light-years away, too far for detailed study. We will probably never know any more about these particular planets than we do now.

    “We can count as many as we like,” said Sara Seager, a planet theorist at the Massachusetts Institute of Technology who was not involved in the new work, “but until we can observe the atmospheres and assess their greenhouse gas power, we don’t really know what the surface temperatures are like.”

    Still, she added, “it’s heartening to have such a growing list.”

    Finding Goldilocks planets closer to home will be the job of the Transiting Exoplanet Survey Satellite, to be launched in 2017. But if we want to know what the weather is like on these worlds, whether there is water or even life, more powerful instruments will be needed.

    NASA TESS
    TESS

    Dr. Seager is heading a NASA study investigating the concept of a starshade, which would float in front of a space telescope and block light from a star so that its much fainter planets would be visible.

    Another group, led by Karl Stapelfeldt of NASA’s Goddard Space Flight Center, is studying a method known as a coronagraph, in which the occulting disk is inside the telescope.

    Both studies are expected to be completed in the next few months, and could affect plans for a former spy telescope bequeathed to NASA three years ago. Astronomers hope to launch it in the early 2020s to study dark energy, and they plan to include a coronagraph to search for exoplanets, according to Paul Schechter of M.I.T., chairman of a design team. Depending on the probe’s orbit, Dr. Seager said, it could also be made “starshade ready.”

    NASA’s James Webb Space Telescope, due for a 2018 launch, will have a coronagraph capable of seeing Jupiter-size planets, but it is too late to adapt it to a starshade.

    NASA Webb Telescope
    Webb

    Meanwhile, Dr. Seager and Julianne Dalcanton of the University of Washington are writing a separate report for a consortium of universities that runs observatories. The goal is to have a pool of dozens of “exo-Earths” to study in order to have any chance of seeing signs of life or understanding terrestrial planets, Dr. Seager said. Amassing them will require a space telescope 10 or 12 meters in diameter (the Webb will be 6.5 meters, and the largest currently on Earth is 10).

    All of this will be grist for the mill at the end of the decade when a panel of the National Academy of Sciences produces its wish list for astronomy in the 2020s.

    For all of Kepler’s bounty, a planet like Earth, of the same size orbiting the same type of star, has not yet been confirmed. The most terrestrial of the new worlds announced Tuesday are a pair known as Kepler 438b and Kepler 442b, both orbiting stars slightly smaller, cooler and redder than our sun. Kepler 438b is only 12 percent larger than Earth in diameter and has a 35-day year; Kepler 442 is a third larger than Earth and has a 112-day year.

    “All these are small, all are potentially habitable,” said Doug Caldwell of the SETI Institute and NASA Ames at a news conference in Seattle.

    In a news release, Dr. Torres said, “Most of these planets have a good chance of being rocky, like Earth.” That thought was reinforced by his colleagues, led by Ms. Dressing, a doctoral candidate at Harvard. Her group combined data from Kepler, which measures the sizes of planets, with spectrographic observations from an Italian telescope in the Canary Islands. That instrument measures planets’ masses to determine their densities, and by combining the information Ms. Dressing’s group was able to infer the densities and compositions of a set of small planets.

    Telescoipio Nazionale Galileo
    Telescopio Nazionale Galileo Interior
    Telescopio Nazionale Galileo

    All five of the planets smaller than 1.6 times the size of Earth fell on a line consistent with Earth and Venus. Planets larger than that, Ms. Dressing and her colleagues found, were fluffier, perhaps because as planets get bigger their mass and gravity increase, and they are better able to hang on to gas and lighter components.

    The work complements and tightens studies done last year by Geoffrey Marcy and his colleagues at the University of California, Berkeley; that group looks into the nature of so-called super Earths, planets bigger than ours and smaller than Neptune.

    There are no planets in this range in our solar system, but according to Kepler they are common in the galaxy. Are they rocks like Earth or blobs like Neptune? The break point now seems to be 1.6 times the size of Earth, according to Ms. Dressing, and it is on those planets, perhaps, that we should concentrate our search for cosmic company.

    As she said in her presentation, “Doubling the recipe doesn’t work.”

    See the full article here.

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  • richardmitnick 7:34 am on January 7, 2015 Permalink | Reply
    Tags: , Astrophysics, , ,   

    From ESO: “Where Did All the Stars Go?” 


    European Southern Observatory

    7 January 2015
    Richard Hook
    ESO education and Public Outreach Department
    Garching bei München, Germany

    Tel: +49 89 3200 6655
    Email: rhook@eso.org

    Some of the stars appear to be missing in this intriguing new ESO image. But the black gap in this glitteringly beautiful starfield is not really a gap, but rather a region of space clogged with gas and dust. This dark cloud is called LDN 483 — for Lynds Dark Nebula 483. Such clouds are the birthplaces of future stars. The Wide Field Imager, an instrument mounted on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile, captured this image of LDN 483 and its surroundings.

    ESO Wide Field Imager 2.2m LaSilla
    WFI

    ESO MPG 2.2 meter telescope
    MPG/ESO 2.2-metre telescope

    ESO LaSilla Long View
    ESO LaSilla

    l

    LDN 483 [1] is located about 700 light-years away in the constellation of Serpens (The Serpent). The cloud contains enough dusty material to completely block the visible light from background stars. Particularly dense molecular clouds, like LDN 483, qualify as dark nebulae because of this obscuring property. The starless nature of LDN 483 and its ilk would suggest that they are sites where stars cannot take root and grow. But in fact the opposite is true: dark nebulae offer the most fertile environments for eventual star formation.

    Astronomers studying star formation in LDN 483 have discovered some of the youngest observable kinds of baby stars buried in LDN 483’s shrouded interior. These gestating stars can be thought of as still being in the womb, having not yet been born as complete, albeit immature, stars.

    In this first stage of stellar development, the star-to-be is just a ball of gas and dust contracting under the force of gravity within the surrounding molecular cloud. The protostar is still quite cool — about –250 degrees Celsius — and shines only in long-wavelength submillimetre light [2]. Yet temperature and pressure are beginning to increase in the fledgling star’s core.

    This earliest period of star growth lasts a mere thousands of years, an astonishingly short amount of time in astronomical terms, given that stars typically live for millions or billions of years. In the following stages, over the course of several million years, the protostar will grow warmer and denser. Its emission will increase in energy along the way, graduating from mainly cold, far-infrared light to near-infrared and finally to visible light. The once-dim protostar will have then become a fully luminous star.

    As more and more stars emerge from the inky depths of LDN 483, the dark nebula will disperse further and lose its opacity. The missing background stars that are currently hidden will then come into view — but only after the passage of millions of years, and they will be outshone by the bright young-born stars in the cloud [3].
    Notes

    [1] The Lynds Dark Nebula catalogue was compiled by the American astronomer Beverly Turner Lynds, and published in 1962. These dark nebulae were found from visual inspection of the Palomar Sky Survey photographic plates.

    [2] The Atacama Large Millimeter/submillimeter Array (ALMA), operated in part by ESO, observes in submillimetre and millimetre light and is ideal for the study of such very young stars in molecular clouds.

    [3] Such a young open star cluster can be seen here, and a more mature one here.

    See the full article here.

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  • richardmitnick 6:06 pm on January 6, 2015 Permalink | Reply
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    From LLNL: “NuSTAR Peers Into the Neutron Star Zoo” 


    Lawrence Livermore National Laboratory

    December 2014
    Caryn Meissner

    n

    NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) is the first focusing observatory deployed in orbit for measuring hard x-ray energies between 3 and 80 kiloelectronvolts (keV). NuSTAR contains two focusing telescopes and an array of detectors and is more sensitive than previous technologies for this energy range. The composite background image shows low-energy (soft) x-ray data collected by NASA’s Chandra X-Ray Observatory, infrared data captured by the Spitzer Space Telescope, and pulsar PSR J1640-4631 (blue), which was discovered by NuSTAR and lies in the inner Milky Way galaxy. (Courtesy of NASA, Jet Propulsion Laboratory [JPL], and California Institute of Technology [Caltech].)

    NASA Chandra Telescope
    Chandra

    NASA Spitzer Telescope
    Spitzer

    The deaths of stars are not as final as they seem. These often-violent events give rise to exotic stellar remnants that are dispersed throughout the cosmos. Neutron stars, for example, are created when very massive stars (those with a mass between 10 and 30 times that of our Sun) exhaust their supply of nuclear fuel and die in supernovae explosions. The star generated from such a spectacular event has a radius of about 10 kilometers, mass around 1.5 times that of the Sun, and density of roughly 1017 kilograms per cubic meter (close to the density of a black hole). Neutron stars are thus some of the tiniest, densest celestial objects in the known universe, and they exhibit some of the strongest magnetic fields ever observed. As they are born, they spin rapidly, and this spinning in conjunction with their high magnetic fields produces intermittent pulses of intense radio, x-ray, and gamma-ray emissions.

    More than 40 years after their discovery in the late 1960s, neutron stars continue to intrigue and astonish scientists. “Neutron stars are extreme objects,” says Livermore astrophysicist Julia Vogel, who works in the Physical and Life Sciences Directorate. “Just imagine something with the mass of our Sun squeezed into the San Francisco peninsula spinning at the speed of a household blender.” Although neutron stars were initially believed to belong to a uniform, simple class of stars, research over the last decade has revealed a “zoo” of objects with remarkably diverse properties and behaviors.

    The study of neutron stars has been given a significant boost with the Nuclear Spectroscopic Telescope Array (NuSTAR), a NASA Small Explorer Mission launched in 2012. The technology behind NuSTAR has its roots in Livermore-based research and development. (See S&TR, March 2006, Floating into Thin Air.) With its two x-ray telescopes and advanced semiconductor detectors, NuSTAR achieves sensitivity 100 times greater and resolution 10 times better than previous high-energy satellite observatories.

    In 2013, Vogel began leading a Laboratory Directed Research and Development (LDRD) project that uses NuSTAR to study the hard x-ray emission produced by magnetars—neutron stars with extremely strong magnetic fields. Her team, which includes Laboratory scientist Michael Pivovaroff and astrophysicist Victoria Kaspi from Canada’s McGill University, are using data from NuSTAR to delve further into the energetic nature of neutron stars. NuSTAR’s ability to observe emission at higher angular and energy resolutions will help the researchers better understand how neutron stars produce x rays and whether a star’s properties are determined at birth or are influenced by its environment.

    “Our goal is to develop a ‘grand unification theory’—an overarching theory of neutron star physics and the birth properties of these objects—to explain their incredible diversity,” says Vogel. “NuSTAR observations are helping us understand these ubiquitous and mysterious stellar objects, which will improve our knowledge of stellar evolution, galactic population synthesis, and the study of matter under extreme conditions.”

    m
    Magnetars, such as the one in this artist’s rendering, are thought to be newly formed, isolated stars that have extremely powerful magnetic fields and emit radiation from their magnetic poles. Their irregular bursts of energy affect their rotational period and visibility. (Courtesy of European Southern Observatory.)

    Unpredictable Behavior

    Neutron star types are characterized by the star’s rotational period and the rate at which it slows. By measuring these two properties, scientists can derive the strength of a star’s magnetic field and its age. Most neutron stars were discovered by detecting the radio-frequency signals emitted when kinetic energy is converted into electromagnetic energy (via the stars’ magnetic braking). Because a radio pulsar’s spin axis does not align with its magnetic field, its emissions seem to pulse when viewed from Earth. Radio pulsars are thousands to hundreds of millions of years old, and they exhibit a very large range of magnetic field strengths.

    Magnetars, on the other hand, are the youngest neutron stars and have the most powerful magnetic fields among pulsars, measuring up to a quadrillion (1015) gauss. Magnetars also produce emission observable as periodic pulsation, but they spin more slowly than typical radio pulsars, completing a revolution in 1 to 10 seconds instead of 1 millisecond or less. Interestingly, kinetic energy in spinning magnetars is insufficient for explaining the intensity of their energetic x-ray pulses. “Way more energy comes from magnetars than their kinetic energy alone would allow,” says Pivovaroff, whose expertise is in x-ray optics and astronomy. In addition, the temperamental stars are prone to irregular outbursts of electromagnetic radiation that can affect their rotational period and visibility. “We know their location precisely,” adds Pivovaroff. “Yet sometimes magnetars cannot be detected, and at other times, they are really bright, with intensity increasing by a factor of 10 to several hundreds.”

    The current theory is that magnetars produce x-ray and gamma radiation through the decay of their inner magnetic fields, but the underlying physics and production mechanisms for electromagnetic generation are not well understood. Previous attempts to study magnetar properties in detail were hindered by the limited imaging capabilities of the available hard x-ray observatories. The hard x-ray band is important because it is a transition region from thermal processes to nonthermal ones. NuSTAR is the first focusing hard x-ray observatory deployed in orbit for measuring energies between 3 and 80 kiloelectronvolts (keV). Its two multilayer-coated telescopes image hard x rays onto a sophisticated detector array, which is separated from the optics by a 10-meter mast. The optics, which the Livermore team helped design, build, and calibrate, are key to NuSTAR’s improved resolution.

    During the first year of the LDRD study, the research team created data-analysis tools, including novel algorithms based on existing codes, to interpret the NuSTAR measurements. “Prior to conducting scientific observations, we had the instrument look at well-documented stellar objects as part of our in-orbit calibration efforts,” says Vogel. “We then compared the data to our physics-based computational models, which were designed to predict what we would see in space.”

    The NuSTAR team discovered that ground calibration models could not fully explain the instrument’s in-orbit measurements. This finding was not completely unexpected because simplified models were being used to describe extremely complex phenomena. “The calibration data helped us further improve the models and better understand the discrepancies,” says Vogel. “At Livermore, we were responsible for precision metrology, evaluation, and implementation of results into the ray trace modeling.” Ultimately, the NuSTAR team improved the physics models in the simulations, which reduced the discrepancies between model results and observed data to a level comparable to that achieved for other missions.

    With NuSTAR, researchers can retrieve more detailed images of stellar objects by measuring hard-x-ray emissions. The ROSAT (Röntgen Satellite) Mission, which records emissions between 0.1 and 2.4 keV, captured the left image of supernova remnant CTB109 and magnetar 1E 2259+586 (bright point). The white frame indicates the NuSTAR field of view. (right) Spectroscopic data recorded by NuSTAR in the 3- to 80-keV range provide more details on the magnetar and its environment.

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    With NuSTAR, researchers can retrieve more detailed images of stellar objects by measuring hard-x-ray emissions. The ROSAT (Röntgen Satellite) Mission, which records emissions between 0.1 and 2.4 keV, captured the left image of supernova remnant CTB109 and magnetar 1E 2259+586 (bright point). The white frame indicates the NuSTAR field of view. (right) Spectroscopic data recorded by NuSTAR in the 3- to 80-keV range provide more details on the magnetar and its environment.

    NASA ROSAT staellite
    ROSAT

    A High-Energy Revelation

    In 2014, the research team focused on detecting and analyzing the hard x-ray spectra from several magnetars. “We took an extensive look at one of the most studied magnetars (1E 2259+586), which prior to NuSTAR had been only marginally detected in the hard x-ray energy range,” says Vogel. Spectroscopic techniques determine what energies are emitted by the magnetars and how the spectra differ for the pulsed and constant emission. “We detected hard x-ray pulsations above 20 keV for the first time and studied the magnetar’s spectrum at higher energies than were previously accessible,” she adds. “The hard x-ray data revealed that additional spectral components, which were not required for lower energy (or soft) x-ray measurements alone, were needed to describe the magnetar’s hard and soft x-ray emission together.”

    The team fit the x-ray data obtained from NuSTAR to a recently developed electron–positron outflow model called the Beloborodov model, which could explain the properties and origin of the x-ray emission. “We determined spectral parameters, pulse profile, and pulsed fractions for the NuSTAR data and were able to support the theoretical model,” says Vogel. “Even though current data do not tightly constrain the model parameters, we found that the outflow is likely to originate from a ring on the magnetar rather than from its polar cap, which is surprising.” The team’s findings also support a connection between the spectral turnover and the star’s magnetic fields, consistent with previous observations of other magnetars.

    Using a similar analysis approach, the team characterized a newly discovered magnetar. “We obtained the first timing information of the star, showing that its spin-down rate increased without a glitch,” says Vogel, explaining that a glitch is the sudden spin-up or spin-down that can occur when fluid inside a neutron star rotates faster than the star’s crust. “Because no glitch was observed, the increase is likely to be of magnetospheric origin.”

    The researchers also analyzed spectra from pulsar wind nebulae. These objects form when charged particles are accelerated to relativistic speeds by the neutron star’s rapidly spinning, extremely strong magnetic fields, and they are shocked when constrained by the environment surrounding the star. Observing pulsar wind nebulae will help the team identify the composition of outflowing matter and the relative amount of energy stored in the outflow particle versus the magnetic fields. “Hard x-ray studies enable us to analyze systems where soft x rays are absorbed by interstellar dust,” says Vogel. “The first observations of the Geminga pulsar wind nebula were used for spectroscopy, and the rotation-powered pulsar was detected for the first time in hard x rays above 10 keV.”

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    This composite image of the nebula around pulsar PSR B1509-58 illustrates pulsar wind nebulae. Data were recorded by the Chandra X-Ray Observatory at 0.5 to 2 keV (red) and 2 to 4 keV (green) and by NuSTAR at 7 to 25 keV (blue). NuSTAR’s hard x-ray view reveals the central pulsar. Similar images were obtained for Geminga. (Courtesy of NASA, JPL, Caltech, and McGill University.)

    Resolving Mysteries in X-Ray Astronomy

    “What is being achieved with NuSTAR and Julia’s team is a culmination of more than 10 years of LDRD support,” says Pivovaroff, who worked on the NuSTAR design and helped build the instrument. “Livermore had the long-term commitment and vision to invest in early technology development. Now that it has transitioned into a satellite instrument, we are using the technology to further our understanding of fundamental science.”

    As Vogel and her team continue to advance knowledge of neutron star physics, they look forward to resolving other mysteries in x-ray astronomy. “We can leverage the experience gained from NuSTAR for developing the next generation of x-ray telescopes,” she says. “By being involved in building NuSTAR and its science mission, we can gain a better understanding of what capabilities will be needed for future astrophysics research.” As this research continues, Vogel eagerly anticipates the discoveries to be made during the next year. Only time will tell whether the “animals” in the neutron star zoo share a common connection or if each is a breed of its own.

    See the full article here.

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