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  • richardmitnick 3:44 pm on June 14, 2016 Permalink | Reply
    Tags: , FU Orionis Gluttonous Star May Hold Clues to Planet Formation, , ,   

    From JPL-Caltech: “Gluttonous Star May Hold Clues to Planet Formation” 

    NASA JPL Banner

    JPL-Caltech

    June 14, 2016
    Elizabeth Landau
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-6425
    elizabeth.landau@jpl.nasa.gov

    1
    The brightness of outbursting star FU Orionis has been slowly fading since its initial flare-up in 1936. Researchers found that it has dimmed by about 13 percent in short infrared wavelengths from 2004 (left) to 2016 (right). Credit: NASA/JPL-Caltech

    In 1936, the young star FU Orionis began gobbling material from its surrounding disk of gas and dust with a sudden voraciousness. During a three-month binge, as matter turned into energy, the star became 100 times brighter, heating the disk around it to temperatures of up to 12,000 degrees Fahrenheit (7,000 Kelvin). FU Orionis is still devouring gas to this day, although not as quickly.

    This brightening is the most extreme event of its kind that has been confirmed around a star the size of the sun, and may have implications for how stars and planets form. The intense baking of the star’s surrounding disk likely changed its chemistry, permanently altering material that could one day turn into planets.

    “By studying FU Orionis, we’re seeing the absolute baby years of a solar system,” said Joel Green, a project scientist at the Space Telescope Science Institute, Baltimore, Maryland. “Our own sun may have gone through a similar brightening, which would have been a crucial step in the formation of Earth and other planets in our solar system.”

    Visible light observations of FU Orionis, which is about 1,500 light-years away from Earth in the constellation Orion, have shown astronomers that the star’s extreme brightness began slowly fading after its initial 1936 burst. But Green and colleagues wanted to know more about the relationship between the star and surrounding disk. Is the star still gorging on it? Is its composition changing? When will the star’s brightness return to pre-outburst levels?

    To answer these questions, scientists needed to observe the star’s brightness at infrared wavelengths, which are longer than the human eye can see and provide temperature measurements.

    Green and his team compared infrared data obtained in 2016 using the Stratospheric Observatory for Infrared Astronomy, SOFIA, to observations made with NASA’s Spitzer Space Telescope in 2004.

    NASA/DLR SOFIA
    NASA/DLR SOFIA

    NASA/Spitzer Telescope
    NASA/Spitzer Telescope

    SOFIA, the world’s largest airborne observatory, is jointly operated by NASA and the German Aerospace Center and provides observations at wavelengths no longer attainable by Spitzer. The SOFIA data were taken using the FORCAST instrument (Faint Object infrared Camera for the SOFIA Telescope).

    NASA/SOFIA Forcast
    NASA/SOFIA Forcast

    “By combining data from the two telescopes collected over a 12-year interval, we were able to gain a unique perspective on the star’s behavior over time,” Green said. He presented the results at the American Astronomical Society meeting in San Diego, this week.

    Using these infrared observations and other historical data, researchers found that FU Orionis had continued its ravenous snacking after the initial brightening event: The star has eaten the equivalent of 18 Jupiters in the last 80 years.

    The recent measurements provided by SOFIA inform researchers that the total amount of visible and infrared light energy coming out of the FU Orionis system decreased by about 13 percent over the 12 years since the Spitzer observations. Researchers determined that this decrease is caused by dimming of the star at short infrared wavelengths, but not at longer wavelengths. That means up to 13 percent of the hottest material of the disk has disappeared, while colder material has stayed intact.

    “A decrease in the hottest gas means that the star is eating the innermost part of the disk, but the rest of the disk has essentially not changed in the last 12 years,” Green said. “This result is consistent with computer models, but for the first time we are able to confirm the theory with observations.”

    Astronomers predict, partly based on the new results, that FU Orionis will run out of hot material to nosh on within the next few hundred years. At that point, the star will return to the state it was in before the dramatic 1936 brightening event. Scientists are unsure what the star was like before or what set off the feeding frenzy.

    “The material falling into the star is like water from a hose that’s slowly being pinched off,” Green said. “Eventually the water will stop.”

    If our sun had a brightening event like FU Orionis did in 1936, this could explain why certain elements are more abundant on Mars than on Earth. A sudden 100-fold brightening would have altered the chemical composition of material close to the star, but not as much farther from it. Because Mars formed farther from the sun, its component material would not have been heated up as much as Earth’s was.

    At a few hundred thousand years old, FU Orionis is a toddler in the typical lifespan of a star. The 80 years of brightening and fading since 1936 represent only a tiny fraction of the star’s life so far, but these changes happened to occur at a time when astronomers could observe.

    “It’s amazing that an entire protoplanetary disk can change on such a short timescale, within a human lifetime,” said Luisa Rebull, study co-author and research scientist at the Infrared Processing and Analysis Center (IPAC), based at Caltech, Pasadena, California.

    Green plans to gain more insight into the FU Orionis feeding phenomenon with NASA’s James Webb Space Telescope, which will launch in 2018.

    NASA/ESA/CSA Webb Telescope annotated
    NASA/ESA/CSA Webb Telescope annotated

    SOFIA has mid-infrared high-resolution spectrometers and far-infrared science instrumentation that complement Webb’s planned near- and mid-infrared capabilities. Spitzer is expected to continue exploring the universe in infrared light, and enabling groundbreaking scientific investigations, into early 2019.

    NASA’s Jet Propulsion Laboratory, Pasadena, California, manages the Spitzer Space Telescope mission for NASA. Science operations are conducted at the Spitzer Science Center at Caltech. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at IPAC at Caltech. Caltech manages JPL for NASA.

    SOFIA is a joint project of NASA and the German Aerospace Center (DLR). The aircraft is based at NASA Armstrong Flight Research Center’s facility in Palmdale, California. NASA’s Ames Research Center in Moffett Field, California, manages the SOFIA science and mission operations in cooperation with the Universities Space Research Association (USRA) headquartered in Columbia, Maryland, and the German SOFIA Institute (DSI) at the University of Stuttgart.

    For more information about Spitzer, visit:

    http://www.nasa.gov/spitzer

    http://spitzer.caltech.edu

    For more information about SOFIA, visit:

    http://www.nasa.gov/sofia

    http://www.dlr.de/en/sofia

    See the full article here .

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    NASA JPL Campus

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

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  • richardmitnick 2:51 pm on June 10, 2016 Permalink | Reply
    Tags: 80 Percent of Humankind Can’t See the Milky Way Anymore, , , ,   

    From natgeo: “80 Percent of Humankind Can’t See the Milky Way Anymore” 

    National Geographic

    National Geographics

    June 10, 2016
    Michelle Z. Donahue

    1
    The Milky Way illuminates the sky over Dinosaur National Monument, which spreads across Colorado and Utah. Photograph by Dan Duriscoe

    The Milky Way galaxy, that torrent of stars that slashes across a deeply darkened night sky, has been a deep well of inspiration from humanity’s earliest days. The ancient Egyptians saw it as a pool of cow’s milk, while in Hindu mythology the arcing galactic arm was likened to a dolphin swimming through the sky. Countless scientists, philosophers, and artists, including Galileo, Aristotle, and Vincent Van Gogh, have drawn upon the galaxy as their muse. (Read “How Much Does the Milky Way Weigh?”)

    But a new atlas of the night sky across the entire globe shows that more than 80 percent of the planet’s land areas—and 99 percent of the population of the United States and Europe—live under skies so blotted with man-made light that the Milky Way has become virtually invisible.

    Fabio Falchi, a researcher at the Light Pollution Science and Technology Institute (ISTIL) in Thiene, Italy, announced Friday the release of a new survey that quantifies nighttime sky quality for every region in the world. Produced using over 35,000 ground-based observations and six months of data from 2014 collected with the Suomi National Polar-orbiting Partnership (NPP) satellite, the atlas is an update to a 2001 work and shows the planet’s darkest and brightest locations in stark contrast.

    NASA/Goddard Suomi NPP satellite
    NASA/Goddard Suomi NPP satellite

    Woe to Singapore, a place of eternal twilight, with the entire population living under skies so bright their eyes cannot fully adjust to night vision, let alone see the Milky Way. Kuwait, Qatar, and the United Arab Emirates have it nearly as bad.

    On the other hand, more than 75 percent of the population of Chad, the Central African Republic, and Madagascar live under near-pristine skies, or places where background light represents less than one percent of the sky’s overall brightness. And according to Falchi’s analysis, residents of the Azores have the distinction of living the farthest from land with unspoiled skies: They’d have to travel nearly 1,100 miles, to the western Sahara, to experience an ancestrally darkened landscape (unless they travel out into the ocean).

    2
    Light pollution clouds the view over Joshua Tree National Park, California. Photograph by Dan Duriscoe

    “In the first atlas we had a hint of what was happening, but these numbers are shocking,” Falchi says. “We have lost the connection with our roots, of literature, of philosophy, of science, of religion—all are connected with the contemplation of the night sky. A new generation can no longer appreciate this beauty.” (“See a Stunning New View of the Milky Way.”)

    Study co-author Dan Duriscoe, a physical scientist with the National Park Service’s Natural Sounds and Night Skies Division, has worked in the Park Service for 36 years and has collected light measurements in national parks since 1994. On the East Coast, apart from a few scattered points in West Virginia, Pennsylvania, and New England, it’s extremely difficult to get to a place with an unfettered view of stars.

    “People could get that experience closer to home decades ago, but now they’re forced out into Utah or Death Valley or Yellowstone, somewhere far from their backyards,” Duriscoe says. “There’s an increased public awareness of how this is a rare experience and becoming one that will cost them some money to go see.”

    High-Tech Eyes on the Sky

    Sweeping over the Earth’s poles 14 times a day, the Suomi satellite generates a complete global set of high-resolution day and night images every 24 hours. Falchi, along with ISTIL colleague Pierantonio Cinzano, worked with data from partners including the National Park Service (NPS) and the National Oceanographic and Atmospheric Administration (NOAA) to produce the atlas. The 2001 atlas looked at only light escaping from Earth into space, while the new data reveal where light is reflected from the sky down to the Earth’s surface. (Read “Graveyard of Stars May Lie at Milky Way’s Center.”)

    Falchi plans to release a print version of the atlas, and an interactive digital atlas, similar to one from 2006 produced using the 2001 data, is also in the works.

    3
    A map illustrates light pollution in North and South America. Illustration by Fabio Falchi, Google Earth

    Chris Elvidge, a co-author of the study and a scientist with NOAA’s National Centers for Environmental Information, says he expects that the satellite data and analysis will be useful not only for astronomers, who have a vested interest in a dark night sky, but also for biologists studying light impacts on nocturnal organisms, medical researchers interested in the human health effects, and city planners.

    One drawback of the satellite’s imaging instruments is limited detection of the blue and violet parts of the visible spectrum—the very zone where white LEDs would show up on satellite scans. Though highly efficient, white LEDs can be excessively bright, and as municipalities begin to install them in streetlights and for other outdoor purposes, the impact of LEDs may actually worsen overall light pollution in the long run.

    “Several cities have jumped on the LED bandwagon without getting their citizens’ approval,” says Connie Walker, an astronomer with the National Optical Astronomy Observatory in Tucson, Arizona, and a board member of the International Dark-Sky Association. Jurisdictions interested in effectively reducing light pollution can turn to the two atlases to research before-and-after maps, and compare what’s worked and what hasn’t, she says.

    “This atlas affords a consistent way of comparing light pollution in different areas of the world over the last 15 years,” she says.

    4
    This map shows light pollution in the Eastern Hemisphere. Illustration by Fabio Falchi, Google Earth

    Falchi’s work, done completely in his off hours as a labor of love, helps put the extent of the problem into perspective, Duriscoe says.

    “To tackle this on a global scale, nobody else before has attempted it,” he says. “When you can stand back and look at the whole Earth and the impact of our modern lifestyle on the ability of all cultures to enjoy the natural nocturnal environment, it shows how we just take it for granted.”

    Protecting Natural Cycles

    At one time, communities with large telescopes, like the Palomar Observatory outside of San Diego, California, prided themselves on their efforts to protect the night sky, though that attitude seems to have waned over the last several decades, Duriscoe notes. Now, however, with more research emerging about the negative impacts on humans of overexposure to light, there has been an uptick of interest in combating the 24-hour lifestyle.

    Falchi has been personally involved in his own community in changing approaches to outdoor lighting. As the current president of the nonprofit CieloBuio dark skies advocacy organization, he spearheaded a petition effort in the late 1990s to enact lighting reform laws in Lombardia, the region where he lives and works. With controls on the types of new fixtures being installed and limits on light intensity in given areas, despite a twofold increase in the number of new lights, light-pollution levels in the region have remained constant from 2000 to today.

    Though much of Italy is now governed by similar laws, it’s still only a start, Falchi says.

    “This is not a sufficient measure for controlling light pollution, but simply a stop in the increase,” he adds. “For almost all other pollutants—chemical, particulate, carbon monoxide, or anything else, graphs show that almost all of them have decreased over the last 20 years. We need to decrease pollution from light as well.”

    See the full article here .

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    The National Geographic Society has been inspiring people to care about the planet since 1888. It is one of the largest nonprofit scientific and educational institutions in the world. Its interests include geography, archaeology and natural science, and the promotion of environmental and historical conservation.

     
  • richardmitnick 1:27 pm on June 10, 2016 Permalink | Reply
    Tags: , , , T-Tauri stars   

    From CfA: “T-Tauri Stars” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    1
    Young stars and nebulosity in Chamaeleon, a constellation visible predominantly in the southern sky. A new study of young (T-Tauri) stars in this region has determined their ages as being between about five – six million years old, as well as determining other properties. FORS Team, 8.2-meter VLT Antu, ESO

    ESO/VLT at Cerro Paranal, Chile
    ESO/VLT at Cerro Paranal, Chile

    ESO/FORS1
    “ESO/FORS1

    A newborn star typically goes through four stages of adolescence. It begins life as a protostar still enshrouded in its natal molecular cloud, accreting new material and developing a proto-planetary disc. Slowly, stellar winds and radiation blow away the surrounding shell of gas and dust, and the third stage, when the surrounding envelope has cleared, is called the T-Tauri phase. T-Tauri stars (the class is named after the first star of this type that was so identified) are less than about ten million years old, and provide astronomers with promising candidates in which to study the early lives of stars and planets. They were among the first young stars to be identified because the earlier stages, still embedded in their birth clouds, were blocked from optical observations by the dust. In the fourth stage, the disk stops accreting and the source’s radiation comes from the star’s photosphere. T-Tauri stars produce strong X-rays, primarily by what is thought to be coronal activity much like the coronal activity in our own Sun, although in some cases a component might be coming from hot material in the dusty disk.

    Measurements of T-Tauri circumstellar disks provide important tests for theories of planet formation and migration. Near-infrared results, for example, sample the hotter temperature dust grains, and can reveal the presence of gaps in the disk (perhaps cleared by massive planets) when an expected ring of warm dust around the star is not detected. Astronomers during the past few decades have been able to use infrared space telescopes like Spitzer to probe T-Tauri disks, but there are still many puzzles, in particular about the mechanisms responsible for the accretion, the subsequent dissipation of material, and the evolutionary ages when these processes occur.

    CfA astronomer Philip Cargile was a member of a team of seven scientists studying the evolution of these stars and their disks. They took detailed optical observations (including spectra) of a sample of twenty-five X-ray selected T-Tauri stars in two nearby star-forming clouds to derive their ages and stellar masses. They find that most of the sources in one cloud are between about five and six million year old; a couple turn out to be more like twenty-five million years old and can now be excluded from the T-Tauri class. In the other cloud, most of the sources are younger than about ten million years. The results agree well with theoretical models and other observations. Perhaps more usefully, the results help to identify true T-Tauri stars with disks that would be suitable for imaging observations with a new generation of large telescopes.

    Reference(s):

    Fundamental Stellar Parameters for Selected T-Tauri Stars in the Chamaeleon and Rho Ophiuchus Star-Forming Regions,” D.J. James, A.N. Aarnio, A.J.W. Richert, P.A. Cargile, N.C. Santos, C.H.F. Melo, and J. Bouvier, MNRAS 459, 1363.

    See the full article here .

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    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 12:16 pm on June 10, 2016 Permalink | Reply
    Tags: , , ,   

    From Ethan Siegel: “NASA’s big mistake: LIGO’s merging black holes were invisible after all” 

    Ethan Siegel
    6.10.16

    1
    Image Credit: SXS, the Simulating eXtreme Spacetimes (SXS) project (http://www.black-holes.org).

    The gravitational waves were real. But earlier announcements that X-rays and gamma-rays were detected, too? Not so much.

    What’s really exciting is what comes next. I think we’re opening a window on the universe — a window of gravitational wave astronomy.” -Dave Reitze

    On September 14, 2015, a tiny effect lasting 200 milliseconds passed through the Earth at the speed of light. The entire planet compressed and expanded in two mutually perpendicular directions by less than the width of a proton, oscillating back and forth roughly seven times in that span. And in two detectors separated by 2,000 miles, an interference pattern formed by two isolated lasers, reflected back-and-forth in a vacuum and then brought together again, gave us the telltale explanation for this effect.

    Caltech/MIT   Advanced Ligo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation

    Caltech/MIT Advanced aLigo detector in Livingston, LA, USA
    Caltech/MIT Advanced aLigo detector installation in Livingston, LA, USA

    From 1.3 billion light years away, two black holes some 30 times the mass of the Sun had spiraled into one another, merging together and sending energetic ripples through the fabric of space itself. For the first time, a gravitational wave — one of the oldest unverified predictions of Einstein’s General Relativity — had been directly detected.

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib
    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

    3
    Image credit: ESA–C.Carreau, of the “ripple” effect on spacetime that a passing gravitational wave imparts.

    Optical telescopes didn’t see anything, as expected. Merging black holes weren’t anticipated to emit any light, unlike merging stars (which create a larger star), white dwarfs (which create a supernova), or neutron stars (which are thought to create a gamma ray burst); they should only be detectable by their gravitational wave signal. Yet there was a curious possible exception, as a team from NASA’s Fermi satellite claimed to detect gamma rays coincident with this event, offset by a meagre 0.4 seconds. An array of 14 crystal detectors on board — the Gamma-ray Burst detection Monitor (GBM) instrument — detected an unexpected burst of X-rays, and claimed there was only a 0.2% chance of a false positive.

    4
    This image, taken in May 2008 as the Fermi Gamma-ray Space Telescope was being readied for launch, highlights the detectors of its Gamma-ray Burst Monitor (GBM). The GBM is an array of 14 crystal detectors. Image credit: NASA/Jim Grossmann.

    While NASA was celebrating, however, cautious scientists all over the world were skeptical. Not only would this overthrow the leading theoretical models for black hole mergers, and not only does a 99.8% chance of success correspond only to a 3-σ significance (rather than the 5-σ significance typically required for a discovery in physics), but a complimentary satellite in orbit — the ESA’s INTEGRAL satellite — failed to see the corroborating evidence it should have if this signal were real.

    ESA/Integral
    ESA/Integral

    On the contrary, INTEGRAL searched through all the data and failed to find any interesting signal coincident with LIGO’s gravitational wave at all. Far from a definitive detection, this conflicting data raised more questions than it answered.

    5
    A marginal detection only is available for the gravitational wave event associated with LIGO’s detection on September 14, 2015. Image credit: D. Bagoly et al., 2016 (submitted to A&A), via http://arxiv.org/abs/1603.06611.

    Thanks to a new paper now available from J. Greiner, J.M. Burgess, V. Savchenko and H.-F. Yu, however, the apparent conflict may at last be resolved. The secret lies in understanding how the GBM instrument aboard NASA’s Fermi satellite actually works. Rather than measuring an absolute signal, it measures a steady, continuous background of photons over a large energy range. The spikes above that background, when they appear, can show us either a real, physical event (like a burst or merger), or they can simply be evidence of a random fluctuation that has no physical origin at all. If you use an imperfect algorithm for discriminating which fluctuations are physical vs. non-physical, you could wind up drawing invalid conclusions about what’s real and what’s phantasmal. The huge advance of the new paper, submitted to the Astrophysical Journal as a Letter, isn’t observational or theoretical, but rather statistical; it more robustly and successfully discriminates between normal noise and a burst of high-energy light from an astrophysical source.

    6
    Various statistical techniques analyzing the Fermi data. The original analysis (purple) shows a signal, but the improved analysis (orange) shows only something consistent with pure noise. Image credit: Figure 5 from J. Greiner, J.M. Burgess, V. Savchenko and H.-F. Yu, retrieved from the preprint at http://arxiv.org/abs/1606.00314.

    Above, you can see a number of different ways of reconstructing the apparent signal coincident with LIGO’s gravitational wave. The original Fermi team’s analysis is shown in purple: a clear detection. However, the superior reconstruction of this new paper is shown in orange, and lines up with both the raw data (blue) and also — more importantly — is consistent with a non-detection, meaning that there is no electromagnetic signal here. According to one of the paper’s authors, J. Michael Burgess, the original paper (claiming a detection) had some statistical flaws his team was able to spot, relating the following:

    When I saw the announcement and the paper, the spectrum looked like what I always see as background.

    After pulling his team together and developing some new analysis tools, they confirmed their suspicions:

    We instantly saw that we got a much different answer. The spectrum of the event was basically zero: nothing there.

    The new statistical technique developed by Burgess and his collaborators has proven to be incredibly powerful, successfully pulling out even faint gamma ray signals from noisy data and drastically reducing the number of false positives. By combining this new technique with the existing Fermi data, it should be possible to make huge strides forward in identifying true astrophysical events.

    Gamma ray burst artist depiction Credit NASA Swift Mary Pat Hrybyk-Keith and John Jones
    Gamma ray burst artist depiction Credit NASA Swift Mary Pat Hrybyk-Keith and John Jones

    It’s important to remember that there can and will be correlations in the future not only between gravitational waves and gamma rays, but between LIGO and Fermi’s GBM instrument. When asked for comment, Burgess said the following:

    “GBM is an amazing instrument and its synergy with LIGO provides an amazing way for us to view the Universe. The GBM team has made a huge effort for this, and when a neutron star merger happens nearby, it is very likely GBM and LIGO (and others) will see something… and this will be amazing!”

    But in order to make sure we aren’t fooling ourselves, we have to do it right. Collaboration between the teams — the Fermi team, the INTEGRAL team, and the gravitational wave teams — are incredibly important. But the necessity of calibrating the signals that multiple observatories will see is essential to getting the right results. Merging black holes may, in fact, sometimes lead to electromagnetic radiation, a possibility which future events will hopefully test. But the golden rule in situations like these is the null hypothesis: in the absence of extraordinary evidence, as is the case here, bet on exactly what the leading physics ideas predict.

    See the full article here .

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 11:32 am on June 10, 2016 Permalink | Reply
    Tags: , , , Jets from Merging Neutron Stars   

    From AAS NOVA: “Jets from Merging Neutron Stars” 

    AASNOVA

    Amercan Astronomical Society

    1
    Still from a simulation of the merger of two neutron stars. In this late stage of the simulation, the neutron stars have merged to form a black hole, which has launched a powerful jet. [Adapted from Ruiz et al. 2016]

    With the recent discovery of gravitational waves from the merger of two black holes, it’s especially important to understand the electromagnetic signals resulting from mergers of compact objects. New simulations successfully follow a merger of two neutron stars that produces a short burst of energy via a jet consistent with short gamma-ray burst (sGRB) detections.

    2
    Still from the authors’ simulation showing the two neutron stars, and their magnetic fields, before merger. [Adapted from Ruiz et al. 2016]

    Challenging System

    We have long suspected that sGRBs are produced by the mergers of compact objects, but this model has been difficult to prove. One major hitch is that modeling the process of merger and sGRB launch is very difficult, due to the fact that these extreme systems involve magnetic fields, fluids and full general relativity.

    Traditionally, simulations are only able to track such mergers over short periods of time. But in a recent study, Milton Ruiz (University of Illinois at Urbana-Champaign and Industrial University of Santander, Colombia) and coauthors Ryan Lang, Vasileios Paschalidis and Stuart Shapiro have modeled a binary neutron star system all the way through the process of inspiral, merger, and the launch of a jet.

    A Merger Timeline

    How does this happen? Let’s walk through one of the team’s simulations, in which dipole magnetic field lines thread through the interior of each neutron star and extend beyond its surface (like magnetic fields found in pulsars). In this example, the two neutron stars each have a mass of 1.625 solar masses.

    Simulation start (0 ms)
    Loss of energy via gravitational waves cause the neutron stars to inspiral.
    Merger (3.5 ms)
    The neutron stars are stretched by tidal effects and make contact. Their merger produces a hypermassive neutron star that is supported against collapse by its differential (nonuniform) rotation.
    Delayed collapse into a black hole (21.5 ms)
    Once the differential rotation is redistributed by magnetic fields and partially radiated away in gravitational waves, the hypermassive neutron star loses its support and collapses to a black hole.
    Plasma velocities turn around (51.5 ms)
    Initially the plasma was falling inward, but as the disk of neutron-star debris is accreted onto the black hole, energy is released. This turns the plasma near the black hole poles around and flings it outward.
    Magnetic field forms a helical funnel (62.5 ms)
    The fields near the poles of the black hole amplify as they are wound around, creating a funnel that provides the wall of the jet.
    Jet outflow extends to heights greater than 445 km (64.5 ms)
    The disk is all accreted and, since the fuel is exhausted, the outflow shuts off (within 100ms)

    Neutron-Star Success

    3
    Plot showing the gravitational wave signature for one of the authors’ simulations. The moments of merger of the neutron stars and collapse to a black hole are marked. [Adapted from Ruiz et al. 2016]

    These simulations show that no initial black hole is needed to launch outflows; a merger of two neutron stars can result in an sGRB-like jet. Another interesting result is that the magnetic field configuration doesn’t affect the formation of a jet: neutron stars with magnetic fields confined to their interiors launch jets as effectively as those with pulsar-like magnetic fields. The accretion timescale for both cases is consistent with the duration of an sGRB.

    While this simulation models milliseconds of real time, it’s enormously computationally challenging and takes months to simulate. The successes of this simulation represent exciting advances in numerical relativity, as well as in our understanding of the electromagnetic counterparts that may accompany gravitational waves.

    Bonus

    Check out this awesome video of the authors’ simulations. The colors differentiate the plasma density and the white lines depict the pulsar-like magnetic field that initially threads the two merging neutron stars. Watch as the neutron stars evolve through the different stages outlined above, eventually forming a black hole and launching a powerful jet. [Simulations and visualization by M. Ruiz, R. Lang, V. Paschalidis, S. Shapiro and the Illinois Relativity Group REU team: S. Connelly, C. Fan, A. Khan, and P. Wongsutthikoson]


    Access mp4 video here .

    Citation

    Milton Ruiz et al 2016 ApJ 824 L6. doi:10.3847/2041-8205/824/1/L6

    See the full article here .

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  • richardmitnick 3:52 pm on June 9, 2016 Permalink | Reply
    Tags: 2002 image of Cone Nebula, , ,   

    From Hubble: “Hubble’s newest camera images ghostly star-forming pillar of gas and dust” 2002 

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    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    1

    Resembling a nightmarish beast rearing its head from a crimson sea, this celestial object is actually just a pillar of gas and dust. Called the Cone Nebula (in NGC 2264) – so named because in ground-based images it has a conical shape – this monstrous pillar resides in a turbulent star-forming region. This picture, taken by the newly installed Advanced Camera for Surveys (ACS) aboard the NASA/ESA Hubble Space Telescope, shows the upper 2.5 light-years of the Cone, a height that equals 23 million roundtrips to the Moon. The entire pillar is seven light-years long.

    NASA/ESA Hubble ACS
    NASA/ESA Hubble ACS

    Radiation from hot, young stars (located beyond the top of the image) has slowly eroded the nebula over millions of years. Ultraviolet light heats the edges of the dark cloud, releasing gas into the relatively empty region of surrounding space. There, additional ultraviolet radiation causes the hydrogen gas to glow, which produces the red halo of light seen around the pillar. A similar process occurs on a much smaller scale to gas surrounding a single star, forming the bow-shaped arc seen near the upper left side of the Cone. This arc, seen previously with the Hubble telescope, is 65 times larger than the diameter of our Solar System. The blue-white light from surrounding stars is reflected by dust. Background stars can be seen peeking through the evaporating tendrils of gas, while the turbulent base is pockmarked with stars reddened by dust.

    Over time, only the densest regions of the Cone will be left. But inside these regions, stars and planets may form. The Cone Nebula resides 2500 light-years away in the constellation Monoceros.

    The Cone is a cousin of the M16 pillars, which the Hubble telescope imaged in 1995.

    Pillars of Creation. NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
    Pillars of Creation. NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

    Consisting mainly of cold gas, the pillars in both regions resist being eroded away by the blistering ultraviolet radiation from young, massive stars. Pillars like the Cone and M16 are common in large regions of star birth. Astronomers believe that these pillars may be incubators for developing stars.

    The ACS made this observation on 2 April 2002. The colour image is constructed from three separate images taken in blue, near-infrared, and hydrogen-alpha filters.

    Image credit: NASA, the ACS Science Team (H. Ford, G. Illingworth, M. Clampin, G. Hartig, T. Allen, K. Anderson, F. Bartko, N. Benitez, J. Blakeslee, R. Bouwens, T. Broadhurst, R. Brown, C. Burrows, D. Campbell, E. Cheng, N. Cross, P. Feldman, M. Franx, D. Golimowski, C. Gronwall, R. Kimble, J. Krist, M. Lesser, D. Magee, A. Martel, W. J. McCann, G. Meurer, G. Miley, M. Postman, P. Rosati, M. Sirianni, W. Sparks, P. Sullivan, H. Tran, Z. Tsvetanov, R. White, and R. Woodruff) and ESA

    Credit:
    NASA, Holland Ford (JHU), the ACS Science Team and ESA

    See the full article here .

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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.

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  • richardmitnick 3:40 pm on June 9, 2016 Permalink | Reply
    Tags: An ancient tale in astronomical time, , , ESO FORS   

    From ESO: “FORS1 at the VLT UT1: First Spectra Obtained” 1998, but too good to pass up 

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    This post is dedicated to the well traveled ESO ambassador O.S. I hope she sees it.

    European Southern Observatory

    7 October 1998 (retrieved from current post http://www.eso.org/public/images/eso9846a/)
    No writer credit in those ancient days

    First commissioning phase successfully completed

    1

    The FORS Team at Paranal has concluded the first phase of the extensive FORS1 commissioning tests at the first 8.2-m VLT Unit Telescope (UT1), successfully and according to the plan. Although this work was primarily aimed at testing the technical performance of this new instrument, it has also been possible to obtain some spectacular images already at this early stage. And now, for the first time, spectra [1] have also been observed with the VLT.

    ESO/FORS1
    ESO/FORS1

    After three weeks of intense work, the FORS team reports that FORS1 has now been trimmed to a very high level of performance. A large amount of test data was obtained in all FORS1 observing modes. They include direct images through various optical filtres of star fields, galactic nebulae, galaxies, galaxy clusters, gravitational arcs as well as spectroscopic and also spectro-polarimetric observations of single and multiple objects. Towards the end, the work concentrated on streamlining certain functions of the control software in order to make observations safe and easy to perform, thereby further optimizing the use of the telescope time.

    The purpose of this Commission Phase 1 was first of all to get the instrument on-line and to prove that all observing modes work correctly. This goal was fully achieved and mostly involved observations of comparatively bright objects although, already now, a spectrum of a 25-magnitude galaxy proved to be no problem. Later, during Commission Phase 2 and especially the subsequent FORS Science Verification programme, observations will also be made of extremely faint objects at the limit of what is possible with FORS1.

    The FORS team is now on its way back to Europe, elated but also quite exhausted after one month of continuous hard work, from the initial installation of the instrument to the final checks during this commissioning phase.

    The following pictures are based on test observations done during the commissioning period now terminated. Full details about the exposures are given below as “Technical Information”.

    The Dumbbell Nebula

    The Dumbbell Nebula – also known as Messier 27 or NGC 6853 – is a typical planetary nebula and is located in the constellation Vulpecula (The Fox). The distance is rather uncertain, but is believed to be around 1200 light-years. It was first described by the French astronomer and comet hunter Charles Messier who found it in 1764 and included it as no. 27 in his famous list of extended sky objects [2].

    Despite its class, the Dumbbell Nebula has nothing to do with planets. It consists of very rarified gas that has been ejected from the hot central star (well visible on this photo), now in one of the last evolutionary stages. The gas atoms in the nebula are excited (heated) by the intense ultraviolet radiation from this star and emit strongly at specific wavelengths.

    2
    eso9846a

    eso9846a is the beautiful by-product of a technical test of some FORS1 narrow-band optical interference filtres. They only allow light in a small wavelength range to pass and are used to isolate emissions from particular atoms and ions.

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    eso9846b

    eso9846b is an enlargment that shows well the intricate structure in the central part of the nebula.
    In this three-colour composite, a short exposure was first made through a wide-band filtre registering blue light from the nebula. It was then combined with exposures through two interference filtres in the light of double-ionized oxygen atoms and atomic hydrogen. They were colour-coded as “blue”, “green” and “red”, respectively, and then combined to produce this picture that shows the structure of the nebula in “approximately true” colours.

    4
    eso9846c

    eso9846c shows a direct image of the entire sky field (square and outlined by a blue line) with 19 horizontal strips that define the allowed areas for each of the 19 vertical slits. The positions of the slits that were chosen for this exposure are also indicated by vertical double lines.

    5
    eso9846d

    eso9846d shows the recorded spectra of the stars in this cluster that were selected for this observation. They appear as bright lines spanning the full field in horizontal direction. Spectrum no. 4 from the top (of star “Be41”) is indicated. The shorter, bright vertical lines are spectral emission lines originating in the terrestrial atmosphere (air glow); they show the extent of the individual slits. Note that in some slits, more than one star spectrum has been registered, thus further increasing the observing efficiency.

    6
    eso9846e
    FORS1 at the VLT UT1: First Spectra

    Multi-object spectra of extragalactic stars

    One of the main features of the FORS instruments is their ability to do multi-object spectroscopy (MOS), i.e., to obtain spectra of several objects at the same time. Many conventional spectrographs in use at telescopes around the world are only capable of observing one spectrum at a time. This necessitates a large amount of precious observing time when spectra of several stars or galaxies shall be observed, e.g., for comparison, or when searching for objets with unusual physical properties.

    FORS1 and FORS2 are designed in such a way that they can register spectra of up to 19 astronomical objects simultaneously. Moreover, they can change from one set of objects to the next within seconds. This greatly increases the observing efficiency and ensures that valuable data can be obtained much faster. That is particularly useful during especially excellent, but relatively rare observing conditions.

    The MOS mode of FORS1 is here illustrated by example of spectra of stars in the open cluster NGC 330 in the Small Magellanic Cloud (SMC)[No illustration present]. The SMC is a companion galaxy of our Milky Way galaxy at a distance of about 150,000 light-years. It is seen deep down in the southern sky and will be a main object of future studies with the VLT.

    Small Magellanic Cloud. NASA/ESA Hubble and ESO/Digitized Sky Survey 2
    Small Magellanic Cloud. NASA/ESA Hubble and ESO/Digitized Sky Survey 2

    Sophisticated software was written by the FORS consortium that allows interactive allocation of target objects in the sky field to the individual slits of the multi-object spectroscopy unit (MOS) of FORS1. The dispersing element that separates the incoming light into different wavelengths (colours) is a grism (a glass prism with a ruled grating replicated onto a thin resin layer on one of the prism surfaces). FORS1 has different grisms that produce spectra with different spectral resolutions. This allows a wide range of projects to be carried out, from quite detailed spectra of brighter objects, to low-resolution spectra of very faint objects, e.g., extremely distant galaxies.

    The FORS1 MOS spectrum was taken for technical reasons, in order to verify the accuracy with which the positions of the individual MOS slits can be set. Therefore, fairly bright stellar objects (down to about 19th magnitude) and a comparatively short exposure time were used. However, already on such “technical” spectra, it will be possible to perform very useful science, as explained below.

    NGC 330 is an extraordinary, young open star cluster. It is famous because it is extremely metal poor, even more than its surroundings in the Small Magellanic Cloud. It furthermore contains unusually many Be stars . In fact, no less than about 70% of its B stars belong to this peculiar variety, compared to about 10% in star clusters of our own Milky Way Galaxy. Be stars are fairly young and hot (~30,000 K) and rotate comparatively fast. Their spectra show broad emission lines of hydrogen from a rotating circumstellar disk. The reason for the overabundance of Be stars in NGC 330 is not known with certainty; the reason may be the very low content of heavy elements.

    Until now, the fainter Be stars in NGC 330 have only been identified by means of photometric observations of their colours. Now, however, the FORS Team was able to obtain the first spectra of some of these stars and confirm the presence of emission lines. eso9846e displays the tracing (brightness vrs. wavelength) of the spectrum of star “Be41” in NGC 330. It is of magnitude 17 and the spectrum isa the fourth from the top in eso9846d. In addition to broad absorption lines of hydrogen and helium (a doppler effect of the rapid rotation), there is a sharp H-beta emission peak from hydrogen near the center of the spectrum, thus confirming it as a Be star . Note that this emission line can also be seen as a bright spot in spectrum no. 4 in eso9846d.
    Notes

    [1] A spectrum is the dispersion of light from an object into the colours of the rainbow. Spectroscopy is a key technique in astronomy: From a spectrum, it is possible to deduce important information about the object emitting the light, e.g. its chemical composition, surface temperature and the direction and speed of its motion (relative to us). This is especially important in the investigation of very distant objects as it allows the determination of their distance due to the expansion of the universe. This will be one of the main domains of the work with FORS.

    [2] More information about this impressive object is available on the web at various locations, e.g., http://messier.seds.org/m/m027.html.

    See the full article here .

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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

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  • richardmitnick 3:14 pm on June 9, 2016 Permalink | Reply
    Tags: , , DRAGON at TRIUMF, ,   

    From Ohio U: “Probing Red Giants with a DRAGON” 

    Ohio U bloc

    Ohio University

    June 9, 2016
    Jean Andrews

    1
    Scientists study stars called red giants to better understand processes such as nuclear fusion—the dominant source of energy for stars in the universe. L to R: Dr. Carl Brune, Dr. Annika Lennarz, a TRIUMF postdoctoral researcher, OHIO doctoral students Som Nath Paneru, and Rikam Giri

    Dr. Carl Brune, Professor of Physics & Astronomy and member of the Institute of Nuclear and Particle Physics (INPP), traveled recently to TRIUMF, Canada’s national lab for nuclear and particle physics, located in Vancouver. With him were his doctoral students Rekam Giri and Som Nath Paneru. The purpose of their visit was to use the DRAGON, a specialized instrument which measures the fusion of helium and carbon — an important process that occurs in red giant stars.

    DRAGON at TRIUMF

    “These measurements will help us to understand where the oxygen in the universe comes from and help to confirm that our models for how stars evolve and produce elements are correct, “ Brune says. “The DRAGON is an ideal instrument for this type of experiment.”

    The DRAGON apparatus is used to study nuclear reactions important in astrophysics. By recreating the nuclear reactions that occur inside exploding stars, researchers are better able to understand reactions that produce the chemical elements and energy generation in stars. DRAGON is an acronym for Detector of Recoils And Gammas Of Nuclear reactions.

    How Stars Evolve into Red Giants

    Brune is particularly interested in energy processes taking place within red giants. These are stars in the last stages of stellar evolution that have exhausted the supply of hydrogen in their cores and have begun thermonuclear fusion of hydrogen in a shell surrounding the core.

    “Most stars, including our sun, are burning hydrogen in the cores,” Brune explains. “Once the hydrogen in the core is exhausted, the stars begin to burn helium and become red giants. They expand in diameter and their outer edge is lower in temperature, giving them a reddish-orange hue. Helium is burned by two fusion reactions within a red giant: the fusion of three helium nuclei into carbon and the fusion of helium with carbon to form oxygen.”

    The fusion of helium with carbon at this stage is thought to be the main source of oxygen in the universe – even the oxygen on the earth.

    The DRAGON instrument at TRIUMF is a recoil separator that is used to detect the oxygen nuclei produced. A carbon beam was used to bombard a helium target. The oxygen nuclei produced by fusion are separated from the carbon beam by the DRAGON instrument and counted.

    Brune, Giri, and Paneru are part of a team of nuclear physicists that includes researchers from TRIUMF, the Colorado School of Mines, and Michigan State University. The group convened the week of May 3-10 to run the experiment using the DRAGON.

    See the full article here .

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    Ohio U campus

    n 1786, 11 men gathered at the Bunch of Grapes Tavern in Boston to propose development of the area north of the Ohio River and west of the Allegheny Mountains known then as the Ohio Country. Led by Manasseh Cutler and Rufus Putnam, the Ohio Company petitioned Congress to take action on the proposed settlement. The eventual outcome was the enactment of the Northwest Ordinance of 1787, which provided for settlement and government of the territory and stated that “…schools and the means of education shall forever be encouraged.”

    In 1803, Ohio became a state and on February 18, 1804, the Ohio General Assembly passed an act establishing “The Ohio University.” The University opened in 1808 with one building, three students, and one professor, Jacob Lindley. One of the first two graduates of the University, Thomas Ewing, later became a United States senator and distinguished himself as cabinet member or advisor to four presidents.

    Twenty-four years after its founding, in 1828, Ohio University conferred an A.B. degree on John Newton Templeton, its first black graduate and only the third black man to graduate from a college in the United States. In 1873, Margaret Boyd received her B.A. degree and became the first woman to graduate from the University. Soon after, the institution graduated its first international alumnus, Saki Taro Murayama of Japan, in 1895.

     
  • richardmitnick 2:30 pm on June 9, 2016 Permalink | Reply
    Tags: , , , , VLASS begins   

    From NRAO: “The VLA Sky Survey Pilot Begins” 

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    National Radio Astronomy Observatory

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    6.9.16

    1
    Claire Chandler, VLASS Project Director

    1

    The Very Large Array Sky Survey (VLASS) will be a three-epoch (32-month cadence), all-sky, S-band (2-4 GHz) continuum polarimetry survey with 2.5-arcsecond spatial resolution. The survey will span seven years and six VLA configuration cycles, and will begin in 2017, pending successful achievement of the design phase milestones. The total VLA telescope time required for the survey is ~5400 hours, or ~900 hours per configuration cycle.

    With the decision to proceed with the VLASS (see 17 Dec 2015 e-News), a 200-hr pilot in the recently commenced VLA B-configuration of semester 2016A has been approved, with the first observations starting June 2016. This pilot survey will inform VLASS implementation and operational issues associated with the full survey as input to design reviews, while at the same time providing the community with early VLASS-type data products. The pilot will be observed in as similar a mode to the full VLASS as possible, including:

    S-band (2-4 GHz), 1024 x 2 MHz channels
    VLA B-configuration, 2.5-arcsec resolution
    On-The-Fly (OTF) mosaics scanning at 3.31 arcmin/sec in right ascension, at constant declination
    Net mapping speed ~20 deg2/hr, 4-hr scheduling blocks covering 80 deg2 (10o x 8o tiles)

    Some areas will be covered with three passes to provide a similar sensitivity as that expected from three epochs of the full VLASS (70 microJy/beam), while others will be observed with a single pass (120 microJy/beam) to maximize sky coverage. The pilot will cover key galactic and extragalactic fields that have good multi-wavelength ancillary data, as well as covering areas of sky with good prior radio observations for technical validation of the OTF mosaicking observing mode. The total area to be covered will be ~2500 deg2, and will include:

    VLASS Pilot Fields, 3 passes (70 microJy/beam):

    Galactic Plane fields: Galactic Center, Cygnus, Cepheus
    Extragalactic fields: Cosmological Evolution Survey, Sloane Digital Sky Survey (SDSS) Stripe 82, Chandra Deep Field South

    VLASS Pilot Fields, 1 pass (120 microJy/beam):

    SDSS South Galactic Cap / FIRST southern sky for declination > 0 deg
    SDSS North Galactic Cap fields: Great Observatories Origins Deep Survey – North, Elais-N1, Lockman Hole, H-ATLAS North, Bootes

    Raw visibility data will be immediately available through the NRAO archive under project code TVPILOT. Data products (calibrated visibility data, images) will be made available after undergoing quality assurance.

    At this time, we encourage community participation in various Science Working Groups as we define and refine the operational aspects of the pilot survey:

    Extragalactic Working Group
    Galactic Working Group
    Transients Working Group
    Polarization Working Group
    EPO Working Group
    Survey Implementation Working Group
    NRAO Data Products, Archiving and Enhanced Data Products Working Group

    A Google Group has been set up to facilitate discussion and communication within the working groups, please visit to sign up.

    See the full article here .

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    The NRAO operates a complementary, state-of-the-art suite of radio telescope facilities for use by the scientific community, regardless of institutional or national affiliation: the Very Large Array (VLA), the Robert C. Byrd Green Bank Telescope (GBT), and the Very Long Baseline Array (VLBA)*.

    ALMA Array

    NRAO ALMA

    NRAO/GBT radio telescope
    NRAO GBT

    NRAO VLA
    NRAO VLA

    The NRAO is building two new major research facilities in partnership with the international community that will soon open new scientific frontiers: the Atacama Large Millimeter/submillimeter Array (ALMA), and the Expanded Very Large Array (EVLA). Access to ALMA observing time by the North American astronomical community will be through the North American ALMA Science Center (NAASC).
    *The Very Long Baseline Array (VLBA) comprises ten radio telescopes spanning 5,351 miles. It’s the world’s largest, sharpest, dedicated telescope array. With an eye this sharp, you could be in Los Angeles and clearly read a street sign in New York City!

    Astronomers use the continent-sized VLBA to zoom in on objects that shine brightly in radio waves, long-wavelength light that’s well below infrared on the spectrum. They observe blazars, quasars, black holes, and stars in every stage of the stellar life cycle. They plot pulsars, exoplanets, and masers, and track asteroids and planets.

     
  • richardmitnick 11:07 am on June 9, 2016 Permalink | Reply
    Tags: , , Likely new giant planet PTFO8-8695 b, New planet may be in slow death spiral,   

    From Rice: “Likely new planet may be in slow death spiral” 

    Rice U bloc

    Rice University

    June 9, 2016
    Jade Boyd

    1
    An artist’s impression of likely new giant planet PTFO8-8695 b, which is believed to orbit a star in the constellation Orion every 11 hours. Gravity from the newborn star appears to be pulling away the outer layers of the Jupiter-like planet. (Image by A. Passwaters/Rice University based on original available under CC license at https://commons.wikimedia.org/wiki/File:Kepler-70b.png)

    Astronomers searching for the galaxy’s youngest planets have found compelling evidence for one unlike any other, a newborn “hot Jupiter” whose outer layers are being torn away by the star it orbits every 11 hours.

    “A handful of known planets are in similarly small orbits, but because this star is only 2 million years old this is one of the most extreme examples,” said Rice University astronomer Christopher Johns-Krull, lead author of a new study that makes a case for a tightly orbiting gas giant around the star PTFO8-8695 in the constellation Orion. The peer-reviewed study will be published in The Astrophysical Journal and was made available online this week.

    “We don’t yet have absolute proof this is a planet because we don’t yet have a firm measure of the planet’s mass, but our observations go a long way toward verifying this really is a planet,” Johns-Krull said. “We compared our evidence against every other scenario we could imagine, and the weight of the evidence suggests this is one of the youngest planets yet observed.”

    2
    Christopher Johns-Krull (Photo by Jeff Fitlow/Rice University)

    Dubbed “PTFO8-8695 b,” the suspected planet orbits a star about 1,100 light years from Earth and is at most twice the mass of Jupiter. The team that compiled the evidence was co-led by Johns-Krull and Lowell Observatory astronomer Lisa Prato and included 10 co-authors from Rice, Lowell, the University of Texas at Austin, NASA, the California Institute of Technology and Spain’s National Institute of Aerospace.

    “We don’t know the ultimate fate of this planet,” Johns-Krull said. “It likely formed farther away from the star and has migrated in to a point where it’s being destroyed. We know there are close-orbiting planets around middle-aged stars that are presumably in stable orbits. What we don’t know is how quickly this young planet is going to lose its mass and whether it will lose too much to survive.”

    Astronomers have discovered more than 3,300 exoplanets, but almost all of them orbit middle-aged stars like the sun. On May 26, Johns-Krull, Prato and co-authors announced the discovery of ‘CI Tau b,’ the first exoplanet found to orbit a star so young that it still retains a disk of circumstellar gas. Johns-Krull said finding such young planets is challenging because there are relatively few candidate stars that are young enough and bright enough to view in sufficient detail with existing telescopes. The search is further complicated by the fact that young stars are often active, with visual outbursts and dimmings, strong magnetic fields and enormous starspots that can make it appear that planets exist where they do not.

    PTFO8-8695 b was identified as a candidate planet in 2012 by the Palomar Transit Factory’s Orion survey.

    Caltech Palomar Transit Factory interior
    Caltech Palomar Transit Factory interior

    The planet’s orbit sometimes causes it to pass between its star and our line of sight from Earth, therefore astronomers can use a technique known as the transit method to determine both the presence and approximate radius of the planet based on how much the star dims when the planet “transits,” or passes in front of the star.

    Planet transit. NASA
    Planet transit. NASA

    “In 2012, there was no solid evidence for planets around 2 million-year-old stars,” Prato said. “Light curves and variations of this star presented an intriguing technique to confirm or refute such a planet. The other thing that was very intriguing about it was that the orbital period was only 11 hours. That meant we wouldn’t have to come back night after night after night, year after year after year. We could potentially see something happen in one night. So that’s what we did. We just sat on the star for a whole night.”

    4
    Lisa Prato. No image credit.

    A spectroscopic analysis of the light coming from the star revealed excess emission in the H-alpha spectral line, a type of light emitted from highly energized hydrogen atoms. The team found that the H-alpha light is emitted in two components, one that matches the very small motion of the star and another than seems to orbit it.

    “We saw one component of the hydrogen emission start on one side of the star’s emission and then move over to the other side,” Prato said. “When a planet transits a star, you can determine the orbital period of the planet and how fast it is moving toward you or away from you as it orbits. So, we said, ‘If the planet is real, what is the velocity of the planet relative to the star?’ And it turned out that the velocity of the planet was exactly where this extra bit of H-alpha emission was moving back and forth.”

    Johns-Krull said transit observations revealed that the planet is only about 3 to 4 percent the size of the star, but the H-alpha emission from the planet appears to be almost as bright as the emission coming from the star.

    U Texas at Austin McDonald Observatory Harlan J Smith Telescope
    U Texas at Austin McDonald Observatory Harlan J Smith Telescope

    “There’s no way something confined to the planet’s surface could produce that effect,” he said. “The gas has to be filling a much larger region where the gravity of the planet is no longer strong enough to hold on to it. The star’s gravity takes over, and eventually the gas will fall onto the star.”

    Additional team members were Wei Chen and Sarah Frazier, both of Rice; Jacob McLane of the University of Texas at Austin; David Ciardi and Julian van Eyken, both of NASA’s Exoplanet Science Institute; Charles Beichman of NASA’s Jet Propulsion Laboratory; Maria Morales-Calderón of Spain’s National Institute of Aerospace Technology; and John Stauffer, Andrew Boden and Luisa Rebull, all of the California Institute of Technology.

    The team observed the star PTFO8-8695 dozens of times from the University of Texas at Austin’s McDonald Observatory near Fort Davis, Texas, and the Kitt Peak National Observatory 4-meter telescope in southern Arizona.

    NOAO Mayall 4 m telescope at Kitt Peak, Arizona, USA
    NOAO Mayall 4 m telescope at Kitt Peak, Arizona, USA

    The research was supported by NASA’s Origins of Solar Systems program, the National Science Foundation and the NAU/NASA Space Grant Undergraduate Research Internship program.

    See the full article here .

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    Rice U campus

    In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

    This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

     
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