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  • richardmitnick 9:23 pm on October 16, 2014 Permalink | Reply
    Tags: , , , , NRAO GBT,   

    From NRAO: “Milky Way Ransacks Nearby Dwarf Galaxies, Stripping All Traces of Star-Forming Gas” 

    NRAO Icon
    National Radio Astronomy Observatory

    NRAO Banner

    October 15, 2014
    Contact: Charles E. Blue, Public Information Officer
    (434) 296-0314; cblue@nrao.edu

    Astronomers using the National Science Foundation’s Green Bank Telescope (GBT) in West Virginia, along with data from other large radio telescopes, have discovered that our nearest galactic neighbors, the dwarf spheroidal galaxies, are devoid of star-forming gas, and that our Milky Way Galaxy is to blame.

    mw

    These new radio observations, which are the highest sensitivity of their kind ever undertaken, reveal that within a well-defined boundary around our Galaxy, dwarf galaxies are completely devoid of hydrogen gas; beyond this point, dwarf galaxies are teeming with star-forming material.

    The Milky Way Galaxy is actually the largest member of a compact clutch of galaxies that are bound together by gravity. Swarming around our home Galaxy is a menagerie of smaller dwarf galaxies, the smallest of which are the relatively nearby dwarf spheroidals, which may be the leftover building blocks of galaxy formation. Further out are a number of similarly sized and slightly misshaped dwarf irregular galaxies, which are not gravitationally bound to the Milky Way and may be relative newcomers to our galactic neighborhood.

    “Astronomers wondered if, after billions of years of interaction, the nearby dwarf spheroidal galaxies have all the same star-forming ‘stuff’ that we find in more distant dwarf galaxies,” said astronomer Kristine Spekkens, assistant professor at the Royal Military College of Canada and lead author on a paper published in the Astrophysical Journal Letters.

    Previous studies have shown that the more distant dwarf irregular galaxies have large reservoirs of neutral hydrogen gas, the fuel for star formation. These past observations, however, were not sensitive enough to rule out the presence of this gas in the smallest dwarf spheroidal galaxies.

    By bringing to bear the combined power of the GBT (the world’s largest fully steerable radio telescope) and other giant telescopes from around the world, Spekkens and her team were able to probe the dwarf galaxies that have been swarming around the Milky Way for billions of years for tiny amounts of atomic hydrogen.

    “What we found is that there is a clear break, a point near our home Galaxy where dwarf galaxies are completely devoid of any traces of neutral atomic hydrogen,” noted Spekkens. Beyond this point, which extends approximately 1,000 light-years from the edge of the Milky Way’s star-filled disk to a point that is thought to coincide with the edge of its dark matter distribution, dwarf spheroidals become vanishingly rare while their gas-rich, dwarf irregular counterparts flourish.

    There are many ways that larger, mature galaxies can lose their star-forming material, but this is mostly tied to furious star formation or powerful jets of material driven by supermassive black holes. The dwarf galaxies that orbit the Milky Way contain neither of these energetic processes. They are, however, susceptible to the broader influences of the Milky Way, which itself resides within an extended, diffuse halo of hot hydrogen plasma.

    The researchers believe that, up to a certain distance from the galactic disk, this halo is dense enough to affect the composition of dwarf galaxies. Within this “danger zone,” the pressure created by the million-mile-per-hour orbital velocities of the dwarf spheroidals can actually strip away any detectable traces of neutral hydrogen. The Milky Way thus shuts down star formation in its smallest neighbors.

    “These observations therefore reveal a great deal about size of the hot halo and about how companions orbit the Milky Way,” concludes Spekkens.

    See the full article here.

    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)*.

    NRAO ALMA
    NRAO ALMA

    NRAO GBT
    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.

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  • richardmitnick 8:25 pm on September 2, 2014 Permalink | Reply
    Tags: , , , , , NRAO GBT   

    From Astronomy: “Orion rocks! Pebble-sized particles may jump-start planet formation” 

    Astronomy magazine

    Astronomy Magazine

    September 02, 2014
    By NRAO, Charlottesville, VA

    Astronomers have discovered that filaments of star-forming gas near the Orion Nebula may be brimming with planetary building blocks 100 to 1,000 times larger than the dust grains typically found around protostars.

    orion
    In one of the most detailed astronomical images ever produced, NASA/ESA’s Hubble Space Telescope captured an unprecedented look at the Orion Nebula. … This extensive study took 105 Hubble orbits to complete. All imaging instruments aboard the telescope were used simultaneously to study Orion. The Advanced Camera mosaic covers approximately the apparent angular size of the full moon.

    NASA Hubble Telescope
    NASA/ESA Hubble

    Rocky planets like Earth start out as microscopic bits of dust tinier than a grain of sand, or so theories predict.

    orion2
    Radio/optical composite of the Orion Molecular Cloud Complex showing the OMC-2/3 star-forming filament. GBT data is shown in orange. Uncommonly large dust grains there may kick-start planet formation. S. Schnee, et al.; B. Saxton, B. Kent (NRAO/AUI/NSF)

    Astronomers using the National Science Foundation’s (NSF) Green Bank Telescope (GBT) have discovered that filaments of star-forming gas near the Orion Nebula may be brimming with pebble-sized particles — planetary building blocks 100 to 1,000 times larger than the dust grains typically found around protostars. If confirmed, these dense ribbons of rocky material may well represent a new mid-sized class of interstellar particles that could help jump-start planet formation.

    NRAO GBT
    NRAO Green Bank Radio Telescope

    “The large dust grains seen by the GBT would suggest that at least some protostars may arise in a more nurturing environment for planets,” said Scott Schnee from the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia. “After all, if you want to build a house, it’s best to start with bricks rather than gravel, and something similar can be said for planet formation.”

    The new GBT observations extend across the northern portion of the Orion Molecular Cloud Complex,

    oht
    Photo taken by Rogelio Bernal Andreo in October 2010 of the Orion constellation showing the surrounding nebulas of the Orion Molecular Cloud complex. Also captured is the red supergiant Betelgeuse (top left) and the famous belt of Orion composed of the OB stars Altitak, Alnilam and Mintaka. To the bottom right can be found the star Rigel. The red crescent shape is Barnard’s Loop. The photograph appeared as the Astronomy Picture of the Day on October 23, 2010.

    a star-forming region that includes the famed Orion Nebula. The star-forming material in the section studied by the GBT, called OMC-2/3, has condensed into long dust-rich filaments. The filaments are dotted with many dense knots known as cores. Some of the cores are just starting to coalesce, while others have begun to form protostars — the first early concentrations of dust and gas along the path to star formation. Astronomers speculate that in the next 100,000 to 1 million years, this area will likely evolve into a new star cluster. The OMC-2/3 region is located approximately 1,500 light-years from Earth and is roughly 10 light-years long.

    Based on earlier maps of this region made with the IRAM 30-meter radio telescope in Spain, the astronomers expected to find a certain brightness to the dust emission when they observed the filaments at slightly longer wavelengths with the GBT.

    IRAM
    IRAM 30m Radio Telescope

    Instead, the GBT discovered that the area was shining much brighter than expected in millimeter-wavelength light.

    “This means that the material in this region has different properties than would be expected for normal interstellar dust,” said Schnee. “In particular, since the particles are more efficient than expected at emitting at millimeter wavelengths, the grains are very likely to be at least a millimeter, and possibly as large as a centimeter across, or roughly the size of a small Lego-style building block.”

    Though incredibly small compared to even the most modest of asteroids, dust grains on the order of a few millimeters to a centimeter are incredibly large for such young star-forming regions. Due to the unique environment in the Orion Molecular Cloud Complex, the researchers propose two intriguing theories for their origin.

    The first is that the filaments themselves helped the dust grains grow to such unusual proportions. These regions, compared to molecular clouds in general, have lower temperatures, higher densities, and lower velocities — all of which would encourage grain growth.

    The second scenario is that the rocky particles originally grew inside a previous generation of cores or perhaps even protoplanetary disks. The material could then have escaped back into the surrounding molecular cloud rather than becoming part of the original newly forming star system.

    “Rather than typical interstellar dust, these researchers appear to have detected vast streamers of gravel — essentially a long and winding road in space,” said Jay Lockman from NRAO. “We’ve known about dust specks, and we have known that there are things the size of asteroids and planets, but if we can confirm these results, it would add a new population of rocky particles to interstellar space.”

    The most recent data were taken with the GBT’s high-frequency imaging camera, MUSTANG. These data were compared with earlier studies as well as temperature estimates obtained from observations of ammonia molecules in the clouds.

    mus
    NRAO GBT MUSTANG Camera

    “Though our results suggest the presence of unexpectedly large dust grains, measuring the mass of dust is not a straightforward process, and there could be other explanations for the bright signature we detected in the emission from the Orion Molecular Cloud,” said Brian Mason of NRAO. “Our team continues to study this fascinating area. Since it contains one of the highest concentrations of protostars of any nearby molecular cloud, it will continue to excite the curiosity of astronomers.”

    See the full article here.

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  • richardmitnick 4:41 am on May 24, 2014 Permalink | Reply
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    From NRAO: “Failed Dwarf Galaxy Survives Galactic Collision Thanks to Full Dark-Matter Jacket” 

    NRAO Icon
    National Radio Astronomy Observatory

    NRAO Banner

    May 23, 2014
    Charles E. Blue, Public Information Officer
    (434) 296-0314; cblue@nrao.edu

    Like a bullet wrapped in a full metal jacket, a high-velocity hydrogen cloud hurtling toward the Milky Way appears to be encased in a shell of dark matter, according to a new analysis of data from the National Science Foundation’s Robert C. Byrd Green Bank Telescope (GBT). Astronomers believe that without this protective shell, the high-velocity cloud (HVC) known as the Smith Cloud would have disintegrated long ago when it first collided with the disk of our Galaxy.

    smith cloud

    If confirmed by further observations, a halo of dark matter could mean that the Smith Cloud is actually a failed dwarf galaxy, an object that has all the right stuff to form a true galaxy, just not enough to produce stars.

    “The Smith Cloud is really one of a kind. It’s fast, quite extensive, and close enough to study in detail,” said Matthew Nichols with the Sauverny Observatory in Switzerland and principal author on a paper accepted for publication in the Monthly Notices of the Royal Astronomical Society. “It’s also a bit of a mystery; an object like this simply shouldn’t survive a trip through the Milky Way, but all the evidence points to the fact that it did.”

    Previous studies of the Smith Cloud revealed that it first passed through our Galaxy many millions of years ago. By reexamining and carefully modeling the cloud, astronomers now believe that the Smith Cloud contains and is actually wrapped in a substantial “halo” of dark matter — the gravitationally significant yet invisible stuff that makes up roughly 80 percent of all the matter in the Universe.

    “Based on the currently predicted orbit, we show that a dark matter free cloud would be unlikely to survive this disk crossing,” observed Jay Lockman, an astronomer at the National Radio Astronomy Observatory in Green Bank, West Virginia, and one of the coauthors on the paper. “While a cloud with dark matter easily survives the passage and produces an object that looks like the Smith Cloud today.”

    The Milky Way is swarmed by hundreds of high-velocity clouds, which are made up primarily of hydrogen gas that is too rarefied to form stars in any detectable amount. The only way to observe these objects, therefore, is with exquisitely sensitive radio telescopes like the GBT, which can detect the faint emission of neutral hydrogen. If it were visible with the naked eye, the Smith Cloud would cover almost as much sky as the constellation Orion.

    Most high-velocity clouds share a common origin with the Milky Way, either as the leftover building blocks of galaxy formation or as clumps of material launched by supernovas in the disk of the galaxy. A rare few, however, are interlopers from farther off in space with their own distinct pedigree. A halo of dark matter would strengthen the case for the Smith Cloud being one of these rare exceptions.

    Currently, the Smith Cloud is about 8,000 light-years away from the disk of our Galaxy. It is moving toward the Milky Way at more than 150 miles per second and is predicted to impact again in approximately 30 million years.

    “If confirmed to have dark matter this would in effect be a failed galaxy,” said Nichols. “Such a discovery would begin to show the lower limit of how small a galaxy could be.” The researchers believe this could also improve our understanding of the Milky Way’s earliest star formation.

    See the full article here.

    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)*.

    NRAO ALMA
    NRAO ALMA

    NRAO GBT
    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.


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  • richardmitnick 5:30 am on February 27, 2014 Permalink | Reply
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    From NRAO: :Radio Astronomers Develop New Technique for Studying Dark Energy: 

    NRAO Icon
    National Radio Astronomy Observatory

    NRAO Banner

    July 21, 2010
    Dave Finley, Public Information Officer
    Socorro, NM
    (575) 835-7302
    dfinley@nrao.edu

    Pioneering observations with the National Science Foundation’s giant Robert C. Byrd Green Bank Telescope (GBT) have given astronomers a new tool for mapping large cosmic structures. The new tool promises to provide valuable clues about the nature of the mysterious “dark energy” believed to constitute nearly three-fourths of the mass and energy of the Universe.

    NRAO GBT
    Robert C. Byrd Green Bank Telescope
    CREDIT: NRAO/AUI/NSF

    Dark energy is the label scientists have given to what is causing the Universe to expand at an accelerating rate. While the acceleration was discovered in 1998, its cause remains unknown. Physicists have advanced competing theories to explain the acceleration, and believe the best way to test those theories is to precisely measure large-scale cosmic structures.

    Sound waves in the matter-energy soup of the extremely early Universe are thought to have left detectable imprints on the large-scale distribution of galaxies in the Universe. The researchers developed a way to measure such imprints by observing the radio emission of hydrogen gas. Their technique, called intensity mapping, when applied to greater areas of the Universe, could reveal how such large-scale structure has changed over the last few billion years, giving insight into which theory of dark energy is the most accurate.

    “Our project mapped hydrogen gas to greater cosmic distances than ever before, and shows that the techniques we developed can be used to map huge volumes of the Universe in three dimensions and to test the competing theories of dark energy,” said Tzu-Ching Chang, of the Academia Sinica in Taiwan and the University of Toronto.

    To get their results, the researchers used the GBT to study a region of sky that previously had been surveyed in detail in visible light by the Keck II telescope in Hawaii. This optical survey used spectroscopy to map the locations of thousands of galaxies in three dimensions. With the GBT, instead of looking for hydrogen gas in these individual, distant galaxies — a daunting challenge beyond the technical capabilities of current instruments — the team used their intensity-mapping technique to accumulate the radio waves emitted by the hydrogen gas in large volumes of space including many galaxies.

    Keck Observatory
    Keck

    “Since the early part of the 20th Century, astronomers have traced the expansion of the Universe by observing galaxies. Our new technique allows us to skip the galaxy-detection step and gather radio emissions from a thousand galaxies at a time, as well as all the dimly-glowing material between them,” said Jeffrey Peterson, of Carnegie Mellon University.

    The astronomers also developed new techniques that removed both man-made radio interference and radio emission caused by more-nearby astronomical sources, leaving only the extremely faint radio waves coming from the very distant hydrogen gas. The result was a map of part of the “cosmic web” that correlated neatly with the structure shown by the earlier optical study. The team first proposed their intensity-mapping technique in 2008, and their GBT observations were the first test of the idea.

    “These observations detected more hydrogen gas than all the previously-detected hydrogen in the Universe, and at distances ten times farther than any radio wave-emitting hydrogen seen before,” said Ue-Li Pen of the University of Toronto.

    “This is a demonstration of an important technique that has great promise for future studies of the evolution of large-scale structure in the Universe,” said National Radio Astronomy Observatory Chief Scientist Chris Carilli, who was not part of the research team.

    In addition to Chang, Peterson, and Pen, the research team included Kevin Bandura of Carnegie Mellon University. The scientists reported their work in the July 22 issue of the scientific journal Nature.

    See the full article here.

    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)*.

    NRAO ALMA
    NRAO ALMA

    NRAO GBT
    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.


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  • richardmitnick 4:38 pm on December 9, 2013 Permalink | Reply
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    From NRAO: “Hidden Details Revealed in Nearby Starburst Galaxy: Green Bank Telescope’s new vision debuts” 

    NRAO Icon
    National Radio Astronomy Observatory

    NRAO Banner

    December 9, 2013
    Charles E. Blue, Public Information Officer 434-296-0314 cblue@nrao.edu

    Using the new, high-frequency capabilities of the National Science Foundation’s Robert C. Byrd Green Bank Telescope (GBT), astronomers have captured never-before-seen details of the nearby starburst galaxy M82. These new data highlight streamers of material fleeing the disk of the galaxy as well as concentrations of dense molecular gas surrounding pockets of intense star formation.

    M82
    This composite image of starburst galaxy M82 shows the distribution of dense molecular gas as seen by the GBT (yellow and red) and the background stars and dust as seen by Hubble (blue). The yellow areas correspond to regions of intense star formation. The red areas trace outflows of gas from the disk of the galaxy.
    CREDIT: Bill Saxton (NRAO/AUI/NSF); Hubble/NASA

    M82A
    This is a composite image made from three satellite observation projects. Visible aspects of the galaxy were taken by the HST. It is also shown in invisible infrared and X-ray spectrums: Spitzer
    photographed it in infrared, which shows dust emission, and Chandra photographed it in X-ray (showing mostly synchrotron emissions from fast electrons). The X-ray emission is shown in the blue parts.

    M82, which is located approximately 12 million light-years away in the constellation Ursa Major, is a classic example of a starburst galaxy — one that is producing new stars tens- to hundreds-of-times faster than our own Milky Way. Its relatively nearby location made it an ideal target for the GBT’s newly equipped “W-Band” receiver, which is capable of detecting the millimeter wavelength light that is emitted by molecular gas. This new capability makes the GBT the world’s largest single-dish, millimeter-wave telescope.

    “With this new vision, we were able to look at M82 to explore how the distribution of molecular gas in the galaxy corresponded to areas of intense star formation,” said Amanda Kepley, a post-doctoral fellow at the National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia, and lead author on a paper accepted for publication in the Astrophysical Journal Letters. “Having this new capability may help us understand why stars form where they do.”

    Astronomers recognize that dense molecular gas goes hand-in-hand with areas of star formation, but the connection is poorly understood and this relationship may be different in different types of galaxies. By creating wide-angle maps of the gas in galaxies, astronomers hope to better understand this complex interplay.

    To date, however, these kinds of observations have not been easy since molecules that are used to map the distribution of dense gas, like HCN (hydrogen cyanide) and HCO+ (formylium), shine feebly in millimeter light. With its new W-Band receiver, the GBT was able to make highly sensitive, wide-angle images of these gases in and around M82.

    “The GBT data clearly show billowing concentrations of dense molecular gas huddled around areas that are undergoing bursts of intense star formation,” said Kepley. “They also reveal giant outflows of ionized gas fleeing the disk of the galaxy. These outflows are driven by star formation deep within the galaxy.”

    This capability will enable astronomers to quickly survey entire galaxies and different parts within galaxies. Such surveys would complement higher resolution observations with new Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile.

    The 100-meter GBT is located in the National Radio Quiet Zone and the West Virginia Radio Astronomy Zone, which protect the incredibly sensitive telescope from unwanted radio interference.

    See the full article here.

    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)*.

    NRAO ALMA
    NRAO ALMA

    NRAO GBT
    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 3:48 pm on November 19, 2013 Permalink | Reply
    Tags: , , , , , NRAO GBT,   

    From NRAO: “Birth of a Millisecond Pulsar” 

    NRAO Icon
    National Radio Astronomy Observatory

    NRAO Banner

    November 19, 2013
    F.J. Lockman

    A radio pulsar is a neutron star whose strong magnetic field accelerates particles as it rotates, gradually slowing with time. One class of pulsars, however, appears to have been re-accelerated to rotational periods of a few milli-seconds through mass transfer from a binary companion. During the transfer the accreting material is heated to a temperature such that it emits X-rays, and indeed, many low-mass X-ray binaries observed throughout the Milky Way are thought to be produced by this mechanism, which must operate over many millions of years. It is thought that the se systems go on to produce radio milli-second pulsars when accretion ends.

    Recently, however, by combining multiple satellite X-ray observations with radio-wavelength data from the Green Bank Telescope (GBT) and other telescopes worldwide, scientists have identified a neutron star in a binary system that appears sometimes as an accreting X-ray emitting neutron star, and at other times as a radio pulsar.

    NRAO GBT
    NRAO’s Green Bank Telescope

    The system is in the globular cluster M28 which hosts many radio pulsars. It was discovered using the GBT in 2006, and observed to cease radio emission for months to years at a time. Thanks to the new observations it is now understood that the actual accretion process is sporadic and may vary on time scales as short as weeks. During episodes of accretion inflowing matter disrupts particle acceleration processes in the neutron star’s magnetic field, quenching the radio emission, and causing bright, pulsed X-rays. When the accretion tapers off the pulsar’s magnetosphere can accelerate particles again, and the object appears once more as a radio pulsar.

    m28
    Messier 28

    These observations establish without question the link between radio pulsars and X- ray binaries, and will allow study of the accretion process in detail.

    Reference: A. Papitto, C. Ferrigno, E. Bozzo, N. Rea, L. Pavan, L. Burderi, M. Burgay, S. Campana, T. Di Salvo, M. Falanga, M. D. Filipović, P. C. C. Freire, J. W. T. Hessels, A. Possenti, S. M. Ransom, A. Riggio, P. Romano, J. M. Sarkissian, I. H. Stairs, L. Stella, D. F. Torres, M. H. Wieringa & G. F. Wong, Nature, 501, 517 (26 Sep 2013).

    See the full article here.

    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)*.

    NRAO ALMA
    NRAO ALMA

    NRAO GBT
    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 6:46 pm on August 15, 2013 Permalink | Reply
    Tags: , , , , , NRAO GBT   

    From NRAO: “Venerable NRAO Telescope Reborn as Earth-based Antenna for Orbiting RadioAstron Satellite” 

    NRAO Icon

    National Radio Astronomy Observatory

    NRAO Banner

    August 15, 2013
    Charles Blue, Public Information Officer
    Charlottesville, Virginia
    (434) 296-0314
    cblue@nrao.edu

    “The trailblazing 43 Meter (140 Foot) Telescope at the National Radio Astronomy Observatory (NRAO) in Green Bank, W.Va., has been given new life as one of only two Earth stations for the Russian-made RadioAstron satellite, the cornerstone of astronomy’s highest-resolution telescope.

    43
    Initial testing of the 43 Meter Telescope. The service tower is to the left and the 100m diameter GBT is in the middle background.

    ra
    RadioAstron Antenna

    RadioAstron is the farthest element of an Earth-to-space spanning radio telescope system. Launched in July 2011, RadioAstron — when linked to large, ground-based radio telescopes like NRAO’s massive Robert C. Byrd Green Bank Telescope (GBT) — creates a virtual radio telescope that extends up to 220,000 miles (350,000 kilometers) across, which is about the same distance as the Earth to the Moon.

    GBT
    Robert C. Byrd Green Bank Telescope (GBT)

    From late July 2013 through early August, engineers and astronomers from the United States and Russia successfully installed sophisticated receiving and signal processing instruments on NRAO’s 43 Meter Telescope, which was completed in 1965 and retired from routine astronomical observations in 2001. The telescope has now been transformed into one of only two antennas (the other near Moscow) that can receive and process the scientific data from RadioAstron. The addition of the antenna at Green Bank effectively doubles the spacecraft’s scientific capabilities.

    ‘NRAO has built the most capable radio telescopes in the world. After nearly half a century of service, the 43 Meter Telescope is once again proving its innovative design and precision construction have much to offer the astronomical community,’ said Karen O’Neil, the NRAO site director at Green Bank and project lead for the Green Bank portion of RadioAstron.

    ‘The international scientific community is excited about RadioAstron because of the unique science that it will enable,’ said Ken Kellermann, a scientist at the NRAO in Charlottesville, Va. ‘By combining its data with leading ground-based telescopes, we will have an incredibly powerful research tool, which will provide extraordinary angular resolution enabling the study of quasars, cosmic masers, and the interstellar medium in unprecedented detail.'”

    See the full article here.

    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)*.

    NRAO ALMA
    NRAO ALMA

    NRAO GBT
    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 2:05 pm on May 9, 2013 Permalink | Reply
    Tags: , , , , Green Bank, , NRAO GBT,   

    From NRAO: “Astronomers Discover Surprising Clutch of Hydrogen Clouds Lurking among Our Galactic Neighbors” 

    NRAO Icon
    National Radio Astronomy Observatory

    NRAO Banner

    “In a dark, starless patch of intergalactic space, astronomers have discovered a never-before-seen cluster of hydrogen clouds strewn between two nearby galaxies, Andromeda (M31) and Triangulum (M33). The researchers speculate that these rarefied blobs of gas — each about as massive as a dwarf galaxy — condensed out of a vast and as-yet undetected reservoir of hot, ionized gas, which could have accompanied an otherwise invisible band of dark matter.

    gas
    Intergalactic clouds between Andromeda and Triangulum galaxies

    The astronomers detected these objects using the National Science Foundation’s Green Bank Telescope (GBT) at the National Radio Astronomy Observatory (NRAO) in Green Bank, W.Va. The results were published in the journal Nature.

    ‘We have known for some time that many seemingly empty stretches of the Universe contain vast but diffuse patches of hot, ionized hydrogen,’ said Spencer Wolfe of West Virginia University in Morgantown. ‘Earlier observations of the area between M31 and M33 suggested the presence of colder, neutral hydrogen, but we couldn’t see any details to determine if it had a definitive structure or represented a new type of cosmic feature. Now, with high-resolution images from the GBT, we were able to detect discrete concentrations of neutral hydrogen emerging out of what was thought to be a mainly featureless field of gas.'”

    See the full article here.

    NRAO ALMA
    NRAO ALMA

    NRAO GBT
    NRAO GBT

    NRAO VLA
    NRAO VLA

    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)*.

    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 1:44 pm on January 10, 2013 Permalink | Reply
    Tags: , , , , , NRAO GBT   

    From NRAO: “Mapping the Milky Way: Radio Telescopes Give Clues to Structure, History” 

    NRAO Icon
    National Radio Astronomy Observatory

    NRAO Banner

    January 9, 2013
    Dave Finley

    Astronomers have discovered hundreds of previously-unknown sites of massive star formation in the Milky Way, including the most distant such objects yet found in our home Galaxy. Ongoing studies of these objects promise to give crucial clues about the structure and history of the Milky Way.

    image way
    Red areas mark locations of a string of newly-discovered HII regions
    stretching across a portion of the MIlky Way.

    CREDIT: HRDS Survey Team, NRAO/AUI/NSF (radio); Axel Mellinger (optical)

    The scientists found regions where massive young stars or clusters of such stars are forming. These regions, which astronomers call HII (H-two) regions, serve as markers of the Galaxy’s structure, including its spiral arms and central bar.

    The astronomers are using the National Science Foundation’s (NSF) Green Bank Telescope (GBT) in West Virginia and Arecibo Telescope in Puerto Rico, and data from NASA’s Spitzer and WISE (Widefield Infrared Survey Explorer) satellites. They plan to expand the effort to include Australian radio telescopes.”

    See the full article here.

    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)*.

    NRAO ALMA
    NRAO ALMA

    NRAO GBT
    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.

     
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