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  • richardmitnick 5:35 pm on December 17, 2014 Permalink | Reply
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    From ALMA: “‘Perfect Storm’ Suffocating Star Formation around a Supermassive Black Hole” 

    ESO ALMA Array
    ALMA

    Wednesday, 17 December 2014
    Valeria Foncea
    Education and Public Outreach Officer
    Joint ALMA Observatory
    Santiago, Chile
    Tel: +56 2 467 6258
    Cell: +56 9 75871963
    Email: vfoncea@alma.cl

    Charles E. Blue
    Public Information Officer
    National Radio Astronomy Observatory
    Charlottesville, Virginia, USA
    Tel: +1 434 296 0314
    Cell: +1 434.242.9559
    E-mail: cblue@nrao.edu

    Masaaki Hiramatsu
    Education and Public Outreach Officer, NAOJ Chile
    Observatory Tokyo, Japan
    Tel: +81 422 34 3630
    E-mail: hiramatsu.masaaki@nao.ac.jp

    Richard Hook
    Public Information Officer, ESO
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    High-energy jets powered by supermassive black holes can blast away a galaxy’s star-forming fuel — resulting in so-called “red and dead” galaxies: those brimming with ancient red stars yet little or no hydrogen gas available to create new ones.

    Now astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have discovered that black holes don’t have to be nearly so powerful to shut down star formation. By observing the dust and gas at the center NGC 1266, a nearby lenticular galaxy with a relatively modest central black hole, the astronomers have detected a “perfect storm” of turbulence that is squelching star formation in a region that would otherwise be an ideal star factory.

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    NGC 1266

    This turbulence is stirred up by jets from the galaxy’s central black hole slamming into an incredibly dense envelope of gas. This dense region, which may be the result of a recent merger with another smaller galaxy, blocks nearly 98 percent of material propelled by the jets from escaping the galactic center.

    “Like an unstoppable force meeting an immovable object, the molecules in these jets meet so much resistance when they hit the surrounding dense gas that they are almost completely stopped in their tracks,” said Katherine Alatalo, an astronomer with the California Institute of Technology in Pasadena and lead author on a paper published in the Astrophysical Journal. This energetic collision produces powerful turbulence in the surrounding gas, disrupting the first critical stage of star formation. “So what we see is the most intense suppression of star formation ever observed,” noted Alatalo.

    Previous observations of NGC 1266 revealed a broad outflow of gas from the galactic center traveling up to 400 kilometers per second. Alatalo and her colleagues estimate that this outflow is as forceful as the simultaneous supernova explosion of 10,000 stars. The jets, though powerful enough to stir the gas, are not powerful enough to give it the velocity it needs to escape from the system.

    “Another way of looking at it is that the jets are injecting turbulence into the gas, preventing it from settling down, collapsing, and forming stars,” said National Radio Astronomy Observatory astronomer and co-author Mark Lacy.

    The region observed by ALMA contains about 400 million times the mass of our Sun in star-forming gas, which is 100 times more than is found in giant star-forming molecular clouds in our own Milky Way. Normally, gas this concentrated should be producing stars at a rate at least 50 times faster than the astronomers observed in this galaxy.

    Previously, astronomers believed that only extremely powerful quasars and radio galaxies contained black holes that were powerful enough to serve as a star-forming “on/off” switch.

    c
    A combined Hubble Space Telescope / ALMA image of NGC 1266. The ALMA data (orange) are shown in the central region. Credit: NASA/ESA Hubble; ALMA (NRAO/ESO/NAOJ)

    NASA Hubble Telescope
    NASA Hubble schematic
    NASA/ESA Hubble

    “The usual assumption in the past has been that the jets needed to be powerful enough to eject the gas from the galaxy completely in order to be effective at stopping start formation,” said Lacy.

    To make this discovery, the astronomers first pinpointed the location of the far-infrared light being emitted by the galaxy. Normally, this light is associated with star formation and enables astronomers to detect regions where new stars are forming. In the case of NGC 1266, however, this light was coming from an extremely confined region of the galaxy. “This very small area was almost too small for the infrared light to be coming from star formation,” noted Alatalo.

    With ALMA’s exquisite sensitivity and resolution, and along with observations from CARMA (the Combined Array for Research in Millimeter-wave Astronomy), the astronomers were then able to trace the location of the very dense molecular gas at the galactic center. They found that the gas is surrounding this compact source of the far-infrared light.

    CARMA Array
    CARMA

    Under normal conditions, gas this dense would be forming stars at a very high rate. The dust embedded within this gas would then be heated by young stars and seen as a bright and extended source of infrared light. The small size and faintness of the infrared source in this galaxy suggests that NGC 1266 is instead choking on its own fuel, seemingly in defiance of the rules of star formation.

    The astronomers also speculate that there is a feedback mechanism at work in this region. Eventually, the black hole will calm down and the turbulence will subside so star-formation can begin anew. With this renewed star formation, however, comes greater motion in the dense gas, which then falls in on the black hole and reestablishes the jets, shutting down star formation once again.

    NGC 1266 is located approximately 100 million light-years away in the constellation Eridanus. Leticular galaxies are spiral galaxies, like our own Milky Way, but they have little interstellar gas available to form new stars.

    See the full article here.

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    The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

    ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

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  • richardmitnick 9:39 pm on December 11, 2014 Permalink | Reply
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    From ALMA: “ALMA detects Pluto-Size Objects Kicking-up Dust around Sun-Like Star” 

    ESO ALMA Array
    ALMA

    Thursday, 11 December 2014
    Luca Ricci
    Harvard-Smithsonian Center for Astrophysics
    Email: lucaricci83@gmail.com

    Nicolás Lira
    Education and Public Outreach Assistant
    Joint ALMA Observatory
    Santiago, Chile
    Tel: +56 2 467 6519
    Cell: +56 9 9445 7726
    Email: nlira@alma.cl

    Charles E. Blue
    Public Information Officer
    National Radio Astronomy Observatory
    Charlottesville, Virginia, USA
    Tel: +1 434 296 0314
    Cell: +1 434.242.9559
    E-mail: cblue@nrao.edu

    Masaaki Hiramatsu
    Education and Public Outreach Officer, NAOJ Chile
    Observatory Tokyo, Japan
    Tel: +81 422 34 3630
    E-mail: hiramatsu.masaaki@nao.ac.jp

    Richard Hook
    Public Information Officer, ESO
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) may have detected the dusty hallmarks of an entire family of Pluto-size objects swarming around an adolescent version of our own Sun.

    By making detailed observations of the protoplanetary disk surrounding the star known as HD 107146, the astronomers detected an unexpected increase in the concentration of millimeter-size dust grains in the disk’s outer reaches. This surprising increase, which begins remarkably far — about 13 billion kilometers — from the host star, may be the result of Pluto-size planetesimals stirring up the region, causing smaller objects to collide and blast themselves apart.

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    ALMA image of the dust surrounding the star HD 107146. Dust in the outer reaches of the disk is thicker than in the inner regions, suggesting that a swarm of Pluto-size planetesimals is causing smaller objects to smash together. The dark ring-like structure in the middle portion of the disk may be evidence of a gap where a planet is sweeping its orbit clear of dust. Credit: L. Ricci ALMA (NRAO/NAOJ/ESO); B. Saxton (NRAO/AUI/NSF).

    The new ALMA data also hint at another intriguing feature in the outer reaches of the disk: a possible “dip” or depression in the dust about 1.2 billion kilometer wide, beginning approximately 2.5 times the distance of the Sun to Neptune from the central star. Though only suggested in these preliminary observations, this depression could be a gap in the disk, which would be indicative of an Earth-mass planet sweeping the area clear of debris. Such a feature would have important implications for the possible planet-like inhabitants of this disk and may suggest that Earth-size planets could form in an entirely new range of orbits than have ever been seen before.

    “ALMA is critical for the study of these systems that are transitioning from forming planets to having mature planet systems,” said ALMA Deputy Director and coauthor Stuartt Corder. “The material is very tenuous and the combination of sensitivity and resolution offered by ALMA not only makes details in these sorts of objects observable, it makes such observations routine.”

    The star HD 107146 is of particular interest to astronomers because it is in many ways a younger version of our own Sun. It also represents a period of transition from a solar system’s early life to its more mature, final stages where planets have finished forming and have settled into their billions-of-years-long orbits around their host star.

    “This system offers us the chance to study an intriguing time around a young, Sun-like star,” explained Corder. “We are possibly looking back in time here, back to when the Sun was about two percent of its current age.”

    The star HD 107146 is located approximately 90 light-years from Earth in the direction of the constellation Coma Berenices. It is approximately 100 million years old. Further observations with ALMA’s new long baseline, high resolution capabilities will shed more light on the dynamics and composition of this intriguing object. “At longer baselines, we expect to clearly determine the nature of the gap: is it created by a planet or not?” added Corder.

    Additional authors on the paper include John M. Carpenter and B. Fu, Caltech; A. M. Hughes, Wesleyan University; and Andrea Isella, Rice University.

    See the full article here.

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    The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

    ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

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  • richardmitnick 2:42 pm on December 9, 2014 Permalink | Reply
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    From SETI: “Answers Blowing in the Titan Wind” 


    SETI Institute

    Monday, December 08 2014
    Devon Burr
    University of Tennessee, Knoxville
    E-mail: dburr1@utk.edu
    Tel: +1 865-974-6010

    John Marshall
    SETI Institute
    E-mail: jmarshall@seti.org
    Tel: +1 650-325-2239

    Seth Shostak, Media Contact
    SETI Institute
    E-mail: seth@seti.org,
    Tel: +1 650 960-4530

    Using a specially engineered wind tunnel, scientists have solved a puzzle about wind-blown dunes on a world that has some striking similarities to our own.

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    Titan wind tunnel with important components labelled. The downwind observation side port through which the data of record are observed is the rightmost of the labelled observation ports.

    Titan, Saturn’s largest moon, has both a thick atmosphere and lakes filled with methane and ethane, making it the only solar system body other than our own with liquid on its surface. In its lower latitudes, the Cassini orbiter has found wind-driven dunes reminiscent of those seen in the deserts of Earth, but hundreds of feet high and hundreds of miles in length.

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    This natural color composite was taken during the Cassini spacecraft’s April 16, 2005, flyby of Titan.
    NASA Cassini Spacecraft
    NASA/Cassini

    It is a combination of images taken through three filters that are sensitive to red, green and violet light. It shows approximately what Titan would look like to the human eye: a hazy orange globe surrounded by a tenuous, bluish haze. The orange color is due to the hydrocarbon particles which make up Titan’s atmospheric haze. This obscuring haze was particularly frustrating for planetary scientists following the NASA Voyager mission encounters in 1980-81. Fortunately, Cassini is able to pierce Titan’s veil at infrared wavelengths (see PIA06228). North on Titan is up and tilted 30 degrees to the right. The images to create this composite were taken with the Cassini spacecraft wide angle camera on April 16, 2005, at distances ranging from approximately 173,000 to 168,200 kilometers (107,500 to 104,500 miles) from Titan and from a Sun-Titan-spacecraft, or phase, angle of 56 degrees. Resolution in the images is approximately 10 kilometers per pixel. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo. For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org.

    Dunes are also known to exist on Venus and Mars, but Titan is unlike those worlds. This raises two questions: (a) what are the dunes made of, and (b) why do they appear to be formed in a direction opposite to that of Titan’s prevailing east-to-west winds?

    “The dunes are not made of silicates – sand – as on Earth or Mars,” says Devon Burr, a planetary scientist at the University of Tennessee, Knoxville and formerly with the SETI Institute, and lead author of a paper in the journal Nature describing the new results. “They’re hydrocarbons, and may possibly include particles of water ice that are coated with these organic materials.”

    While the source of this otherworldly sand remains a mystery, more puzzling is the direction of the winds producing the dunes. This direction can be deduced from the streamline appearance of the dunes when they wrap around high points, such as craters or mountains. These streamlines indicate winds that are more west-to-east, contrary to the prevailing easterlies.

    This conflict of reasonable expectation and appearance was solved when the research team realized that the usual models for wind transport need to be adjusted for Titan’s thicker atmosphere and more viscous sand. The team found that the threshold – or minimum – wind speed needed to transport Titan’s hydrocarbon-rich sand was higher than typical for the prevailing winds on that moon.

    Burr and her coauthors made this discovery using a wind tunnel that had been constructed in the 1980s for modeling aeolian physics on Venus, notes co-author John Marshall of the SETI Institute. “It was a bear to operate, but Dr. Burr’s refurbishment of the facility as a Titan simulator has tamed the beast. It is now an important addition to NASA’s arsenal of planetary simulation facilities.”

    This greater threshold wind speed solved the mystery of the dunes’ alignment. The winds on Titan occasionally reverse direction and dramatically increase in intensity due to the changing position of the Sun in its sky. Because the threshold wind speed is so high, only these stronger winds blowing from the west can move the sand and streamline the dunes.

    “This work highlights the fact that the winds that blow 95 percent of the time might have no effect on what we see,” Burr says. Much like the damage produced by infrequent, but “perfect” storms at sea, it is the relatively rare events that have shaped the dunes of this intriguing moon.

    The new research provides important insights into wind-borne transport on other bodies, both those with very thin atmospheres (Mars, Pluto and comets) and thick, such as might be encountered in Earth-like exoplanets.

    Burr says that these results also have down-to-Earth applications.

    “We see today sediment being wafted over the Sahara desert, across the Atlantic to South America. This wind-blow material accounts for much of the fertility of the Amazon Basin. So understanding this process is essential.”

    Wind transport dynamics are also important to unraveling climate changes in the past, including the ice ages, and the so-called “snowball Earth” episode when the entire planet was encased in ice and snow.

    Marshall says that the research “has raised many questions about Titan. There we have low gravity, a dense atmosphere, and light-weight materials – a recipe for unusual aeolian activity. Our work has just begun.”

    See the full article here.

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    Mountain View, CA 94043
    Phone 650.961.6633 – Fax 650-961-7099
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  • richardmitnick 2:16 pm on December 9, 2014 Permalink | Reply
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    From SKA: “SKA talk – Jill Tarter – The SKA in the world of 2050″ 

    SKA Square Kilometer Array

    SKA

    Live from Jodrell Bank Observatory, Dr. Jill Tarter from SETI is the final keynote speaker concluding a day-long workshop on the wider benefits of the SKA in society. Dr. Tarter will present her vision of the SKA’s impact and role in tomorrow’s society, in 2050.

    Bio:
    Jill Tarter holds the Bernard M. Oliver Chair for SETI Research at the SETI Institute in Mountain View, California and serves as a member of the Board of Trustees for that institution. Tarter received her Bachelor of Engineering Physics Degree with Distinction from Cornell University and her Master’s Degree and a Ph.D. in Astronomy from the University of California, Berkeley.

    She has spent the majority of her professional career attempting to answer the old human question “Are we alone?” by searching for evidence of technological civilizations beyond Earth. She served as Project Scientist for NASA’s SETI program, the High Resolution Microwave Survey and has conducted numerous observational programs at radio observatories worldwide.

    She is a Fellow of the AAAS, the California Academy of Sciences, and the Explorers Club, she was named one of the Time 100 Most Influential People in the World in 2004, and one of the Time 25 in Space in 2012, received a TED prize in 2009, two public service awards from NASA, multiple awards for communicating science to the public, and has been honored as a woman in technology.

    She is an Adjunct Professor in the Department of Physics and Astronomy at USC, Asteroid 74824 Tarter (1999 TJ16) has been named in her honor. She is the Jansky Lecturer in 2014.
    Since the termination of funding for NASA’s SETI program in 1993, she has served in a leadership role to design and build the Allen Telescope Array and to secure private funding to continue the exploratory science of SETI. Many people are now familiar with her work as portrayed by Jodie Foster in the movie Contact.

    See the full article here.

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    About SKA

    The Square Kilometre Array will be the world’s largest and most sensitive radio telescope. The total collecting area will be approximately one square kilometre giving 50 times the sensitivity, and 10 000 times the survey speed, of the best current-day telescopes. The SKA will be built in Southern Africa and in Australia. Thousands of receptors will extend to distances of 3 000 km from the central regions. The SKA will address fundamental unanswered questions about our Universe including how the first stars and galaxies formed after the Big Bang, how dark energy is accelerating the expansion of the Universe, the role of magnetism in the cosmos, the nature of gravity, and the search for life beyond Earth. Construction of phase one of the SKA is scheduled to start in 2016. The SKA Organisation, with its headquarters at Jodrell Bank Observatory, near Manchester, UK, was established in December 2011 as a not-for-profit company in order to formalise relationships between the international partners and centralise the leadership of the project.

     
  • richardmitnick 5:43 pm on December 4, 2014 Permalink | Reply
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    From RAS: “Astronomers detect atomic hydrogen emission in galaxies at record breaking distances” 

    Royal Astronomical Society

    Royal Astronomical Society

    Wednesday, 03 December 2014
    Media contact (UK)

    Dr Robert Massey
    Royal Astronomical Society
    Tel: +44 (0)20 7734 3307 x214
    Mob: +44 (0)794 124 8035
    rm@ras.org.uk

    Science contact

    Dr Barbara Catinella
    Australian Research Council Future Fellow
    Centre for Astrophysics & Supercomputing
    Swinburne University of Technology
    Australia
    Tel: +61 3 9214 4918
    bcatinella@swin.edu.au

    Using the world’s largest radio telescope, two astronomers from Swinburne University of Technology in Australia have detected the faint signal emitted by atomic hydrogen gas in galaxies three billion light years from Earth, breaking the previous record distance by 500 million light years. Their results appear in a paper published in the journal Monthly Notices of the Royal Astronomical Society.

    a
    The 305-m Arecibo radio observatory in Puerto Rico, which was used to detect the hydrogen gas in these distant galaxies. Credit: Arecibo Observatory/NAIC.

    Using the 305-m diameter Arecibo radio telescope in Puerto Rico, Dr Barbara Catinella and Dr Luca Cortese measured the hydrogen gas content of nearly 40 galaxies at distances of up to three billion light years. By doing so, the two scientists found a unique population of galaxies hosting huge reservoirs of hydrogen gas, the fuel for forming new stars like our Sun.

    These very gas-rich systems each contain between 20 and 80 billion times the mass of the Sun in atomic gas. Such galaxies are rare, but astronomers believe that they were more common in the past, when the Universe was younger.

    “Atomic hydrogen gas is the fuel out of which new stars are formed, hence it is a crucial component to study if we are to understand how galaxies form and evolve,” study leader Dr Catinella said.

    “Because of the limitations of current instruments, astronomers still know very little about the gas content of galaxies beyond our local neighbourhood.”

    Local Group
    Local Group

    Co-author Dr Luca Cortese said detecting atomic hydrogen emission from distant galaxies is very challenging.

    “The signals are not only weak, but they appear at radio frequencies that are used by communication devices and radars, which generate signals billions of times stronger than the cosmic ones that we are trying to detect.”

    4
    Images of four distant galaxies observed with the Arecibo radio telescope, which have been found to host huge reservoirs of atomic hydrogen gas. Credit: Sloan Digital Sky Survey.Measuring the atomic hydrogen signal emitted by distant galaxies is one of the main scientific drivers behind the billion dollar Square Kilometre Array (SKA) project, for which technology demonstrators like the Australian SKA Pathfinder are under construction. The Arecibo observations give astronomers a glimpse into the population of gas-rich galaxies that will be routinely discovered by these instruments in coming decades.

    Sloan Digital Sky Survey Telescope
    Sloan Digital Sky Survey Telescope

    SKA Square Kilometer Array

    SKA Pathfinder Radio Telescope
    SKA Pathfinder Radio Telescope

    This project started as an experiment to see at what distances astronomers were able to detect the signal from atomic hydrogen in galaxies.

    “The outcome vastly exceeded our initial expectations,” Dr Catinella said.

    “Not only did we detect radio signals emitted by distant galaxies when the Universe was three billion years younger, but their gas reservoirs turned out to be unexpectedly large, about 10 times larger than the mass of hydrogen in our Milky Way. Such a huge amount of fuel will be able to feed star formation in these galaxies for several billion years in the future.”

    Further studies will seek to understand why these galaxies have not yet converted a great part of their gas into stars. The SKA and its pathfinders will be the key to solving this mystery.

    Further information

    The new results are published in B. Catinella & L. Cortese, HIGHz: A Survey of the Most HI-Massive Galaxies at z~0.2, Monthly Notices of the Royal Astronomical Society, in press, published by Oxford University Press (link will go live on 9 December 2014). A preprint is available on the arXiv.

    The research was supported under the Australian Research Council’s Future Fellowship and Discovery funding schemes.

    See the full article here.

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    The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science.

     
  • richardmitnick 3:29 pm on December 4, 2014 Permalink | Reply
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    From NRAO: “Strange Galaxy Perplexes Astronomers” 

    NRAO Icon
    National Radio Astronomy Observatory

    NRAO Banner

    2 December 2014

    Contact:
    Dave Finley, Public Information Officer
    (575) 835-7302
    dfinley@nrao.edu

    With the help of citizen scientists, a team of astronomers has found an important new example of a very rare type of galaxy that may yield valuable insight on how galaxies developed in the early Universe. The new discovery technique promises to give astronomers many more examples of this important and mysterious type of galaxy.

    The galaxy they studied, named J1649+2635, nearly 800 million light-years from Earth, is a spiral galaxy, like our own Milky Way, but with prominent “jets” of subatomic particles propelled outward from its core at nearly the speed of light. The problem is that spiral galaxies are not supposed to have such large jets.

    “The conventional wisdom is that such jets come only from elliptical galaxies that formed through the merger of spirals. We don’t know how spirals can have these large jets,” said Minnie Mao, of the National Radio Astronomy Observatory (NRAO).

    J1649+2635 is only the fourth jet-emitting spiral galaxy discovered so far. The first was found in 2003, when astronomers combined a radio-telescope image from the Karl G. Jansky Very Large Array (VLA) and a visible-light image of the same object from the Hubble Space Telescope. The second was revealed in 2011 by images from the Sloan Digital Sky Survey and the VLA, and the third, found earlier this year, also was discovered by combining radio and visible-light images.

    NRAO VLA
    NRAO/VLA

    NASA Hubble TelescopeNASA Hubble schematic
    NASA/ESA Hubble

    Sloan Digital Sky Survey Telescope
    Sloan Digital Sky Survey Telescope

    “In order to figure out how these jets can be produced by the ‘wrong’ kind of galaxy, we realized we needed to find more of them,” Mao said.

    To do that, the astronomers looked for help. That help came in the form of large collections of images from both radio and optical telescopes, and the hands-on assistance of volunteer citizen scientists. The volunteers are participants in an online project called the Galaxy Zoo, in which they look at images from the visible-light Sloan Digital Sky Survey and classify the galaxies as spiral, elliptical, or other types. Each galaxy image is inspected by multiple volunteers to ensure accuracy in the classification.

    So far, more than 150,000 Galaxy Zoo participants have classified some 700,000 galaxies. Mao and her collaborators used a “superclean” subset of more than 65,000 galaxies, for which 95 percent of those viewing each galaxy’s image agreed on the classification. About 35,000 of those are spiral galaxies. J1649+2635 had been classified by 31 Galaxy Zoo volunteers, 30 of whom agreed that it is a spiral.

    Next, the astronomers decided to cross-match the visible-light spirals with galaxies in a catalog that combines data from the NRAO VLA Sky Survey and the Faint Images of the Radio Sky at Twenty Centimeters survey, both done using the VLA. This job was done by Ryan Duffin, a University of Virginia undergraduate working as an NRAO summer student. Duffin’s cross-matching showed that J1649+2635 is both a spiral galaxy and has powerful twin radio jets.

    “This is the first time that a galaxy was first identified as a spiral, then subsequently found to have large radio jets,” Duffin said. “It was exciting to make such a rare find,” he added.

    Jets such as those seen coming from J1649+2635 are propelled by the gravitational energy of a supermassive black hole at the core of the galaxy. Material pulled toward the black hole forms a rapidly-rotating disk, and particles are accelerated outward along the poles of the disk. The collision that presumably forms an elliptical galaxy disrupts gas in the merging galaxies and provides “fuel” for the disk and acceleration mechanism. That same disruption, however, is expected to destroy any spiral structure as the galaxies merge into one.

    J1649+2635 is unusual not only because of its jets, but also because it is the first example of a “grand design” spiral galaxy with a large “halo” of visible-light emission surrounding it.

    “This galaxy presents us with many mysteries. We want to know how it became such a strange beast,” Mao said. “Did it have a unique type of merger that preserved its spiral structure? Was it an elliptical that had another collision that made it re-grow spiral arms? Is its unique character the result of interaction with its environment?”

    “We will study it further, but in addition, we need to see if there are more like it,” Mao said.

    “We hope that with projects like the Galaxy Zoo and another called Radio Galaxy Zoo, those thousands of citizen scientists can help us find many more galaxies like this one so we can answer all our questions,” Mao said. Mao and her colleagues have dubbed these rare galaxies “Spiral DRAGNs,” an acronym for the technical description, “Double-lobed Radio sources Associated with Galactic Nuclei.”

    Mao and Duffin worked with Frazer Owen, Emmanuel Momjian, and Mark Lacy, also of the NRAO; Bill Keel of the University of Alabama; Glenn Morrison of the University of Hawaii and the Canada-France-Hawaii Telescope; Tony Mroczkowski of the Naval Research Laboratory; Susan Neff of NASA’s Goddard Space Flight Center; Ray Norris of CSIRO Astronomy and Space Science in Australia; Henrique Schmitt of the Naval Research Laboratory; and Vicki Toy and Sylvain Veilleux of the University of Maryland. The scientists are reporting their findings in the Monthly Notices of the Royal Astronomical Society.

    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)*.

    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 9:35 am on December 4, 2014 Permalink | Reply
    Tags: , , , , , Radio Astronomy   

    From ALMA: “ALMA Identifies Gas Spirals as a Nursery of Twin Stars” 

    ESO ALMA Array
    ALMA

    Thursday, 04 December 2014
    Shigehisa Takakuwa
    Associate Research Fellow, Institute of Astronomy Astrophysics,
    Academia Sinica
    Taipei, Taiwan
    Email: takakuwa@asiaa.sinica.edu.tw
    Tel: +886-2-2366-5395

    Valeria Foncea
    Education and Public Outreach Officer
    Joint ALMA Observatory
    Santiago, Chile
    Tel: +56 2 467 6258
    Cell: +56 9 75871963
    Email: vfoncea@alma.cl

    Masaaki Hiramatsu
    Education and Public Outreach Officer, NAOJ Chile
    Observatory Tokyo, Japan
    Tel: +81 422 34 3630
    E-mail: hiramatsu.masaaki@nao.ac.jp

    Richard Hook
    Public Information Officer, ESO
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    Charles E. Blue
    Public Information Officer
    National Radio Astronomy Observatory
    Charlottesville, Virginia, USA
    Tel: +1 434 296 0314
    Cell: +1 434.242.9559
    E-mail: cblue@nrao.edu

    With new Atacama Large Millimeter/submillimeter Array (ALMA) observations, astronomers led by Shigehisa Takakuwa, Associate Research Fellow at the Institute of Astronomy and Astrophysics, Academia Sinica (ASIAA), Taiwan, have found spiral arms of molecular gas and dust around “baby twin” stars. Gas motions supplying materials to the twin were also identified. These results unveil for the first time, the mechanism of the birth and growth of binary stars, which are ubiquitous throughout the Universe. The study was published on November 20 in The Astrophysical Journal.

    b
    Fig 1. Gas and dust disks around L1551 NE spotted by ALMA. Credit: ALMA (ESO/NAOJ/NRAO)/Takakuwa et al.

    Stars form in interstellar clouds of molecular gas and dust. Previous studies of star formation focused primarily on single stars like the Sun, and a standard picture of single star formation has been established. According to this picture, a dense gas condensation in an interstellar cloud collapses gravitationally to form a single protostar at the center. Previous observations have found such collapsing gas motions feeding material toward the central protostars.

    Compared to single star formation, our understanding of binary star formation has been limited, even though more than half of stars with a mass similar to that of the Sun are known to be binaries. It is thus crucial to observe the physical mechanism of binary formation to obtain a more comprehensive understanding of star formation. Theory suggests that a disk surrounding a young binary will feed material to the central “baby twin” in order for them to grow. While recent observations have found such disks (known as “circumbinary disks“), it was not possible to image the structure and gas motions because of the insufficient imaging resolution and sensitivity.

    2
    Fig 2. Comparison of the disks in simulation and observation. The right panel shows the disk image simulated with ATERUI, and the left panel the real ALMA image. Credit: ALMA (ESO/NAOJ/NRAO)/Takakuwa et al.

    The research team, led by Shigehisa Takakuwa, used the ALMA telescope to observe the baby-twin star L1551 NE [1], located in the constellation of Taurus at a distance of 460 light years, with a 1.6 times better imaging resolution and a 6 times better sensitivity than those of their previous observations with the SubMillimeter Array (SMA).

    Submillimeter Array Hawaii SAO
    CfA Submillimeter Array

    They used the emission from dust at a wavelength of 0.9mm to trace the distribution of interstellar material, and emission from carbon monoxide to study gas motions using the Doppler Effect. They found gas associated with each binary star (the two central components can be seen in Figure 1), and a disk surrounding both stars, the circumbinary disk, with a radius of 300 au. The radius corresponds to 10 times the orbital radius of Neptune in our solar system. For the first time, they succeeded in imaging the detailed structure of the circumbinary disk, and found that it consists of a southern U-shaped feature with northern extensions pointing to the northwest and the northeast (Figure 1).

    To understand these newly-identified features, the research team constructed a theoretical model of binary formation in L1551 NE, shown in Figure 2 (right, see also the attached movie), using the supercomputer, “ATERUI” at the National Astronomical Observatory of Japan (NAOJ) [2]. As shown in Figure 2, the southern U-shaped feature and northern emission protrusions observed with ALMA can be reproduced with a pair of spiral arms stemming from each of the baby twins. The research team also investigated the gas motion as seen in carbon monoxide, and found the spiral arms to be rotating faster than the regions between the arms. These inter-arm regions show gas falling toward the central baby twins. This is believed to be the ongoing feeding process of the baby twins. These results show that the twins “shake” the surrounding circumbinary disk and induce the falling gas motion. “Our high-resolution ALMA observation has unveiled live images of the growth of the baby twins for the first time”, said Takakuwa.

    Tomoaki Matsumoto, a professor at Hosei University, who constructed the theoretical model with the supercomputer, said, “The ALMA results match with our theoretical prediction remarkably accurately” [3]. Kazuya Saigo, co-principal investigator along with Takakuwa, explained, “We succeeded in unveiling the structure and motion in the circumbinary disk with high accuracy, because of the high resolution and sensitivity of ALMA. Combining these high-resolution ALMA observations with thorough numerical simulations using a supercomputer will become more and more important, and can be regarded as an upcoming research trend”.

    Notes:

    [1] The mass of each twin of L1551 NE is 0.67 and 0.13 times the mass of the Sun, and their separation is 145 au (astronomical unit; 1 au is the distance between the Sun and the Earth, approximately 150 million km).

    [2] The supercomputer ATERUI (Cray XC30), operated by NAOJ Center for Computational Astrophysics, is the fastest one dedicated for astrophysics research.

    NAOJ Cray ATERUI

    [3] NAOJ’s Subaru Telescope found a spiral structure around a more evolved binary system SR24. The stars in SR24 are close to the final stage of their growth and the gas envelope has almost dissipated, whereas the twin stars in L1551 NE are in the very early, active stage of their growth. The ALMA observation shows that the spiral structure plays an important role in this very early phase of binary formation.

    NAOJ Subaru Telescope
    NAOJ Subaru Telescope interior
    NAOJ Subaru

    Reference:

    First Direct Imaging of a Young Binary System http://subarutelescope.org/Pressrelease/2009/11/19/index.html

    These observational results were published in The Astrophysical Journal as Takakuwa et al. Angular Momentum Exchange by Gravitational Torques and Infall in the Circumbinary Disk of the Protostellar System L1551 NE in November 2014.

    The complete list of authors is: Shigehisa Takakuwa (ASIAA), Masao Saito (NAOJ/SOKENDAI (The Graduate University for Advanced Studies)),Kazuya Saigo (NAOJ), Tomoaki Matsumoto (Hosei Univ.), Jeremy Lim (Univ. of Hong-Kong), Tomoyuki Hanawa (Chiba Univ.), and Paul T. P. Ho (ASIAA).

    The research was supported by research grants from the Ministry of Science and Technology of Taiwan (MOST 102-2119-M-001-012-MY3), GRF grants of the Government of the Hong Kong SAR under HKU 703512P and the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Numbers 24244017, 23540270.

    See the full article, with video, here.

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    The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

    ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

    NRAO Small

    ESO 50

    NAOJ

     
  • richardmitnick 4:55 pm on December 3, 2014 Permalink | Reply
    Tags: , , , , Radio Astronomy, SKA MeerKAT,   

    From SKA via Mail&Guardian: “German institute’s R150m boost for MeerKAT telescope” 

    SKA Square Kilometer Array

    SKA

    mg

    02 Dec 2014
    Sarah Wild

    The Max-Planck Institute for Radio Astronomy in Germany says it is pleased to be part of a “light-house” project for science in Africa.

    r

    Germany’s Max-Planck Institute for Radio Astronomy is to commit R150-million to the construction and installation of radio receivers on South Africa’s MeerKAT radio telescope, Square Kilometre Array (SKA), it was announced on Tuesday.

    The 64-dish MeerKAT, expected to be complete in 2017, will form part of the SKA, which will be the largest radio telescope in the world. The R2-billion MeerKAT is a South African-funded and designed telescope, with 75% of the components sourced locally, and will be the most sensitive radio telescope of its kind in the Southern Hemisphere.

    SKA AfricaIcon

    About five years of observing time on the telescope have already been allocated to more than 500 radio astronomers, 85 of them from Africa. Celestial objects produce radio waves, and by picking up on these signals radio astronomers are able to “see” what the universe looks like.

    Radio telescopes have a number of receivers, each of which focuses on a different part of the radio wave spectrum.

    The receivers to be funded by the institute will be primarily for “research on pulsars, [which are] rapidly spinning neutron stars which emit very regular radio pulses and can be used as highly accurate clocks to test extreme physics”, it said.

    Investment a ‘vote of confidence’

    “We consider MeerKAT to be an important undertaking as it is not only a pre-eminent astronomy project, but also a light-house project for science in Africa in general. The [Max-Plank Institute] is very pleased to enable close collaboration between its scientists and the South African community and looks forward to see MeerKAT’s first glimpse of the universe with the receivers of the [institute],” the institute’s president Martin Stratmann said.

    Science and Technology Minister Naledi Pandor said: “This significant investment by a leading global research organisation of prestigious repute, home to several Nobel Prize winners, [is] an important vote of confidence, in South African science in general and the MeerKAT specifically.”

    See the full article here.

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    SKA Banner

    About SKA

    The Square Kilometre Array will be the world’s largest and most sensitive radio telescope. The total collecting area will be approximately one square kilometre giving 50 times the sensitivity, and 10 000 times the survey speed, of the best current-day telescopes. The SKA will be built in Southern Africa and in Australia. Thousands of receptors will extend to distances of 3 000 km from the central regions. The SKA will address fundamental unanswered questions about our Universe including how the first stars and galaxies formed after the Big Bang, how dark energy is accelerating the expansion of the Universe, the role of magnetism in the cosmos, the nature of gravity, and the search for life beyond Earth. Construction of phase one of the SKA is scheduled to start in 2016. The SKA Organisation, with its headquarters at Jodrell Bank Observatory, near Manchester, UK, was established in December 2011 as a not-for-profit company in order to formalise relationships between the international partners and centralise the leadership of the project.

     
  • richardmitnick 7:33 am on December 2, 2014 Permalink | Reply
    Tags: , , , , Radio Astronomy,   

    From The Conversation: “Monster telescope needs mind-bending mathematics to uncover secrets of the universe “ 

    Conversation
    The Conversation

    November 24 2014
    Yves Wiaux, Associate Professor at Heriot Watt University
    Jason McEwen, Assistant Professor (University Lecturer) at University College London

    Telescopes have come a long way since the days when they were all about lone astronomers watching the night sky through their upstairs windows. Today teams of astrophysicists build and use much more modern instruments, not only to observe light visible to our eyes, but also radio emissions from the universe.

    Radio telescopes used to use large single dishes to pick up these emissions, but have since graduated to arrays of antennae. These act as one dish over much a wider area and make it possible to receive signals from further away. We refer to them as radio-interferomic arrays because they study the interference of radio waves between pairs of antennae.

    NRAO VLA
    NRAO VLA

    p
    A computerised pulsar Michael Taylor

    Radio interferometry was developed by the English scientists Antony Hewish and Martin Ryle, who received the Nobel prize in 1974 for using such telescopes to discover pulsars – highly magnetised rotating neutron stars. Pulsars rotate with extreme stability, making them the most precise clocks in the Universe.

    In 1993 the American astrophysicists Russell Hulse and Joseph Taylor demonstrated the importance of pulsars in understanding our universe by discovering them in a gravitationally coupled pair known as a binary system.. This provided the first indirect evidence for gravitational waves, which are an essential unproven part of [Albert]Einstein’s theory of general relativity.

    Where radio telescopes are headed

    There have been numerous arrays of radio telescopes developed since the 1970s. The state of the art includes the Low-Frequency Array (LOFAR) in western Europe, the Murchison Widefield Array (MWA) in western Australia, and the Atacama Large Millimetre Array (ALMA) in Chile. These are all just coming online and are regarded as a major step forward in our ability to understand the universe.

    LOFAR Map
    LOFAR

    SKA Murchison Widefield Array
    SKA Murchison Widefield Array

    alma
    ALMA in Chile, one of the current generation of radio telescopic arrays EPA

    Yet they will be soon followed by the Square Kilometre Array (SKA), which will be made up of an unprecedented number of antennae spread across two continents for the first time (Australia and Africa). The SKA will see the radio sky with unprecedented sensitivity and resolution, enabling us to pick up extremely small and faint objects and probe the more distant universe. It is due to come online around 2023.

    It is already the case that interferometric data holds only partial information and does not provide immediately recognisable visual images. This is because the antenna array cannot be dense enough to cover each and every position on the ground. To convert the information into images, complex mathematical algorithms are already used.

    To add to this existing complexity, SKA will record unprecedented volumes of data. To put it in perspective, astronomers anticipate that it will produce as much as ten times the data as global internet traffic. Radio astronomical imaging therefore urgently needs to be re-invented in this ultra-precision and big data context.

    This is where we come in. We have recently received funding to develop new ways to acquire data with radio telescopes using a recent theory called compressed sensing.

    This theory enables us to build up whole pictures with far more fragmented data than before, ensuring that each data point contains the maximum amount of information. We will also design image-recovery algorithms that are scalable to the SKA’s big data regime and can reconstruct ultra-high resolution images of the distant universe.


    ET, Einstein and the dark universe

    This forthcoming radio telescope throws up numerous exciting possibilities. It will be able to observe the formation of Earth-like planets in other galaxies, and detect possible signals sent by extra-terrestrial intelligence. It will also be able to detect amino acids and carbon biomolecules, which are key building blocks for organic life.

    The SKA has the potential to produce new pulsar discoveries. It should be sensitive enough to allow tens of thousands of pulsars to be detected, with very good chances of finding one orbiting a black hole for the first time. This would allow us to test Einstein’s theories about what happens in the unexplored strong gravity regime around black holes. We might also be able to directly observe gravitational waves for the first time by monitoring the change of distance between pulsars as waves pass by.

    The coming leap forward in radio telescopes will also help us to understand the origins of the universe. Although we can infer the existence of the epoch when the first stars formed from our general understanding of the universe and other observations, we have never observed it directly.

    Direct observations of hydrogen emission from this period would tell us a lot about how the first stars formed, and also about cosmology in general, including our understanding of the very first moments following the Big Bang. The LOFAR and MWA telescopes will look for this very weak signal. But if they are able to detect it, it would only be in a statistical sense. The SKA will be the first telescope capable of producing images of this epoch when the first stars formed.

    Another science goal of the SKA is to develop a deeper understanding of dark energy and dark matter. One way of doing this is to study the distortion of the light from background galaxies by intervening matter as it travels towards us.

    In modern cosmology this effect, called weak lensing, has typically been studied with optical telescopes. Yet there is a lot to be gained from similar studies using radio wavelengths. Very high resolution is required, however, so it can’t be done with existing radio telescopes. The SKA will open up this new area, potentially uncovering a deeper understanding of the nature of dark energy and dark matter.
    From astronomy to medicine

    n
    Neuronal connections in the brain Thomas Schultz

    In short, we could be on the verge of a great leap forward in our understanding of the universe. If so, the new theory of compressed sensing could play an essential role in recovering images from tiny fragments of information far in the distant universe.

    Beyond this, compressed sensing has a wide range of other applications. For instance we will transfer our techniques from astronomical to biomedical imaging, using compressed sensing to tackle the challenges of fast high-resolution magnetic resonance imaging (MRI). This is likely to give researchers a much more detailed understanding of neuronal pathways in the human brain.

    See the full article here.

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    The Conversation US launched as a pilot project in October 2014. It is an independent source of news and views from the academic and research community, delivered direct to the public.
    Our team of professional editors work with university and research institute experts to unlock their knowledge for use by the wider public.
    Access to independent, high quality, authenticated, explanatory journalism underpins a functioning democracy. Our aim is to promote better understanding of current affairs and complex issues. And hopefully allow for a better quality of public discourse and conversation.

     
  • richardmitnick 11:24 am on November 25, 2014 Permalink | Reply
    Tags: , , , , , , Radio Astronomy   

    From AAAS: “Complex life may be possible in only 10% of all galaxies” 

    AAAS

    AAAS

    24 November 2014
    Adrian Cho

    The universe may be a lonelier place than previously thought. Of the estimated 100 billion galaxies in the observable universe, only one in 10 can support complex life like that on Earth, a pair of astrophysicists argues. Everywhere else, stellar explosions known as gamma ray bursts would regularly wipe out any life forms more elaborate than microbes. The detonations also kept the universe lifeless for billions of years after the big bang, the researchers say.

    “It’s kind of surprising that we can have life only in 10% of galaxies and only after 5 billion years,” says Brian Thomas, a physicist at Washburn University in Topeka who was not involved in the work. But “my overall impression is that they are probably right” within the uncertainties in a key parameter in the analysis.

    Scientists have long mused over whether a gamma ray burst could harm Earth. The bursts were discovered in 1967 by satellites designed to spot nuclear weapons tests and now turn up at a rate of about one a day. They come in two types. Short gamma ray bursts last less than a second or two; they most likely occur when two neutron stars or black holes spiral into each other. Long gamma ray bursts last for tens of seconds and occur when massive stars burn out, collapse, and explode. They are rarer than the short ones but release roughly 100 times as much energy. A long burst can outshine the rest of the universe in gamma rays, which are highly energetic photons.

    That seconds-long flash of radiation itself wouldn’t blast away life on a nearby planet. Rather, if the explosion were close enough, the gamma rays would set off a chain of chemical reactions that would destroy the ozone layer in a planet’s atmosphere. With that protective gas gone, deadly ultraviolet radiation from a planet’s sun would rain down for months or years—long enough to cause a mass die-off.

    How likely is that to happen? Tsvi Piran, a theoretical astrophysicist at the Hebrew University of Jerusalem, and Raul Jimenez, a theoretical astrophysicist at the University of Barcelona in Spain, explore that apocalyptic scenario in a paper in press at Physical Review Letters.

    Astrophysicists once thought gamma ray bursts would be most common in regions of galaxies where stars are forming rapidly from gas clouds. But recent data show that the picture is more complex: Long bursts occur mainly in star-forming regions with relatively low levels of elements heavier than hydrogen and helium—low in “metallicity,” in astronomers’ jargon.

    Using the average metallicity and the rough distribution of stars in our Milky Way galaxy, Piran and Jimenez estimate the rates for long and short bursts across the galaxy. They find that the more-energetic long bursts are the real killers and that the chance Earth has been exposed to a lethal blast in the past billion years is about 50%. Some astrophysicists have suggested a gamma ray burst may have caused the Ordovician extinction, a global cataclysm about 450 million years ago that wiped out 80% of Earth’s species, Piran notes.

    The researchers then estimate how badly a planet would get fried in different parts of the galaxy. The sheer density of stars in the middle of the galaxy ensures that planets within about 6500 light-years of the galactic center have a greater than 95% chance of having suffered a lethal gamma ray blast in the last billion years, they find. Generally, they conclude, life is possible only in the outer regions of large galaxies. (Our own solar system is about 27,000 light-years from the center.)

    Things are even bleaker in other galaxies, the researchers report. Compared with the Milky Way, most galaxies are small and low in metallicity. As a result, 90% of them should have too many long gamma ray bursts to sustain life, they argue. What’s more, for about 5 billion years after the big bang, all galaxies were like that, so long gamma ray bursts would have made life impossible anywhere.

    But are 90% of the galaxies barren? That may be going too far, Thomas says. The radiation exposures Piran and Jimenez talk about would do great damage, but they likely wouldn’t snuff out every microbe, he contends. “Completely wiping out life?” he says. “Maybe not.” But Piran says the real issue is the existence of life with the potential for intelligence. “It’s almost certain that bacteria and lower forms of life could survive such an event,” he acknowledges. “But [for more complex life] it would be like hitting a reset button. You’d have to start over from scratch.”

    The analysis could have practical implications for the search for life on other planets, Piran says. For decades, scientists with the SETI Institute in Mountain View, California, have used radio telescopes to search for signals from intelligent life on planets around distant stars. But SETI researchers are looking mostly toward the center of the Milky Way, where the stars are more abundant, Piran says. That’s precisely where gamma ray bursts may make intelligent life impossible, he says: “We are saying maybe you should look in the exact opposite direction.”

    Allen Telescope Array
    Allen Telescope Array, part of SETI Institute

    Arecibo
    Arecibo Radio Telescope used by SETI@home

    NRAO GBT
    NRAO Green Bank Radio Telescope

    Jodrell Bank Lovell Telescope
    Jodrell Bank Lovell Radio Telescope

    See the full article here.

    The American Association for the Advancement of Science is an international non-profit organization dedicated to advancing science for the benefit of all people.

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