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  • richardmitnick 10:55 am on April 29, 2016 Permalink | Reply
    Tags: , , , , Radio Astronomy   

    From NRAO: “Gravitational Wave Search Provides Insights into Galaxy Evolution and Mergers” 

    NRAO Icon
    National Radio Astronomy Observatory

    NRAO Banner

    5 April 2016
    Elizabeth Ferrara
    NANOGrav press officer
    elizabeth.ferrara@nanograv.org
    301-286-7057

    Charles Blue
    NRAO Public Information Officer
    cblue@nrao.edu
    (434) 296-0314

    1
    The Earth is constantly jostled by low-frequency gravitational waves from supermassive black hole binaries in distant galaxies. Astrophysicists are using pulsars as a galaxy-sized detector to measure the Earth’s motion from these waves. Credit: B. Saxton (NRAO/AUI/NSF)

    Summary: New results from NANOGrav – the North American Nanohertz Observatory for Gravitational Waves – establish astrophysically significant limits in the search for low-frequency gravitational waves. This result provides insight into how often galaxies merge and how those merging galaxies evolve over time. To obtain this result, scientists required an exquisitely precise, nine-year pulsar-monitoring campaign conducted by two of the most sensitive radio telescopes on Earth, the Green Bank Telescope in West Virginia and the Arecibo Observatory in Puerto Rico.

    NRAO/GBT
    NRAO/GBT, West Virginia, USA

    NAIC/Arecibo Observatory
    NAIC/Arecibo Observatory, Puerto Rico, USA

    The recent LIGO detection of gravitational waves from merging black holes with tens of solar masses has confirmed that distortions in the fabric of space-time can be observed and measured [1].

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

    Caltech/MIT Advanced aLIGO Hanford Washington USA installation
    Caltech/MIT Advanced aLIGO Hanford Washington USA installation

    Researchers from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) have spent the past decade searching for low-frequency gravitational waves emitted by black hole binaries with masses many millions of times larger than those seen by LIGO.

    Analysis of NANOGrav’s nine-year dataset provides very constraining limits on the prevalence of such supermassive black hole binaries throughout the Universe. Given scientists’ current understanding of how often galaxies merge, these limits point to fewer detectable supermassive black hole binaries than were previously expected. This result has significant impacts on our understanding of how galaxies and their central black holes co-evolve.

    Low-frequency gravitational waves are very difficult to detect, with wavelengths spanning light-years and originating from black hole binaries in galaxies spread across the sky. The combination of all these giant binary black holes leads to a constant “hum” of gravitational waves that models predict should be detectable at Earth. Astrophysicists call this effect the “stochastic gravitational wave background,” and detecting it requires special analysis techniques.

    Pulsars are the cores of massive stars left behind after stars go supernova. The fastest pulsars rotate hundreds of times each second and emit a pulse of radio waves every few milliseconds. These millisecond pulsars (MSPs) are considered nature’s most precise clocks and are ideal for detecting the small signal from gravitational waves. “This measurement is possible because the gravitational wave background imprints a unique signature onto the radio waves seen from a collection of MSPs,” said Justin Ellis, Einstein Fellow at NASA’s Jet Propulsion Laboratory, California Institute of Technology in Pasadena, California, and a co-author on the report published in Astrophysical Journal.

    Astrophysicists use computer models to predict how often galaxies merge and form supermassive black hole binaries. Those models use several simplifying assumptions about how black hole binaries evolve when they predict the strength of the stochastic gravitational wave background. By using information about galaxy mergers and constraints on the background, the scientists are able to improve their assumptions about black hole binary evolution.

    Ellis continues: “After nine years of observing a collection of MSPs, we haven’t detected the stochastic background but we are beginning to rule out many predictions based on current models of galaxy evolution. We are now at a point where the non-detection of gravitational waves is actually improving our understanding of black hole binary evolution.”

    “Pulsar timing arrays like NANOGrav are making novel observations of the evolution and nature of our Universe,” says Sarah Burke Spolaor, Jansky Fellow at the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico, and a co-author on the paper.

    According to Spolaor, there are two possible interpretations of this non-detection. “Some supermassive black hole binaries may not be in circular orbits or are significantly interacting with gas or stars. This would drive them to merge faster than simple models have assumed in the past,” she said. An alternate explanation is that many of these binaries inspiral too slowly to ever emit detectable gravitational waves.

    NANOGrav is currently monitoring 54 pulsars, using the National Science Foundation’s Green Bank Telescope in West Virginia and Arecibo Radio Observatory in Puerto Rico, the two most sensitive radio telescopes at these frequencies [2]. Their array of pulsars is continually growing as new MSPs are discovered. In addition, the group collaborates with radio astronomers in Europe and Australia as part of the International Pulsar Timing Array, giving them access to many more pulsar observations. Ellis estimates that this increase in sensitivity could lead to a detection in as little as five years.

    In addition, this measurement helps constrain the properties of cosmic strings, very dense and thin cosmological objects, which many theorists believe evolved when the Universe was just a fraction of a second old. These strings can form loops, which then decay through gravitational wave emission. The most conservative NANOGrav limit on cosmic string tension is the most stringent limit to date, and will continue to improve as NANOGrav continues operating.

    “These new results from NANOGrav have the most important astrophysical implications yet,” said Scott Ransom, an astronomer with the NRAO in Charlottesville, Virginia. “As we improve our detection capabilities, we get closer and closer to that important threshold where the cosmic murmur begins to be heard. At that point, we’ll be able to perform entirely new types of physics experiments on cosmic scales and open up a new window on the Universe, just like LIGO just did for high-frequency gravitational waves.”

    NANOGrav is a collaboration of over 60 scientists at over a dozen institutions in the United States and Canada whose goal is detecting low-frequency gravitational waves to open a new window on the Universe. The group uses radio pulsar timing observations to search for the ripples in the fabric of spacetime. In 2015, NANOGrav was awarded $14.5 million by the National Science Foundation (NSF) to create and operate a Physics Frontiers Center.

    The Physics Frontier Centers bring people together to address frontier science, and NANOGrav’s work in low-frequency gravitational wave physics is a great example,” said Jean Cottam Allen, the NSF program director who oversees the Physics Frontiers Center program. “We’re delighted with their progress thus far, and we’re excited to see where it will lead.”

    1. # #

    Notes

    [1] LIGO is the Laser Interferometer Gravitational-Wave Observatory (https://www.ligo.caltech.edu)
    Press Release: Gravitational waves detected 100 years after Einstein’s prediction http://www.nsf.gov/news/news_summ.jsp?cntn_id=137628&org=NSF&from=news

    [2] National Science Foundation (http://www.nsf.gov)
    Press Release: Advancing physics frontiers: Newest collaborative centers set to blaze trails in basic research
    http://www.nsf.gov/news/news_summ.jsp?cntn_id=134586

    Reference:
    The NANOGrave Nine-year Data Set: Limits on the Isotropic Stochastic Gravitational Wave Background, Z. Arzoumanian et al., 2016, appears in the Astrophysical Journal http://iopscience.iop.org/journal/0004-637X.

    See the full article here .

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

    ALMA Array

    NRAO ALMA

    NRAO GBT
    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 2:19 pm on April 27, 2016 Permalink | Reply
    Tags: Astronomers detect mass of one quadrillion Earths, , , , Radio Astronomy   

    From CSIRO: “Astronomers detect mass of one quadrillion Earths” 

    CSIRO bloc

    Commonwealth Scientific and Industrial Research Organisation

    27th April 2016
    Fiona McFarlane

    SKA ASKAP Phased Array
    SKA ASKAP Phased Array

    Our scientists have weighed in on the idea of measuring a supermassive black hole and it’s come in at a whopping 3.8 billion solar masses – equivalent to one quadrillion Earths.

    At this mass the supermassive black hole at the centre of the distant galaxy being studied, outweighs our own Milky Way’s supermassive black hole by a factor of approximately 1000, estimated at a mass of just 4 million suns. Maybe it’s just as well our closest black hole is relatively small given the fact that material that gets too close gets sucked in and can never escape – a fact put to good use by the Simpsons. Fortunately for us, astronomers assure us that Earth won’t be sucked in anytime soon.

    But how did our scientists actually get to weigh one of these fascinating and mysterious objects?

    Dr Lisa Harvey-Smith, one of our astronomers working on the ASKAP project, made the measurement using the ASKAP and the Australia Telescope Compact Array (ATCA).

    SKA ASKAP telescope
    SKA ASKAP radio telescope

    Australia Telescope Compact Array
    Australia Telescope Compact Array

    What is a mega-maser?

    An astronomical maser can be described simply as clouds of gas that are amplifying radio waves and creating a luminous effect. They are not a single object in a galaxy but more an effect that is occurring in gas clouds throughout the inner regions of the galaxy.
    What causes a mega-maser?

    This particular mega-maser is a result of a trio of spiral galaxies colliding, causing a disruption and in turn a burst of star formation, resulting in a mega-maser at the centre of the range of galaxies in this system.

    A mega-maser is one million times more luminous than the masers we see in our own Galaxy.

    What does the mega-maser have to do with weighing a black hole?

    The clouds of gas that make up the mega-maser are rotating around the black hole in the centre of this distant galaxy. By measuring the speed of their rotation and using a simple mathematical equation, scientists can estimate the mass of the black hole, which in this case turned out to be a super massive black hole with a mass of approximately 3.8 billion suns.

    In the last decade, scientists have come to believe that black holes are not only common throughout the Universe but they play a fundamental role in the formation and evolution of galaxies like the Milky Way Universe that we inhabit today.

    And ASKAP is key to our ability to unlock further secrets and uncover new phenomena that will help us understand the nature of life on earth.

    ASKAP, ACTA and SKA

    An important angle of this research is that it has demonstrated the capacity of ASKAP to provide the data needed by astronomers to study some fundamental questions about the evolution of our Universe. To be sure that the data are accurate, there need to be checks and balances to ensure the ASKAP technology is working as planned. To do this, the team compared two independent data sets, one captured by ASKAP BETA’s array and the other captured by ATCA.

    The results matched, confirming that ASKAP is working as hoped, fulfilling one of its key roles of pioneering revolutionary new technologies as part of Australia’s contribution to the design and development of the international SKA project.

    SKA Square Kilometer Array
    SKA Square Kilometer Array

    For more information about ASKAP, visit our website.

    See the full article here .

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    CSIRO campus

    CSIRO, the Commonwealth Scientific and Industrial Research Organisation, is Australia’s national science agency and one of the largest and most diverse research agencies in the world.

     
  • richardmitnick 7:31 pm on April 20, 2016 Permalink | Reply
    Tags: , , , Dusty doughnut around massive black hole spied for first time, , Radio Astronomy   

    From New Scientist: “Dusty doughnut around massive black hole spied for first time” 

    NewScientist

    New Scientist

    20 April 2016
    Shannon Hall

    1
    A dusty doughnut might look like this. NASA/JPL-Caltech

    It won’t taste very good. We have for the first time imaged one of the doughnuts of dust long thought to encircle some supermassive black holes.

    Astronomers think all galaxies are “active” at some point in their lifetimes, meaning that the central supermassive black hole feeds on a circling disc of gas. Although that disc can be so bright that it outshines the entire galaxy, some seem to be obscured by a doughnut-shaped structure of dust and gas, called a “torus.” Yet because the centres of these active galaxies are so distant, a dusty torus has never been seen – until now.

    Santiago Garcia-Burillo of Spain’s Madrid Observatory and his colleagues used a radio telescope array to image the torus of NGC 1068, a galaxy 50 million light years away. Although it is one of the brightest and nearest active galaxies, its torus still appears tens of thousands of times smaller than the moon.

    The discovery required 35 radio dishes on the Atacama Large Millimeter/submillimeter Array (ALMA) perched in the high desert of the Chilean Andes.

    ESO/NRAO/NAOJ ALMA Array
    ESO/NRAO/NAOJ ALMA Array

    “It’s an absolutely remarkable observation,” says Jack Gallimore of Bucknell University in Lewisburg, Pennsylvania. “It’s a real testament to how much of a powerhouse ALMA is.”

    It should also shed light on a long-standing problem in astrophysics, namely what causes a galaxy to become active, says Gallimore. Although we know that clouds of gas must fall from the galaxy towards the supermassive black hole, it’s not that simple.

    As the gas falls inward, it spins faster, allowing it to reach a circular velocity like Earth’s orbit around the sun. “A cloud would eventually be spinning so fast that it would just achieve a stable orbit around the black hole,” says Gallimore. “So that prevents it from falling in and feeding the black hole.”

    And yet these supermassive black holes actively accrete gas and dust – enough to grow to millions or billions of times the sun’s mass. So if astronomers can see how gas flows through the torus, they are likely to get a better handle on what sparks the black hole feeding frenzy behind an active galaxy.

    Science paper:
    ALMA resolves the torus of NGC 1068: continuum and molecular line emission

    See the full article here .

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  • richardmitnick 1:31 pm on April 20, 2016 Permalink | Reply
    Tags: , , , Could Fast Radio Bursts be of cosmological origin?, Radio Astronomy   

    From CAASTRO: “Could Fast Radio Bursts be of cosmological origin?” 

    CAASTRO bloc

    CAASTRO ARC Centre of Excellence for All Sky Astrophysics

    High time resolution radio surveys over the last decade have discovered a population of millisecond-duration transient bursts called Fast Radio Bursts (FRBs) of unknown. Only 18 of these bursts have been detected to date, and their origin – whether extragalactic or at even cosmological distances – is still uncertain.

    CAASTRO PhD student Manisha Caleb (ANU and Swinburne University of Technology) and colleagues have now scrutinised the FRB properties: energy distribution, spatial density as a function of redshift and properties of the Interstellar and Intergalactic Media. The researchers ran simulations to test whether a cosmological population is a feasible scenario and to compare their simulations to data from the High Time Resolution Universe survey that used the Effelsberg radio telescope in Germany and the 64-m Parkes radio telescope in Australia.

    MPIFR/Effelsberg Radio Telescope
    MPIFR/Effelsberg Radio Telescope

    CSIRO/Parkes Observatory
    CSIRO/Parkes Observatory

    Their Monte Carlo simulations were based on two scenarios for the co-moving numbers of FRBs: a constant co-moving density model and a model in which the number of FRBs is proportional to the known cosmic star formation history (SFH). The most interesting property of the simulated events is their distribution of detections above some fluence (so-called logN-logF curves): if the sources have an even approximately typical luminosity (i.e. are standard candle-like), then the slope of this relation is a probe of their spatial distribution. For standard candles in the standard model of cosmology – LCDM – the slope varies smoothly from -3/2 for the nearby universe, gradually becoming flatter as further distances are probed. To illustrate, at a redshift of z ~0.7, which is typical of FRBs found to date, standard candles yield a relation with a slope of ~ -1. The observed slope of the logN-logF of the 9 FRBs analysed in this study is -0.9 +/- 0.3. The team’s simulations were able, in both scenarios for the number density of the sources with redshift, to match this slope well, yielding -0.8 +/- 0.3 for the cosmic SFH and -0.7 +/- 0.2 for the constant density case. They concluded that the properties of the observed FRBs are generally consistent with arising from sources at cosmological distances.

    The researchers also simulated FRB rates at the upgraded Molonglo telescope, UTMOST, and at Parkes for the Multibeam and the planned Phased Array Feed (PAF) receivers.

    Molonglo Observatory Synthesis Telescope (MOST)
    Molonglo Observatory Synthesis Telescope (MOST)

    Parkes Phased Array Feed
    Parkes Phased Array Feed

    They applied conservative assumptions about the spectral index of FRBs and the sensitivity of the instruments. According to those simulations, UTMOST has the capability, at full design sensitivity, to dominate the FRB detection rate. Uncertainty in the final PAF design sensitivity make predictions difficult for Parkes but its wide sky coverage has the potential to increase the FRB discovery rate close to the fluence limit. The fully sensitive UTMOST will dominate the event detection rate at all fluences.

    See the full article here .

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    Astronomy is entering a golden age, in which we seek to understand the complete evolution of the Universe and its constituents. But the key unsolved questions in astronomy demand entirely new approaches that require enormous data sets covering the entire sky.

    In the last few years, Australia has invested more than $400 million both in innovative wide-field telescopes and in the powerful computers needed to process the resulting torrents of data. Using these new tools, Australia now has the chance to establish itself at the vanguard of the upcoming information revolution centred on all-sky astrophysics.

    CAASTRO has assembled the world-class team who will now lead the flagship scientific experiments on these new wide-field facilities. We will deliver transformational new science by bringing together unique expertise in radio astronomy, optical astronomy, theoretical astrophysics and computation and by coupling all these capabilities to the powerful technology in which Australia has recently invested.

    PARTNER LINKS

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  • richardmitnick 9:38 am on April 14, 2016 Permalink | Reply
    Tags: , , , Radio Astronomy,   

    From Science Alert: “Astronomers have discovered a region in space where black holes have mysteriously aligned” 

    ScienceAlert

    Science Alert

    12 APR 2016
    BEC CREW

    1

    What the hell’s going on out there?

    There’s a region in the distant Universe where a handful of supermassive black holes have mysteriously aligned, and as a result, they’re spewing out incredibly powerful radio jets in the same direction. This is the first time astronomers have seen such a phenomenon, and they say it could be the result of fluctuations of primordial mass that appeared in the early Universe.

    “Since these black holes don’t know about each other, or have any way of exchanging information or influencing each other directly over such vast scales, this spin alignment must have occurred during the formation of the galaxies in the early Universe,” explains one of the team, Andrew Russ Taylor, director of South Africa’s Institute for Data Intensive Astronomy.

    As with many discoveries that happen in outer space, no one was expecting to find a region where supermassive black holes had mysteriously managed to sync up their spins.

    Taylor and his team were actually on the hunt for the faintest radio sources in the Universe, using data from the Giant Metrewave Radio Telescope (GMRT) in India – one of the largest and most sensitive radio telescope arrays in the world.

    Giant Metrewave Radio Telescope near Pune in India
    Giant Metrewave Radio Telescope near Pune in India

    The GMRT had just completed a three-year deep radio imaging survey, detecting radio waves spewed forth by black holes in a distant region of the Universe called ELAIS, which encompasses several galaxies.

    By looking at the direction these radio waves were coming from, the researchers figured out that within ELAIS-N1, the supermassive black holes at the centre of each of these galaxies were all spinning in the same direction. But how?

    Taylor and his colleagues suggest that the black holes are too far apart to have influenced each other’s alignment in their current positions in space, so whatever forced them into the same spin must happened very early on in the formation of the Universe.

    “[T]he alignment of the black holes is probably caused by an overall spin in the structure of this region of space, triggered by fluctuations of primordial matter in the early Universe, way before galaxies even formed,” Yasmin Tayag reports for Inverse.

    But if we accept that, then something even greater must have given rise to the fluctuations of primordial matter that caused these supermassive black holes to align. In other words, what caused the fluctuations that forced these black holes into the same spin?

    It’s not yet clear, and a large-scale spin distribution has not been predicted by our current understanding of the physics that govern the Universe, but the researchers suggest that it could be anything from incredibly strong cosmic magnetic fields – possibly associated with exotic particles such as axions – to something called cosmic strings, which are theoretical fault lines in the Universe that exist between different regions of space.

    “This is not obviously expected based on our current understanding of cosmology. It’s a bizarre finding,” astronomer Romeel Dave from the University of Western Cape in South Africa, who was not involved in the discovery, said in a press statement.

    We’re going to need much more sensitive telescopes to figure that out, and with the South African MeerKAT radio telescope and the Square Kilometre Array (SKA) – the world’s most powerful radio telescope and one of the biggest scientific instruments ever devised – currently under construction, we might not have to wait too long.

    SKA Meerkat telescope
    SKA Meerkat telescope

    “[We really need MeerKAT to make the very sensitive maps, over a very large area and with great detail, that will be necessary to differentiate between possible explanations,” says Taylor. “It opens up a whole new research area for these instruments, which will probe as deeply into the and as far back as we can go – it’s going to be an exciting time to be an astronomer.”

    The discovery has been reported* in the Monthly Notices of the Royal Astronomical Society.

    *Science paper:
    Alignments of radio galaxies in deep radio imaging of ELAIS N1

    Science team:
    A. R. Taylor 1,2,★ and P. Jagannathan 1,3

    Affiliations:
    1 Department of Astronomy, University of Cape Town, Rondebosch 7701, South Africa
    2 Department of Physic and Astronomy, University of the Western Cape, Bellville 7535, South Africa
    3 National Radio Astronomy Observatory, Socorro, NM, USA

    See the full article here .

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  • richardmitnick 5:02 pm on April 10, 2016 Permalink | Reply
    Tags: , , Challenging the Brightness Limits of Quasars, Radio Astronomy,   

    From SAO: “Challenging the Brightness Limits of Quasars” 

    Smithsonian Astrophysical Observatory
    Smithsonian Astrophysical Observatory

    Friday, April 1, 2016
    No writer credit found

    Quasars are galaxies with massive black holes at their cores from which vast amounts of energy are being radiated.

    Quasar. ESO/M. Kornmesser
    Quasar. ESO/M. Kornmesser

    So much light is emitted that the nucleus of a quasar is much brighter than the rest of the entire galaxy, and these tremendous luminosities allow quasars to be seen even when they are very far away. Much of the radiation is at radio wavelengths, and is produced by electrons in powerful jets ejected from the core at speeds very close to that of light. Such fast-moving charged particles can scatter photons of light, kicking them up in energy while losing a corresponding amount of their own energy. In extreme situations, as is found in quasars, the moving particles will scatter the photons they emit, with the result that the velocities they can attain are self-limited. Astronomers quantify these conditions with a brightness temperature, and conventional estimates conclude that the maximum such temperature is about a trillion (!) degrees.

    Brightness is a quantity that depends on size: A small source that emits as much energy as a large source appears to be brighter. In an effort to constrain the size of the emitting region in quasars, the Russian Federal Space Agency launched the ten meter RadioAstron Space Radio Telescope in 2011 with a goal of conducting unprecedented, high spatial resolution radio “very long baseline interferometry” measurements when combined with ground-based radio dishes.

    RadioAstron Spektr R satellite
    RadioAstron Spektr R satellite

    The instrument was used to study the very luminous quasar 3C 273, located about two billion light-years away. Previous observations of 3C 273 suggested that its emission region was less than about a light-month in size (the distance light can travel in one month, one twelfth of a light-year), in part because the light varies on a timescale of months. The corresponding brightness temperature is close to the nominal limit.

    1
    C3 273. CSIRO/Parkes Radio Telescope [no image found from RadioAstron]

    CSIRO/Parkes Observatory
    CSIRO/Parkes Observatory

    CfA astronomers Michael Johnson and Ramesh Narayan, together with their RadioAstron teammates, measured the brightness temperature of 3C 273 and discovered that it appeared to exceed the so-called limit by nearly a factor of one hundred. The scientists considered a number of possible effects that might ameliorate the dramatic conclusion, for example, the angle at which we view the beam of fast-moving particles is not well known but enters into the calculation. Their conclusion is that the discrepancy appears to be real. In a series of two papers, the scientists describe the results and offer some possible explanations. One is that turbulent gas in our galaxy is distorting the light from the quasar, an effect that had not been seen until these higher resolution measurements. Another, more dramatic option, is that some unknown physical processes are at work in the vicinity of the supermassive black hole.

    Reference(s) [science papers]:

    Extreme Brightness Temperatures and Refractive Substructure in 3C 273 with RadioAstron,”

    Science team:

    Michael D. Johnson,1; Yuri Y. Kovalev, 2,3; Carl R. Gwinn, 4; Leonid I. Gurvits, 5,6; Ramesh Narayan, 1; Jean-Pierre Macquart, 7,8; David L. Jauncey, 9,10; Peter A. Voitsik 2; James M. Anderson11, 3; Kirill V. Sokolovsky, 2,12; and Mikhail M. Lisakov, 2 ApJLett 820, L10, 2016

    Affiliations:
    1 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

    2 Astro Space Center of Lebedev Physical Institute, Profsoyuznaya 84/32, 117997 Moscow, Russia

    3 Max-Planck-Institute for Radio Astronomy, Auf dem Hügel 69, D-53121, Germany

    4 Department of Physics, University of California, Santa Barbara, CA 93106, USA

    5 Joint Institute for VLBI ERIC, P.O. Box 2, 7990 AA Dwingeloo, The Netherlands

    6 Department of Astrodynamics & Space Missions, Delft University of Technology, 2629 HS Delft, Delft, The Netherlands

    7 ICRAR/Curtin University, Curtin Institute of Radio Astronomy, Perth, WA 6845, Australia

    8 ARC Centre of Excellence for All-Sky Astrophysics (CAASTRO), Australia

    9 CSIRO Astronomy and Space Sciences, Epping, NSW 1710, Australia, Australia

    10 Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT, 2611, Australia

    11 Helmholtz-Zentrum Potsdam, Deutsches GeoForschungsZentrum GFZ, Department 1: Geodesy, Telegrafenberg, D-14473, Potsdam, Germany

    12 Sternberg Astronomical Institute, Moscow State University, Universitetskii pr. 13, 119992 Moscow, Russia

    and

    RadioAstron Observations of the Quasar 3C 273: A Challenge to the Brightness Temperature Limit,”

    Science team:
    Y. Y. Kovalev, 1,2; N. S. Kardashev, 1; K. I. Kellermann, 3; A. P. Lobanov, 2,4; M. D. Johnson, 5; L. I. Gurvits, 6,7; P. A. Voitsik, 1; J. A. Zensus, 2; J. M. Anderson, 2,8; U. Bach, 2; D. L. Jauncey, 9,10; F. Ghigo,11; T. Ghosh, 12; A. Kraus, 2; Yu. A. Kovalev, 1; M. M. Lisakov, 1; L. Yu. Petrov, 13; J. D. Romney, 14; C. J. Salter, 12; and K. V. Sokolovsky, 1,15
    ApJLett 820,L9, 2016.

    Author affiliations

    1 Astro Space Center of Lebedev Physical Institute, Profsoyuznaya 84/32, 117997 Moscow, Russia

    2 Max-Planck-Institute for Radio Astronomy, Auf dem Hügel 69, D-53121, Germany

    3 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, USA

    4 Institut für Experimentalphysik, Universität Hamburg, Luruper Chaussee 147, D-22761 Hamburg, Germany

    5 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

    6 Joint Institute for VLBI ERIC, P.O. Box 2, 7990 AA Dwingeloo, The Netherlands

    7 Department of Astrodynamics and Space Missions, Delft University of Technology, 2629 HS Delft, The Netherlands

    8 Helmholtz-Zentrum Potsdam, Deutsches GeoForschungsZentrum, Department 1: Geodesy and Remote Sensing, Telegrafenberg, D-14473, Potsdam, Germany

    9 CSIRO Astronomy and Space Sciences, Epping, NSW 1710, Australia

    10 Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT, 2611, Australia

    11 National Radio Astronomy Observatory, Rt. 28/92, Green Bank, WV 24944-0002, USA

    12 Arecibo Observatory, NAIC, HC3 Box 53995, Arecibo, Puerto Rico, PR 00612, USA

    13 Astrogeo Center, 7312 Sportsman Drive, Falls Church, VA 22043, USA

    14 National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801-0387, USA

    15 Sternberg Astronomical Institute, Moscow State University, Universitetskii prospekt 13, 119992 Moscow, Russia

    See the full article here .

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    About CfA

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy. The long relationship between the two organizations, which began when the SAO moved its headquarters to Cambridge in 1955, was formalized by the establishment of a joint center in 1973. The CfA’s history of accomplishments in astronomy and astrophysics is reflected in a wide range of awards and prizes received by individual CfA scientists.

    Today, some 300 Smithsonian and Harvard scientists cooperate in broad programs of astrophysical research supported by Federal appropriations and University funds as well as contracts and grants from government agencies. These scientific investigations, touching on almost all major topics in astronomy, are organized into the following divisions, scientific departments and service groups.

     
  • richardmitnick 1:19 pm on April 7, 2016 Permalink | Reply
    Tags: , , Radio Astronomy,   

    From SKA: “Parkes telescope granted SKA Pathfinder status” 

    SKA Square Kilometer Array

    SKA

    CSIRO/Parkes Observatory
    CSIRO/Parkes Observatory

    The iconic Parkes telescope in Australia, run by the Commonwealth Scientific and Industrial Research Organisation (CSIRO), has been granted pathfinder status by SKA Organisation.

    This announcement welcomes Parkes into the group of other world-leading instruments and systems engaged in SKA-related technology development and science studies, such as the Arecibo Observatory, LOFAR and the EVLA.

    NAIC/Arecibo Observatory
    NAIC/Arecibo Observatory

    ASTRON LOFAR Radio Antenna Bank
    ASTRON LOFAR Radio Antenna Bank

    ASTRON LOFAR Map
    ASTRON LOFAR Map

    Parkes Observatory in New South Wales hosts the 64-metre Parkes radio telescope, affectionately known by many as ‘The Dish’.

    Parkes has been in operation since 1961 and continues to be at the forefront of astronomical discovery thanks to regular upgrades. Its many contributions include playing an instrumental role in the Apollo 11 Moon landing in 1969, the detection of the majority of currently-known Fast Radio Bursts (FRBs), and significant discoveries in the study of pulsars – a field in which the SKA will play a fundamental role.

    Parkes’ newly-granted pathfinder status is based on its role in testing innovative new receivers. This includes deploying, commissioning and developing phased array feed (PAF) receivers for radio astronomy, based on the receivers designed and commissioned on CSIRO’s Australian SKA Pathfinder (ASKAP) telescope – itself one of three SKA precursor telescopes.

    Parkes Phased Array Feed
    Parkes Phased Array Feed

    SKA ASKAP telescope
    SKA ASKAP telescope

    The PAF work at Parkes will play a key role in the technological development of these receivers, which are under consideration for the SKA.

    The Dish recently welcomed the arrival of a PAF receiver, designed and built as part of an agreement with the Max Planck Institute for Radioastronomy (MPIfR). Once characterisation testing is complete on the Parkes telescope, this PAF will be deployed on the Effelsberg telescope in Germany.

    MPIFR/Effelsberg Radio Telescope
    MPIFR/Effelsberg Radio Telescope

    Into the future Parkes will also develop ultra-wideband single pixel feed receivers, similar to those currently being developed by Onsala Space Observatory in Sweden as part of the development of SKA technologies.

    Onsala 20 meter telescope exterior Sweden
    Onsala Twenty meter telescope interior  Sweden
    Onsala 20 meter telescope Sweden

    A full list of SKA precursors and pathfinders is available on the SKA website.

    See the full article here .

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    SKA Banner

    SKA CSIRO  Pathfinder Telescope
    SKA ASKAP Pathefinder Telescope

    SKA Meerkat telescope
    SKA Meerkat Telescope

    SKA Murchison Widefield Array
    SKA Murchison Wide Field Array

    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 5:23 pm on April 4, 2016 Permalink | Reply
    Tags: , , , Radio Astronomy   

    From astrobites: “Globular Clusters as Cradles of Life and Advanced Civilizations” 

    Astrobites bloc

    Astrobites

    Apr 4, 2016
    Steph Greis

    Title: Globular Clusters as Cradles of Life and Advanced Civilizations
    Authors: R. Di Stefano, A. Ray
    First Author’s Institution: Harvard-Smithsonian Center for Astrophysics
    Status: submitted to arxiv

    The alien looked up at the night sky. Not that it was easy to tell the difference between day and night, with all those bright nearby stars in the globular cluster. She looked over to a nearby star a mere 2 light-weeks away where her family was waiting for her – and she wondered what her family might think of a trip to one of the planets on the outer edges of the cluster…

    Back to Earth… Where the nearest neighbouring star is not light-weeks by several light-years away!
    The authors of today’s astrobite consider the possibility that life, and even advanced civilizations, could develop in globular clusters.

    Omega Centauri globular cluster from WFI camera on 2.2 meter MPG/ ESO telescope at La Silla Observatory
    Omega Centauri globular cluster from WFI camera on 2.2 meter MPG/ ESO telescope at La Silla Observatory

    ESO WFI LaSilla 2.2-m MPG/ESO telescope at La Silla
    ESO WFI LaSilla 2.2-m MPG/ESO telescope at La Silla

    MPG/EMPG/ESO 2.2 meter telescope at La Silla
    MPG/EMPG/ESO 2.2 meter telescope at La Silla

    ESO/LaSilla
    ESO/LaSilla

    Habitable Zones in Globular Clusters – or: “Can we take a trip to the cluster rim?”

    In establishing whether life could support itself on a given planet, researchers use the concept of a “habitable zone“. This term indicates a regions around a star in which Earth-like planets could sustain liquid water on their surfaces.

    Similarly, the authors of this paper suggest that a globular cluster has a habitable zone, or “sweet spot”. Two competing factors have to be weighed off: if the planet’s orbit is too far from its host star, it is more likely to be ripped out of its solar system through interaction with a passing neighbouring star. On the other hand, a civilization is more likely to be able to survive if it can spread to other planets, suggesting that for any civilization to become advanced it is necessary for it to be able to establish interstellar travel to nearby stars. Hence a balance has to be found where the habitable-zone orbits are stable without being disrupted by nearby stars, and yet the density of stars is such that the nearest star is not too far away and interstellar travel takes little time. Thus the ideal place for civilizations to grow is in the outer parts of the cluster where stars aren’t too concentrated and yet separated by less than about ten-thousand astronomical units (an astronomical unit is the average distance between the Earth and the Sun), or about two light-months.

    Floating Freely

    Another interesting possibility to consider is the fate of life-harbouring planets which have been indeed been kicked out of its solar system, for example by interacting with a passing stellar neighbour. Since it is the outermost planets in a stellar system that are most at risk to the gravitational pull from another nearby star, any civilization on these planets would already have had to be accustomed to receiving only a small amount of stellar light. The authors argue that is might be possible for such a civilization to survive the expulsion if they can devise ways to shield themselves from harmful impacts and radiation, and develop energy sources which don’t rely on nearby stars.

    The Drake Equation* – or: “Anybody out there?”

    Drake Equation

    where:

    N = the number of civilizations in our galaxy with which communication might be possible (i.e. which are on our current past light cone);

    and

    R* = the average rate of star formation in our galaxy
    fp = the fraction of those stars that have planets
    ne = the average number of planets that can potentially support life per star that has planets
    fl = the fraction of planets that could support life that actually develop life at some point
    fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations)
    fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
    L = the length of time for which such civilizations release detectable signals into space

    • Frank Drake, SETI Institute

    Having suggested that globular clusters might be ideal places for life to arise and evolve, the authors perform a “back-of-the-envelope” calculation to guess the likelihood of such civilizations. They make use of the Drake equation which identifies several factors to “determine the number of communicating civilizations in existence in the Galaxy at a typical time.” Estimating this number involves investigating terms such as the total number of stars, the fraction of stars which has planets, the average number of planets per star, the fraction of planets on which life develops and the fraction of these which become intelligent, and the fraction of these which start to try communicating with other civilizations.

    Searching for Extraterrestrial Life

    The authors indicate that globular clusters might be the ideal environments for life to have developed – and hence suggest that our search for alien life, commonly known as SETI (Search for ExtraTerrestrial Intelligence), would best be focused on these places.

    SETI Institute

    SETI/Allen Telescope Array
    SETI/Allen Telescope Array

    Since stars are relatively stable, life would have plenty of time to develop on an orbiting planet. Even if one attempt didn’t succeed, there might well have been multiple opportunities over the course of the past 12 billion years. Additionally, “reset” events like nearby gamma-ray bursts or supernovae, which might destroy any fledgling lifeforms, are thought to be very uncommon in globular clusters, compared to how often they occur in the disk of the Galaxy. Hence, the authors argue, it should be more likely to find lifeforms and advanced civilizations in globular clusters. By looking at typical numbers of stars in the globular clusters around the Milky Way, the authors suggest that many of them “could presently host advanced civilizations that have spread throughout the cluster.” They further suggest that if such advanced civilizations do exist in the clusters, “they will tend to be old civilizations.” Even if only every tenth cluster star has life-supporting planets, and if only 1% of those hosts intelligent life, and if only 1% of those is able to set up communications – then even with these small probabilities, “could be enough to ensure that every globular cluster hosts a long-lived communicating civilization.”

    Actually detecting these civilizations using SETI will however be more difficult: since globular clusters are very crowded with dim stars, it is very difficult to detect planets through conventional methods, such as the the transit method where the planet briefly eclipses its host star, or the radial velocity one where the “wobble” of a star is detected as the orbiting planet pulls at it. So far only one exoplanet has been detected with these methods, but the authors are confident that there should be many more exoplanets within these intriguing environments.

    The alien continued to observe the night sky. She felt a certain sense of peace whenever she looked at the mass of brilliant spots surrounding her – like many generations before her, she had grown up with stories of the first settler to this or that planet, as well as occasional stories about the demise of certain planets hit by meteors or other catastrophic events. Having established a multitude of self-sustaining outposts, however, had given her species a far greater chance to survive. By making the jump across interstellar space, she was certain that hers, like other civilizations in the cluster, could, in a sense, become immortal…

    Globular Clusters as Cradles of Life and Advanced Civilizations

    Science team:
    R. Di Stefano, a; A. Ray, b

    Afiliations:
    a Harvard-Smithsonian Center for Astrophysics
    b Tata Institute of Fundamental Research

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 2:09 pm on April 2, 2016 Permalink | Reply
    Tags: , , Radio Astronomy,   

    From SPACE.com: “Cataclysm Hunters: The Search for Monster Black-Hole Collisions” 

    space-dot-com logo

    SPACE.com

    April 1, 2016
    Sarah Lewin

    1
    Supermassive black holes at the heart of merging galaxies will circle closer and closer until they come together, releasing a titanic wave of energy. The process may help explain how black holes get so huge to begin with. Credit: NASA

    Julie Comerford has built a career searching for galaxies that contain not one, but two supermassive black holes — light-devouring monsters that have masses millions or billions of times that of the sun. So far, the count is up to 12.

    “The mergers of two supermassive black holes is second only to the Big Bang as the most energetic phenomena in the universe,” Comerford, an astrophysicist at the University of Colorado, Boulder, told Space.com. Yet that titanic, violent dance — essential to galaxy growth and evolution — has not been spotted very often.

    Each galaxy has a supermassive black hole at its core. When two galaxies merge, the two central black holes circle faster and faster, coming closer and closer until they merge into one as well.

    Cornell SXS team. Two merging black holes simulation
    Cornell SXS team. Two merging black holes simulation

    Black holes merging Swinburne Astronomy Productions
    Black holes merging Swinburne Astronomy Productions

    Once light crosses the threshold of a black hole, it can never escape, but galactic sleuths like Comerford have spent years looking for other kinds of evidence revealing those monster black holes headed for a cataclysmic collision.

    Relatively small “stellar mass” black holes form when a huge star dies in a supernova explosion and its core collapses. A black hole can grow as more mass falls into it, but nobody can fully explain how the supermassive ones lurking at the cores of galaxies are able to get so enormous — the one at the center of the Milky Way has a mass 4 million times that of the sun, and it’s comparatively small.

    Sag A* NASA's Chandra X-Ray Observatory 23 July 2014
    Sag A* NASA’s Chandra X-Ray Observatory 23 July 2014, the supermassive black hole at the center of the Milky Way

    The process of two galaxies merging could explain this extraordinary growth.

    “One theory is that maybe a lot of the black hole mass growth actually occurs during galaxy mergers, because that’s when all this gas is being slammed together and funneled towards a black hole — so there’s a lot of fuel available for the black hole to eat and build up its mass,” Comerford said.

    Solving the growth mystery promises to reveal insight into how galaxies, and the black holes at their hearts, grow and change over time. Plus, it should help hone scientists’ newly proven powers of detecting gravitational waves.

    Searching for light

    The ultralarge black holes at the centers of galaxies don’t let any light slip out, but pairs of structures so massive leave their mark on the environment around them in other ways. For one thing, they’re always at the hearts of merging galaxies.

    “The Milky Way just has one central big sphere of stars, so it would not be a good candidate for one of these potential double black holes,” Comerford said. “We’re looking for things that look different from the usual galaxies that you see images of, like a normal spiral galaxy or elliptical galaxy — that’s not what we want. [We want] the ones that look like they’re two merging spheres of stars.”

    That merging process also puts a lot of extra material in the path of each of the black holes, which can gain whirling “accretion disks” of dust around them that glow brightly andemit jets of energy. Supermassive black holes with that kind of ultrabright beacon are called quasars, and they’re far from invisible — in fact, they often outshine the galaxies that surround them.

    2
    This artist’s concept illustrates a quasar, or feeding black hole, similar to APM 08279+5255, where astronomers discovered huge amounts of water vapor. Gas and dust likely form a torus around the central black hole, with clouds of charged gas above and below. Credit: NASA/ESA

    NASA/ESA Hubble Telescope
    NASA/ESA Hubble Telescope

    Comerford first started searching for these double-black-hole galaxies when she was in graduate school. Her group first recognized the black holes by the unusual spectrum of light their host galaxies emit, as measured in big survey studies like the Sloan Digital Sky Survey [SDSS].

    SDSS Telescope at Apache Point, NM, USA
    SDSS Telescope at Apache Point, NM, USA

    Galaxies with a quasar at their center — a supermassive black hole taking in large quantities of material — emit a narrow band of radiation that’s very bright. But the galaxies Comerford was looking for were more complex: Instead of a nice, tall peak indicating the intense glow emitted by the quasar, she saw two peaks — one slightly redder and one slightly bluer.

    The two peaks showed that there were two significant light sources in the system: one moving toward Earth and one moving away. By following up with an X-ray or radio telescope, or with NASA’s Hubble Space Telescope looking in visible light, she could verify that those two light sources were embedded in a merging set of galaxies.

    Comerford’s systematic search could find supermassive black holes that are around 3,000 light-years away from each other — that’s about 1/8 the distance from Earth’s solar system to the center of the galaxy — and that are orbiting one another at about 500,000 mph (800,000 kph). Looking straight at such systems, it might be impossible to distinguish the two quasars from each other because they’d be too close together, so the wavelengths of light emitted provided a crucial first clue.

    More recently, because of the increasing amount of Hubble galaxy imagery available, Comerford has started relying on visual images to pinpoint the supermassive black hole pairs. First, she finds quasar activity in telescope data, and then she checks with a Hubble image of the galaxy to see if it looks like it might be two merging galaxies, with two tight cores of stars that might each surround a supermassive black hole. Finally, she follows up with higher-resolution infrared or radio telescopes to try and distinguish whether there are two separate quasars there.

    4
    Diagrams of 30 merging galaxies. The edges show signal strength from carbon monoxide, while colors show where the gas is moving. Red represents gas moving away from Earth, and blue moving towards.
    Credit: ALMA (ESO/NAOJ/NRAO)/SMA/CARMA/IRAM/J. Ueda et al.

    ESO/NRAO/NAOJ ALMA Array
    ESO/NRAO/NAOJ ALMA Array

    CfA Submillimeter Array Hawaii SAO
    CfA Submillimeter Array Hawaii SAO

    CARMA Array no longer in service
    CARMA Array no longer in service

    IRAM NOEMA interferometer
    IRAM NOEMA interferometer

    “There may be one [supermassive black hole pair] in every something like a thousand to a million galaxies,” Sarah Spolaor, a researcher at the National Radio Astronomy Observatory in New Mexico, told Space.com. “The chance of just finding one by chance is pretty low, but if you have a sky catalog of thousands upon thousands of galaxies, then you’re much more likely to see that kind of weird-looking one that you think, ‘What is that?’ — and it’s maybe a binary black hole.”

    The growing mystery

    Researchers know that supermassive black holes are intimately tied to the galaxies surrounding them. There’s one at every galaxy’s heart, and the galaxy’s size is reflected in the size of the black hole. Even early galaxies, born close to the beginning of the universe, show that correlation. Finding black hole mergers can help solve the mystery of how those black holes got so big, so early in the universe’s history. Plus, even the existence of quasars at all, which can only form once black holes get massive enough, raises questions.

    “Why are we doing this stamp collecting?” Comerford said. “There’s scientific questions that we want to answer, and that is one of the big ones: how do black holes get enough gas in the first place to become a quasar?”

    Researchers know that black holes at the center of merging galaxies ultimately form into one larger supermassive black hole, but it’s unclear whether that’s the whole picture.

    “Galaxy mergers are definitely an effective way to get supermassive black holes to grow,” said Scott Barrows, an astronomer also at the University of Colorado, Boulder. “But how important is this process relative to other processes that could just be happening in a galaxy that’s not interacting?” Barrows said. “There’s not a good consensus on how this works as of yet,” he told Space.com.

    Barrows’ own research searches for supermassive black hole systems where only one black hole has bloomed into a quasar — an indicator, he said, that the black holes are uneven; one is growing faster than the other and taking in more material kicked up in the merger. That uneven matchup could help scientists understand exactly what role the events play in growing black holes and the galaxies surrounding them.

    Besides solving that mystery, a better understanding of the epic systems should reveal more about the overall universe’s evolution, researchers say.

    “Supermassive black holes are thought to play a huge role in how the universe evolves,” Spolaor said. “They are the most massive compact single objects in the universe.”

    See the full article here .

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  • richardmitnick 5:36 pm on March 31, 2016 Permalink | Reply
    Tags: , , , Extraterrestrial life, Radio Astronomy,   

    From SETI: “New Search for Signals from 20,000 Star Systems Begins” 


    SETI Institute

    March 30 2016
    No writer credit found

    The SETI Institute has inaugurated a greatly expanded hunt for deliberately produced radio signals that would indicate the presence of extraterrestrial intelligence. Over the course of the next two years, it will scrutinize the vicinities of 20,000 so-called red dwarf stars.

    SETI/Allen Telescope Array
    SETI/Allen Telescope Array

    “Red dwarfs – the dim bulbs of the cosmos – have received scant attention by SETI scientists in the past,” notes Institute engineer Jon Richards. “That’s because researchers made the seemingly reasonable assumption that other intelligent species would be on planets orbiting stars similar to the Sun.”

    This conservative assessment was bolstered by the argument that few planets were likely to be found in the habitable zone of a red dwarf star, simply because that zone is far narrower than for brighter stars like the Sun. Additionally, any worlds that were in this zone would be orbiting so close to their suns that they would quickly become tidally locked – with one hemisphere perpetually facing the star. It was assumed that this would produce a planet that was intolerably hot on one side, and brutally cold on the other, ruling it out as an abode for life.

    However, more recent research has indicated that, if these worlds have oceans and atmospheres, heat would be transported from the lit side to the dark, and a significant fraction of the planet would be habitable. In addition, exoplanet data have suggested that somewhere between one sixth and one half of red dwarf stars have planets in their habitable zones, a percentage comparable to, and possibly greater, than for Sun-like stars.

    “Significantly, three-fourths of all stars are red dwarfs,” notes SETI Institute astronomer Seth Shostak. “That means that if you observe a finite set of them – say the nearest twenty thousand – then on average they will be at only half the distance of the nearest twenty thousand Sun-like stars.”

    Closer stars mean that any signals would be stronger.

    Also, red dwarfs burn for a period of time that’s greater than the current age of the universe: every red dwarf ever born is still shining today. They are, on average, billions of years older than stars than Sun-like stars.

    “This may be one instance in which older is better,” Shostak says. “Older solar systems have had more time to produce intelligent species.”

    The search is being conducted on the SETI Institute’s Allen Telescope Array, located in the Cascade Mountains of northern California. This grouping of 42 antennas can currently observe three stars simultaneously.

    “We’ll scrutinize targeted systems over several frequency bands between 1 and 10 GHz,” says Institute scientist Gerry Harp. “Roughly half of those bands will be at so-called ‘magic frequencies’ – places on the radio dial that are directly related to basic mathematical constants. It’s reasonable to speculate that extraterrestrials trying to attract attention might generate signals at such special frequencies.”

    The new red dwarf survey is planned to take two years. Targets are being chosen from a list of approximately 70,000 red dwarfs compiled by Boston University astronomer Andrew West. The search will also incorporate relevant new data as generated by NASA’s TESS (Transiting Exoplanet Survey Satellite) project, which will examine nearby stars, including red dwarfs, for planets.

    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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