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  • richardmitnick 9:06 am on April 21, 2015 Permalink | Reply
    Tags: , , Dartmouth College, , Supermassive Black Holes   

    From Dartmouth College via phys.org: “Black hole hunters tackle a cosmic conundrum” 

    physdotorg
    phys.org

    1
    Dartmouth

    April 20, 2015
    No Writer Credit

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    A Hubble Space Telescope image shows the Henize 2-10 galaxy, with a hidden supermassive black hole at its center. Credit: NASA

    NASA Hubble Telescope
    NASA/ESA Hubble

    Dartmouth astrophysicists and their colleagues have not only proven that a supermassive black hole exists in a place where it isn’t supposed to be, but in doing so have opened a new door to what things were like in the early universe.

    Henize 2-10 is a small irregular galaxy that is not too far away in astronomical terms—30 million light-years. “This is a dwarf starburst galaxy—a small galaxy with regions of very rapid star formation—about 10 percent of the size of our own Milky Way,” says co-author Ryan Hickox, an assistant professor in Dartmouth’s Department of Physics and Astronomy. “If you look at it, it’s a blob, but it surprisingly harbors a central black hole.”

    Hickox says there may be similar small galaxies in the known universe, but this is one of the only ones close enough to allow detailed study. Lead author Thomas Whalen, Hickox and a team of other researchers have now analyzed a series of four X-ray observations of Henize 2-10 using three space telescopes over 13 years, providing conclusive evidence for the existence of a black hole.

    Their findings appear as an online preprint to be published in The Astrophysical Journal Letters. A PDF also is available on request.

    Suspicions about Henize 2-10 first arose in 2011 when another team, that included some of the co-authors, first looked at galaxy Henize 2-10 and tried to explain its behavior. The observed dual emissions of X-ray and radio waves, often associated with a black hole, gave credence to the presence of one. The instruments utilized were Japan’s Advanced Satellite for Cosmology and Astrophysics (1997), the European Space Agency’s XMM-Newton (2004, 2011) and NASA’s Chandra X-ray Observatory (2001).

    JAXA ASCA ASTRO-D satellite
    JAXA/ASCA

    ESA XMM Newton
    ESA/XMM-Newton

    NASA Chandra Telescope
    NASA/Chandra

    “The galaxy was bright in 2001, but it has gotten less bright over time,” says Hickox. “This is not consistent with being powered only by star formation processes, so it almost certainly had to have a small supermassive black hole—small compared to the largest supermassive black holes in massive elliptical galaxies, but is still a million times the mass of the sun.”

    A characteristic of supermassive black holes is that they do change with time—not a huge amount, explains Hickox, “and that is exactly what Tom Whalen found,” he says. “This variability definitely tells us that the emission is coming from a compact source at the center of this system, consistent with it being a supermassive black hole.”

    While supermassive black holes are typically found in the central bulges of galaxies, Henize 2-10 has no bulge. “All the associations that people have made between galaxies and black holes tell us there ought to be no black hole in this system,” says Whalen, but the team has proven otherwise. Whalen, a recent Dartmouth graduate, is now a member of the Chandra X-ray Center team at the Harvard-Smithsonian Center for Astrophysics.

    A big question is where black holes come from. “When people try to simulate where the galaxies come from, you have to put in these black holes at the beginning, but we don’t really know what the conditions were. These dwarf starburst galaxies are the closest analogs we have in the universe around us now, to the first galaxies early in the universe,” says Whalen.

    The authors conclude: “Our results confirm that nearby star-forming galaxies can indeed form massive black holes and that by implication so can their primordial counterparts.”

    “Studying those to get some sense of what might have happened very early in the universe is very powerful,” says Hickox.

    See the full article here.

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  • richardmitnick 1:32 pm on April 16, 2015 Permalink | Reply
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    From ALMA: “ALMA Reveals Intense Magnetic Field Close to Supermassive Black Hole” 

    ESO ALMA Array
    ALMA

    16 April 2015
    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

    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

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

    1
    This artist’s impression shows the surroundings of a supermassive black hole, typical of that found at the heart of many galaxies. The black hole itself is surrounded by a brilliant accretion disc of very hot, infalling material and, further out, a dusty torus. There are also often high-speed jets of material ejected at the black hole’s poles that can extend huge distances into space. Observations with ALMA have detected a very strong magnetic field close to the black hole at the base of the jets and this is probably involved in jet production and collimation.

    The Atacama Large Millimeter/submillimeter Array (ALMA) has revealed an extremely powerful magnetic field, beyond anything previously detected in the core of a galaxy, very close to the event horizon of a supermassive black hole. This new observation helps astronomers to understand the structure and formation of these massive inhabitants of the centres of galaxies, and the twin high-speed jets of plasma they frequently eject from their poles. The results appear in the 17 April 2015 issue of the journal Science.

    Supermassive black holes, often with masses billions of times that of the Sun, are located at the heart of almost all galaxies in the Universe. These black holes can accrete huge amounts of matter in the form of a surrounding disc. While most of this matter is fed into the black hole, some can escape moments before capture and be flung out into space at close to the speed of light as part of a jet of plasma. How this happens is not well understood, although it is thought that strong magnetic fields, acting very close to the event horizon, play a crucial part in this process, helping the matter to escape from the gaping jaws of darkness.

    Up to now only weak magnetic fields far from black holes — several light-years away — had been probed [1]. In this study, however, astronomers from Chalmers University of Technology and Onsala Space Observatory in Sweden have now used ALMA to detect signals directly related to a strong magnetic field very close to the event horizon of the supermassive black hole in a distant galaxy named PKS 1830-211. This magnetic field is located precisely at the place where matter is suddenly boosted away from the black hole in the form of a jet.

    The team measured the strength of the magnetic field by studying the way in which light was polarised, as it moved away from the black hole.

    “Polarisation is an important property of light and is much used in daily life, for example in sun glasses or 3D glasses at the cinema,” says Ivan Marti-Vidal, lead author of this work. “When produced naturally, polarisation can be used to measure magnetic fields, since light changes its polarisation when it travels through a magnetised medium. In this case, the light that we detected with ALMA had been travelling through material very close to the black hole, a place full of highly magnetised plasma.”

    The astronomers applied a new analysis technique that they had developed to the ALMA data and found that the direction of polarisation of the radiation coming from the centre of PKS 1830-211 had rotated [2]. These are the shortest wavelengths ever used in this kind of study, which allow the regions very close to the central black hole to be probed [3].

    “We have found clear signals of polarisation rotation that are hundreds of times higher than the highest ever found in the Universe,” says Sebastien Muller, co-author of the paper. “Our discovery is a giant leap in terms of observing frequency, thanks to the use of ALMA, and in terms of distance to the black hole where the magnetic field has been probed — of the order of only a few light-days from the event horizon. These results, and future studies, will help us understand what is really going on in the immediate vicinity of supermassive black holes.”

    Notes

    [1] Much weaker magnetic fields have been detected in the vicinity of the relatively inactive supermassive black hole at the centre of the Milky Way. Recent observations have also revealed weak magnetic fields in the active galaxy NGC 1275, which were detected at millimetre wavelengths.

    [2] Magnetic fields introduce Faraday rotation, which makes the polarisation rotate in different ways at different wavelengths. The way in which this rotation depends on the wavelength tells us about the magnetic field in the region.

    [3] The ALMA observations were at an effective wavelength of about 0.3 millimetres, earlier investigations were at much longer radio wavelengths. Only light of millimetre wavelengths can escape from the region very close to the black hole, longer wavelength radiation is absorbed.

    More Information

    This research was presented in a paper entitled “A strong magnetic field in the jet base of a supermassive black hole” to appear in Science on 16 April 2015.

    The team is composed of I. Martí-Vidal (Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, Onsala, Sweden), S. Muller (Onsala Space Observatory), W. Vlemmings (Onsala Space Observatory), C. Horellou (Onsala Space Observatory), S. Aalto (Onsala Space Observatory).

    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.

    NRAO Small

    ESO 50

    NAOJ

     
  • richardmitnick 5:18 pm on March 25, 2015 Permalink | Reply
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    From U Maryland: “Supermassive Black Hole Clears Star-making Gas From Galaxy’s Core” 

    U Maryland bloc

    University of Maryland

    March 24, 2015
    Matthew Wright, 301-405-9267, mewright@umd.edu

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    The galaxy IRAS F11119+3257 (background) has a central supermassive black hole (inset) that creates winds capable of sweeping away the galaxy’s reservoir of raw star-building material. This is the first solid proof that black-hole winds are depriving their host galaxies of molecular gas and might ultimately stop their star formation activity. Image: ESA/ATG medialab

    Many nearby galaxies blast huge, wide-angled outpourings of material from their center, ejecting enough gas and dust to build more than a thousand stars the size of our sun every year. Astronomers have sought the driving force behind these massive molecular outflows, and now a team led by University of Maryland scientists has found an answer.

    A new study in the journal Nature, published March 26, 2015, provides the first observational evidence that a supermassive black hole at the center of a large galaxy can power these huge molecular outflows from deep inside the galaxy’s core. These outflows remove massive quantities of star-making gas, thus influencing the size, shape and overall fate of the host galaxy.

    The galaxy highlighted in the study, known as IRAS F11119+3257, has an actively growing supermassive black hole at its center. This means that, unlike the large black hole at the center of our own Milky Way galaxy, this black hole is actively consuming large amounts of gas. As material enters the black hole, it creates friction, which in turn gives off electromagnetic radiation—including X-rays and visible light.

    Black holes that fit this description are called active galactic nuclei (AGN), and their intense radiation output also generates powerful winds that force material away from the galactic center. The study found that these AGN winds are powerful enough to drive the large molecular outflows that reach to the edges of the galaxy’s borders.

    Although theorists have suspected a connection between AGN winds and molecular outflows, the current study is the first to confirm the connection with observational evidence.

    “This is the first galaxy in which we can see both the wind from the active galactic nucleus and the large-scale outflow of molecular gas at the same time,” said lead author Francesco Tombesi, an assistant research scientist in UMD’s astronomy department who has a joint appointment at NASA’s Goddard Space Flight Center via the Center for Research and Exploration in Space Science and Technology.

    The team analyzed data collected in 2013 by Suzaku, an X-ray satellite operated by the Japan Aerospace Exploration Agency (JAXA) and NASA, as well as data from the European Space Agency’s Herschel Space Observatory.

    JAXA Suzaku ISAS telescope
    Suzaku

    ESA Herschel
    ESA/Herschel

    While many previous studies independently described AGN winds and molecular outflows in separate galaxies, Tombesi and his colleagues needed to find a galaxy in which they could see both at the same time. IRAS F11119+3257 turned out to be a perfect candidate.

    2
    A red-filter image of IRAS F11119+3257 (inset) from the University of Hawaii’s 2.2-meter telescope shows faint features that may be tidal debris, a sign of a galaxy merger. Background: A wider view of the region from the Sloan Digital Sky Survey [SDSS]. Photo: NASA GSFC/SDSS/Sylvain Veilleux

    U Hawaii 2.2 meter telescope
    U Hawaii 2.2 meter telescope interior
    U Hawaii 2.2 meter telescope

    Sloan Digital Sky Survey Telescope
    SDSS telescope

    An alternate theory says that active star formation near the galactic center could drive molecular outflows. However, the brightness of IRAS F11119+3257’s active nucleus—which is responsible for about 80 percent of the galaxy’s overall radiation—suggested otherwise. Star formation alone cannot explain this intense concentration of energy, leading the researchers to conclude that the AGN winds must be the primary driver.

    “The temptation is to ignore the supermassive black hole when studying galactic dynamics and evolution, but our study shows that you can’t because it influences galaxies on the larger scale,” said Marcio Meléndez, a research associate in UMD’s astronomy department and a co-author of the study.

    Limited satellite time means that, at least for now, the team has only this one galaxy as a baseline for study. But now that they have a better idea what they are looking for, they will be able to find more candidate galaxies in the future. Within the next year, JAXA and NASA will launch ASTRO-H, a successor satellite to Suzaku. The instruments aboard ASTRO-H will make it possible to study more galaxies like IRAS F11119+3257 in greater detail.

    JAXA ASTRO-H telescope
    ASTRO-H

    “These are not like normal spiral or elliptical galaxies. They’re like train wrecks,” said Sylvain Veilleux, a professor of astronomy at UMD and a fellow at the Joint Space-Science Institute (JSI) who is also a co-author of the study. “Two galaxies collided with each other, and it’s now a single object. This train wreck provided all the material to feed the supermassive black hole that is now driving the huge galactic-scale outflow.”

    In addition to Tombesi, Meléndez and Veilleux, study authors included UMD astronomy professor and JSI fellow Chris Reynolds; James Reeves of Keele University in the United Kingdom; and Eduardo González-Alfonso of the Universidad de Alcalá in Spain.

    This research was supported by NASA (Award Nos. NNX12AH40G, NNX14AF86G, NHSC/JPL RSA grants 1427277 and 1454738), the U.S. National Science Foundation (Award Nos. AST1333514 and AST1009583), the Spanish Ministerio de Economía y Competitividad (Award Nos. AYA2010-21697-C05-0 and FIS2012-39162-C06-01) and the U.K. Science and Technology Facilities Council. The content of this article does not necessarily reflect the views of these organizations.

    The research paper, Wind from the black hole accretion disk driving a molecular outflow in an active galaxy, Francesco Tombesi, Marcio Meléndez, Sylvain Veilleux, James Reeves, Eduardo González-Alfonso and Chris S. Reynolds, was published on March 26, 2015, in the journal Nature.

    See the full article here.

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    U Maryland Campus

    Driven by the pursuit of excellence, the University of Maryland has enjoyed a remarkable rise in accomplishment and reputation over the past two decades. By any measure, Maryland is now one of the nation’s preeminent public research universities and on a path to become one of the world’s best. To fulfill this promise, we must capitalize on our momentum, fully exploit our competitive advantages, and pursue ambitious goals with great discipline and entrepreneurial spirit. This promise is within reach. This strategic plan is our working agenda.

    The plan is comprehensive, bold, and action oriented. It sets forth a vision of the University as an institution unmatched in its capacity to attract talent, address the most important issues of our time, and produce the leaders of tomorrow. The plan will guide the investment of our human and material resources as we strengthen our undergraduate and graduate programs and expand research, outreach and partnerships, become a truly international center, and enhance our surrounding community.

    Our success will benefit Maryland in the near and long term, strengthen the State’s competitive capacity in a challenging and changing environment and enrich the economic, social and cultural life of the region. We will be a catalyst for progress, the State’s most valuable asset, and an indispensable contributor to the nation’s well-being. Achieving the goals of Transforming Maryland requires broad-based and sustained support from our extended community. We ask our stakeholders to join with us to make the University an institution of world-class quality with world-wide reach and unparalleled impact as it serves the people and the state of Maryland.

     
  • richardmitnick 5:25 pm on February 25, 2015 Permalink | Reply
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    From NBC: “Astronomers Find Supermassive Black Hole 12 Billion Times Size of the Sun” 

    NBC News

    NBC News

    February 25th 2015
    No Writer Credit

    Astronomers say they have have discovered a black hole so big that it challenges the theory about how they grow. Scientists said this black hole was formed about 900 million years after the Big Bang. But with measurements indicating it is 12 billion times the size of the sun, the black hole challenges a widely accepted hypothesis of growth rates. “Based on previous research, this is the largest black hole found for that period of time,” Fuyan Bian, Research School of Astronomy and Astrophysics, Australian National University (ANU), told Reuters on Wednesday. “Current theory is for a limit to how fast a black hole can grow, but this black hole is too large for that theory.” The discovery was described in a study published Wednesday in Nature.

    1
    This artist’s impression shows the surroundings of the supermassive black hole at the heart of the active galaxy NGC 3783 in the southern constellation of Centaurus (The Centaur). New observations using the Very Large Telescope Interferometer at ESO’s Paranal Observatory in Chile have revealed not only the torus of hot dust around the black hole but also a wind of cool material in the polar regions.

    ESO VLT Interferometer
    ESO/VLTI

    The creation of supermassive black holes remains an open topic of research. However, many scientists have long believed the growth rate of black holes was limited. Black holes grow, scientific theory suggests, as they absorb mass. However, as mass is absorbed, it will be heated creating radiation pressure, which pushes the mass away from the black hole. “Basically, you have two forces balanced together which sets up a limit for growth, which is much smaller than what we found,” said Bian.

    The black hole was discovered a team of global scientists led by Xue-Bing Wu at Peking University, China, as part of the Sloan Digital Sky Survey [SDSS], which provided imagery data of 35 percent of the northern hemisphere sky.

    SDSS Telescope
    SDSS Telescope

    The ANU is leading a comparable project, known as SkyMapper, to carry out observations of the Southern Hemisphere sky. Bian expects more black holes to be observed as the project advances.

    See the full article here.

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  • richardmitnick 6:15 pm on February 19, 2015 Permalink | Reply
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    From NASA: “NASA, ESA Telescopes Give Shape to Furious Black Hole Winds” 

    NASA

    NASA

    February 19, 2015

    Felicia Chou
    Headquarters, Washington
    202-358-0257
    felicia.chou@nasa.gov

    Whitney Clavin
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-4673
    whitney.clavin@jpl.nasa.gov

    1
    Supermassive black holes at the cores of galaxies blast out radiation and ultra-fast winds, as illustrated in this artist’s conception. NASA’s NuSTAR and ESA’s XMM-Newton telescopes show that these winds, containing highly ionized atoms, blow in a nearly spherical fashion. Image Credit: NASA/JPL-Caltech

    NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) and ESA’s (European Space Agency) XMM-Newton telescope are showing that fierce winds from a supermassive black hole blow outward in all directions — a phenomenon that had been suspected, but difficult to prove until now.

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    NuSTAR

    2
    XMM-Newton

    “We know black holes in the centers of galaxies can feed on matter, and this process can produce winds. This is thought to regulate the growth of the galaxies,” said Fiona Harrison of the California Institute of Technology (Caltech) in Pasadena, California. Harrison is the principal investigator of NuSTAR and a co-author on a new paper about these results appearing in the journal Science. “Knowing the speed, shape and size of the winds, we can now figure out how powerful they are.”

    Supermassive black holes blast matter into their host galaxies, with X-ray-emitting winds traveling at up to one-third the speed of light. In the new study, astronomers determined PDS 456, an extremely bright black hole known as a quasar more than 2 billion light-years away, sustains winds that carry more energy every second than is emitted by more than a trillion suns.

    “Now we know quasar winds significantly contribute to mass loss in a galaxy, driving out its supply of gas, which is fuel for star formation,” said the study’s lead author Emanuele Nardini of Keele University in England.

    NuSTAR and XMM-Newton simultaneously observed PDS 456 on five separate occasions in 2013 and 2014. The space telescopes complement each other by observing different parts of the X-ray light spectrum: XMM-Newton views low-energy and NuSTAR views high-energy.

    Previous XMM-Newton observations had identified black hole winds blowing toward us, but could not determine whether the winds also blew in all directions. XMM-Newton had detected iron atoms, which are carried by the winds along with other matter, only directly in front of the black hole, where they block X-rays. Combining higher-energy X-ray data from NuSTAR with observations from XMM-Newton, scientists were able to find signatures of iron scattered from the sides, proving the winds emanate from the black hole not in a beam, but in a nearly spherical fashion.

    “This is a great example of the synergy between XMM-Newton and NuSTAR,” said Norbert Schartel, XMM-Newton project scientist at ESA. “The complementarity of these two X-ray observatories is enabling us to unveil previously hidden details about the powerful side of the universe.”

    With the shape and extent of the winds known, the researchers could then determine the strength of the winds and the degree to which they can inhibit the formation of new stars.

    Astronomers think supermassive black holes and their home galaxies evolve together and regulate each other’s growth. Evidence for this comes in part from observations of the central bulges of galaxies — the more massive the central bulge, the larger the supermassive black hole.

    This latest report demonstrates a supermassive black hole and its high-speed winds greatly affect the host galaxy. As the black hole bulks up in size, its winds push vast amounts of matter outward through the galaxy, which ultimately stops new stars from forming.

    Because PDS 456 is relatively close, by cosmic standards, it is bright and can be studied in detail. This black hole gives astronomers a unique look into a distant era of our universe, around 10 billion years ago, when supermassive black holes and their raging winds were more common and possibly shaped galaxies as we see them today.

    “For an astronomer, studying PDS 456 is like a paleontologist being given a living dinosaur to study,” said study co-author Daniel Stern of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena. “We are able to investigate the physics of these important systems with a level of detail not possible for those found at more typical distances, during the ‘Age of Quasars.'”

    NuSTAR is a Small Explorer mission led by Caltech and managed by JPL for NASA’s Science Mission Directorate in Washington.

    For more information, visit:

    http://www.nasa.gov/nustar

    and

    http://www.nustar.caltech.edu/

    This discovery has given astronomers their first opportunity to measure the strength of these ultra-fast winds and prove they are powerful enough to inhibit the host galaxy’s ability to make new stars.

    See the full article here.

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    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

     
  • richardmitnick 4:38 pm on December 5, 2014 Permalink | Reply
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    From Daily Galaxy: “Discovery of a Pulsar and Supermassive Black Hole Pairing Could Help Unlock the Enigma of Gravity” 

    Daily Galaxy
    The Daily Galaxy

    Last year, the very rare presence of a pulsar (named SGR J1745-2900) was also detected in the proximity of a supermassive black hole (Sgr A**, made up of millions of solar masses), but there is a combination that is still yet to be discovered: that of a pulsar orbiting a ‘normal’ black hole; that is, one with a similar mass to that of stars.

    b

    sgr

    Supermassive Black Hole Sagittarius A*

    The center of the Milky Way galaxy, with the supermassive black hole Sagittarius A* (Sgr A*), located in the middle, is revealed in these images. As described in our press release, astronomers have used NASA’s Chandra X-ray Observatory to take a major step in understanding why material around Sgr A* is extraordinarily faint in X-rays.

    NASA Chandra Telescope
    NASA/Chandra

    The large image contains X-rays from Chandra in blue and infrared emission from the Hubble Space Telescope in red and yellow. The inset shows a close-up view of Sgr A* in X-rays only, covering a region half a light year wide. The diffuse X-ray emission is from hot gas captured by the black hole and being pulled inwards. This hot gas originates from winds produced by a disk-shaped distribution of young massive stars observed in infrared observations.

    NASA Hubble Telescope
    NASA/ESA Hubble

    These new findings are the result of one of the biggest observing campaigns ever performed by Chandra. During 2012, Chandra collected about five weeks worth of observations to capture unprecedented X-ray images and energy signatures of multi-million degree gas swirling around Sgr A*, a black hole with about 4 million times the mass of the Sun. At just 26,000 light years from Earth, Sgr A* is one of very few black holes in the universe where we can actually witness the flow of matter nearby.

    The authors infer that less than 1% of the material initially within the black hole’s gravitational influence reaches the event horizon, or point of no return, because much of it is ejected. Consequently, the X-ray emission from material near Sgr A* is remarkably faint, like that of most of the giant black holes in galaxies in the nearby Universe.

    The captured material needs to lose heat and angular momentum before being able to plunge into the black hole. The ejection of matter allows this loss to occur.

    This work should impact efforts using radio telescopes to observe and understand the “shadow” cast by the event horizon of Sgr A* against the background of surrounding, glowing matter. It will also be useful for understanding the impact that orbiting stars and gas clouds might make with the matter flowing towards and away from the black hole.

    The paper is available online and is published in the journal Science. The first author is Q.Daniel Wang from University of Massachusetts at Amherst, MA; and the co-authors are Michael Nowak from Massachusetts Institute of Technology (MIT) in Cambridge, MA; Sera Markoff from University of Amsterdam in The Netherlands, Fred Baganoff from MIT; Sergei Nayakshin from University of Leicester in the UK; Feng Yuan from Shanghai Astronomical Observatory in China; Jorge Cuadra from Pontificia Universidad de Catolica de Chile in Chile; John Davis from MIT; Jason Dexter from University of California, Berkeley, CA; Andrew Fabian from University of Cambridge in the UK; Nicolas Grosso from Universite de Strasbourg in France; Daryl Haggard from Northwestern University in Evanston, IL; John Houck from MIT; Li Ji from Purple Mountain Observatory in Nanjing, China; Zhiyuan Li from Nanjing University in China; Joseph Neilsen from Boston University in Boston, MA; Delphine Porquet from Universite de Strasbourg in France; Frank Ripple from University of Massachusetts at Amherst, MA and Roman Shcherbakov from University of Maryland, in College Park, MD. Image credit: X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI

    k.
    This image was taken with NASA’s Chandra X-Ray Observatory.

    The intermittent light emitted by pulsars, the most precise timekeepers in the universe, allows scientists to verify Einstein’s theory of relativity, especially when these objects are paired up with another neutron star or white dwarf that interferes with their gravity. However, this theory could be analysed much more effectively if a pulsar with a black hole were found, except in two particular cases, according to researchers from Spain and India.

    Pulsars are very dense neutron stars that are the size of a city (their radius approaches ten kilometres), which, like lighthouses for the universe, emit gamma radiation beams or X-rays when they rotate up to hundreds of times per second. These characteristics make them ideal for testing the validity of the theory of general relativity, published by Einstein between 1915 and 1916.

    “Pulsars act as very precise timekeepers, such that any deviation in their pulses can be detected,” Diego F. Torres, ICREA researcher from the Institute of Space Sciences (IEEC-CSIC), explains to SINC. “If we compare the actual measurements with the corrections to the model that we have to use in order for the predictions to be correct, we can set limits or directly detect the deviation from the base theory.”

    These deviations can occur if there is a massive object close to the pulsar, such as another neutron star or a white dwarf. A white dwarf can be defined as the stellar remnant left when stars such as our Sun use up all of their nuclear fuel. The binary systems, comprised of a pulsar and a neutron star (including double pulsar systems) or a white dwarf, have been very successfully used to verify the theory of gravity.

    Until now scientists had considered the strange pulsar/black hole pairing to be an authentic ‘holy grail’ for examining gravity, but there exist at least two cases where other pairings can be more effective. This is what is stated in the study that Torres and the physicist Manjari Bagchi, from the International Centre of Theoretical Sciences (India) and now postdoc at the IEEC-CSIC, have published in the Journal of Cosmology and Astroparticle Physics. The work also received an Honourable Mention in the 2014 Essays of Gravitation prize.

    The first case occurs when the so-called principle of strong equivalence is violated. This principle of the theory of relativity indicates that the gravitational movement of a body that we test only depends on its position in space-time and not on what it is made up of, which means that the result of any experiment in a free fall laboratory is independent of the speed of the laboratory and where it is found in space and time.

    The other possibility is if one considers a potential variation in the gravitational constant that determines the intensity of the gravitational pull between bodies. Its value is G = 6.67384(80) x 10-11 N m2/kg2. Despite it being a constant, it is one of those that is known with the least accuracy, with a precision of only one in 10,000.

    In these two specific cases, the pulsar-black hole combination would not be the perfect ‘holy grail’, but in any case scientists are anxious to find this pair, because it could be used to analyse the majority of deviations. In fact, it is one of the desired objectives of X-ray and gamma ray space telescopes (such as Chandra, NuStar or Swift), as well as that of large radio telescopes that are currently being built, such as the enormous ‘Square Kilometre Array’ (SKA) in Australia and South Africa.

    NASA NuSTAR
    NASA/Nu-STAR

    NASA SWIFT Telescope
    NASA/Swift

    SKA Square Kilometer Array

    The image at the top of the page shows dynamic rings, wisps and jets of matter and antimatter around the pulsar in the Crab Nebula as observed in X-ray light by Chandra Space Observatory in 2001.

    Manjari Bagchi y Diego F. Torres. “In what sense a neutron star−black hole binary is the holy grail for testing gravity?”. Journal of Cosmology and Astroparticle Physics, 2014. Doi:10.1088/1475-7516/2014/08/055.

    See the full article here.

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  • richardmitnick 4:04 pm on December 5, 2014 Permalink | Reply
    Tags: Andrea Ghez, , , , , , Supermassive Black Holes,   

    From NSF: “After the Lecture…Andrea Ghez” 

    nsf
    National Science Foundation

    December 5, 2014

    NSF-funded UCLA astrophysicist Andrea Ghez on probing our galaxy’s supermassive black hole

    Andrea Ghez
    Dr.Andrea Ghez is an astrophysicist at UCLA who has been recognized many times for her research in galactic astronomy, including receiving a MacArthur Fellowship, a Packard Fellowship award, and several other awards early on in her career. Credit: Courtesy of the John D. and Catherine T. MacArthur Foundation via Wikimedia Commons

    Andrea's Favorite SO-2
    Andrea’s Favorite SO-2
    December 5, 2014

    We sat down with UCLA’s Andrea Ghez after her recent talk on Unveiling the Heart of the Galaxy as part of the NSF Distinguished Lectures in Mathematical and Physical Sciences. A few minutes later, we were probing the connection between ballet and astrophysics and why sometimes being outside of mainstream science can offer a scientist creative license that seeds transformational research.

    I was not a science fiction buff. I was always a puzzle buff, and I absolutely loved math. I still think of my job as puzzle solving. As a child, I also was fascinated by stories of women explorers–my favorite was Amelia Earhart.

    At some point in high school, I got fascinated by the concepts of black holes and the beginning of time.

    It’s asking the biggest questions we can possibly ask. It’s understanding our position in the universe. It’s what makes us uniquely human–to try and understand our context in the biggest possible terms. It’s what inspires us.

    Adaptive optics has transformed what we can do. When we started with speckle imaging, it was this bizarre little technique only a few people knew how to do. It was a niche-like a boutique technique. Adaptive optics has opened up the world of science so we can ask a much richer set of questions. It’s made it a technique for every astronomer.

    I used to be tremendously afraid of public speaking. I would shake if you asked me to introduce myself. I chose grad school for places where I would not have to teach because I was so deathly afraid of getting in front of an audience. But my adviser made me give a lunchtime talk, and every bone in my body shook. He was sweet but said I needed to teach. I’ve always been strongly committed to encouraging young girls to go into science, so I figured if I was going to teach, I would do it in a meaningful way for me. You just can’t get nervous every day, and I learned how to translate nervousness into excitement. That becomes your style. You are no longer nervous.

    I haven’t seen Interstellar. It’s on the top of my why-haven’t-I-seen-it list.

    You’re basically an idiot until you prove you’re smart. That’s what it’s like to be in science.

    My approach has always been to give myself the highest credentials possible. So when I thought about where to go to school, I really did think about the school that would give me the best “coat of armor” for dealing with any doubt. At every stage of my career, I think there’s been someone who pipes up with “you’ve only done this because you’re a woman” comment. And it’s not like everyone says this. It’s just that that’s the one comment you listen to.

    It’s really important to pick a good mentor. I think this is true, independent of gender.

    I almost increasingly think that there is an advantage to being outside mainstream because a lot of progress in science comes from the ability to think differently and to not necessarily accept what everyone has put out there. If you propose something different from what people are doing, how comfortable are you with being outside the group?

    To do science, it’s so important to take risks and accept failure. How do you train your students to do that? It’s a very important characteristic.

    I was really interested in dancing when I was young; I wanted to be a ballerina. At one point I got more interested in choreography. For some reason, I now think of my work as this combination of puzzle solving and choreography. I would never have made the connection between that kind of thinking and what I do today, yet it’s totally there.

    There have definitely been moments where I felt like I’m not playing on the right playground because I’m not seeing anyone I can relate to. Meeting people you can relate to is remarkably powerful and sometimes you find those people who inspire you to go onto the next step in very unexpected places.

    I think if I were not a physicist, I’d be some other sort of scientist or mathematician who is focused on solving problems.

    Ivy F. Kupec, (703) 292-8796 ikupec@nsf.gov

    Investigators
    Andrea Ghez

    Related Institutions/Organizations
    California Institute of Technology
    University of California-Los Angeles

    Locations
    Los Angeles , California

    Related Awards
    #0909218 A Laser Guide Star Adaptive Optics Study of Stellar Dynamics at the Galactic Center: A Laboratory for Understanding Interactions with a Central Supermassive Black Holes
    #1412615 New Probes of the Galactic Black Hole and its Environs

    See the full article http://www.nsf.gov/discoveries/disc_summ.jsp?cntn_id=133541&WT.mc_id=USNSF_1
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    The National Science Foundation (NSF) is an independent federal agency created by Congress in 1950 “to promote the progress of science; to advance the national health, prosperity, and welfare; to secure the national defense…we are the funding source for approximately 24 percent of all federally supported basic research conducted by America’s colleges and universities. In many fields such as mathematics, computer science and the social sciences, NSF is the major source of federal backing.

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  • richardmitnick 9:38 am on November 20, 2014 Permalink | Reply
    Tags: , , , , , , Supermassive Black Holes   

    From AAAS: “What powers a black hole’s mighty jets?” 

    AAAS

    AAAS

    19 November 2014
    Daniel Clery

    Black holes have a reputation for devouring everything in their path. But some of them like to give as well as receive. A small fraction of supermassive black holes—the ginormous ones that lurk at the centers of galaxies—fire off light-speed jets of particles as they snack. A new survey of more than 200 of these cosmic beasts finds that the jets are much more powerful than scientists thought. Astronomers don’t know what powers jets, but this new result, the team says, supports one proposed explanation: The jets are tapping into the rotational energy of the black hole itself.

    bh
    A black hole’s gravity can heat up the disk around it to shine brightly, but what powers the jets some of them produce remains a mystery. (NASA/JPL-Caltech)

    “It’s very exciting,” says Andrew Fabian, director of the Institute of Astronomy at the University of Cambridge in the United Kingdom, who was not involved in the research. “It’s long been debated whether this is possible.”

    About 1% of supermassive black holes have an “accretion disk” of gas and dust swirling around them. When material from this disk falls toward the black hole, the plunging debris gets so hot that it shines more brightly than the whole rest of its galaxy. One in 10 of these active black holes also produces jets that fire out particles at 99.995% of the speed of light. Astrophysicists suspect that accretion disks produce the jets, but they don’t know how.

    To get a better idea, a team led by astrophysicist Gabriele Ghisellini of the National Institute for Astrophysics in Merate, Italy, surveyed archival data and picked out a sample of 217 bright supermassive black holes for which they could find gamma ray observations (which reveal the brightness of the jets) and optical observations (to get the luminosity of the accretion disks). Key to the survey were data from NASA’s Fermi Gamma-ray Space Telescope, launched in 2008. “It took time to build up a collection of samples with the required information,” Ghisellini says.

    NASA Fermi Telescope
    NASA/Fermi

    Plotting the luminosity of the accretion disks against the gamma ray power of their jets, the team reports online today in Nature that there is a clear linear relationship between the two. The brighter the disk, the more powerful the jets—cementing the idea that accretion disks and jets are linked. But in terms of total power being beamed out into space, Ghisellini says, most of the jets were producing 10 times that of their accretion disks. “There must be another engine, not just the gravitational energy [of accreting matter falling toward the black hole].”

    The most popular explanation of how jets form is that the fast-spinning accretion disk, which contains charged particles, will produce a powerful magnetic field that is in contact with the black hole. If the black hole is spinning, it drags on the field, winding it into a tight cone at the rotational poles of the black hole. It is this twisted field that accelerates particles away from the black hole as jets and, in the process, extracts energy from the rotation of the black hole. Ghisellini says the group’s finding that jets are so much more powerful than accretion disks shows that disks alone can’t power the jets; the black hole’s spin must also be involved.

    Fabian says he still has a “slight reservation” about the assertion that the results prove the role of black hole spin. It’s also possible, he says, that the magnetic field is sucking power out of the accretion disk, making it appear less bright.

    “The next step for science is to measure the spin of a black hole,” Ghisellini says, to see whether spin rate is related to jet power. “But it is very hard to measure.” Fabian says researchers using NASA’s NuSTAR x-ray telescope have measured the spin rate of stellar-sized black holes formed from just one or a few stars. Confusingly, some of these small spinning black holes have jets and some don’t. “There must be some other parameter [defining whether a black hole has jets], but we don’t know what that is,” Fabian says.

    NASA NuSTAR
    NASA/Nu-STAR

    So although evidence is mounting that black hole spin is powering jets, astrophysicists may have to wait until they can measure the spin of a supermassive black hole before they can nail it. Ghisellini thinks Europe’s Athena x-ray observatory will be able to do the job, but he’s got a long wait ahead: Athena’s launch is slated for 2028.

    ESA Athena spacecraft
    Athena

    See the full article here.

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  • richardmitnick 11:04 am on October 24, 2014 Permalink | Reply
    Tags: , , , , , , Supermassive Black Holes   

    From CfA: “Accreting Supermassive Black Holes in the Early Universe” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    October 24, 2014
    No Writer Credit

    Supermassive black holes containing millions or even billions of solar-masses of material are found at the nuclei of galaxies. Our Milky Way, for example, has a nucleus with a black hole with about four million solar masses of material. Around the black hole, according to theories, is a torus of dust and gas, and when material falls toward the black hole (a process called accretion) the inner edge of the disk can be heated to millions of degrees. Such accretion heating can power dramatic phenomena like bipolar jets of rapidly moving charged particles. Such actively accreting supermassive black holes in galaxies are called active galactic nuclei (AGN).

    torus
    Torus

    The evolution of AGN in cosmic time provides a picture of their role in the formation and co-evolution of galaxies. Recently, for example, there has been some evidence that AGN with more modest luminosities and accretion rates (compared to the most dramatic cases) developed later in cosmic history (dubbed “downsizing”), although the reasons for and implications of this effect are debated. CfA astronomers Eleni Kalfontzou, Francesca Civano, Martin Elvis and Paul Green and a colleague have just published the largest study of X-ray selected AGN in the universe from the time when it was only 2.5 billion years old, with the most distant AGN in their sample dating from when the universe was about 1.2 billion years old.

    The astronomers studied 209 AGN detected with the Chandra X-ray Observatory.

    NASA Chandra Telescope
    NASA/Chandra

    image
    A multicolor image of galaxies in the field of the Chandra Cosmic Evolution Survey. A large, new study of 209 galaxies in the early universe with X-ray bright supermassive black holes finds that more modest AGN tend to peak later in cosmic history, and that obscured and unobscured AGN evolve in similar ways.
    X-ray: NASA/CXC/SAO/F.Civano et al. Optical: NASA/STScI

    They note that the X-ray observations are less contaminated by host galaxy emission than optical surveys, and consequently that they span a wider, more representative range of physical conditions. The team’s analysis confirms the proposed trend towards downsizing, while it also can effectively rule out some alternative proposals. The scientists also find, among other things, that this sample of AGN represents nuclei with a wide range of molecular gas and dust extinction. Combined with the range of AGN dates, this result enables them to conclude that obscured and unobscured phases of AGN evolve in similar ways.

    See the full article here.

    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.

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  • richardmitnick 10:54 am on August 19, 2014 Permalink | Reply
    Tags: , , , , , , Supermassive Black Holes   

    From SPACE.com: “Supermassive Death: 3 Stars Eaten by Black Holes” 

    space-dot-com logo

    SPACE.com

    August 19, 2014
    Ian O’Neill

    Astrophysicists have analyzed two decades-worth of X-ray data and discovered three events inside galactic cores that can be interpreted in only one way: stellar destruction.

    ANALYSIS: Supermassive Black Hole Jet Mystery Solved

    For any given galaxy, it is estimated that a star will be destroyed by the central supermassive black hole approximately once every 10,000 years. The vast majority of known galaxies are thought to contain at least one supermassive black hole in their cores, having a dramatic effect on galactic and stellar evolution. [Images: Black Holes of the Universe]

    As a star drifts too close to a supermassive black hole, intense tidal stresses rip the star to shreds. As this happens, the shredded material will be dragged into the black hole’s accretion disk — a hot disk of gas that is gradually pulled into the black hole’s event horizon, bulking up the black hole’s mass, or blasted as energetic jets from its poles.

    Should there be a rapid injection of material — i.e. a star becoming blended and ingested into the accretion disk — powerful X-rays of a specific signature will be generated.

    NEWS: Supermassive Black Holes are Not Doughnuts!

    In a new study by the Moscow Institute of Physics and Technology and Space Research Institute of the Russian Academy of Sciences, astrophysicists trawled through observations from two space observatories to discover three likely occasions where stars have been eaten by supermassive black holes. Their work has been accepted for publication in the journal Monthly Notices of the Royal Astronomical Society.

    Using data from the German ROSAT and European XMM-Newton space observatories, X-ray data from 1990 (to today) could be accessed and three events in different galaxies were positively identified — designated 1RXS J114727.1 + 494302, 1RXS J130547.2 + 641252 and 1RXS J235424.5-102053. Invaluable to this study was the long-duration observations by ROSAT (which operated from 1990 to 1999) and XMM-Newton (launched in 1999) that could detect the moment of stellar death, keeping track of the X-ray emissions over the years as the star’s material was gradually ingested.

    ROSAT Spacecraft
    ROSAT

    ESA XMM Newton
    ESA/XMM-Newton

    NEWS: Intermediate Black Hole Implicated in Star’s Death

    No more than two dozen other stellar death event candidates were seen in the observations, but positive identifications probably won’t be available until the launch of the multi-instrument Spectrum-X-Gamma space observatory in 2016.

    Spectrum GammaX
    Spectrum-X-Gamma space observatory

    This work has added some much needed detail to these rare events, indicating that (on average) one star every 30,000 years in any given galaxy will be destroyed by the central supermassive black hole, though the researchers caution that more observations of stars being eaten by supermassive black holes are needed.

    See the full article here.

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