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  • richardmitnick 11:21 am on March 27, 2015 Permalink | Reply
    Tags: Astronomy, , , Calar Alto Observatory   

    From Astronomy: “I ZW 18: The galaxy that reveals the universe’s history” 

    Astronomy magazine

    Astronomy Magazine

    March 26, 2015
    By Institute of Astrophysics of Andalusia, Granada, Spain

    1

    The first galaxies were formed some 13.3 billion years ago, mainly composed of hydrogen and helium, the primary elements that emerged from the Big Bang. Their study to date has been technically challenging due to their great distance from us, but the observation of analogous galaxies in our vicinity has turned out to be an excellent shortcut.

    “Dwarf galaxy I Zw 18 is the least abundant in metals — in astrophysics, elements heavier than hydrogen and helium — in the nearby universe and one of the most akin to the primeval galaxies. Its study therefore allows us to catch glimpses of the conditions that prevailed in the primordial universe,” said Carolina Kehrig from the Institute of Astrophysics of Andalusia.

    The study has found a large region in this small galaxy of ionized helium, which tends to be more frequent in distant galaxies with low presence of metals. The ionization of helium implies the presence of objects emitting a radiation intense enough to knock electrons off the helium atoms. “In this study, we propose a new interpretation of the origin of this radiation in galaxy I Zw 18, a subject that is still enigmatic,” Kehrig said.

    Using the PMAS integral field spectrograph of the 3.5-meter telescope at the Calar Alto Observatory (CAHA), researchers have obtained the first detailed map of this region of I Zw 18 and have analyzed possible ionizing sources.

    Calar Alto 3.5 meter Telescope
    Calar Alto 3.5 meter telescope interior with PMAS spectrograph
    Calar Alto 3.5 meter Telescope with PMAS Spectrograph

    Conventional sources of ionization, such as Wolf-Rayet stars — massive and with violent stellar winds — or shocks generated by remnants of supernovae, cannot provide the energy necessary to explain the halo of ionized helium present on I Zw 18, so researchers considered other possibilities.

    “Our data point to the fact that extremely hot stars, such as supermassive stars with low metal content or massive stars practically devoid of metals may hold the key to the enigma of the excitement of helium on I Zw 18, even though the existence of these stars has not yet been confirmed by observations on any galaxy,” said Carolina Kehrig from IAA-CSIC.

    We would be talking about hot stars analogous to first generation stars — known as Population III star — which according to theoretical models, would be composed only of hydrogen and helium and could be hundreds of times more massive than the Sun. These stars are believed to have played a decisive role in the “reionization” of the universe, during which period the first stars and galaxies became visible and which is still little known.

    This study shows how it is possible to extract information about the history of the universe within our own galactic vicinity.

    See the full article here.

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  • richardmitnick 8:30 am on March 27, 2015 Permalink | Reply
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    From DESY: “Negotiations for CTA northern site to start” 

    DESY
    DESY

    2015/03/26
    No Writer Credit

    Cherenkov Telescope Array
    Proposed Cherenkov Telescope Array for hunting Gamma Rays

    On 26 March 2015, the partner countries of Cherenkov Telescope Array (CTA) have decided to start negotiations for the location of the telescope array in the northern hemisphere. At a meeting in Heidelberg representatives of ministries and funding agencies have decided to begin negotiations with Spain for a possible location on La Palma and Mexico for one in San Pedro Mártir. Another candidate site in Arizona (USA) is considered as a possible back-up site.

    “I appreciate that we have successfully chosen the northern candidate sites with whom we would like to start negotiations as soon as possible,” said Beatrix Vierkorn-Rudolph from the German Federal Ministry of Research and Education, chair of the CTA Resource Board, after the decision of the voting members representing Argentina, Austria, Brazil, Czech Republic, France, Germany, Italy, Japan, Poland, South Africa, Spain, Switzerland and the UK. After negotiations, the Board will select the final site in November 2015. In regards to the southern hemisphere site, negotiations with the candidates Namibia and Chile are progressing and are expected to end in August 2015. Christian Stegmann from DESY added: “I’m very much looking forward to the final site decisions later this year; scientists worldwide are eager to see CTA advancing towards implementation.”

    Currently in its pre-construction phase, determining the northern and southern hemisphere sites will be a critical step towards the realization of the Cherenkov Telescope Array. “I’m looking forward to converging on final designs for the telescope arrays now that negotiations will start with specific locations in mind,” said Christopher Townsley, CTA project manager. Following the site selection, the project will move forward with construction of the first telescopes on site planned for 2016.

    See the full article here.

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    desi

    DESY is one of the world’s leading accelerator centres. Researchers use the large-scale facilities at DESY to explore the microcosm in all its variety – from the interactions of tiny elementary particles and the behaviour of new types of nanomaterials to biomolecular processes that are essential to life. The accelerators and detectors that DESY develops and builds are unique research tools. The facilities generate the world’s most intense X-ray light, accelerate particles to record energies and open completely new windows onto the universe. 
That makes DESY not only a magnet for more than 3000 guest researchers from over 40 countries every year, but also a coveted partner for national and international cooperations. Committed young researchers find an exciting interdisciplinary setting at DESY. The research centre offers specialized training for a large number of professions. DESY cooperates with industry and business to promote new technologies that will benefit society and encourage innovations. This also benefits the metropolitan regions of the two DESY locations, Hamburg and Zeuthen near Berlin.

     
  • richardmitnick 7:39 am on March 27, 2015 Permalink | Reply
    Tags: Astronomy, ,   

    From NatGeo: A Hundred Million Stars in Three Minutes 

    National Geographic

    National Geographics

    In January 2015, NASA released the largest image ever of the Andromeda galaxy, taken by the Hubble telescope.

    NASA Hubble Telescope
    NASA/ESA Hubble

    Totaling 1.5 billion pixels and requiring 4.3 gigabytes of disk space, this photo provides a detailed glimpse at the sheer scale of our nearest galactic neighbor. By zooming into the incredible shot, filmmaker Dave Achtemichuk creates an unforgettable interactive experience.

    See the full article here.

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

     
  • richardmitnick 2:18 pm on March 26, 2015 Permalink | Reply
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    From JPL: “Astronomers Upgrade Their Cosmic Light Bulbs” 

    JPL

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

    1
    A new study analyzes several sites where dead stars once exploded. Image credit: SDSS

    Sloan Digital Sky Survey Telescope
    SDSS Telescope at Apache Point, NM, USA

    The brilliant explosions of dead stars have been used for years to illuminate the far-flung reaches of our cosmos. The explosions, called Type Ia supernovae, allow astronomers to measure the distances to galaxies and measure the ever-increasing rate at which our universe is stretching apart.

    But these tools aren’t perfect. In the cosmic hardware store of our universe, improvements are ongoing. In a new report, appearing March 27 in the journal Science, astronomers identify the best, top-of-the-line Type Ia supernovae for measuring cosmic distances, pushing other, more clunky tools to the back of the shelf.

    Using archived data from NASA’s Galaxy Evolution Explorer (GALEX), scientists show that a particular class of Type Ia supernovae that occur near youthful stars can improve these measurements with a precision of more than two times that achieved before.

    NASA Galex telescope
    GALEX

    “We have discovered a population of Type Ia supernovae whose light output depends very precisely on how quickly they fade, making it possible to measure very exact distances to them,” said Patrick Kelly of the University of California, Berkeley, lead author of the new study. “These supernovae are found close to populations of bright, hot young stars.”

    The findings will help light the way to understanding dark energy, one of the greatest mysteries in the field of cosmology, the study of the origin and development of the universe. Dark energy is the leading culprit behind the baffling acceleration of our cosmos, a phenomenon discovered in 1998. The acceleration was uncovered when astronomers observed that galaxies are pulling away from each other at increasing speeds.

    The key to measuring this acceleration — and thus the nature of dark energy — lies with Type Ia supernovae, which work much like light bulbs strung across space. Imagine lining up 60-watt light bulbs across a field and standing at one end. The farthest light bulb wouldn’t appear as bright as the closest one due to its distance. Since you know how bright the light bulb inherently is, you can use the extent of its dimming to figure out the distance.

    Type Ia supernovae, also referred to as “standard candles,” work in a similar way because they consistently shine with about the same amount of light. While the process that leads to these explosions is still not clear, they occur when the burnt-out core of a star, called a white dwarf, blasts apart in a regular way, briefly lighting up the host galaxy.

    However, the explosions aren’t always precisely uniform. They can differ considerably depending on various factors, which appear to be connected to the environments and histories of the exploding stars. It’s as if our 60-watt bulbs sometimes give off 55 watts of light, skewing distance measurements.

    Kelly and his team investigated the reliability of these tools by analyzing the surroundings of nearly 100 previous Type Ia explosions. They used data from GALEX, which detects ultraviolet light. Populations of hot, young stars in galaxies will shine brightly with ultraviolet light, so GALEX can distinguish between young and older star-forming communities.

    The results showed that the Type Ia supernovae affiliated with the hot, young stars were significantly more reliable at indicating distances than their counterparts.

    “These explosions are likely the result of youthful white dwarfs,” said Kelly.

    By focusing on this particular brand of Type Ia tools, astronomers will be able to, in the future, make even sharper measurements of the size and scale of our universe. According to the science team, this class of tools could work at distances up to six billion light-years away, and perhaps farther.

    “GALEX surveyed the entire sky, allowing past and future eruptions of these high-quality standard candles to be identified easily,” said Don Neill, a member of the GALEX team at the California Institute of Technology in Pasadena, not affiliated with the study. “Any improvement in the standard candles will have a direct impact on theories of dark energy, allowing us to home in on this mysterious force propelling the acceleration of the universe.”

    Caltech led the Galaxy Evolution Explorer mission and was responsible for science operations and data analysis. The mission ended in 2013 after more than a decade of scanning the skies in ultraviolet light. NASA’s Jet Propulsion Laboratory in Pasadena, California, managed the mission and built the science instrument. The mission was developed under NASA’s Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Maryland. Researchers sponsored by Yonsei University in South Korea and the Centre National d’Etudes Spatiales (CNES) in France collaborated on this mission. ?

    Graphics and additional information about the Galaxy Evolution Explorer are online at:

    http://www.nasa.gov/galex

    http://www.galex.caltech.edu

    See the full article here.

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    NASA JPL Campus

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

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  • richardmitnick 1:57 pm on March 26, 2015 Permalink | Reply
    Tags: Astronomy, ,   

    From Hubble: “Dark matter even darker than once thought” 

    NASA Hubble Telescope

    Hubble

    26 March 2015
    David Harvey
    École Polytechnique Fédérale de Lausanne
    Lausanne, Switzerland
    Tel: +41 22 3792475
    Cell: +41 7946 38283
    Email: david.harvey@epfl.ch

    Richard Massey
    Durham University
    Durham, UK
    Tel: +44 7740 648080
    Email: r.j.massey@durham.ac.uk

    Georgia Bladon
    ESA/Hubble, Public Information Officer
    Garching bei München, Germany
    Tel: +44 7816 291261
    Email: gbladon@partner.eso.org

    Hubble explores the dark side of cosmic collisions

    1
    Image credit: NASA, ESA, D. Harvey (École Polytechnique Fédérale de Lausanne, Switzerland)and R. Massey (Durham University, UK)

    Astronomers using observations from the NASA/ESA Hubble Space Telescope and NASA’s Chandra X-ray Observatory have studied how dark matter in clusters of galaxies behaves when the clusters collide. The results, published in the journal Science on 27 March 2015, show that dark matter interacts with itself even less than previously thought, and narrows down the options for what this mysterious substance might be.

    NASA Chandra Telescope
    NASA/CHandra

    Dark matter is a giant question mark looming over our knowledge of the Universe. There is more dark matter in the Universe than visible matter, but it is extremely elusive; it does not reflect, absorb or emit light, making it invisible. Because of this, it is only known to exist via its gravitational effects on the visible Universe (see e.g. heic1215a).

    To learn more about this mysterious substance, researchers can study it in a way similar to experiments on visible matter — by watching what happens when it bumps into things [1]. For this reason, researchers look at vast collections of galaxies, called galaxy clusters, where collisions involving dark matter happen naturally and where it exists in vast enough quantities to see the effects of collisions [2].

    Galaxies are made of three main ingredients: stars, clouds of gas and dark matter. During collisions, the clouds of gas spread throughout the galaxies crash into each other and slow down or stop. The stars are much less affected by the drag from the gas [3] and, because of the huge gaps between them, do not have a slowing effect on each other — though if two stars did collide the frictional forces would be huge.

    “We know how gas and stars react to these cosmic crashes and where they emerge from the wreckage. Comparing how dark matter behaves can help us to narrow down what it actually is,” explains David Harvey of the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland, lead author of a new study.

    Harvey and his team used data from the NASA/ESA Hubble Space Telescope and NASA’s Chandra X-ray Observatory to study 72 large cluster collisions. The collisions happened at different times, and are seen from different angles — some from the side, and others head-on [4].

    The team found that, like the stars, the dark matter continued straight through the violent collisions without slowing down. However, unlike in the case of the stars, this is not because the dark matter is far away from other dark matter during the collisions. The leading theory is that dark matter is spread evenly throughout the galaxy clusters so dark matter particles frequently get very close to each other. The reason the dark matter doesn’t slow down is because not only does it not interact with visible particles, it also interacts even less with other dark matter than previously thought.

    “A previous study had seen similar behaviour in the Bullet Cluster,” says team member Richard Massey of Durham University, UK.

    2
    Bullet Cluster
    X-ray photo by Chandra X-ray Observatory. Exposure time was 140 hours. The scale is shown in megaparsecs. Redshift (z) = 0.3, meaning its light has wavelengths stretched by a factor of 1.3.

    “But it’s difficult to interpret what you’re seeing if you have just one example. Each collision takes hundreds of millions of years, so in a human lifetime we only get to see one freeze-frame from a single camera angle. Now that we have studied so many more collisions, we can start to piece together the full movie and better understand what is going on.”

    By finding that dark matter interacts with itself even less than previously thought, the team have successfully narrowed down the properties of dark matter. Particle physics theorists have to keep looking, but they now have a smaller set of unknowns to work with when building their models[5].

    Dark matter could potentially have rich and complex properties, and there are still several other types of interaction to study. These latest results rule out interactions that create a strong frictional force, causing dark matter to slow down during collisions. Other possible interactions could make dark matter particles bounce off each other like billiard balls, causing dark matter to be thrown out of collisions or for dark matter blobs to change shape. The team will be studying these next.

    To further increase the number of collisions that can be studied, the team are also looking to study collisions involving individual galaxies, which are much more common.

    “There are still several viable candidates for dark matter, so the game is not over, but we are getting nearer to an answer,” concludes Harvey. “These ‘Astronomically Large’ particle colliders are finally letting us glimpse the dark world all around us but just out of reach.”

    Notes

    [1] On Earth scientists use particle accelerators to find out more about the properties of different particles. Physicists can investigate what substances are made of by accelerating particles into a collision, and examining the properties and trajectory of the resulting debris.

    [2] Clusters of galaxies are a swarm of galaxies permeated by a sea of hot X-ray emitting ionised hydrogen gas that is all embedded in a massive cloud of dark matter. It is the interactions of these, the most massive structures in the Universe that are observed to test dark matter’s properties.

    [3] The gas-gas interaction in cluster collisions is very strong, while the gas-star drag is weak. In a similar way to a soap bubble and a bullet in the wind where the bubble would interact a great deal more with the wind than the bullet.

    [4] To find out where the dark matter was located in the cluster the researchers studied the light from galaxies behind the cluster whose light had been magnified and distorted by the mass in the cluster. Because they have a good idea of the visible mass in the cluster, the amount the light is distorted tells them how much dark matter there is in a region.

    [5] A favoured theory is that dark matter might be constituted of “supersymmetric” particles. Supersymmetry is a theory in which all particles in our Standard Model — electrons, protons, neutrons, and so on — have a more massive “supersymmetric” partner. While there has been no experimental confirmation for supersymmetry as yet, the theory would solve a few of the gaps in our current thinking. One of supersymmetry’s proposed particles would be stable, electrically neutral, and only interact weakly with the common particles of the Standard Model — all the properties required to explain dark matter.

    Supersymmetry standard model
    Standard Model of Supersymmetry

    4
    Standard Model of Particle Physics. The diagram shows the elementary particles of the Standard Model (the Higgs boson, the three generations of quarks and leptons, and the gauge bosons), including their names, masses, spins, charges, chiralities, and interactions with the strong, weak and electromagnetic forces. It also depicts the crucial role of the Higgs boson in electroweak symmetry breaking, and shows how the properties of the various particles differ in the (high-energy) symmetric phase (top) and the (low-energy) broken-symmetry phase (bottom).

    Notes for editors

    The research paper, entitled The non-gravitational interactions of dark matter in colliding galaxy clusters, will be published in the journal Science on 27 March 2015.

    The international team of astronomers in this study consists of D. Harvey (École Polytechnique Fédérale de Lausanne, Switzerland; University of Edinburgh, UK), R. Massey (Durham University, UK), T. Kitching (University College London, UK), A. Taylor (University of Edinburgh, UK), and E. Tittley (University of Edinburgh, UK).
    More information

    See the full article here.

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    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 8:57 am on March 26, 2015 Permalink | Reply
    Tags: Astronomy, , ,   

    From Space.com: “The Strangest Black Holes in the Universe” 2013 But Interesting 

    space-dot-com logo

    SPACE.com

    July 08, 2013
    Charles Q. Choi

    Black holes are gigantic cosmic monsters, exotic objects whose gravity is so strong that not even light can escape their clutches.

    The Biggest Black Holes
    1
    Credit: Pete Marenfeld

    Nearly all galaxies are thought to harbor at their cores supermassive black holes millions to billions of times the mass of our sun. Scientists recently discovered the largest black holes known in two nearby galaxies.

    One of these galaxies, known as NGC 3842 — the brightest galaxy in the Leo cluster nearly 320 million light years away — has a central black hole containing 9.7 billion solar masses. The other, NGC 4889, the brightest galaxy in the Coma cluster more than 335 million light years away, has a black hole of comparable or larger mass.

    3
    NGC 4889
    Credit: Sloan Digital Sky Survey, Spitzer Space Telescope
    Sloan Digital Sky Survey Telescope
    SDSS telescope

    NASA Spitzer Telescope
    NASA/Spitzer

    The Smallest Black Hole
    2
    Credit: NASA/Goddard Space Flight Center/CI Lab

    The gravitational range, or “event horizon,” of these black holes is about five times the distance from the sun to Pluto. For comparison, these blaVck holes are 2,500 times as massive as the black hole at the center of the Milky Way galaxy, whose event horizon is one-fifth the orbit of Mercury.

    The smallest black hole discovered to date may be less than three times the mass of our sun. This would put this little monster, officially called IGR J17091-3624, near the theoretical minimum limit needed for a black hole to be stable. As tiny as this black hole may be, it looks fierce, capable of 20 million mph winds (32 million kph) — the fastest yet observed from a stellar-mass black hole by nearly 10 times.

    Cannibalistic Black Holes
    3
    Credit: X-ray: NASA/CXC/SAO/G.Fabbiano et al; Optical: NASA/STScI

    NASA Chandra schematic
    NASA/Chandra

    NASA Hubble Telescope
    NASA/ESA Hubble [not in notes but in credit]

    Black holes devour anything unlucky enough to drift too close, including other black holes. Scientists recently detected the monstrous black hole at the heart of one galaxy getting consumed by a still larger black hole in another.

    The discovery is the first of its kind. Astronomers had witnessed the final stages of the merging of galaxies of equal mass — so-called major mergers — but minor mergers between galaxies and smaller companions had long eluded researchers.

    Using NASA’s Chandra X-ray Observatory, investigators detected two black holes at the center of a galaxy dubbed NGC3393, with one black hole about 30 million times the mass of the sun and the other at least 1 million times the mass of the sun, separated from each other by only about 490 light-years.

    Bullet-shooting Black Hole
    4
    Credit: Greg Sivakoff/University of Alberta

    Black holes are known for sucking in matter, but researchers find they can shoot it out as well. Observations of a black hole called H1743-322, which harbors five to 10 times the mass of the sun and is located about 28,000 light-years from Earth, revealed it apparently pulled matter off a companion star, then spat some of it back out as gigantic “bullets” of gas moving at nearly a quarter the speed of light.

    The Oldest Known Black Hole
    5
    Credit: ESO/M. Kornmesser

    The oldest black hole found yet, officially known as ULAS J1120+0641, was born about 770 million years after the Big Bang that created our universe. (Scientists think the Big Bang occurred about 13.7 billion years ago.)

    The ancient age of this black hole actually poses some problems for astronomers. This brilliant enigma appears to be 2 billion times the mass of the sun. How black holes became so massive so soon after the Big Bang is difficult to explain.

    The Brightest Black Hole
    6
    Credit: HST

    Although the gravitational pulls of black holes are so strong that even light cannot escape, they also make up the heart of quasars, the most luminous, most powerful and most energetic objects in the universe.

    As supermassive black holes at the centers of galaxies suck in surrounding gas and dust, they can spew out huge amounts of energy. The brightest quasar we see in the visible range is 3C 273, which lies about 3 billion light-years away.

    Rogue Black Holes
    7
    Credit: David A. Aguilar (CfA)

    When galaxies collide, black holes can get kicked away from the site of the crash to roam freely through space. The first known such rogue black hole, SDSSJ0927+2943, may be approximately 600 million times the mass of the sun and hurtle through space at a whopping 5.9 million mph (9.5 million kph). Hundreds of rogue black holes might wander the Milky Way.

    Middleweight Black Holes
    8
    Credit: NASA

    Scientists have long thought that black holes come in three sizes — essentially small, medium and large. Relatively small black holes holding the mass of a few suns are common, while supermassive black holes millions to billions of solar masses are thought to lurk at the heart of nearly every galaxy. One more massive than four million suns, for example, is thought to hide in the center of the Milky Way.

    However, middle-weight black holes had eluded astronomers for years. Scientists recently discovered an intermediate-mass black hole, called HLX-1 (Hyper-Luminous X-ray source 1), approximately 290 million light-years from Earth, which appears to be about 20,000 solar masses in size.

    Medium-size black holes are thought to be the building blocks of supermassive black holes, so understanding more about them can shed light on how these monsters and the galaxies that surround them evolved.

    Fastest-spinning Black Hole
    9
    Credit: NASA / NASA / CXC / M.Weiss

    Black holes can whirl the fabric of space around themselves at extraordinary speeds. One black hole called GRS 1915+105, in the constellation Aquila (The Eagle) about 35,000 light-years from Earth, is spinning more than 950 times per second.

    An item placed on the edge of the black hole’s event horizon — the edge past which nothing can escape — would spin around it at a speed of more than 333 million mph (536 million kph), or about half the speed of light.

    Tabletop Black Holes
    10
    Credit: Chris Kuklewicz

    Black holes are thankfully quite far away from Earth, but this distance makes it difficult to gather clues that could help solve the many mysteries that surround them. However, researchers are now recreating the enigmatic properties of black holes on tabletops.

    For instance, black holes possess gravitational pulls so powerful that nothing, including light, can escape after falling past a border known as the event horizon. Scientists have created an artificial event horizon in the lab using fiber optics. They have also recreated the so-called Hawking radiation thought to escape from black holes.

    See the full article here.

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  • richardmitnick 6:46 am on March 26, 2015 Permalink | Reply
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    From ESO: “Best View Yet of Dusty Cloud Passing Galactic Centre Black Hole” 


    European Southern Observatory

    26 March 2015
    Andreas Eckart
    University of Cologne
    Cologne, Germany
    Email: eckart@ph1.uni-koeln.de

    Monica Valencia-S.
    University of Cologne
    Cologne, Germany
    Email: mvalencias@ph1.uni-koeln.de

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

    VLT observations confirm that G2 survived close approach and is a compact object

    Temp 0

    The best observations so far of the dusty gas cloud G2 confirm that it made its closest approach to the supermassive black hole at the centre of the Milky Way in May 2014 and has survived the experience. The new result from ESO’s Very Large Telescope shows that the object appears not to have been significantly stretched and that it is very compact. It is most likely to be a young star with a massive core that is still accreting material. The black hole itself has not yet shown any increase in activity.

    A supermassive black hole with a mass four million times that of the Sun lies at the heart of the Milky Way galaxy. It is orbited by a small group of bright stars and, in addition, an enigmatic dusty cloud, known as G2, has been tracked on its fall towards the black hole over the last few years. Closest approach, known as peribothron, was predicted to be in May 2014.

    The great tidal forces in this region of very strong gravity were expected to tear the cloud apart and disperse it along its orbit. Some of this material would feed the black hole and lead to sudden flaring and other evidence of the monster enjoying a rare meal. To study these unique events, the region at the galactic centre has been very carefully observed over the last few years by many teams using large telescopes around the world.

    A team led by Andreas Eckart (University of Cologne, Germany) has observed the region using ESO’s Very Large Telescope (VLT) [1] over many years, including new observations during the critical period from February to September 2014, just before and after the peribothron event in May 2014. These new observations are consistent with earlier ones made using the Keck Telescope on Hawaii [2].

    Keck Observatory
    Keck Observatory Interior
    UCO/Keck

    The images of infrared light coming from glowing hydrogen show that the cloud was compact both before and after its closest approach, as it swung around the black hole.

    As well as providing very sharp images, the SINFONI instrument on the VLT also splits the light into its component infrared colours and hence allows the velocity of the cloud to be estimated [3].

    ESO SINFONI
    SINFONI

    Before closest approach, the cloud was found to be travelling away from the Earth at about ten million kilometres/hour and, after swinging around the black hole, it was measured to be approaching the Earth at about twelve million kilometres/hour.

    Florian Peissker, a PhD student at the University of Cologne in Germany, who did much of the observing, says: “Being at the telescope and seeing the data arriving in real time was a fascinating experience,” and Monica Valencia-S., a post-doctoral researcher also at the University of Cologne, who then worked on the challenging data processing adds: “It was amazing to see that the glow from the dusty cloud stayed compact before and after the close approach to the black hole.”

    Although earlier observations had suggested that the G2 object was being stretched, the new observations did not show evidence that the cloud had become significantly smeared out, either by becoming visibly extended, or by showing a larger spread of velocities.

    In addition to the observations with the SINFONI instrument the team has also made a long series of measurements of the polarisation of the light coming from the supermassive black hole region using the NACO instrument on the VLT.

    ESO NACO
    NACO

    These, the best such observations so far, reveal that the behaviour of the material being accreted onto the black hole is very stable, and — so far — has not been disrupted by the arrival of material from the G2 cloud.

    The resilience of the dusty cloud to the extreme gravitational tidal effects so close to the black hole strongly suggest that it surrounds a dense object with a massive core, rather than being a free-floating cloud. This is also supported by the lack, so far, of evidence that the central monster is being fed with material, which would lead to flaring and increased activity.

    Andreas Eckart sums up the new results: “We looked at all the recent data and in particular the period in 2014 when the closest approach to the black hole took place. We cannot confirm any significant stretching of the source. It certainly does not behave like a coreless dust cloud. We think it must be a dust-shrouded young star.”

    Notes

    [1] These are very difficult observations as the region is hidden behind thick dust clouds, requiring observations in infrared light. And, in addition, the events occur very close to the black hole, requiring adaptive optics to get sharp enough images. The team used the SINFONI instrument on ESO’s Very Large Telescope and also monitored the behaviour of the central black hole region in polarised light using the NACO instrument.

    [2] The VLT observations are both sharper (because they are made at shorter wavelengths) and also have additional measurements of velocity from SINFONI and polarisation measurement using the NACO instrument.

    [3] Because the dusty cloud is moving relative to Earth — away from Earth before closest approach to the black hole and towards Earth afterwards — the Doppler shift changes the observed wavelength of light. These changes in wavelength can be measured using a sensitive spectrograph such as the SINFONI instrument on the VLT. It can also be used to measure the spread of velocities of the material, which would be expected if the cloud was extended along its orbit to a significant extent, as had previously been reported.

    More information

    This research was presented in a paper Monitoring the Dusty S-Cluster Object (DSO/G2) on its Orbit towards the Galactic Center Black Hole by M. Valencia-S. et al. in the journal Astrophysical Journal Letters.

    The team is composed of M. Valencia-S. (Physikalisches Institut der Universität zu Köln, Germany), A. Eckart (Universität zu Köln; Max-Planck-Institut für Radioastronomie, Bonn, Germany [MPIfR]), M. Zajacek (Universität zu Köln; MPIfR; Astronomical Institute of the Academy of Sciences Prague, Czech Republic), F. Peissker (Universität zu Köln), M. Parsa (Universität zu Köln), N. Grosso (Observatoire Astronomique de Strasbourg, France), E. Mossoux (Observatoire Astronomique de Strasbourg), D. Porquet (Observatoire Astronomique de Strasbourg), B. Jalali (Universität zu Köln), V. Karas (Astronomical Institute of the Academy of Sciences Prague), S. Yazici (Universität zu Köln), B. Shahzamanian (Universität zu Köln), N. Sabha (Universität zu Köln), R. Saalfeld (Universität zu Köln), S. Smajic (Universität zu Köln), R. Grellmann (Universität zu Köln), L. Moser (Universität zu Köln), M. Horrobin (Universität zu Köln), A. Borkar (Universität zu Köln), M. García-Marín (Universität zu Köln), M. Dovciak (Astronomical Institute of the Academy of Sciences Prague), D. Kunneriath (Astronomical Institute of the Academy of Sciences Prague), G. D. Karssen (Universität zu Köln), M. Bursa (Astronomical Institute of the Academy of Sciences Prague), C. Straubmeier (Universität zu Köln) and H. Bushouse (Space Telescope Science Institute, Baltimore, Maryland, USA).

    See the full article here.

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

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  • richardmitnick 8:36 pm on March 25, 2015 Permalink | Reply
    Tags: Astronomy, , , ,   

    From U Wisconsin: “Automation offers big solution to big data in astronomy” 

    U Wisconsin

    University of Wisconsin

    March 24, 2015
    David Tenenbaum

    SKA Map

    It’s almost a rite of passage in physics and astronomy. Scientists spend years scrounging up money to build a fantastic new instrument. Then, when the long-awaited device finally approaches completion, the panic begins: How will they handle the torrent of data?

    That’s the situation now, at least, with the Square Kilometer Array (SKA), a radio telescope planned for Africa and Australia that will have an unprecedented ability to deliver data — lots of data points, with lots of details — on the location and properties of stars, galaxies and giant clouds of hydrogen gas.

    SKA Square Kilometer Array

    In a study published in The Astronomical Journal, a team of scientists at the University of Wisconsin-Madison has developed a new, faster approach to analyzing all that data.

    Hydrogen clouds may seem less flashy than other radio telescope targets, like exploding galaxies. But hydrogen is fundamental to understanding the cosmos, as it is the most common substance in existence and also the “stuff” of stars and galaxies.

    2
    Hubble telescope image of stars forming inside a cloud of cold hydrogen gas and dust in the Carina Nebula, 7,500 light-years away.
    Credit: Space Telescope Science Institute

    As astronomers get ready for SKA, which is expected to be fully operational in the mid-2020s, “there are all these discussions about what we are going to do with the data,” says Robert Lindner, who performed the research as a postdoctoral fellow in astronomy and now works as a data scientist in the private sector. “We don’t have enough servers to store the data. We don’t even have enough electricity to power the servers. And nobody has a clear idea how to process this tidal wave of data so we can make sense out of it.”

    Lindner worked in the lab of Associate Professor Snežana Stanimirović, who studies how hydrogen clouds form and morph into stars, in turn shaping the evolution of galaxies like our own Milky Way.

    In many respects, the hydrogen data from SKA will resemble the vastly slower stream coming from existing radio telescopes. The smallest unit, or pixel, will store every bit of information about all hydrogen directly behind a tiny square in the sky. At first, it is not clear if that pixel registers one cloud of hydrogen or many — but answering that question is the basis for knowing the actual location of all that hydrogen.

    1
    Robert Lindner

    People are visually oriented and talented in making this interpretation, but interpreting each pixel requires 20 to 30 minutes of concentration using the best existing models and software. So, Lindner asks, how will astronomers interpret hydrogen data from the millions of pixels that SKA will spew? “SKA is so much more sensitive than today’s radio telescopes, and so we are making it impossible to do what we have done in the past.”

    In the new study, Lindner and colleagues present a computational approach that solves the hydrogen location problem with just a second of computer time.

    For the study, UW-Madison postdoctoral fellow Carlos Vera-Ciro helped write software that could be trained to interpret the “how many clouds behind the pixel?” problem. The software ran on a high-capacity computer network at UW-Madison called HTCondor. And “graduate student Claire Murray was our ‘human,’” Lindner says. “She provided the hand-analysis for comparison.”

    Those comparisons showed that as the new system swallows SKA’s data deluge, it will be accurate enough to replace manual processing.

    Ultimately, the goal is to explore the formation of stars and galaxies, Lindner says. “We’re trying to understand the initial conditions of star formation — how, where, when do they start? How do you know a star is going to form here and not there?”

    To calculate the overall evolution of the universe, cosmologists rely on crude estimates of initial conditions, Lindner says. By correlating data on hydrogen clouds in the Milky Way with ongoing star formation, data from the new radio telescopes will support real numbers that can be entered into the cosmological models.

    “We are looking at the Milky Way, because that’s what we can study in the greatest detail,” Lindner says, “but when astronomers study extremely distant parts of the universe, they need to assume certain things about gas and star formation, and the Milky Way is the only place we can get good numbers on that.”

    With automated data processing, “suddenly we are not time-limited,” Lindner says. “Let’s take the whole survey from SKA. Even if each pixel is not quite as precise, maybe, as a human calculation, we can do a thousand or a million times more pixels, and so that averages out in our favor.”

    See the full article here.

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    In achievement and prestige, the University of Wisconsin–Madison has long been recognized as one of America’s great universities. A public, land-grant institution, UW–Madison offers a complete spectrum of liberal arts studies, professional programs and student activities. Spanning 936 acres along the southern shore of Lake Mendota, the campus is located in the city of Madison.

     
  • 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

    1
    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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    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 4:05 pm on March 25, 2015 Permalink | Reply
    Tags: Astronomy, , ,   

    From CAASTRO: “At least a quarter of supernovae eject sub-Chandrasekhar masses” 

    CAASTRO bloc

    CAASTRO ARC Centre of Excellence for All Sky Astrophysics

    25 March 2015
    No Writer Credit

    Despite their ongoing use as tools for cosmology, type Ia supernovae (SNe Ia) are still not fully understood physically. In the classic scenario, a white dwarf and a larger star orbit each other, with the white dwarf gradually accreting material from its companion until reaching the Chandrasekhar limiting mass (1.4 times the mass of our Sun) when it is expected to become unstable and explode. This scenario is now being actively challenged, due to tight observational limits on signatures of the accretion process (such as X-ray emission from host galaxies or hydrogen lines in SN Ia spectra) and to the low predicted rate of Chandrasekhar-mass explosions. Alternative models, such as white dwarf mergers or collisions, may eject different amounts of material.

    2
    A critical aspect of these models is that they imply that a Type Ia supernova happens when the mass passes the Chandrasekhar threshold of 1.44 solar masses, and therefore all start at essentially the same mass. One would expect that the energy output of the resulting detonation would always be the same. It is not quite that simple, but they seem to have light curves that are closely related, and can be related to a common template. [This image is not from the article. It is put in here for better illustration]

    1
    Previous observational work by CAASTRO Associate Investigator Dr Richard Scalzo (ANU) has shown that for “normal” SNe Ia used to study the cosmological dark energy, ejected mass correlates strongly with rate of luminosity decline after peak. It also confirms that the mass of radioactive nickel-56 synthesised in the explosion correlates with the peak luminosity. The relation between decline rate and luminosity, used to calibrate SNe Ia as “standard candles” in cosmology, may thus reflect an underlying relation between ejected mass and nickel mass, giving a clue to the explosion mechanism.

    In a recent paper with CAASTRO co-authors Dr Ashley Ruiter (ANU) and Dr Stuart Sim (Queens University Belfast), Dr Scalzo has exploited these relations to measure the detailed distribution of ejected masses for a sample of over 300 type Ia supernovae used in cosmological analyses. While the distribution has a sharp peak at the Chandrasekhar mass, it also shows a long tail towards lower masses and very few (< 2%) high-mass events. This picture shows for the first time that both Chandrasekhar-mass and sub-Chandrasekhar-mass explosions occur at significant rates. While white dwarf mergers or detonations of low-mass white dwarfs could explain some of the distribution's tail, some events with inferred sub-Chandrasekhar ejected masses are fainter than predicted in these scenarios – suggesting that these models need revision to explain the SN Ia calibration relation.

    Publication details:

    R. A. Scalzo, A. J. Ruiter, S. A. Sim in MNRAS 445 (2014) The ejected mass distribution of Type Ia supernovae: a significant rate of non-Chandrasekhar-mass progenitors

    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.

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