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Mars Base

Ancient Quasar Shines Brightly, But All the Galaxy's Stars Are Missing - 0 views

www.universetoday.com/...-the-galaxys-stars-are-missing

scibyte69 quasar

shared by Mars Base on 24 Oct 12 - No Cached
  • Quasars have been the best and most easily observed beacons for astronomers to probe the distant Universe
  • one of the most distant and brightest quasars is providing a bit of a surprise
  • Astronomers studying a distant galaxy, dubbed J1148+5251 and which contains a bright quasar, are seeing only the quasar and not the host galaxy itself
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  • has been thought that the quasar has been feeding on a handful of stars every year in order to bulk up to its size of three billion solar masses over just a few hundred million years. But where are all the stars
  • Near infrared views with the Hubble Space Telescope’s Wide Field Camera 3 are only providing hints of what might be taking place
  • galaxy is so enshrouded with dust that none of the starlight can be seen
  • only the bright, blaring quasar shines through
  • most early galaxies contain hardly any dust
  • the early universe was dust-free until the first generation of stars started making dust through nuclear fusion
  • quasar was first identified in the Sloan Digital Sky Survey (SDSS) and the follow-up submillimeter observations showed significant dust but not how and where
  • If you want to hide the stars with dust
  • make lots of short-lived massive stars earlier on that lose their mass at the end of their lifetime
  • used Hubble to very carefully subtract light from the quasar image and look for the glow of surrounding stars.
  • remarkable
  • Hubble didn’t find any of the underlying galaxy
  • Because we don’t see the stars, we can rule out that the galaxy that hosts this quasar is a normal galaxy
  • It’s among the dustiest galaxies in the universe
  • so widely distributed that not even a single clump of stars is peeking through
Mars Base

Hubble directly observes the disc around a black hole - 0 views

www.physorg.com/...11-hubble-disc-black-hole.html

scibyte20 black holes quasar

shared by Mars Base on 06 Nov 11 - No Cached
  • Scientists have used the NASA/ESA Hubble Space Telescope to observe a quasar accretion disc -- a glowing disc of matter that is slowly being sucked into its galaxy's central black hole
  • Scientists have used the NASA/ESA Hubble Space Telescope to observe a quasar accretion disc -- a glowing disc of matter that is slowly being sucked into its galaxy's central black hole.
  • the team measured the disc's size and studied the colours (and hence the temperatures) of different parts of the disc
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  • Using the NASA/ESA Hubble Space Telescope, combined with the gravitational lensing effect of stars in a distant galaxy, the team measured the disc's size and studied the colours (and hence the temperatures) of different parts of the disc.
  • Until now, the minute apparent size of quasars has meant that most of our knowledge of their inner structure has been based on theoretical extrapolations, rather than direct observations.
  • show a level of precision equivalent to spotting individual grains of sand on the surface of the Moon
  • Quasars — short for quasi-stellar objects — are glowing discs of matter that orbit supermassive black holes, heating up and emitting extremely bright radiation as they do so.
  • These observations show a level of precision equivalent to spotting individual grains of sand on the surface of the Moon.
  • using the stars in an intervening galaxy as a scanning microscope to probe features in the quasar's disc that would otherwise be far too small to see
  • As these stars move across the light from the quasar, gravitational effects amplify the light from different parts of the quasar, giving detailed colour information for a line that crosses through the accretion disc.
  • the team were able to reconstruct the colour profile across the accretion disc
  • allowed the team to measure the diameter of the disc of hot matter, and plot how hot it is at different distances from the centre
  • Quasars' physical properties are not yet well understood
  • This new ability to obtain observational measurements is therefore opening a new window to help understand the nature of these objects."
Mars Base

Quasar may be embedded in unusually dusty galaxy - 0 views

phys.org/...ed-unusually-dusty-galaxy.html

scibyte69 quasar

shared by Mars Base on 24 Oct 12 - No Cached
  • Quasars (short for quasi-stellar object) are the brilliant cores of galaxies where infalling material fuels a super-massive black hole
  • black hole is so engorged that some of the energy escapes as powerful blasts of radiation from the surrounding disk of accreting material
  • can appear as a jet-like feature
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  • If the beam shines in Earth's direction
  • can appear as a quasar that can outshine its surrounding galaxy a hundred or a thousand times.
  • first identified in the Sloan Digital Sky Survey (SDSS).
  • Only a handful of these very distant ultra-luminous quasars were found by the SDSS in about one quarter of the whole sky
Mars Base

Early Black Holes were Grazers Rather than Glutonous Eaters - 0 views

www.universetoday.com/...s-rather-than-glutonous-eaters

scibyte52 black holes

shared by Mars Base on 21 Jun 12 - No Cached
  • Black holes powering distant quasars in the early Universe grazed on patches of gas or passing galaxies rather than glutting themselves in dramatic collisions according to new observations from NASA’s Spitzer and Hubble space telescopes
  • A black hole doesn’t need much gas to satisfy its hunger and turn into a quasar
  • Quasars are distant and brilliant galactic powerhouses. These far-off objects are powered by black holes that glut themselves on captured material; this in turn heats the matter to millions of degrees making it super luminous
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  • team studied 30 quasars with NASA’s orbiting telescopes Hubble and Spitzer
  • These quasars, glowing extremely bright in the infrared images
  • telltale sign that resident black holes are actively scooping up gas and dust into their gravitational whirlpool
  • formed during a time of peak black-hole growth between eight and twelve billion years
  • supports evidence that the creation of the most massive black holes in the early Universe was fueled not by dramatic bursts of major mergers but by smaller, long-term events
  • found 26 of the host galaxies
  • about the size of our own Milky Way Galaxy, showed no signs of collisions
  • Quasars that are products of galaxy collisions are very bright
  • the process powering the quasars and their black holes lies below the detection of Hubble
  • prime targets for the upcoming James Webb Space Telescope, a large infrared orbiting observatory scheduled for launch in 2018
Mars Base

Astronomers discover the largest structure in the universe - 0 views

phys.org/...ronomers-largest-universe.html

scibyte77 LQG

shared by Mars Base on 13 Jan 13 - No Cached
  • The large quasar group (LQG) is so large that it would take a vehicle travelling at the speed of light some 4 billion years to cross it.
  • Quasars are the nuclei of galaxies from the early days of the universe that undergo brief periods of extremely high brightness that make them visible across huge distances.
  • 'brief' in astrophysics terms but actually last 10-100 million years.
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  • Since 1982 it has been known that quasars tend to group together in clumps or 'structures' of surprisingly large sizes, forming large quasar groups or LQGs.
  • the LQG which is so significant in size it also challenges the Cosmological Principle: the assumption that the universe, when viewed at a sufficiently large scale, looks the same no matter where you are observing it from.
  • The modern theory of cosmology is based on the work of Albert Einstein, and depends on the assumption of the Cosmological Principle
  • he Principle is assumed but has never been demonstrated observationally 'beyond reasonable doubt'.
  • the Milky Way, is separated from its nearest neighbour, the Andromeda Galaxy, by about 0.75 Megaparsecs (Mpc) or 2.5 million light-years.
  • Whole clusters of galaxies can be 2-3 Mpc
  • LQGs can be 200 Mpc or more across.
  • Based on the Cosmological Principle and the modern theory of cosmology, calculations suggest that astrophysicists should not be able to find a structure larger than 370 Mpc.
  • newly discovered LQG however has a typical dimension of 500 Mpc.
  • it is elongated, its longest dimension is 1200 Mpc (or 4 billion light years)
  • some 1600 times larger than the distance from the Milky Way to Andromed
Mars Base

Quasar - Wikipedia, the free encyclopedia - 0 views

en.wikipedia.org/Quasar

scibyte69 quasar

shared by Mars Base on 26 Oct 12 - Cached
  • size is 10–10,000 times the Schwarzschild radius of the black hole
  • powered by an accretion disc around the black hole.
  • among the most luminous, powerful, and energetic objects known in the universe
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  • emit up to a thousand times the energy output of the Milky Way.
  • More than 200,000 quasars are known
Mars Base

Biggest Thing in Universe Found-Defies Scientific Theory - 0 views

news.nationalgeographic.com/...iverse-science-space-evolution

scibyte77 LQG

shared by Mars Base on 13 Jan 13 - No Cached
  • Using data from the Sloan Digital Sky Survey, an international team of researchers has discovered a record-breaking cluster of quasars—young active galaxies
  • the Milky Way, is just a hundred thousand light-years across
  • the local supercluster of galaxies in which it's located, the Virgo Cluster, is only a hundred million light-years wide
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  • "It could mean that our mathematical description of the universe has been oversimplified-and that would represent a serious difficulty and a serious increase in complexity,"
Mars Base

Black Hole 'Bonanza': Millions Found by NASA Space Telescope | WISE | Space.com - 0 views

www.space.com/ound-nasa-space-telescope.html

scibyte61

shared by Mars Base on 30 Aug 12 - No Cached
  • A jackpot of previously unknown black holes across the universe has been discovered by the infrared eyes of a prolific NASA sky-mapping telescope
  • astronomers are still poring through this celestrial trove for discoveries.
  • These black holes aren't the average tiny, dense objects created by the collapse of dead stars, but rather humongous "supermassive" black holes that have been caught feasting on matter falling into them
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  • We expected that there should be this large population of hidden quasars in the universe, but WISE can now identify them across the sky
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