 |
|
Accretion Discs Show Their True Colours
July 25, 2008Quasars are the brilliant cores of remote galaxies, at the hearts of which lie supermassive black holes that can generate enough power to outshine the Sun a trillion times. These mighty power sources are fuelled by interstellar gas, thought to be sucked into the hole from a surrounding 'accretion disc'. A paper in this week's issue of the journal Nature, partly based on observations collected with ESO's Very Large Telescope, verifies a long-standing prediction about the intensely luminous radiation emitted by these accretion discs.
"Astronomers were puzzled by the fact that the best models of these discs couldn't quite be reconciled with some of the observations, in particular, with the fact that these discs did not appear as blue as they should be," explains lead-author Makoto Kishimoto.
Such a discrepancy could be the signal that there was something very wrong with the models. With his colleagues, he investigated this discrepancy by studying the polarised light from six quasars. This enabled them to demonstrate that the disc spectrum is as blue as predicted.
"The crucial observational difficulty here has been that the disc is surrounded by a much larger torus containing hot dust, whose light partly outshines that of the disc," says Kishimoto. "Because the light coming from the disc is scattered in the disc vicinity and thus polarised, by observing only polarised light from the quasars, one can uncover the buried light from the disc."
In a similar way that a fisherman would wear polarised sunglasses to help get rid of the glare from the water surface and allow him to see more clearly under the water, the filter on the telescope allowed the astronomers to see beyond surrounding clouds of dust and gas to the blue colour of the disc in infrared light.
The observations were done with the FORS and ISAAC instruments on one of the 8.2-m Unit Telescopes of ESO's Very Large Telescope, located in the Atacama Desert, in Chile, as well as several other telescopes, including STFC's UKIRT.
The standard picture of the accretion disc is therefore vindicated. The authors believe that further measurements could eventually provide valuable insight into how and where the disc ends, and how material is being supplied to the disc.
ESO
"The crucial observational difficulty here has been that the disc is surrounded by a much larger torus containing hot dust, whose light partly outshines that of the disc," says Kishimoto. "Because the light coming from the disc is scattered in the disc vicinity and thus polarised, by observing only polarised light from the quasars, one can uncover the buried light from the disc."
In a similar way that a fisherman would wear polarised sunglasses to help get rid of the glare from the water surface and allow him to see more clearly under the water, the filter on the telescope allowed the astronomers to see beyond surrounding clouds of dust and gas to the blue colour of the disc in infrared light.
The observations were done with the FORS and ISAAC instruments on one of the 8.2-m Unit Telescopes of ESO's Very Large Telescope, located in the Atacama Desert, in Chile, as well as several other telescopes, including STFC's UKIRT.
The standard picture of the accretion disc is therefore vindicated. The authors believe that further measurements could eventually provide valuable insight into how and where the disc ends, and how material is being supplied to the disc.
ESO
Quasars Current Events and Quasars News RSSNew Celestial Map Gives Directions for GPS
Many of us have been rescued from unfamiliar territory by directions from a Global Positioning System (GPS) navigator. GPS satellites send signals to a receiver in your GPS navigator, which calculates your position based on the location of the satellites and your distance from them.
Vanderbilt astronomers participate in new search for dark energy
The most ambitious attempt yet to trace the history of the universe has seen "first light." The Baryon Oscillation Spectroscopic Survey (BOSS), part of the Sloan Digital Sky Survey III (SDSS-III), took its first astronomical data on the night of Sept. 14-15 at the Sloan Foundation telescope in New Mexico.
Precise Radio-Telescope Measurements Advance Frontier Gravitational Physics
Scientists using a continent-wide array of radio telescopes have made an extremely precise measurement of the curvature of space caused by the Sun's gravity, and their technique promises a major contribution to a frontier area of basic physics.
First Black Holes Born Starving
The first black holes in the universe had dramatic effects on their surroundings despite the fact that they were small and grew very slowly, according to recent supercomputer simulations carried out by astrophysicists Marcelo Alvarez and Tom Abel of the Kavli Institute for Particle Astrophysics and Cosmology, jointly located at the Department of Energy's SLAC National Accelerator Laboratory and Stanford University, and John Wise, formerly of KIPAC and now of NASA Goddard Space Flight Center.
Dark Energy From the Ground Up: Make Way for BigBOSS
Several ways have been proposed to examine dark energy, in hopes of finding out just what it is. One of them, "supernovae" for short, certainly works: it's how dark energy was discovered in the first place. Other independent techniques, such as weak gravitational lensing and baryon acoustic oscillation, also promise great power but are as yet unproven.
Hubble repair mission carrying $70 million CU-Boulder instrument on track for May 11 launch
A $70 million instrument designed by the University of Colorado at Boulder to probe the evolution of galaxies, stars and intergalactic matter from its perch on the orbiting Hubble Space Telescope is on schedule for its slated May 11 launch from Kennedy Space Center in Florida aboard NASA's space shuttle Atlantis.
Erratic Black Hole Regulates Itself
New results from NASA's Chandra X-ray Observatory have made a major advance in explaining how a special class of black holes may shut off the high-speed jets they produce. These results suggest that these black holes have a mechanism for regulating the rate at which they grow.
Colors of Quasars Reveal a Dusty Universe
The vast expanses of intergalactic space appear to be filled with a haze of tiny, smoke-like "dust" particles that dim the light from distant objects and subtly change their colors, according to a team of astronomers from the Sloan Digital Sky Survey (SDSS-II).
Astronomers discover link between supermassive black holes and galaxy formation
A pair of astronomers from Texas and Germany have used a telescope at The University of Texas at Austin's McDonald Observatory together with Hubble Space Telescope and many other telescopes around the world to uncover new evidence that the largest, most massive galaxies in the universe and the supermassive black holes at their hearts grew together over time.
Milagro detects cosmic ray hot spots
The University of Maryland-led Milagro collaboration, comprised of scientists from 16 institutions across the United States, has discovered two nearby regions with an unexpected excess of cosmic rays.
More Quasars Current Events and Quasars News Articles
 |
Fellowes Quasar 500 Comb Binding Machine (52168) by Fellowes This stylish, user-friendly binding machine can handle virtually any office application. Designed for moderate to heavy use, the Quasar is perfect for mid-sized to large offices. This hard-working machine can easily punch up to 20 sheets at a time and bind documents as large as 500 sheets with a 2" comb. Vertical document loading ensures accurate punch alignment and the efficient design allows the user to punch and bind in a continuous manner for maximum productivity. Features built-in comb storage tray with document measurement device for added convenience and quick set-up. Adjustable rotary edge guide centers documents with ease. Includes binding starter pack. |
 |
Baby Quasar Photorejuvenation Light Therapy by AdvanThera Beautiful, more clear skin begins from within. There's actually good science behind light therapy which shows how cell rejuvenation will create a more youthful appearance. The Baby Quasar uses four different wavelengths, between 600 and 1200 nm, both red and infrared, to stimulate maximum cellular activity. Other devices only use either one or two wavelengths. Using SequePulse Technology, our patent pending answer to the problems associated with using multiple wavelengths, the Baby Quasar is the perfect solution for someone trying to achieve more youthful look without having to spend both time and money on a Skincare Therapist. The Baby Quasar is very compact and requires no extra valuable tabletop space. Keep it safely tucked out of the way when not in use. |
 |
Quasars and Active Galactic Nuclei: An Introduction by Ajit K. Kembhavi (Author), Jayant V. Narlikar (Author) This book provides an up-to-date and comprehensive account of quasars and active galactic nuclei (AGN). The latest observations and theoretical models are combined in this clear, pedagogic textbook for advanced undergraduates and graduate students. Researchers will also find this wide-ranging and coherent review invaluable. Throughout, detailed derivations of important results are provided to ensure the book is self contained. And theories and models are critically compared with detailed and often puzzling observations from across the spectrum. We are led through all the key topics, including quasar surveys, continuum radiation, time variability, relativistic beaming, accretion disks, jet sidedness, gravitational lensing, unification and detailed, multi-wavelength studies of individual... |
 |
Fellowes Quasar Wire Binding Machine by Fellowes Inc Wire Binding Machine,Binds 130 SH,18-1/8"x1-1/2"x5-1/8" |
 |
Quasar Baby Quasar + Baby Blue Power Pack 1 set by Silver Bay, LLC Bringing the Spa Home Package Contains: Baby Quas |
 |
Quasar By Jesus Del Pozo For Men. Eau De Toilette Spray 4.2 Ounces by Jesus Del Pozo Introduced in 1994. Fragrance notes: the scent of newsprint, banana peel, lavender and moss. Recommended use: daytime. |
 |
Cosmological Enigmas: Pulsars, Quasars, and Other Deep-Space Questions by Mark Kidger (Author) The universe is big. Really big. And it gets bigger every day. In Cosmological Enigmas, Mark Kidger weaves together history, science, and science fiction to consider questions about the bigness of space and the strange objects that lie trembling at the edge of infinity. What are quasars, blazars, and gamma-ray bursters? Could we ever travel to the stars? Can we really expect aliens to contact us? From the profound (what evidence do we have to support the big bang theory?) to the bizarre (can there be more than one universe and, if so, how many dimensions does it possess?) to the everyday-yet-profound (why is the sky dark at night?), Kidger explains not only what we know but how we came to know it. Reflecting on how stars shine and what may lie beyond the edge of the universe,... |
 |
Quasar Pen with Continuously Changing Lights by Quasar QP1-CTM |
|
Memories In The Making Emagination Small Punch, Quasar by MEMORIES IN THE MAKING | |
 |
Duracell Camcorder Battery for: Quasar VM-L153 by Battery-Biz, Inc. Battery-Biz is a leading manufacturer and distributor of batteries, adapters and chargers and the industry's source for Hi-Capacity(TM) brand power products. Hi-Capacity(TM) products are made using the finest components available and carry a one year warranty against defects in material and workmanship. Hi-Capacity(TM) products are guaranteed to meet or exceed original specifications. |
| © 2009 BrightSurf.com |