xilihutu
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加入时间: 2007/03/29
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来自: 美国
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作者：xilihutu 在 驴鸣镇 发贴, 来自 http://www.hjclub.org
http://zeenews.india.com/news/space/hubble-telescope-finds-disc-around-black-hole_740285.html
Hubble telescope finds disc around black hole
Washington: For the first time, scientists using the Hubble Space Telescope were able to find a distant dusty disc slowly spiralling into a supermassive black hole at the centre of a galaxy.
The observations of the quasar's accretion disc – the glowing disc of matter that has been heated up as it is sucked into the central black hole -- have revealed unique details of its size and temperature.
The scientists, who observed the quasar disc using the gravitational lensing technique, said this method relies on stars in an intervening galaxy located between the space telescope and the distant black hole magnifying light streaming from the quasar, 'astronomynow.com' reported.
For one quasar, known as HE 1104-1805, the stars in the intervening galaxy passed through the path of the light from the quasar such that they amplified the signals from different parts of the accretion disc, enabling astronomers to construct a colour profile across the disc.
The colours could then be translated into temperatures, since hot matter closest to the black hole emits at bluer wavelengths than material further out.
These temperature readings could then be converted into distance measurements, allowing the astronomers to arrive at an estimate of the diameter of the disc of between four and eleven light-days across, or 100 to 300 billion kilometres.
"These kinds of observations are quite difficult," said lead scientist Jose Munoz of the University of Valencia.
Although quasars are light days across, they are billions of light years from Earth, which means that most of what scientists know about them comes from extrapolations and not direct evidence, the scientists said.
"This result is very relevant because it implies we are now able to obtain observational data on the structure of these systems, rather than relying on theory alone," Munoz added.
作者：xilihutu 在 驴鸣镇 发贴, 来自 http://www.hjclub.org
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