Saturday, October 21, 2006

Evidence that quasars are powered by black holes

Astronomers see inside a quasar for the first time
For the first time, astronomers have looked inside quasars -- the brightest objects in the universe -- and have seen evidence of black holes.

The study lends further confirmation to what scientists have long suspected -- that quasars are made up of super-massive black holes and the super-heated disks of material that are spiraling into them.

The suspicion that quasars are powered by supermassive black holes has, until now, been based only on the fact that astrophysicists couldn't think of any other plausible explanation. The new evidence that supports this hypothesis is that it has been possible to observe what looks like a black hole accretion disk inside two quasars:
[The researchers] were able to measure the size of the so-called accretion disk around the black hole inside each quasar.

In each, the disk surrounded a smaller area that was emitting X-rays, as if the disk material was being heated up as it fell into the black hole in the center.

Further supporting their conclusion was the fact that the hightest-energy emissions (X-rays) occurred near the center of the quasar, while optical light originated much farther out. (Since gas and dust would be heated most near a central black hole.) It was possible to make these observations on two quasars only because they were magnified by gravitational lensing due to intervening massive objects, and only by by combining results from ground-based optical telescopes and the orbiting Chandra X-Ray Observatory.

Other references:

Black Holes Power the Brightest Cosmic Objects –

Quasars Under the Lens – ScienceNow (subscription rqd)

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