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Two for one

23 March 2002

A PAIR of quasars long thought to be an optical illusion are actually two distinct objects. The chance of finding two identical-looking quasars, or supermassive black holes, in the same place is “virtually nil”, according to Paul Green of the Harvard-Smithsonian Center for Astrophysics. So astronomers assumed that light from a single quasar must be getting bent by a massive object in its path, making it look like a pair, dubbed Q2345+007 A and B.

But when Green focused the Chandra X-ray telescope on the spot for 20 hours, he found no such mass and that the pair’s X-ray spectra…

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