Finally found: Binary black hole systems (pictured) should be common, but have been hard to find. Now researchers think they’ve discovered a pair that orbit around each other once every 100 years.
Credit: P. Marenfeld, NOAO
Another possible explanation is that the quasar in question might actually be two separate quasars that happen to be in the same line of sight from Earth, but Boroson said the probability of two such objects lining up exactly is very low and one of the objects still would not behave like other quasars.
John Dickey, an astronomer at the University of Tasmania in Hobart, Australia, said that, while it was hard to calculate the probability of two quasars lining up, the case for the binary black hole explanation was very convincing. "It's pretty strong evidence," he said.
Boroson and his colleagues hope to bolster that evidence by observing the quasar over the next few years, because the velocity of the broad emission lines should gradually change as the black holes orbit each other.
"We are also hoping to get an image of the object with the Hubble Space Telescope, to confirm that it doesn't look like two separate objects," said Boroson.
