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Bloated Blackhole Babies
23 June 2004 (All day)
Astronomers have found a gargantuan black hole that menaces theoretical models of supermassive black holes in the early universe. At 10 billion times the mass of the sun and 12.5 billion light-years away, the heavyweight existed when the universe was only 1 billion years old. Current theories have a hard time creating something so big so fast.
To create a supermassive black hole, you first have to form massive stars. At the end of their brief lives, the stars explode and their debris collapses to form a black hole. This infant can then grow into a monster by rapidly accreting gas from its surroundings. But theory says there's a limit to how fast this can happen, because the fierce radiation from the black hole's immediate surroundings can keep fresh gas from falling in. Moreover, the average growth rate is probably much lower than this theoretical cap. That's why astrophysicists didn't expect to see any supermassive black holes in the very early universe.
Nature had a surprise in store. Roger Romani and colleagues at Stanford University found the whopping black hole by studying radio sources that had all the hallmarks of blazars. Like the more common quasars, blazars are massive black holes in the cores of distant galaxies that shoot two energetic jets of matter into space, but with one jet pointing more or less in our direction. For one object in the big dipper, the jet was imaged by the Very Long Baseline Array, a continent-wide network of linked radio telescopes, while the distance to the blazar--and thus its maximum age since the big bang--was measured with the 9-meter Hobby-Eberly Telescope at McDonald Observatory in Texas. As for the mass of 10 billion solar masses, Romani admits that it's a "fairly rough estimate." They described the black hole in the Astrophysical Journal Web site on 10 June.
James Rhoads of the Space Telescope Science Institute in Baltimore says it's "sort of tight" for this black hole to have grown to be so big in just 1 billion years. But Avi Loeb of the Harvard-Smithsonian Center for Astrophysics says there's "certainly not a crisis from a theoretical perspective," because models can still explain the formation of a heavyweight like this in just about a billion years. So theorists won't be in real trouble, unless billion-solar-mass black holes are found at a time when the universe was only half a billion years old.