Two biggest black holes ever found
Two huge black holes may be the largest yet measured. Supermassive black holes inhabit most large galaxies. One, in the galaxy Messier 87, has the mass of about 6 billion suns but it is no longer the record holder.
There's one in galaxy NGC 3842 with the mass of about 10 billion suns, and NGC 4889's could weigh up to 37 billion suns, say Nicholas McConnell at the University of California, Berkeley, and colleagues.
The estimates were made by clocking the motion of stars near these galaxies' cores, since a black hole's mass dictates how fast objects orbit around them.
In 2008, a mass of 18 billion suns was claimed for the black hole inside a distant bright galaxy called OJ287. But that number relies on an assumption that periodic flares from OJ287 are created by a second black hole orbiting the first. "Observations cannot rule out alternative ways of creating those outbursts," says McConnell.
The mass of galaxies tends to correlate with that of their central black holes, but both of these holes are heavier than predicted. Collisions with other galaxies could have force-fed the holes with gas, the team speculates. "Another possibility is that the black holes we discovered grew to huge masses early on, and their host galaxies never caught up," says McConnell.