'Big black hole' baffles scientists
29 November 2012 Last updated at 13:00 GMT
Astronomers say they have discovered what they think could be the second most massive black hole ever found - in a tiny galaxy.
The galaxy NGC 1277 is just a quarter of the size of our Milky Way, but the black hole at its centre is 4,000 times larger than the black hole in our galaxy's centre.
The surprise finding is hard to reconcile with existing models of black hole growth, which hold that they evolve in tandem with host galaxies.
Dr Karl Gebhardt of the University of Texas explained to the BBC that the black hole "effectively has 17 billion suns as its mass," making it the dominant part of its galaxy.