Running the model on a supercomputer, the team found the mass of M87's black hole to be 6.4 billion times the mass of our sun--two to three times larger than previous estimates. The model provided similar results for four other nearby galaxies, multiplying their black hole masses by factors of 1.5 to 3.
The results, which will be published in The Astrophysical Journal later this summer, "caught us off guard," says Gebhardt. "It looks like we've been systematically underestimating the mass of black holes."
It's a good think black holes don't take up much room to start with, because now we need to clear out more closet space for them.