Researchers have confirmed that a black hole lurking in the dwarf galaxy IC 10, and dubbed IC 10 X-1, weighs in at up to 33 Suns, double the previous record for a "single star" black hole held by M33 X-7 which tips the scales at 16 Suns.
IC 10 X-1, lying 1.8 million light years from Earth, was first spotted back in 2007 by the US's Harvard-Smithsonian Centre for Astrophysics in Cambridge, New Scientist reports. Researchers estimated its weight at between 24 and 33 times the weight of our own Sun, but the result was speculative.
More: http://www.theregister.co.uk/2008/02/22/hefty_black_hole/