The new black hole has a mass of 3.8 Suns and would be about 15 miles across, they estimate. "This makes theone of the smallest objects ever discovered outside our solar system," Shaposhnikov said.
The smallest black hole previously identified was GRO 1655-40, with a mass of about 6.3 Suns.
"Amazingly, equations frompredict that a black hole with 3.8 times the mass of our Sun would be only 15 miles across -- the size of a city," NASA said in a statement.
A collapsing star that was much smaller than J1650 would likely form a