Astronomers discover smallest black hole
U.S. and Israeli astronomers said they have measured the
smallest galactic-central black hole ever discovered. Astronomers
at Ohio State University and the Technion-Israel Institute of
Technology said early results indicate the black hole --
located at the center of a galaxy called NGC 4395 -- weighs
less than 1 million times the mass of our sun. If confirmed,
the black hole at the center of NGC 4395 would be perhaps 100
times smaller than others of its type. The team used the Hubble
Space Telescope and a technique similar to Doppler radar -- the
method that meteorologists use to track weather systems. The
black hole lies about 14 million light-years away, the astronomers
said. One light-year equals approximately six trillion miles --
the distance a beam of light can travel in one year. The discovery
confounds current theory about how supermassive black holes form
at the center of galaxies. NGC 4395 is considered an active galaxy,one with a very bright center, or nucleus. In such galaxies, central black holes are supposed to be very massive. One clue, the astronomers said, is NGC 4395 does not appear to have a dense spherical nucleus, called a galactic bulge, at its center, so it could be that the black hole quickly consumed all the stars
in the bulge and therefore lacked enough nearby mass to continue absorbing to grow larger.