Astronomers have clocked a black hole with a mass six times that of the sun racing through the flattened disk of the Milky Way galaxy at some 400,000 km/h. According to Félix Mirabel of the French Atomic Energy Commission in Saclay, the dizzying speed beautifully confirms the theory that black holes are the remains of detonated stars. "I can't explain such a high velocity in any other way," he says.
Artist's impression of black hole whose enormous gravity sucks material from companion star.
CREDIT: ESA/NASA/F. MIRABEL
Black holes are thought to form when the dense core of an exploding massive star, or supernova, collapses. If, as in this case, the supernova is orbiting a companion star, its corpse can be kicked away violently.
Mirabel and his colleagues detected the motion of this black hole by measuring the position of its dim companion star in 1996 and again in 2001 using the Hubble Space Telescope, they report in the 19 November issue of Astronomy & Astrophysics. Last year, astronomers found another speedy black hole, but that object resides in the Milky Way's extended halo, where high velocities are the rule. In contrast, this one, known as GRO J1655-40, moves four times as fast as neighboring stars.
The team's goal is to trace stellar corpses back to their origins, which in this case could be anywhere between 3000 and 10,000 light-years away. Gijs Nelemans of Cambridge University in the U.K. says the find will help astronomers understand the forces that send the holes flying through space. Astronomers have found high "natal kick" velocities for some neutron stars but never for black holes, which are more massive.
