First 'middleweight' black hole discovered

CAMBRIDGE, Mass., Feb. 15 (UPI) -- U.S. astronomers say a newly discovered black hole, the first intermediate-mass one ever found, may have once been the core of a now-disintegrated dwarf galaxy.

The discovery could lead to better understanding of the evolution of supermassive black holes and galaxies, researchers said.

Massive stars collapse to form stellar-mass black holes, about 10 times the mass of our sun, but it's not clear how supermassive black holes -- like the four million solar-mass monster at the center of the Milky Way -- form in the cores of galaxies.

One theory is that supermassive black holes may build up through the merger of smaller, intermediate-mass black holes weighing hundreds to thousands of suns.

"For the first time, we have evidence on the environment, and thus the origin, of this middle-weight black hole," said Mathieu Servillat, who worked at the Harvard-Smithsonian Center for Astrophysics when the research was conducted.

Scientists say they believe the black hole, dubbed HLX-1, was the central black hole in a dwarf galaxy that was then captured by a larger host galaxy

The collision between the galaxies stripped away most of the dwarf galaxy's stars, they theorize.

The future of the black hole is uncertain, astronomers said; it may spiral into the center of the host galaxy and eventually merge with the supermassive black hole there, or it could settle into a stable orbit around the galaxy.

"This black hole is unique in that it's the only intermediate-mass black hole we've found so far. Its rarity suggests that these black holes are only visible for a short time," Servillat said in a Harvard-Smithsonian release Wednesday.