Milky Way core may harbor thousands of black holes – study

Astrophysicists have detected a dozen black holes at the center of our Milky Way galaxy, and said there could be as many as 10,000.

The find provides the first evidence for a long-held theory that the massive black hole at the core of every large galaxy should be surrounded by thousands of smaller ones, they wrote in the science journal Nature.

"We observed a dozen black holes" around Sagittarius A, the black hole at the centre of the Milky Way, said study co-author Chuck Hailey, an astrophysicist at New York's Columbia University. But this is the tip of the iceberg," he told AFP. Black holes are generally "pretty impossible" to see, according to the physicist.

They feast on gas and dust in their vicinity, but the X-rays they burp are sporadic and hard to observe from Earth. To try and overcome this difficulty, Hailey and a team decided to track down black hole "binaries" – duos occasionally formed when a black hole captures a passing star and binds to it.

When the captured star has a low mass, the binary emits X-ray bursts that are weak but consistent and easier to detect. The team observed the X-ray signatures of 12 black hole binaries within three light years of Sagittarius A.

Based on data from studying black holes closer to Earth, they extrapolated there must be about 500 binaries around our galaxy's core in all, most of them too dim to observe.