Australasian Science: Australia's authority on science since 1938

Mid-sized Black Hole Found

By Stephen Luntz

The first intermediate-sized black hole has had its status confirmed in Science.

The full text of this article can be purchased from Informit.

Supermassive black holes containing more than a million solar masses lie at the centre of galaxies, and stellar remnants 30 solar masses or smaller have been detected elsewhere. However, no object filling the vast gap in between had been authenticated until now.

For 3 years the object HLX-1 has been considered the most promising option (AS, Jan/Feb 2010, pp.17–20). Now Dr Sean Farrell of the University of Sydney’s School of Physics has established an upper bound for HLX-1’s mass at 90,000 solar masses.

“From studying other black holes we know that sucking in the gas creates X-rays, but there’s then a sort of reflux, with the region around the black hole shooting out jets of high-energy particles that hit gas around the black hole and generate radio waves,” Farrell says. The brightness of the radio waves and the delay after the X-ray emissions relate to the mass, enabling Farrell to establish the black hole’s upper limit.

On the other hand, HLX-1 was first noticed because of its bright X-ray emissions, and Farrell says it is 700 times as bright in this part of the spectrum as the theoretical limit for a 20 solar mass black hole.

“A number of other bright X-ray sources have been put forward as possibly being middleweight black holes. But all of those sources could be explained as resulting from lower mass black holes,” Farrell says. “Only this...

The full text of this article can be purchased from Informit.