Black holes do join together,say astronomers

Until now,identified black holes have been either super-massive (several million to several billion times the mass of the Sun) in the centre of galaxies,or about the size of a typical star (between three and 20 Solar masses).

Now,an international team has discovered the black hole HLX-1,290 million light years from Earth,which it is more than 500 times the mass of the Sun,using the European Space Agency’s telescope,the ‘Nature’ journal reported.

Team member Dr Sean Farrell of the University of Leicester said: “While it is widely accepted that stellar mass black holes are created during death throes of massive stars,it is still unknown how super-massive black holes are formed.

“One theory is that super-massive black holes may be formed by the merger of a number of intermediate mass black holes. To ratify such a theory,however,you must first prove the existence of intermediate black holes.

“The identification of HLX-1 is therefore an important step towards a better understanding of the formation of the super-massive black holes that exist at the centre of the Milky Way and other galaxies.”

In fact,the HLX-1 (Hyper-Luminous X-ray source 1) lies towards the edge of the galaxy ESO 243-49. It is ultra- luminous in X-rays,with a maximum X-ray brightness of approximately 260 million times that of the Sun.

The X-ray signature of HLX-1 and the lack of a counterpart in optical images confirm that it is neither a foreground star nor a background galaxy,and its position indicates that it is not the central engine of that galaxy.

And,using XMM-Newton observations carried out on the 23rd November 2 04 and the 28th November 2008,the team showed that HLX-1 displayed a variation in its X-ray signature. This indicated that it must be a single object and not a group of many fainter sources.

The huge radiance observed can only be explained if HLX-1 contains a black hole more than 500 times the mass of the Sun. No other physical explanation can account for the data.