Universe Today
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It's the Goldilocks variety of black holes: not too big and not too small.
The new source HLX-1, the light blue object to the top left of the galactic bulge, is the ambassador for a new class of
black
holes, more than 500 times the mass of the Sun. It lies on the periphery of the edge-on spiral galaxy ESO 243-49, about 290 million light years from Earth.
The discovery, led by Sean Farrell at Britain's University of Leicester, appears today in the journal
Nature
.
Until now, identified
black
holes
have been either super-massive (several million to several billion times the mass of the Sun) in the center of galaxies, or about the size of a typical star (between three and 20 solar masses).
The new discovery is the first solid evidence of a new class of medium-sized
black
holes and was made using the European Space Agency's XMM-Newton X-ray space telescope. At the time of the discovery, Farrell and his
team were working at the Centre d'Etude Spatiale des Rayonnements in France.
A
black
hole is a remnant of a collapsed star with such a powerful gravitational field that it absorbs all the light that passes near it and reflects nothing.
"While it is widely accepted that stellar mass
black
holes
are created during the death throes of massive stars, it is still unknown how super-massive
black
holes
are formed," Farrell said.
It had been long believed by astrophysicists that there might be a third, intermediate class ofblackholes, with masses between a hundred and several hundred thousand times that of the Sun. However, suchblackholeshad not been reliably detected until now.
One theory suggests that super-massiveblackholesmay be formed by the merger of a number of intermediate massblackholes, Farrell said.
"To ratify such a theory, however, you must first prove the existence of intermediate
black
holes
. This is the best detection to date of such long sought after intermediate mass
black
holes
. "
Using XMM-Newton observations carried out in 2004 and 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. The authors say that no other physical explanation can account for the data.
Lead image caption: Artist's impression of HLX-1 in the periphery of the edge-on spiral galaxy ESO 243-49. Credit: Heidi Sagerud.
Sources:
Nature
and the
University of Leicester