Little Giant

A black hole about 20,000 times as massive as the Sun may inhabit a star cluster indicated by the small circle on the outskirts of the galaxy ESO 243-49. The intermediate-mass black hole -- one of the few yet detected -- appears to be taking a bite out of an orbiting star about once every year, when the star comes closest to the black hole. The cluster could be the leftover core of a smaller galaxy that has been taken over by ESO 243-49. Intermediate-mass black holes, which are larger than those that form from the collapse of stars but smaller than those in the hearts of most galaxies, have been hypothesized, but only a few possible examples have been detected. The black hole is designated ESO 243-49 HLX-1, which indicates that it is the first "hyperluminous X-ray object" discovered in the galaxy. We have more details about ESO 243-49 HLX-1 in our Black Hole Encyclopedia. [NASA/ESA/S. Farrell (University of Sydney)]