In 2009, a team of astronomers led by Sean Farrell discovered HLX-1, an intermediate-mass black hole with a smaller cluster of stars around it,Soria, Roberto; Hau, George K. T.; Graham, Alister W.; Kong, Albert K. H.; Kuin, N. Paul M.; Li, I.-Hui; Liu, Ji-Feng; Wu, Kinwah (2010), "Discovery of an optical counterpart to the hyperluminous X-ray source in ESO 243-49" in the galaxy ESO 243-49. This evidence suggested that ESO 243-49 had a galactic collision with HLX-1's galaxy and absorbed the majority of the smaller galaxy's matter.
