Dwarf Galaxy Near M60
Looking almost like a bright star near the massive elliptical galaxy M60 (also called NGC 4649), the dwarf galaxy M60-UCD1 crams 140 million stars within a diameter of about 300 light-years. The dwarf galaxy may actually be the stripped remnant of a larger galaxy that was torn apart during a close encounter with the more massive galaxy. Circumstantial evidence comes from the recent discovery of a monster black hole (too small to be seen in this Hubble Space Telescope picture) at the center of the dwarf. The black hole is 15 percent the mass of the entire galaxy – way too big for it to have formed inside a dwarf galaxy. But the black hole would be the right proportional mass if the galaxy had once been more massive. The galaxy lies 50 million light-years away inside the immense Virgo Cluster of 2,500 galaxies. M60-UCD1 orbits the giant elliptical galaxy in this image. M60 is 120 million light-years across and contains an estimated 400 billion stars.
NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration;
Acknowledgment: J. Tonry (University of Hawaii), P. Cote (Dominion Astrophysical Observatory), and G. Fabbiano (Harvard-Smithsonian Center for Astrophysics)