Galaxy ARP 220

ARP 220 is, in fact, two galaxies that collided, and are merging. It is about 250 million light-years away, and is classified as an Ultraluminous Infrared Galaxy as most of the energy it emits is in the far infrared.  The collision resulted in the formation of a huge number of new stars, several hundred million, located in a large number of star clusters in the central region of the galaxy.  There is an X-ray source at what was the center of one of the two pre-merger galaxies, with another less luminous source near to it.  These are probably supermassive black holes that were present in the two galaxies prior to the collision.  Over time, several hundred million years, the two black holes will probably merge into a larger supermassive black hole in the center of the combined galaxy.  The full size image includes  a second image for comparison taken by a ground based telescope.  It shows the phenomenal clarity and resolving power of the Hubble, which is equivalent to reading the date on a quarter from a mile away.