M51 is a spiral galaxy, about 30 million light years away, that is in the process of merging with a smaller galaxy seen to its upper left.
This image is part of a "quartet of galaxies."
Quartet is a collaboration of professional and amateur astronomers that combines optical data from amateur telescopes with data from the archives of NASA missions.
NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington.
The Smithsonian Astrophysical Observatory in Cambridge, Mass., controls Chandra's science and flight operations.
