Galactic merger

The process which takes place when two galaxies 'collide' with one another. If the galaxies become caught in one another's gravitational fields they will not simple make a close pass and travel off again into intergalactic space. Instead they will spiral into one another and form a single galaxy at the end of the interaction. It is thought that elliptical galaxies are the products of mergers between spiral galaxies . Since the spaces in between the individual stars in galaxies are so large, even though the galaxies appear to collide, the stars contained within them do not. There is enough space for the two galaxies to virtually pass through one another like interlinking fingers. The huge gravitational fields of the galaxies, however, distort their shapes and the close stellar encounters swing the stars into randomly orientated orbits. Often the interstellar clouds will collapse in the merger and many new stars will be formed. This process is called a starburst. As the galaxies become closer and closer, long tails of stars are strung out behind the galaxies. Sometimes these tail fragments contain enough matter to be thought of a dwarf irregular galaxiesin their own right.