What is a guitar doing in a cluster of galaxies? Colliding.
Clusters of galaxies are sometimes packed so tight that the
galaxies that compose them
A prominent example occurs on the left of the
above image of the rich
cluster of galaxies Abell 1185.
There at least two galaxies, cataloged as
Arp 105 and dubbed
for their familiar appearance, are pulling each other apart gravitationally.
Most of Abell 1185's hundreds of galaxies are
elliptical galaxies, although
irregular galaxies are all clearly evident.
Many of the spots on the above image are fully galaxies themselves containing
billions of stars, but some spots are foreground stars in our own
Milky Way Galaxy.
Recent observations of
Abell 1185 have found unusual globular clusters of stars that appear to belong
only to the galaxy cluster and not to any individual galaxy.
Abell 1185 spans about one million
light years and lies 400 million light years distant.