Explanation:
These are galaxies of the
Hercules
Cluster, an archipelago of
island universes a mere
500 million light-years away.
Also known as
Abell 2151,
this cluster is loaded with gas and dust rich,
star-forming spiral galaxies
but has relatively few elliptical galaxies,
which lack gas and dust and the associated newborn stars.
The colors in
this remarkably
deep composite image
clearly show the star forming galaxies with a blue tint and
galaxies with older stellar populations with a yellowish cast.
The sharp picture spans about 1/2 degree across the
cluster center, corresponding to over 4 million light-years at the
cluster's estimated distance.
In the cosmic vista many galaxies seem to be
colliding or
merging
while others seem
distorted - clear evidence that
cluster galaxies
commonly interact.
In fact, the Hercules Cluster itself may be seen as the result of
ongoing mergers of smaller galaxy clusters and is thought to be
similar to young galaxy clusters in
the much more distant,
early Universe.
