Even prior to the servicing mission this was considered an impressive HST image. The star density is high and none of the stars are bright enough to show the halo caused by a flaw in Hubble's primary mirror. A preliminary analysis of the data reveals the apparent presence of white dwarf stars in the image. Prior to the Hubble observation white dwarfs have generally been too dim to be seen within such a cluster. A globular cluster is a tight aggregate of thousands to millions of very old stars.
White dwarfs are the earth-sized remains of ordinary stars like the sun.
Finding them in a known globular cluster allows accurate estimates of their age and provides clues to reconstructing their history.