Space Telescope Science
Globular star clusters are favorite targets for amateur sky watchers. To the naked eye they appear as fuzzy-looking stars. Through a small telescope they resolve into glittering snowball-shaped islands of innumerable stars crowded together. About 150 globular star clusters orbit our Milky Way, like bees buzzing around a hive. They are the earliest homesteaders of our galaxy, containing the universe's oldest known stars.
Hubble is so powerful it can see globular star clusters 300 million light-years away. And, a lot of them. Peering into the heart of the giant Coma cluster of galaxies Hubble captured a whopping 22,426 globular star clusters. The survey found the globular clusters scattered in space among the 1,000 galaxies inside the Coma cluster. They have been orphaned from their home galaxy due to galaxy near-collisions inside the traffic-jammed galaxy cluster. Because they are so numerous in the Coma cluster, they are excellent tracers of the entire gravitational field that keeps the galaxies from flinging off into space. The gravity is a tracer of the distribution of dark matter.