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. During an internship at the Cerro-Tololo Inter-American Observatory in La Serena, Chile, Illinois graduate student Alex Gagliano worked with a team to detect and characterize globular clusters in the Coma Cluster using Hubble images. Their results suggest a large population of intracluster globular clusters that don't orbit any of the 1,000 single galaxies within the Cluster. "We inspected each of the 22,426 globular cluster candidates in the final dataset individually, so I had several late nights trying to reduce all the data before the program ended." Alex said. The star clusters 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. Read the story from NASA here.