The Milky Way is chock full of star clusters. Some contain just a few tens-to-hundreds of young stars. Others, known as globular clusters, are among the oldest objects in the Universe and contain up to a million ancient stars. Some of these globular clusters are thought to be fragments of our galaxy, chiseled off when the Milky Way was in its infancy. Others may have started life as standalone dwarf galaxies before being captured by the Milky Way during its formative years.
Regardless of their origins, many globular clusters reside either in or behind the dusty regions of our galaxy. For ground- and space-based optical telescopes, however, this poses a challenge. Though it is possible to observe the cluster as a whole, the dust hinders astronomers' efforts to study the motions of individual stars.
If astronomers could track the motions of individual stars, they could see how "lumpy" the globular cluster is or if it contains something really dense, like a giant black hole at its center.
Graphic showing locations of millisecond pulsars inside the globular cluster Terzan 5 in an optical image taken by the Hubble space telescope. Pulsars represented in blue are accelerating toward observers on ...