This new space picture shows a group of stars called a ‘globular cluster’. These are some of the oldest objects in space—almost as old as the Universe itself! This means that many of the stars within have already lived out their lives. The most massive have long since exploded, leaving behind several neutron stars. Using neutron stars within this cluster, along with many others, astronomers have worked out the relationship between the stars' mass (how much material they have) and their size.