This diagram shows how white dwarfs are distributed in the globular star cluster 47 Tucanae. White dwarfs are the burned out relics of old stars, but the youngest white dwarfs are the hottest and bluest stars lurking mostly in the cluster’s core where the most massive stars reside. In the process of collapsing to become white dwarfs, a star shed most of its mass. In 47 Tucanae the lightweight white dwarfs, interact gravitationally with more massive stars in the core. These gravitational encounters are much the same as the gravitational assists spacecraft receive during planetary flybys, and the white dwarfs rob enough momentum from their more massive cousins to begin migrating slowly outward from their home. Eventually, the white dwarfs settle on the outskirts of the cluster, where the oldest, coolest, reddest white dwarfs reside. They become older and cooler white dwarfs, depicted as the orange dots in the diagram.
Image Credit: STScI