Like a celestial Rorschach test, I can see so many things when I stare at this wonderful photo captured by the Hubble Space Telescope. It’s like static on a TV. Or like a crowded future city lit by buildings stacked on buildings. But what it really is is even cooler: it’s the first time pictures have been taken of white dwarf stars migrating from the centre of a star cluster to the outskirts.
The picture shows the white dwarf stars of star cluster 47 Tucanae, which is home to hundreds of thousands of stars some 16,700 light years away. NASA writes:
White dwarfs are the burned-out relics of stars that rapidly lose mass, cool down and shut off their nuclear furnaces. As these glowing carcasses age and shed weight, their orbits begin to expand outward from the star cluster’s packed downtown. This migration is caused by a gravitational tussle among stars inside the cluster. Globular star clusters sort out stars according to their mass, governed by a gravitational billiard ball game where lower mass stars rob momentum from more massive stars. The result is that heavier stars slow down and sink to the cluster’s core, while lighter stars pick up speed and move across the cluster to the edge. This process is known as “mass segregation.” Until these Hubble observations, astronomers had never definitively seen the dynamical conveyor belt in action.