Starquakes in Red Giants Reveal Their Cores Spin much Faster than Surfaces

Starquakes in red giants now reveal that their cores spin much faster than their surfaces. According to scientists this discovery could shed light on how the otherwise mysterious interiors of stars evolve over time. Red giants represent the swollen fate that awaits stars such as our own sun as they begin to exhaust their hydrogen fuel. As they do so, their cores contract and their outer envelopes expand and cool. Approximately 5 billion years from now, this process will force our sun to swell to more than 100 times its current size, transforming it into a red giant. The shrinking of the hearts of these stars should make the cores whirl faster, just as spinning ice skaters turn faster if they pull their arms in.

Still, until now, scientists only had indirect evidence of this occurring. Stars experience violent quaking that generates sound waves. These ripples zip around inside the stars and cause tiny rhythmic variations in their brightness. By studying these changes, scientists can better understand stars interiors an emerging scientific field known as asteroseismology.