Mysteriously Slow Pulses From Giant Old Stars May Finally Have an Explanation
The extremely slow, steady pulsations of light from many red giant stars may finally have an explanation.
According to a new analysis, these mysterious fluctuations in brightness are not caused by internal processes after all, but by binary companions obscured in clouds of dust siphoned off the dying giants.
When stars of intermediate mass below around eight times the mass of the Sun reach the twilight of their lives, they go through some pretty dramatic changes.
When they have fused all the hydrogen in their cores to helium, the nuclear fusion within ceases, and the core starts to contract. This brings more hydrogen into the region immediately around the core, forming a hydrogen shell; then, fusion starts up again, dumping helium into the core. This is called hydrogen shell burning.