branch for around 100 million years, becoming slowly more luminous in the same way that main sequence stars increase luminosity as the virial theorem shows. When their core helium is eventually exhausted, they progress to helium shell burning on the asymptotic giant branch (AGB). On the AGB they become cooler and much more luminous.

Horizontal branch morphology

Stars on the horizontal branch all have very similar core masses, following

1.Previous
3.Next