What is stellar evolution?

1 Answer
Feb 2, 2016

Stellar evolution is how a star changes over time.


The primary factor driving stellar evolution is the star's mass.
Stars form from the gravitational collapse of cool, dense molecular clouds. As the cloud collapses, smaller regions form, which combine to form stellar cores. The star forms, and then will change based on its mass.

For smaller stars , with a mass of less than 8 solar masses, the inert carbon in the star will never reach burning temperatures. Two burning shells in the star create thermally unstable conditions, where hydrogen and helium burning occur out of phase with each other. The carbon core contracts until no further contraction is possible. It has formed a white dwarf star. The outer layers of the star expand, causing a period of mass loss. Eventually, the outer layers are ejected and ionized to form a nebula.

For larger stars , with a mass of greater than 8 solar masses, the star will run out of energy to burn and will collapse under its own gravity. Then, depending on its core density, the star will become a black hole, a neutron star, or a supernova.