Editing Rigel (section)

== Evolution ==

[[Stellar evolution]] models suggest the pulsations of Rigel are powered by nuclear reactions in a hydrogen-burning shell that is at least partially non-convective. These pulsations are stronger and more numerous in stars that have evolved through a [[red supergiant]] phase and then increased in temperature to again become a blue supergiant. This is due to the decreased mass and increased levels of fusion products at the surface of the star.<ref name=saio/>

Rigel is likely to be [[Triple-alpha process|fusing helium]] in its core.<ref name=apj2012_749_74 /> Due to strong convection of helium produced in the core while Rigel was on the main sequence and in the hydrogen-burning shell since it became a supergiant, the fraction of helium at the surface has increased from 26.6% when the star formed to 32% now. The surface abundances of carbon, nitrogen, and oxygen seen in the spectrum are compatible with a post-red supergiant star only if its internal convection zones are modeled using non-homogeneous chemical conditions known as the [[Paul Ledoux#Ledoux criterion|Ledoux Criteria]].<ref name=saio/>

Rigel is expected to eventually end its stellar life as a [[type II supernova]].<ref name=apj2012_749_74/> It is one of the closest known potential [[supernova]] progenitors to Earth,<ref name=apj2012_747_108/> and would be expected to have a maximum apparent magnitude of around {{val|-11}} (about the same brightness as a quarter Moon or around 300 times brighter than Venus ever gets).<ref name=guinan/> The supernova would leave behind either a black hole or a neutron star.<ref name=apj2012_749_74/>