Red supergiant star

In Astronomy the term Red supergiant star refers to a massive star that has largely finished its Hydrogen fusing period, and entered its Helium fusing, and it has left the main sequence.

The term only applies to massive stars, of 8 solar masses, or more, that were considered giant stars, when they were on the main sequence. yellow dwarf stars, the mass of Sol, our sun, enter a red Giant star phase, when they exhaust their available Hydrogen. All stars between 0.5 to almost 8 solar masses eventually become red giant stars. This is not the same as red supergiant stars.