What are the large cool stars that are not in the main sequence?

Answer 1

Large cool stars that are not in the main sequence are known as "red giants" or "red supergiants." These stars have exhausted the hydrogen fuel in their cores, causing their inner regions to contract while the outer layers expand. As a result, they become larger and cooler than when they were on the main sequence.

Red giants are typically found in the later stages of stellar evolution, after they have exhausted their core hydrogen and started fusing helium in a shell around the core. They are often reddish in colordue to their lower surface temperature compared to main sequence stars. Red supergiants are even more massive and larger than red giants, representing the final stages of the life cycle of massive stars before they undergo supernova explosions or other dramatic events.

Answer 2

Red giants. They are medium and large stars that have used up all of their hydrogen and gave begun burning the helium. They begin to expand while they are in their "dying" phase. They will ultimately become a white dwarf if they were a medium sized star during their main sequence, or they will become a black hole or a neutron star if they were a large star during their main sequence.