Giant star mass, when on the main sequence, was below approximately , it will never reach the central temperatures necessary to fuse helium. It will therefore remain a hydrogen-fusing red giant until it runs out of hydrogen, at which point it will become a helium white dwarf. According to stellar evolution theory, no star of such low mass can have evolved to that stage within the age of the Universe. In stars above about the core temperature eventually reaches 10 K and helium will begin to fuse to carbon and oxygen in the core by the triple-alpha process. When the core is
Red giant to the planet when the giant expands out to the orbital distance of the planet. Many of the well known bright stars are red giants, because they are luminous and moderately common. The red giant branch variable star Gamma Crucis is the nearest M class giant star at 88 light years. The K0 red giant branch star Arcturus is 36 light years away. In about 5 to 6 billion years, the Sun will have depleted the hydrogen fuel in its core. It will shrink, with the hydrogen outside the core able to compress enough for hydrogen there to fuse, and