What are Giant Stars?
Giant stars are huge stars with a much larger radius and luminosity of a main sequence star with a similar surface temperature. Main sequence stars have a mixed core, composed of hydrogen and helium. Giant stars have a core made of helium or even heavier elements such as carbon. This is because giant stars have begun to exhaust substantial portions of their hydrogen fuel. The giant phase is inevitable for any star with greater than 0.4 solar masses. Stars with between 0.4 and 0.5 solar masses accumulate helium in their core as they age, and eventually a pure helium core builds up, but they lack the pressure and temperature to fuse helium. The hydrogen on the periphery of the core forms a shell of rapid fusion activity, because the massive gravity of the core is compressing hydrogen onto it. The star’s size expands and it becomes much more diffuse. When the Sun becomes a red giant in five billion years, its surface will reach to where Earth’s orbit is today. Stars with greater than 0.5
