What is a red giant?

1 Answer
Nov 18, 2015

A star towards the end of stellar evolution.


Regular "main sequence" stars like our sun fuse hydrogen into helium and that is how stars put out so much energy. The fusion of hydrogen into helium keeps the star from collapsing in on itself from it's own gravity. Eventually, the hydrogen runs out and all the star is left with is helium.

Now that the fusion of hydrogen is stopped, the star will begin to collapse under its own gravity and become even hotter, and more dense, this increase in temperature and density will allow helium to begin fusing together to form carbon. This new fusion causes the star to expand to a much larger size that it was originally.

Our own sun will eventually turn into a red giant in the next few billion years once the hydrogen is depleted.