The sun is burning hydrogen to make
helium. Until the helium core of the sun gets
much more massive, it will not collapse to the
point where it can burn helium to make carbon and
oxygen. This means that there is a shell expanding
outward through the sun where the hydrogen is
being fused, which pushes the envelope out. Beyond
that I'm not sure, but the sun is slowly (very
slowly) becoming a red giant.
Click Here to return to the search form.