Horizontal Branch Stars and Helium Fusion

There is a problem with He tex2html_wrap_inline228 He tex2html_wrap_inline230 Be tex2html_wrap_inline232 because this reaction is endothermic . It does not release energy, but rather requires energy for it to happen.

So, He and He atoms DO fuse to Be sometimes, but the Be decays in tex2html_wrap_inline234 seconds. So, need to have the temperature and density be high enough so that before this decay happens another He collides with the Be to produce Carbon. This is called the Triple Alpha reaction and it is the energy source for horizontal branch stars.

Michael Bolte
Tue Feb 17 13:32:05 PST 1998