[erickejah (OP)]

 []
is it a nuclear reaction?

[Vern]

The sun is a fusion reactor. It fuses mostly hydrogen atoms into helium. When most of its hydrogen has become helium, it will then get very agitated and start fusing helium, eventually going all the way to carbon. Larger stars can take the process all the way to iron when they nova.

[erickejah (OP)]

why it does not decays?

[erickejah (OP)]

are you still there?
  [][diagram=454_0]

[Vern]

why it does not decays?

The sun will eventually burn out; physicists calculate that will be within the next six or seven billion years. The method of burn out will be a red giant star that will swell out to beyond our earth's orbit. Then I think it eventually becomes a brown dwarf star. But it has been awhile since I read up on it, the end game might be different.

[lyner]

Yes it decays - but takes a very long time! Much longer than it takes to establish thermal equilibrium.

[syhprum]

Professor Hoyle of continuous creation fame first worked out the mechanism of how power is generated in stars but never got the recognition he deserved.