–
•Star
continues to shrink till it gets hot enough inside for fusion (rather than gravity)
to balance energy
being radiated away.
•
•Nuclear
thermostat
–If
fusion reactions took place in a “box” with fixed walls:
•Fusion
Þ more energy Þhigher T Þ more fusion (explosion)
•
–If
fusion reactions take place in sun with “soft gravity walls”:
•If
fusion rate is too high T tries to go up but star expands and actually ends up cooling off –
slowing down fusion. (steady rate)
•
•