Pressure-Temperature Thermostat

• In a star, inward pull of gravity balanced by the internal pressure

• As the star loses energy, the T and P would drop, except nuclear fusion is generating just enough energy to maintain the balance

  • If reactions begin to produce too much energy, this extra energy raises T, which raises P, so star expands, which cools it slightly. This slows the nuclear reactions.
  • If reactions slow, then inner T drops, lowering P. Gravity compresses the star slightly. Compression of gas raises T & P increasing nuclear fusion rate.

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