In red-giant stars with mass less than 1.25 Sun mass {Chandrasekhar limit, nova}, outer layers expand away by explosions {nova}|. For several months, nova radiates energy 10^6 times Sun energy. At any moment, galaxy has 1000 novas.
White dwarf remains. White dwarfs are 5% to 10% of all stars. White dwarfs fuse all hydrogen into helium, and then fuse all helium into carbon. Helium fusion is hotter than hydrogen fusion, so star is white. White dwarfs keep contracting and exploding. White dwarfs in binary star systems explode off outer layers every 30 to 50 years.
Physical Sciences>Astronomy>Star>Kinds
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Date Modified: 2022.0224