標題: the deaths of stars(3) [打印本頁] 作者: alexng9843 時間: 2018-5-23 08:29 PM 標題: the deaths of stars(3)
red dwarfs
red dwarfs are less than 0.4 solar mass, they are small, cool and faint, so they cannot form giant.
they are not massive enough to burn heilum. so they contract slowly when fuels are used up. they get hotter and smaller and move from right to left on H-R diagram and become white dwarf.
the Properties of a white dwarf:
a star in equilibrium, very hot, small (~Earth-size),and it has a very high density (~1 solar mass, 1teaspoon of matter ~15 tons)
and the gravity is resisted by electron degeneracypressure, which is predicted byquantum mechanics.
electron degeneracy pressure: When density isvery high, electrons are pressed together. Butquantum mechanics predicts that electrons do notlike to be squeezed together; they exert strongoutward pressure to resist.
strong gravity on its surface (~105 timesthat of Earth’s)
a white dwarf radiates energy slowly, becomes cold and dark after billions of years, becomes a black dwarf, ends with aquiet death