ASTRON 100 Lecture Notes - Planetary Nebula, Horizontal Branch, Triple-Alpha Process
21 Jan 2014
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Document Summary
Fusion will not begin in a contracting cloud if a force stops contraction before the core. Thermal pressure cannot stop contraction because the star is constantly losing thermal temperature rises to about 10 million k. energy from its surface through radiation. Degeneracy pressure: the laws of quantum mechanics prohibit two elections from occupying the same state in same place. Is the main form of pressure in most stars. Particles can"t be in same state in the same place. Degeneracy pressure halts the contraction of objects with <0. 08msun before core temperature becomes hot enough for fusion. Starlike objects not massive enough to star fusion are brown dwarfs. A brown dwarf emits infrared light because of heat left over from contraction. Its luminosity gradually declines with time as it loses thermal energy. Infrared observations reveal recently formed brown dwarfs because they are still relatively warm and luminous. Upper limit on a star"s mass blowing itself apart. even larger.
