AST201H1 Chapter 17: CHAPTER 17 ASTRO.docx
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AST201H1 Full Course Notes
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A star is in equilibrium with thermal pressure balancing gravity and fusion energy from the core balancing the flow of radiative energy from the star"s surface. When fusion stops, gravity regains the upper hand over pressure. Stars of greater mass release larger amounts of gravitational potential energy and therefore heat up more rapidly, achieving the temperatures necessary for fusion more quickly. Relatively low mass stars end up as white dwarfs while high mass stars die violently and either end up as neutron stars or black holes. Low-mass stars: stars born with less than about 2 solar masses of material. Intermediate stars: birth mass between 2 and 8 solar masses. High-mass stars: born with more than 8 solar masses material. Solar thermostat keeps luminosity and fusion rate steady. Convection carries energy out of the cores of high-mass stars, whereas radiative diffusion is responsible for transporting energy from the core in low-mass stars.