ASTRO 001 Study Guide - Midterm Guide: Photon, Stellar Classification, White Dwarf
2 Nov 2017
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The sun, the inverse-square law, and stellar parallax. Stable due to balance of gravity (inward force) and gas pressure in hot interior (outward force) Gas pressure provided by nuclear fusion reactions in core at temperature of 15 million degrees. Diameter is 109x earth; mass is 333,000 times earth; luminosity is . 99. 9% of the mass of the solar system is in the sun. Sun has been shining for 4. 5 billion years and will continue for about another 5. 5 billion years. Sunspots are slightly cooler regions on sun"s surface due to magnetic activity preventing hot material from rising in that region. 4 protons combine to make helium-4 (2 protons and 2 neutrons) and release energy in gamma rays. First step: two protons stick together and one changes into neutron and end with deuterium (1 proton and 1 neutron bound together) Two helium-3 nuclei combine to make helium-4 and 2 protons.
