01:460:120 Lecture Notes - Lecture 2: Stanley Miller, Harold Urey, Lightning
15 Feb 2017
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Document Summary
A galaxy is a huge rotating aggregation of stars, dust, gas and debris held together by gravity. About 100 billion galaxies in the universe. About 100 billion stars in each galaxy. Huge distances: 4. 2 light years (25 trillion miles) to closest star to ours. During the lifetime and death of a star, all the stable elements that make up matter are synthesized. 273 degrees kelvin = 0 degrees celsius. Nebula (cloud of gas and dust) contracts due to gravity. As it contracts, the nebula heats, flattens, and spins faster, becoming a spinning disk of dust and gas. Hydrogen and helium remain gases, but dust can condense into solid "seeds" for building planets. Warm temperatures allow only metal or rack "seeds" to condense near the protostar. Cold temperatures allow "seeds" to contain abundant ice farther from protostar. Larger ones attract others with their gravity, growing larger still. Terrestrial planets are built from metal and rock.
