PCS 181 Lecture 3: PCS 181 Unit 3
19 Feb 2017
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Document Summary
Galaxy theorists hypothesize that galaxies condensed at interface between warmer and cooler volumes of space. First stars formed after big bang were extremely massive hundreds of times mass of our sun. These stars only lived a few million years and exploded as supernovae, leaving black holes as remnants. These massive black holes attracted gas/dust into orbit. Over time, more matter was attracted until a galactic mass was present. Massive black holes are found at centers of most galaxies. A galaxy is a gravitationally-bound collection of stars, gas, dust, radiation. Galaxies range from thousands to hundreds of thousands of lightyears across. Galaxies contain from thousands to trillions of stars. Milky way, our own galaxy, is about 100 000 to 120 000 lightyears across. Our mw is in local group which consists of more than 50 galaxies. Every galaxy has a supermassive black hole in center of galaxy. 26 000 ly) from center of milky way.
