SCI238 Chapter Notes - Chapter 1: Solar System, Star System, Local Group
13 Jun 2016
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Document Summary
Earth is a planet in our solar system. Solar system: the sun, the planets and their moons, and countless smaller objects such as asteroids (rock and small) and comets (icy). Solar system belongs to disk shaped collection of stars: the milky way galaxy. Galaxy: a great island of stars in space, containing between a few hundred million and a trillion or more stars. Milky way contains more than 100 billion stars. Galaxies can often exist in groups i. e. milky way is part of local group with 40 other galaxies. Groups with more than a few dozen galaxies are called galaxy clusters. Regions in which galaxies and galaxy clusters are most tightly packed are called superclusters: clusters of galaxy clusters. All these structures make up the universe: sum total of all matter and energy, encompassing the superclusters and voids and everything within them. One astronomical unit (au) is earth"s average distance from the sun 150 million kilometres.
