ASTR 1000 Study Guide - Final Guide: Zodiac, Lunar Phase, Retrograde And Prograde Motion
11 Sep 2016
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Galaxy: island of stars in space, all held together by gravity and orbiting a common center. Local group: the milky way and about 70 other small galaxies. Galaxy clusters: groups of galaxies with large members. Superclusters: regions in which galaxies and galaxy clusters are most tightly packed. Universe: the sum total of all matter and energy, encompassing the superclusters and voids and everything within them. Astronomical unit (au): earth"s distance from the sun (about 150 million kilometers) Light year (ly): distance light can travel in one year (about 10 trillion kilometers) Jan. 1st the big bang: plasma at extreme temperatures cooled down and collapsed to form stars and galaxies, atmosphere = 90% hydrogen & 10% helium. Dec. 17th cambrian explosion (14 billion years ago) (4. 54 billion years ago) (3. 5 billion years ago) (210 million years ago: explosion of multi-celled and larger animals.
