ASTR-1010 Study Guide - Midterm Guide: Lunar Eclipse, Angular Diameter, Observable Universe
27 Sep 2016
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Document Summary
1 au = earth"s average distance from the sun (150 million kilometers, 93 million miles) 1 lightyear = the distance light can travel in 1 year (10 trillion kilometers, 6 trillion miles) Light-year is a measure of distance, not time. Age of the universe is about 14 billion years. If we look at a galaxy that is 7 billion light years away, we are looking at it as 7 billion years old. The distance of 14 billion light years marks the boundary of our observable universe. Earth"s path around the sun: eccliptic plane. Earth"s axis is tilted by 23 degrees. Celestial sphere: created by the ancient greeks. Celestial equator: projection of earth"s equator into space. North & south celestial pole: directly over earth"s north and south poles. Milky way: band of light around celestial sphere. Local sky: hemisphere or dome that we see. Angular size (of an object): the angle it appears to span in our field of view.
