AST101H1 Lecture Notes - Lecture 4: Light Pollution, Angular Diameter
22 Sep 2016
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The night sky: on the darkest nights, one can identify about 3000 stars, it"s much harder in the city, though (light pollution, air pollution, etc. ) When we look at the sky, we can imagine the stars in shapes: these are called constellations, western constellations (e. g. ursa major) In the ancient times, they believed in the celestial sphere, that contained the stars, which spun around the earth. Instead, what was going on is that stars are mostly fixed in space in comparison to the distance they are from earth (they move very very slowly) However, the earth is rotating, and polaris is straight above the north. If you were at the south pole, you wouldn"t be able to see polaris. If you were at the equator, polaris would be right along the horizon line. The motion of the stars depends completely upon where we are on the sphere.
