ASTR 101 Lecture Notes - Lecture 2: Equinox, Constellation, September Equinox
30 Oct 2017
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Document Summary
Earths axis is tilted by 23. 5 (pointing to polaris, it rotates in the sae direction it orbits, counter clockwise, the sun is orbiting the center of the galaxy. Sun moves randomly relative to the other stars in the local solar neighbourhood. Typical relative speeds of more than 70,000 km/hr. Stars are so far away we cannot notice their motion. And orbits the galaxy every 230 million years. Galaxies are carried along with the expansion of the universe. How did hubble figure out the universe was expanding: cosmology was discovered in the 1920"s and he discovered that: Everything is moving away from us in a straight line (if everything is moving away then the universe is not as stable as we thought it was) The further the galaxy is the faster it is moving away from us and vice versa. Constellation: is a region of the sky, eighty-eight constellations fill the entire sky.
