PHYSICS 20A Lecture Notes - Lecture 2: Celestial Pole, Circumpolar Star, Celestial Equator
Document Summary
Voyager, launched in the 70s, finally left the solar system last year: first man-made thing to leave the solar system. Our galaxy is 100,000 ly in diameter. A massive black hole resides in the center of the galaxy; maybe in the center of every galaxy. There are 6,000 stars visible to the eye in the sky: the furthest is 4,000 ly away. The milky way rotates at around 200 km/s. Rotation of the earth and our view of the sky. At certain points on earth, the stars appear to move in a circular pattern as the result of the rotation of the earth: which rotates eastward, stars appear to move westward. Horizon the line marking the boundary between earth and sky. Zenith the point directly over the observer"s head: nadir is the opposite of a zenith.
