ASTRON 1101 Lecture Notes - Lecture 29: Spiral Galaxy, Parsec, Spheroid
7 Nov 2016
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Document Summary
The milky way galaxy is our home galaxy. It has a flat disk of stars, gas, and dust; a central bulge of stars, and an extended spheroid of stars (some of them in globular clusters) and dark matter. The sun orbits the center of the milky way galaxy. Orbital speed (v) 220 km/s: c = 2 r = 52 kpc = (cid:883). (cid:888) (cid:883)(cid:882)18 kilometers, orbital period = c/v = (cid:889). 3 (cid:883)(cid:882)15 seconds = 230 million years. The andromeda galaxy is the nearest bright spiral galaxy to the milky way galaxy. Andromeda is similar in size, composition, and structure to the milky way galaxy. Bulge near the center of the disk. Spheroid of old stars and globular clusters. Spiral arms (visible when we see a galaxy"s disk face-on) are a type of wave traveling through the disk. Spiral arms are sites of active star formation. Molecular cloud enters arm and is compressed.
