ASTRON 100 Lecture Notes - Density Wave Theory, Milky Way, Cosmic Ray
21 Jan 2014
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Document Summary
Gravitationally bound stars can"t float away. Galaxies also contain black holes, the interstellar medium (ism) and dark matter (90% of mass) Different colors : quiescent (old and redder) /star-forming (new and bluer) Different sizes: dwarf-massive (10^7 10^12 stars, amount of stars) Dusty gas clouds obscure our view because they absorb visible light. This is the interstellar medium that makes new star systems. We see galaxy edge-on because we are inside of it. Primary features: disk, bulge, halo, globular clusters. If we could view the milky way from above the disk, we would see its spiral arms. Stars in the disk all orbit in the same direction with a little up-and-down motion. Orbits of the stars in the bulge and halo have random orientations. (elliptical orbits, circular orbits, different directions) The sun"s orbital motion radius and velocity (v) of circular motion- tells us the mass (mr) within sun"s orbit: mr= (r x v^2) / g.
