PHYSICS C10 Lecture Notes - Lecture 24: Elliptical Galaxy, Irregular Galaxy, Cosmological Constant
Document Summary
Spiral flat with many arms coming off the center. Elliptical no new stars are forming. The stars that exist in elliptical galaxies are mostly of low mass and are very old. Example: the magellanic clouds are irregular galaxies in orbit around the milky way: starburst when a galaxy forms a huge number of stars in a very short time. Rotation of the milky way: the galaxy is not in solid-body rotation. Rather, it is rotating differentially (the things at the outside should take longer to go around than those close to the inside) We can predict the rotation speeds from the mass of all the stars in the universe. However, the stars in the galaxy are all rotating around the galaxy faster than they should be. The only thing that can explain this increase in speed is dark matter. Dark halo surrounding the galaxy has a mass of at least 10x the mass of all the stars in the galaxy.