PHY 2390 Chapter Notes - Chapter 9: Caroline Herschel, Spiral Galaxy, Harlow Shapley

• School: University of Ottawa
• Department: Physics
• Course: PHY 2390
• Professor: Christian Gigault

Document Summary

9. 1 the discovery of the galaxy: the english astronomers sir william herschel and his sister caroline herschel attempted to gauge the true shape of the system by counting stars in 683 different directions in the sky. So about 100 billion stars : the rising rotation curve indicated that the halo contains much more mass. Dirt, dust etc: dark halo the low-density extension of the halo of our galaxy, believed to be composed of dark matter, dark matter nonluminous matter that is detected only by its gravitational influence. Like just regular dirt and dust: rotation curve a graph of orbital velocity versus radius in the disk of a galaxy. 9. 4 the nucleus: sagittarius a, three important points about sagittarius a, observations at radio wavelengths reveal complex structures near sgr a that are caused by magnetic fields and rapid star formation, the centre is very crowded.