The Milky Way and Other Galaxies

Episode 21 of Introduction to Astrophysics

Take in our entire galaxy, called the Milky Way. Locate Earth's position; then survey other galaxies, classifying their structure. Use the virial theorem to analyze a typical galaxy, which can be thought of as a "collisionless gas" of stars. Note that galaxies themselves often collide with each other, as the nearby Andromeda Galaxy is destined to do with the Milky Way billions of years from now.