AST 111 Lecture Notes - Lecture 14: Spiral Galaxy, Hydrogen Atom, Planetary Nebula

• School: Tunxis Community College
• Department: Astronomy
• Course: AST 111
• Professor: Reynolds

Document Summary

Holds over 100 billion stars, and is among 100 billion galaxies in the universe. Is a spiral galaxy with spiral arms that are part of a flat disk, which also contains a central bulge. The disk is surrounded by a round halo. Most stars are found in the disk. Stars in the halo are usually found in globular clusters. 100,000 light years in diameter, 1,000 lights years thick. Clouds of interstellar medium (gas and dust) fill the galactic disk. A relatively large galaxy, with several smaller galaxies orbiting it. Stars orbit in circular paths that all go in the same direction on the same plane, bobbing up and down as they move. The orbital velocities of stars near the edge and those near the centre are about the same. Orbit the centre in random directions, swooping from high above and below the disk. Some bulge stars orbit like halo stars, while others orbit like disk stars.