AST 309 Study Guide - Midterm Guide: Spiral Galaxy, List Of Astronomy Acronyms, H Ii Region
Document Summary
A compact ice skater has to spin more rapidly to have the same amount of angular momentum as she does when she is more extended. A cloud"s angular momentum keeps it from being able to directly collapse into a bill. The clouds are large, and are constantly stirred around as they orbit the galaxy, therefore they have some intrinsic rotation. The cloud"s rotation must also speed up as it collapses and shrinks in size to conserve angular momentum. This is over 3 million times faster than the sun actually rotates. The cloud does not directly collapse into the star, but also collapses into a disk. The rotation of the cloud slows the collapse in the direction perpendicular to the axis of rotation, but not parallel to it. As cloud shrinks, it spins faster, creating centrifugal forces that are greatest at the equator. This causes the rotating, contracting cloud to spread out and form a disk.
