ASTRO-110 Lecture Notes - Lecture 28: Open Cluster, Main Sequence, Protostar
Document Summary
Hr diagrams are used for looking at clusters of stars: a star cluster is a gravitationally bound group of stars that are all formed from the same giant cloud of gas. Pleiades: globular clusters can be found in the disk of a galaxy in a halo surrounding it, older (ex. Clusters are too far for parallax but there are so many that at least one star will be a. Cepheid and we can measure distance to one of these stars. Stellar birth: as protostars begin to heat up, they often emit jets of gas along their rotation axis. Even before protostars begin to fuse hydrogen, they can be quite active. Shortly before fusion begins, protostars can behave very violently, often shining brighter than our sun. The angular momentum that makes a collapsing cloud form a disk is often too great to allow a star form right away.
