AST201H1 Lecture Notes - Lecture 10: Stellar Classification, Main Sequence, Messier 80

• School: UTSG
• Department: Astronomy & Astrophysics
• Course: AST201H1
• Professor: Michael Reid

Document Summary

Mar 1/16 (eg. of globular cluster: messier 80) (eg of open cluster: the pleaides) Open clusters: young, 100-1000 stars found in the disk of the galaxy; up to several thousand stars. Pleiades; spectral type b, 100 million yrs ago. Old, more than million stars found in the halo (region above or below the disk of galaxy), stars densely packed together, contain hundreds of thousands of stars. Star clusters are useful to astronomers because: all the stars in a cluster lie at about the same distance from earth all the stars in a cluster formed about the same time. We can use the hr diagram of a star cluster to figure out how old the cluster is. The precise point on the hr diagram at which a cluster"s stars diverge from the main sequence is called the main sequence turnoff point.