Astronomy 1021 Lecture Notes - Lecture 4: White Dwarf, Density Wave Theory, Main Sequence

• School: Western University
• Department: Astronomy
• Course: Astronomy 1021
• Professor: Sarah Gallagher

Document Summary

At least as old as the oldest objects in it. How do we determine the ages of the oldest stars: main sequence turn off of the oldest star clusters, ages of the coldest white dwarfs. Recall: main sequence turnoff gives age of cluster. The hottest star still on the main sequence is about to run out of h in its core. The oldest globular clusters are 12-13 billion years old. After evolving into a white dwarf, a low mass star will cool over time by radiating away its thermal energy. The coldest white dwarfs are the oldest. Stars form in molecular clouds: coldest and densest regions. The molecular clouds are confined to the disk of the galaxy. All stars are currently forming in the disk of the galaxy. Star formation in the spiral arms: gas and dust flow through spiral structure aka density waves. Disk: stars are younger on average, stars usually orbit in circles, star-forming regions are all here.