ASTR-1010 Lecture Notes - Lecture 7: Main Sequence, Low Mass, Planetary Nebula
6 Oct 2016
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Main sequence turnoff point: the position of the hottest, brightest star on a cluster"s main sequence. All stars in the cluster were born at about the same time. All stars above the turnoff point have used up their h fuel and are dead. Q: two stars that are in different parts of the h-r diagram must be made of different elements. A: no, stars appear in different parts of the h-r diagram due to their different ages and masses. Chapter 15 big picture ideas: all stars are made primarily of h and he. As they evolve, their positions in the h-r diagram change: h-r diagrams of stars clusters allow us to determine their ages. Stars are gborn, grow up, mature, and die. The life of any star can be described as a battle between two forces: gravity vs. pressure (gravitational equilibrium) Gravity always wants to collapse the star.
