ASTRON 100 Lecture Notes - Instability Strip, Stellar Evolution, Stellar Classification
21 Jan 2014
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A star"s full classification includes spectral type (line identities) and luminosity class (line shapes, related to the size of the star): Main-sequence stars are fusing hydrogen into helium in their cores like the sun. Less luminous ones are cooler (yellow or red) Mass measurements of the main-sequence stars show that hot, blue stars are much more massive than the cool, red stars. The mass of a normal hydrogen burning star determines its luminosity and its spectral. Core pressure and temperature of a higher-mass star need to be larger in order to balance type. gravity. Higher core temperature boosts fusion rate, leading to larger luminosity. Mass: from period (p) and average separation (a) of binary star orbit. Sun"s life expectancy: 10 billion years (until core hydrogen is used up) Life expectancy of 10msun star: 10 million years. 10 times as much fuel, uses it 10^4 times as fast. 10 million years = 10 billion years x 10/10^4.
