ASTRON 1F03 Lecture Notes - Lecture 15: Helioseismology, Land Of Oz, Chromosphere
18 Dec 2015
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Document Summary
A few stars are nearby and large enough to measure size directly. For most stars we infer the size from the amount of light emitted. A blackbody surface generates light in proportion to temperature4: stefan-boltzman f = The area of a star"s surface gets bigger as the star"s radius squared: area = 4 r2 m2. 4: double the star"s temperature, make the star 4 times bigger. With luminosity and temperature, we can calculate the size of a star: a larger and hotter star is also more luminous. Stars have radii measuring 1% of the sun"s to 1000x its radius. Star"s cover a broad range: small cold ones (red dwarfs, small hot ones (white dwarfs, large cold ones (red giants, large hot ones (blue giants) Hertzsprung-russell diagram: ejnar hertzsprung (danish, henry russell (american) Nearby stars are mostly small and red. Note the lines of constant radius from size-temperature-luminosity relation. They tend to fall along the main sequence.
