ASTR 1103 Lecture Notes - Lecture 5: Brown Dwarf, Black-Body Radiation, Photosphere
9 Feb 2020
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Document Summary
Surface of a star: called it"s photosphere, not an actual solid surface, has a temperature of thousands of degrees kelvin, our sun is 5800 k on the surface. Hydrogen balmer lines: produced by hydrogen atoms with electrons going from upper energy levels to the second energy level, weak in very cool and very hot stars, strong in medium temperature stars. Intensity vs. wavelength graphs: show more detail than images, are similar to blackbody radiation curves. Temperature spectral classification: devised at harvard university during 1890"s and 1900"s. The spectral sequence: o 40000 k, b 20000 k, a 10000 k, f 7500 k, g 5500 k, k 4500 k, m 3000 k. Luminosity: the luminosity of an object depends on the temperature and area, a star"s luminosity is proportional to its area, a small hot star could be as luminous as a large cool star. Hr diagram categories: the main sequence, giants, super giants, red dwarfs, white dwarfs.
