Astronomy 1021 Lecture Notes - Lecture 20: Isotropy, James Webb Space Telescope, Stellar Classification
4 Oct 2018
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Document Summary
Extragalactic astronomy: the study of the universe outside of the milky way. Bulge and hale: old stars; few gas and dust clouds. Stars of all ages; many gas and dust clouds. Amount of cool gas in between spirals and ellipticals. E + number; the larger the number the more elongated the galaxy. S or sb (when there is a bar) Not a sequence in properties ( age and mass) 1700s revealed andromeda "nebula" had a spiral structure. Option 1: are they vast but distant collections of stars outside of our milky way. Option 2: are they small and nearby objects scattered within our milky way. Shapely: nebulae are vast but distant collections of stars. Later it turned out that some nebulae are distant galaxies and some are small nearby objects. The cosmos was now filled with vast star groups at almost incalculable distances. How bright a star appears in out sky.
