SCEN101 Chapter Notes - Chapter 27: Celestial Sphere, Radiant Energy, Main Sequence
28 Nov 2017
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An imaginary sphere surrounding earth to which the stars are attached. 3 types of motion for celestial bodies: Daily motion - eastward rotation of earth on its axis. Stars do not change their positions relative to each other. Constellations appear to migrate toward the west. Intrinsic motion- celestial bodies appear to move relative to each other. The distance light travels in one year. Used to measure vast distances between earth and the stars. Stars are typically formed of 75% hydrogen and 25% helium. All stars ultimately exhaust their nuclear fuel and die. Brightness relates to how much energy a star produces. Brightness also depends on how far away it is from earth. The intensity of light diminishes as the reciprocal of the square of the distance from the source. Apparent brightness the brightness of a star as it appears to our eyes. Luminosity the total amount of light energy that a star emits into space.
