EPSC 180 Lecture Notes - Lecture 5: Parsec, Apparent Magnitude, Dim Stars
28 Apr 2016
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Document Summary
Feb 2 trying to measure our way through the universe: parallax triangulation, parsecs, apparent magnitude, absolute magnitude, spectral type, Sumerians first studied the heavens, used as means for navigation. Aristarchus recognized that sun is center of universe and solar system. Niklas koppernigk wrote manuscript called commentariolis and he recovered heliocentric point of view. Closer the star is, the more rapidly it moves against background. Parallax half angle: if the star is close, the parallax half-angle is going to be large. Distance of star is inversely proportional to that angle so let"s create distance (parsec) as 1/ . Is parallax half angle (seconds of arc). One second of arc is 1/60th of minute of arc with is 1/60th degree of which there are 360 degrees in a full circle. For stars far away (fixed stars), perspective doesn"t vary sig. For close-by stars, perspective varies, seen at diff times of year at diff places.
