SCI 102 Lecture Notes - Lecture 12: Hipparcos, Hypotenuse, Star Formation
13 Apr 2016
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Document Summary
Stars form in vast interstellar hydrogen and helium clouds. As the universe ages, hydrogen is being transformed into heavier elements inside the stars. The hydrogen component of the universe is always declining the abundances of heavier elements are increasing. Eventually new stars will cease to form and the stelliferous era will end. Sin = opposite = 1 = (for small angles) hypotenuse d. D = 1 if is in seconds of arc ( ), then d is in parsecs (pc) D = 3. 26 if we multiply by 3. 26,then d is in lightyears (ly) This method is good for stars at d < ~ 50pc (163ly) Hipparchus (hipparcos) of greece (2nd century bc) divided the visible stars into 6 groups. M = 1 (brightest star in greek sky) M = 1 is 2. 5x brighter than m = 2. M = 2 is 2. 5x brighter than m = 3 etc. Note that magnitude has no s. i. units.
