ASTR-1010 Lecture Notes - Lecture 13: Inverse-Square Law, Minute And Second Of Arc, Parsec
19 Feb 2017
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Luminosity the total amount of power radiated by a start into space: apparent brightness: refers to the a(cid:373)ou(cid:374)t of a star"s light (cid:449)he(cid:374) rea(cid:272)hes us per unit area. Refers to the received source of light: the farther away a star is, the fainter it appears to us, how much fainter it gets obeys an inverse square law. The apparent brightness of a star depends on two things: how much light is it emitting: luminosity (l) [watts, how far away it is: distance (d) [meters] Apparent brightness = l/ 4 d2: the further away you get, the luminosity stays the same but the brightness decreases. Luminosity: amount of power a star radiates into space. Apparent brightness: amount of starlight that reaches earth. Parallax appare(cid:374)t (cid:449)o(cid:271)(cid:271)le of a star due to earth"s orbiting of the sun: our vantage point from earth looking at some nearby object changes as we are moving by the.
