AST- 105 1st EditionLecture 12Outline of Last LectureI. Solar NeutrinosII. Introduction to StarsOutline of Current Lecture I. The Luminosity of StarsII. Inverse Square Law for RadiationCurrent Lecture I. The Luminosity of Starsa. Star- a fixed luminous point in the night sky that is a large, remote incandescent body like the Sun. b. Luminosity (L)- energy per time radiated by stari. Intrinsic property of starii. Luminosity does not depend on distance. c. Apparent brightness (B)- energy per time per area received at Earth.i. Apparent brightness is dependent on luminosity. II. Inverse Square Law for Radiationa. Inverse Square Law for Radiation- energy radiated by star that spreads out over an area as it increases by d2. i. Apparent brightness of a star decreases by the following formula:B = L / d2Ex. If the luminosity and measure of apparent brightness is known, one can compute distance. III. Ideal Gas Lawa. Ideal Gas Law- obeyed by normal gases: air in this room, as well as hot, ionized gas inside the Sun.b. Form:P V = N k TP = pressureV = volumeT = temperature (in K)N = number of gas particlesk = Boltzmann’s
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