SCI 102 Lecture Notes - Lecture 13: Henrietta Swan Leavitt, Stellar Classification, Apparent Magnitude
13 Apr 2016
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A plot of stellar luminosity (or magnitude) versus surface temperature or spectral type. Harvard spectral classification system (= spectral type) is: obafgkm. The hr diagram has distinct regions: giants, main sequence, white dwarfs. This method enables us to determine the distance to farther stars. Example 1: determine the distance to a main sequence star with apparent. It is more inaccurate than the parallax angle method magnitude of -2 and a surface temperature of 10000k. M = m + 5 5 logd -> logd = (m - m + 5) / 5 d = 10(m m + 5)/5 d = 10(-2 -2 +5)/5 d = 100. 2 d = 1. 6pc = 5. 2ly. Example 2: spice is a main sequence star, spectral class b0, apparent magnitude 0. 91. From hr, m~-3. 5 d = 10(m m + 5)/5 d = 10(0. 91 + 3. 5 + 5)/5 d = 101. 882 d ~ 76pc. A cepheid variable star grows larger and brightens.
