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The Distance Ladder

The Distance Ladder. Part II. Number of stars=N star *V Sphere: V=4πR 3 /3 Cylinder: V=πR 2 H. R. R. H. (a). (b). Cepheid Variable Stars (part III, IV). Special type of variable star that brightens & dims with a regular period P~L, recall F=L/4πd 2 , known P, F, derive d.

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The Distance Ladder

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  1. The Distance Ladder

  2. Part II • Number of stars=Nstar*V • Sphere: V=4πR3/3 • Cylinder: V=πR2H R R H (a) (b)

  3. Cepheid Variable Stars (part III, IV) • Special type of variable star that brightens & dims with a regular period • P~L, recall F=L/4πd2, known P, F, derive d. • Apparent magnitude mv~F, • Absolute magnitude Mv~L, determined from graph on p. 111, or computed using the formula • d~distance modulus (mv-Mv), graph on p. 112 • http://www.astro.psu.edu/headta/labs/Cepheid/ Part V: Apparent size of a galaxy is inversely proportional to its distance

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