Period-luminosity relation
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In astronomy, a period-luminosity relation is a relationship linking the luminosity of pulsating variable stars with their pulsation period. The best-known relation is the direct proportionality law h
Plot from Leavitt's 1912 paper. The horizontal axis is the logarithm of the period of the corresponding Cepheid, and the vertical axis is its apparent magnitude. The lines drawn correspond to the stars' minimum and maximum brightness.
Phase lightcurve of variable star Delta Cephei.
Cepheid variable
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A Cepheid variable is a type of variable star that pulsates radially, varying in both diameter and temperature. It changes in brightness, with a well-defined stable period and amplitude. Cepheids are
Period-luminosity relation
…that there is a simple relation between the brightness of the Cepheid variables and their periods. Using the simplifying assumption that all of the Cepheids within the Small Magellanic Cloud were at approximately the same distance, the apparent magnitude of each star is equivalent to its absolute magnitude…
RS Puppis, one of the brightest known Cepheid variable stars in the Milky Way galaxy (Hubble Space Telescope)
Illustration of Cepheid variables (red dots) at the center of the Milky Way