Standard candles Standard candles A Cepheid variable or Cepheid is a member of a particular class of variable stars, notable for a fairly tight correlation between their period of variability and absolute luminosity. The namesake and prototype of these variables is the star Delta Cephei, discovered to be variable by John Goodricke in 1784. ...more on Wikipedia about "Cepheid variable"
Eddington luminosity (sometimes also called the Eddington limit) is the largest luminosity that can pass through a layer of gas in hydrostatic equilibrium, supposing spherical symmetry. If the luminosity of a star exceeds the Eddington luminosity of a layer on the stellar surface, the gas layer is ejected from the star. This limit is obtained by equating the radiation pressure with gravitational forces. Since both forces decrease as inverse square laws, once equality is obtained this alters the hydrodynamics flow everywhere. ...more on Wikipedia about "Eddington luminosity"
The Red Clump is a region on the Hertzsprung-Russell diagram occupied primarily by metal-rich red giant stars. It is above/right relative to the main sequence and so consequently stars here are brighter than main sequence stars of the same surface temperature (or colder than stars of comparable luminosity). ...more on Wikipedia about "Red clump"
RR Lyrae variables are variable stars often used as standard candles. ...more on Wikipedia about "RR Lyrae variable"
A standard candle is an astronomical object that has a known luminosity. ...more on Wikipedia about "Standard candle"
Supernovae refer to several types of stellar explosions that produce extremely bright objects made of plasma that decline to invisibility over weeks or months. ...more on Wikipedia about "Supernova"
X-ray bursters are a class of binary stars which have periodic outbursts luminous in X-rays. They contain a neutron star and an accreting companion. ...more on Wikipedia about "X-ray burster"
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