Cepheid Variable
A type of variable star which exhibits a regular pattern of changing brightness
as a function of time. The period of the pulsation pattern is directly related
to the star's intrinsic brightness. Thus, Cepheid variables are a powerful tool
for determining distances in modern astronomy.
A Cepheid is a
member of a class of very luminous variable
stars. The strong direct relationship between a Cepheid variable's luminosity and pulsation
period secures for Cepheids their status as
important standard
candles for
establishing the Galactic and extragalactic distance scales.
Cepheid variables are divided into
several subclasses which exhibit markedly different masses, ages, and
evolutionary histories:Classical Cepheids, Type II
Cepheids, Anomalous Cepheids, and Dwarf
Cepheids.
The
term cepheid originates from Delta Cephei in
the constellation Cepheus,
the first star of this type identified, by John Goodricke in 1784. Delta Cephei is
also of particular importance as a calibrator of the Cepheid period-luminosity
relation since its distance is among the most precisely established for a
Cepheid, thanks in part to its membership in a star cluster and
the availability of preciseHubble Space Telescope/Hipparcos parallaxes.
Source: wikipedia, NASA
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