As a member of the category of variable stars known as classical Cepheids, it has a regular pulsation frequency that is determined by its mass.

Classical Cepheids and Type II Cepheids follow different period-luminosity relationships.

Over 700 classical Cepheids are known in the Milky Way Galaxy, and several thousand extragalactic Cepheids have been discovered.

The Hubble Space Telescope has identified classical Cepheids in NGC 4603, which is 100 million light years distant.

Classical Cepheids have also been used to clarify many characteristics of our galaxy, such as the Sun's height above the galactic plane and the Galaxy's local spiral structure.

Classical Cepheids are used to determine distances to galaxies within the Local Group and beyond, and are a means by which the Hubble constant can be established.

Classical Cepheids are younger and more massive population I stars, whereas Type II Cepheids are older fainter population II stars.

The luminosity of Type II Cepheids is, on average, less than classical Cepheids by about 1.5 magnitudes (but still brighter than RR Lyrae stars).

These unresolved matters have resulted in cited values for the Hubble constant (established from Classical Cepheids) ranging between 60 km/s/Mpc and 80 km/s/Mpc.

Classical Cepheids (or Delta Cephei variables) are population I (young, massive, and luminous) yellow supergiants which undergo pulsations with very regular periods on the order of days to months.

The period-luminosity relation for classical Cepheids was discovered in 1908 by Henrietta Swan Leavitt in an investigation of thousands of variable stars in the Magellanic Clouds.

Classical Cepheids discovered in the heavily-obscured dust lane of NGC 5128 yield a distance between 3-3.5 Mpc, depending on the nature of the extinction law adopted and other considerations.

Classical Cepheids are yellow supergiants of spectral class F6 - K2 and their radii change by ( 25% for the longer-period l Car) millions of kilometers during a pulsation cycle.

Calibrating the period-luminosity relation has been problematic, however, a firm Galactic calibration was established by Benedict et al. 2007 using precise HST parallaxes for 10 nearby classical Cepheids.

Classical Cepheids (also known as Population I Cepheids, Type I Cepheids, or Delta Cephei variables) are a type of Cepheid variable star.

Classical Cepheids include: Eta Aquilae, Zeta Geminorum, Beta Doradus, RT Aurigae, Polaris, and the namesake Delta Cephei.

Classical Cepheids (also known as Population I Cepheids, Type I Cepheids, or Delta Cephei variables) pulsate with very regular periods of the order of days to months.

Some fairly bright Classical Cepheids which exhibit variations discernable with the naked eye include: Eta Aquilae, Zeta Geminorum, Beta Doradus, as well as the prototype Delta Cephei.

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.

Most stars observed in the instability strip appear as variables, subgiants as RR Lyrae variables, giants as W Virginis variables (type II Cepheids), and brighter giants and supergiants as Classical Cepheids.

From 1915 to the 1930s, the RR Lyraes became increasingly accepted as a class of star distinct from the Cepheids, due to their shorter periods, differing locations within the galaxy, and chemical differences from classical Cepheids, being mostly metal-poor, Population II stars.

Delta Cephei, the prototypical classical Cepheid variables, is also a member of a star cluster.

The instability strip crosses the region of supergiants, and specifically many Classical Cepheid variables are supergiants.

HST observations of Classical Cepheid variables have enabled firmer constraints on Hubble's law.

RR Lyrae stars are found at all galactic latitudes, as opposed to classical Cepheid variables, which are strongly associated with the galactic plane.

On September 10, 1784 Edward Pigott detected the variability of Eta Aquilae, the first known representative of the class of Classical Cepheid variables.

In 1924, Edwin Hubble established the distance to Classical Cepheid variables in the Andromeda Galaxy, and showed that the variables were not members of the Milky Way.