Nu Cephei (ν Cephei) is a class A2, fourth-magnitude

blue supergiant A blue supergiant (BSG) is a hot, luminous star, often referred to as an OB supergiant. They are usually considered to be those with luminosity class I and spectral class B9 or earlier, although sometimes A-class supergiants are also deemed blu ...

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

Cepheus, visible to the

naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnification, magnifying, Optical telescope#Light-gathering power, light-collecting optical instrument, such as a telescope or microsc ...

. It is a white pulsating α Cygni variable star located about 4,700

light-year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astr ...

s from Earth. ν Cephei is a member of the Cepheus OB2

stellar association A stellar association is a very loose star cluster, looser than both open clusters and globular clusters. Stellar associations will normally contain from 10 to 100 or more visible stars. An association is primarily identified by commonalities in i ...

, which includes stars such as μ Cephei and VV Cephei. It began life as an approximately star around eight million years ago. It has now exhausted its core hydrogen and expanded and cooled into a supergiant. Elemental abundance analyses indicate that it has not yet spent time as a red supergiant, which would have brought about convection of fusion products to the surface in a

Dredge-up A dredge-up is any one of several stages in the evolution of some stars. By definition, during a ''dredge-up'', a convection zone extends all the way from the star's surface down to the layers of material that have undergone fusion. Consequently, ...

. ν Cephei is currently about 15 times as massive as the sun, 190 times as large, and 100,000 times as luminous. Its large size and luminosity cause it to be somewhat unstable and produce irregular pulsations. This is a common feature of class A and B supergiants, which are grouped as α Cygni variable stars. Variability was first reported by

Helmut Abt Helmut Arthur Abt (26 May 1925 – 22 November 2024) was a German-born American astrophysicist, having worked at the National Optical Astronomy Observatory and an Elected Fellow of the American Association for the Advancement of Science. He wa ...

in 1957. The brightness changes by at most a tenth of a magnitude. A variety of values for the variability period have been published, including 5 to 10 days, 7.6 days and 90 days.

References

External links

{{DEFAULTSORT:Nu Cephei Cephei, Nu 207260 A-type supergiants Cepheus (constellation) Alpha Cygni variables Cephei, 10 107418 8335 Durchmusterung objects