Alcyone , is a blue-white

giant star A giant star has a substantially larger radius and luminosity than a main-sequence (or ''dwarf'') star of the same surface temperature. They lie above the main sequence (luminosity class V in the Yerkes spectral classification) on the Hertzsp ...

and the brightest star in the

Pleiades The Pleiades (), also known as Seven Sisters and Messier 45 (M45), is an Asterism (astronomy), asterism of an open cluster, open star cluster containing young Stellar classification#Class B, B-type stars in the northwest of the constellation Tau ...

open cluster. At

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

2.87, it is also the third-brightest star in the

Taurus Taurus is Latin for 'bull' and may refer to: * Taurus (astrology), the astrological sign ** Vṛṣabha, in vedic astrology * Taurus (constellation), one of the constellations of the zodiac * Taurus (mythology), one of two Greek mythological ch ...

constellation. The star has the

Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek alphabet, Greek or Latin letter followed by the genitive case, genitive form of its parent constellation's Latin name. The original list of Bayer design ...

Eta Tauri, Latinized from η Tauri and abbreviated Eta Tau or η Tau. It is about 440 light-years distant.

Nomenclature

''Eta Tauri'' is the star's

. The name ''Alcyone'' originates in

Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...

; she is one of the seven daughters of

Atlas An atlas is a collection of maps; it is typically a bundle of world map, maps of Earth or of a continent or region of Earth. Advances in astronomy have also resulted in atlases of the celestial sphere or of other planets. Atlases have traditio ...

and Pleione known as

the Pleiades The Pleiades (), also known as Seven Sisters and Messier 45 (M45), is an asterism of an open star cluster containing young B-type stars in the northwest of the constellation Taurus. At a distance of about 444 light-years, it is among the nea ...

. In 2016, the

International Astronomical Union The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...

(IAU) organized a

Working Group on Star Names The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize proper names for stars for the international astronomical community. It operates under Division C – Education ...

(WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included ''Alcyone'' for this star. It is now so entered in the IAU Catalog of Star Names. In Chinese, (), meaning ''

Hairy Head The Hairy Head mansion (昴宿, pinyin: Mǎo Xiù) is one of the Twenty-eight mansions of the Chinese constellations. It is one of the western mansions of the White Tiger. This mansion corresponds to the Pleiades The Pleiades (), also known ...

'', refers to an asterism consisting Alcyone,

Electra Electra, also spelt Elektra (; ; ), is one of the most popular Greek mythology, mythological characters in tragedies.Evans (1970), p. 79 She is the main character in two Greek tragedies, ''Electra (Sophocles play), Electra'' by Sophocles and ''Ele ...

, Taygeta, Asterope,

Maia Maia (; Ancient Greek: Μαῖα; also spelled Maie, ; ), in ancient Greek religion and mythology, is one of the Pleiades and the mother of Hermes, one of the major Greek gods, by Zeus, the king of Olympus. Family Maia is the daughter of A ...

, Merope, and

. Consequently, the

Chinese name Chinese may refer to: * Something related to China * Chinese people, people identified with China, through nationality, citizenship, and/or ethnicity **Han Chinese, East Asian ethnic group native to China. **'' Zhonghua minzu'', the supra-ethni ...

for Alcyone itself is (), "the Sixth Star of Hairy Head".

Physical properties

Alcyone is a blue-white B-type

giant In folklore, giants (from Ancient Greek: ''wiktionary:gigas, gigas'', cognate wiktionary:giga-, giga-) are beings of humanoid appearance, but are at times prodigious in size and strength or bear an otherwise notable appearance. The word ''gia ...

, similar to the other bright B-type stars in the Pleiades cluster. With an

of +2.87 and absolute magnitude of −2.39, it is the brightest and most luminous star in the Pleiades. The

spectral type In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

of B7IIIe indicates that

emission lines A spectral line is a weaker or stronger region in an otherwise uniform and continuous spectrum. It may result from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used ...

are present in its

spectrum A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...

. Like many

Be star Be stars are a heterogeneous set of stars with B spectral types and emission lines. A narrower definition, sometimes referred to as ''classical Be stars'', is a non-supergiant B star whose spectrum has, or had at some time, one or more Balmer ...

s, Alcyone has created a gaseous disk flung into orbit around the star from its equator. Alcyone has a high rotational velocity, which causes it to have an ellipsoidal shape. Its effective radius is almost ten times that of the Sun, but the actual radius is lesser at poles and greater at the equator. Its

effective temperature The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...

is 12,258 K, with the actual temperature being greater at the poles and lesser at the equator. Its

bolometric luminosity Luminosity is an absolute measure of radiated electromagnetic energy per unit time, and is synonymous with the radiant power emitted by a light-emitting object. In astronomy, luminosity is the total amount of electromagnetic energy emitted per ...

is 1,750 times

solar Solar may refer to: Astronomy * Of or relating to the Sun ** Solar telescope, a special purpose telescope used to observe the Sun ** A device that utilizes solar energy (e.g. "solar panels") ** Solar calendar, a calendar whose dates indicate t ...

. The rapid rotation causes Alcyone to be an

oblate In Christianity (specifically the Roman Catholic, Orthodox, Lutheran, Anglican and Methodist traditions), an oblate is a person associated with a Benedictine monastery or convent who is specifically dedicated to God and service. Oblates are i ...

shape, with the equatorial radius being and the polar radius to be . The age of the Pleiades is typically calculated to be around 130 million years, but Alcyone itself appears to be younger, less than 100 million years. Alcyone may be a

blue straggler A blue straggler is a type of star that is more luminous and bluer than expected. Typically identified in a stellar cluster, they have a higher effective temperature than the main sequence turnoff point for the cluster, where ordinary stars b ...

or models may not be deriving an accurate age for stars of this type.

Variability

Alcyone has long been suspected to vary in brightness, and a 2017 study using data from the

Kepler Space Telescope The Kepler space telescope is a defunct space telescope launched by NASA in 2009 to discover Earth-sized planets orbiting other stars. Named after astronomer Johannes Kepler, the spacecraft was launched into an Earth-trailing heliocentric orb ...

found definite periodic variations with amplitudes up to 0.001 magnitudes. This is considered undetectable by ground-based observations. The strongest period of 2.3 days is thought to be the rotation period of the star, with an uneven surface causing slight brightness changes, but there are also more rapid pulsations and Alcyone has been classified as both a rotational variable and a

slowly pulsating B-type star A slowly pulsating B-type star (SPB), formerly known as a 53 Persei variable, is a type of pulsating variable star. They may also be termed a long-period pulsating B star (LPB). As the name implies, they are main-sequence stars of spectral type B2 ...

. As of 2025, Alcyone has not been formally listed as a

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are ...

in the

General Catalogue of Variable Stars The General Catalogue of Variable Stars (GCVS) is a list of variable stars in the Milky Way Galaxy. Its first edition, containing 10,820 stars, was published in 1948 by the Academy of Sciences of the USSR, edited by and Pavel Parenago. Second a ...

Companions

The

Catalog of Components of Double and Multiple Stars The Catalog of Components of Double and Multiple Stars, or CCDM, is an astrometry, astrometric star catalogue of double star, double and multiple star, multiple stars. It was made by Jean Dommanget and Omer Nys at the Observatoire Royal de Belgiq ...

lists three companions: B is 24 Tauri, a magnitude 6.28 A0

main-sequence star In astronomy, the main sequence is a classification of stars which appear on plots of stellar color versus brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or dwarf stars, and positions of star ...

117" away; C is V647 Tauri, a δ Sct variable star; and D is a magnitude 9.15 F3 main-sequence star. V647 Tau varies from magnitude +8.25 to +8.30 over 1.13 hours. The

Washington Double Star Catalog The Washington Double Star Catalog, or WDS, is a catalog of double stars, maintained at the United States Naval Observatory. The catalog contains positions, magnitudes, proper motions and spectral types and has entries for (as of January 2024) 1 ...

lists a further four companions, all fainter than 11th magnitude, and also describes component D as itself double with two nearly equal components separated by 0.30". Some previous lunar occultation studies found evidence of sub-

arcsecond A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a tu ...

companions, but more recently, a 2021

interferometric Interferometry is a technique which uses the '' interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber opt ...

study concluded that Alcyone is a single star system.

References

External links

* Jim Kaler's Stars, University of Illinoi
ALCYONE (Eta Tauri)

{{DEFAULTSORT:Alcyone (star) Tauri, Eta Taurus (constellation) B-type giants A-type main-sequence stars F-type main-sequence stars Eclipsing binaries 5 Delta Scuti variables Pleiades

Alcyone In Greek mythology, Alcyone (or dubiously Halcyone) (; ) and Ceyx (; ) were a wife and husband who incurred the wrath of the god Zeus for their romantic hubris. Etymology Alkyóne comes from alkyón (), which refers to a sea-bird with a mour ...