Alcyone (star)

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**Alcyone**
Observation data Equinox J2000.0
Constellation	Taurus
Right ascension	03^h 47^m 29.1^s
Declination	+24° 06' 18"
Apparent magnitude (V)	+2.85
Distance	440 ly (135 pc)
Spectral type	B7IIIe+A0V+A0V+F2V
Other designations
η Tauri, 25 Tauri, HR 1165, HD 23630, BD+23 541, FK5 139, HIP 17702, SAO 76199, GC 4541, BDS 1875, CCDM 03474+2407

For other uses of "Alcyone", see Alcyone (disambiguation).

Alcyone (η Tau / η Tauri / Eta Tauri) is a star system in the constellation Taurus. It is the brightest star in the Pleiades open cluster. Alcyone is approximately 440 light years from Earth.

[edit] Description

The primary component, Alcyone A, is a blue-white B-type giant with an apparent magnitude of +2.85. It is an eclipsing binary, and the two components have a separation of 0.031 arcseconds, or about the distance from the Sun to Jupiter.

The binary star is orbited by three companions. Alcyone B and Alcyone C are both 8th magnitude white A-type dwarfs and are separated from A by 117 and 181 arcseconds respectively. Alcyone D is a yellow-white F-type dwarf, 191 arcseconds from the primary. It has an apparent magnitude of +8.7. Alcyone C is classified as a Delta Scuti type variable star and its brightness varies from magnitude +8.25 to +8.30 over 1.13 hours.

Alcyone A, has a luminosity of 1,400 times that of the Sun and a temperature of almost 13,000 K. The spectral type of B7 IIIe indicates that it is an emission star. A high rotational velocity of some 215 km/s has created a disk of gases flung into orbit around the star from its equator.

It is known as 昴宿六 (the Sixth Star of the Hairy Head) in Chinese.