Alcyone

Alcyone (Eta Tauri, 25 Tauri) is a giant star situated in the constellation of Taurus, the bull.^[2] The star the brightest star in the Pleiades, the fifth brightest in Taurus and can be seen with the unaided eye.^[3] Its name means "the central one" in Greek.^[4] In Greek mythology, Alcyone was the Atlantid nymph who would later become the mother of Hyrieus. In China, it is often referred to as, “the Sixth Star of the Hairy Head.” ^[4]

Like many other stars, Alcyone is actually a system of several stars. The primary (designated Alcyone A) is comprised of an eclipsing binary. Three smaller and fainter stars, designated Alcyone B, C and D, orbit Alcyone A. Alcyone B and C are 8^th magnitude stars. Alcyone C is a Delta-Scuti variable star.^[3] Its magnitude varies slightly with a period of 1.13 hours between +8.25 to +8.30. Alycone D is an F-type star and is a little fainter than all the rest, with a magnitude of +8.7.^[3]

The Alcyone system lies 403.17 light years from Earth and approximately 24,500 light years from the centre fo the galaxy.^[2] With a spectral type of B7 IIIe, Alycone A i thought to have a radius 8.40 solar radii and a mass equal to 6 solar masses. As a blue star is very hot with a surface temperature of some 13,000 kelvin.^[4] It also have an exceptionally quick rotation rate; its equator moves at 200 km/s which is over 100 times larger than the equivalent for the Sun.^[3] The centrifugal force generated by this rotation has caused gas to be spun into a light emitting disk surrounding the star's equator.

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