Alcyone

Observational Data
Designation |  Eta Tauri
25 Tauri
Right ascension |  03h 47m 29.0766s[1]
Declination |  +24° 06′ 18.4883″[1]
Constellation |  Taurus
Type of object |  Giant star
Magnitude |  Apparent Mag: +2.86[1]
Absolute Mag: -2.61[2]
Astrometry
Distance from Earth |  403.17 ly[2]
Radial velocity |  5.4±1.2 km/s[1]
Proper motion |  RA: 19.34 mas/yr[1]
Dec.: -43.67 mas[1]
Parallax |  8.09±0.42 mas[1]

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 8th 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.

## References[edit]

1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Alcyone from the SIMBAD Astronomical Database
2. ↑ 2.0 2.1 2.2 2.3 Alcyone, Eta Tauri, 25 Tauri, HD23630, HIP17702, HR1165. Retrieved on 2019-01-18.
3. ↑ 3.0 3.1 3.2 3.3 Alcyone (Eta Tauri). Retrieved on 2019-01-18.
4. ↑ 4.0 4.1 4.2 Alcyone – Star Facts. Retrieved on 2019-01-18.

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