Alcyone (star)

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This article is about the star. For other uses, see Alcyone (disambiguation).
Alcyone, η Tau
Alcyone is the bright star at the center of the map.
Observation data
Epoch J2000      Equinox J2000
Constellation Taurus
Right ascension 03h 47m 29.077s[1]
Declination 24° 06′ 18.49″[1]
Apparent magnitude (V) 2.873[2]
Spectral type B7IIIe[3]
U−B color index -0.35[4]
B−V color index -0.09[4]
Variable type suspected
Radial velocity (Rv) 10.1[2] km/s
Proper motion (μ) RA: 19.34 ± 0.39[1] mas/yr
Dec.: -43.67 ± 0.33[1] mas/yr
Parallax (π) 8.09 ± 0.42[1] mas
Distance 400 ± 20 ly
(124 ± 6 pc)
Absolute magnitude (MV) -2.39
Mass 6[5] M
Radius 8.2[6] R
Luminosity 2,400[5] L
Surface gravity (log g) 3.5[6] cgs
Temperature 12,753 ± 147[6] K
Rotation 215 km/s[3]
Other designations
η Tau, 25 Tau, HR 1165, HD 23630, BD+23 541, FK5 139, HIP 17702, SAO 76199, GC 4541, BDS 1875, CCDM 03474+2407
Database references

Coordinates: Sky map 03h 47m 29.0765s, +24° 06′ 18.494″

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, which is a young cluster, aged at less than 50 million years. Alcyone is approximately 400 light years from Earth.[1] It is named after the mythological figure Alcyone, one of the mythological Pleiades. It is known as 昴宿六 (the Sixth Star of the Hairy Head) in Chinese.


The main star, known as Alcyone A, is a blue-white B-type giant similar to many of the other B-type stars in the Pleiades cluster. It has an apparent magnitude of +2.87 (absolute magnitude = −2.39), and a radius almost 10 times that of the Sun.[5] Its temperature is approximately 13,000 K giving it a total luminosity that is 2,400 times solar. The spectral type of B7IIIe indicates that emission lines are present in its spectrum. Like many Be stars, Alcyone A has a high rotational velocity of 215 km/s,[3] which has created a gaseous disk flung into orbit around the star from its equator.

Star System[edit]

Alcyone 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.

See also[edit]


  1. ^ a b c d e f van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.  Vizier catalog entry
  2. ^ a b "SIMBAD query result: ALCYONE -- Be Star". Centre de Données astronomiques de Strasbourg. Retrieved 2010-06-30. 
  3. ^ a b c "Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR. Centre de Données astronomiques de Strasbourg. Retrieved 2010-06-30. 
  4. ^ a b Johnson, H. L.; Iriarte, B.; Mitchell, R. I.; Wisniewski, W. Z. (1966). "UBVRIJKL photometry of the bright stars." (PDF). Comm. Lunar Plan. Lab., 4. Bibcode:1966CoLPL...4...99J. 
  5. ^ a b c Professor James B. (Jim) Kaler. "ALCYONE (Eta Tauri)". University of Illinois. Archived from the original on 7 July 2010. Retrieved 2010-06-30. 
  6. ^ a b c Underhill, A. B.; et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society 189: 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601 

External links[edit]