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) 2.87[2]
Spectral type B5IIIe[3]
U−B color index −0.34[2]
B−V color index −0.09[2]
Radial velocity (Rv) 5.40[4] 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 136[5] pc
Absolute magnitude (MV) -2.62[6]
Mass 3.4-3.8[7] M
Radius 8.2[8] R
Luminosity 2,030[9] L
Surface gravity (log g) 3.047[3] cgs
Temperature 12,258[3] K
Rotational velocity (v sin i) 149[3] km/s
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 around 100 million years. Alcyone is approximately 440 light years from Earth. 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.


Alcyone is the brightest member of the nearby Pleiades open cluster. There are a number of fainter stars very close to it, all most probably also member of the same cluster. The Catalog of Components of Double and Multiple Stars lists three companions: B is 24 Tau, a magnitude 6.28 A0 main sequence star 117" away; C is V647 Tau, a δ Sct variable star;[10] and D is a magnitude 9.15 F3 main sequence star.[11] V647 Tau varies from magnitude +8.25 to +8.30 over 1.13 hours.[12]

The Washington Double Star Catalog 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".[13]

Star system[edit]

The main star, Alcyone A, consists of three components, the brightest being a B-type giant star. The closest companion has a very low mass and is less than 1 milli-arcsecond away, with a likely orbital period just over four days. The other star is about half the mass of the giant and they are separated by 0.031 arcseconds, or about the distance from the Sun to Jupiter, orbiting in about 830 days.[14]


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. 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 149 km/s, which has created a gaseous disk flung into orbit around the star from its equator.

See also[edit]


  1. ^ a b c d e 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 c Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues 2237. Bibcode:2002yCat.2237....0D. 
  3. ^ a b c d Touhami, Y.; Gies, D. R.; Schaefer, G. H.; McAlister, H. A.; Ridgway, S. T.; Richardson, N. D.; Matson, R.; Grundstrom, E. D.; Ten Brummelaar, T. A.; Goldfinger, P. J.; Sturmann, L.; Sturmann, J.; Turner, N. H.; Farrington, C. (2013). "A CHARA Array Survey of Circumstellar Disks around Nearby Be-type Stars". The Astrophysical Journal 768 (2): 128. arXiv:1302.6135. Bibcode:2013ApJ...768..128T. doi:10.1088/0004-637X/768/2/128. 
  4. ^ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters 32 (11): 759. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. 
  5. ^ Melis, Carl; Reid, Mark J.; Mioduszewski, Amy J.; Stauffer, John R.; et al. (29 August 2014). "A VLBI resolution of the Pleiades distance controversy". Science 345 (6200): 1029–1032. arXiv:1408.6544. Bibcode:2014Sci...345.1029M. doi:10.1126/science.1256101. PMID 25170147. 
  6. ^ Zhang, P.; Liu, C. Q.; Chen, P. S. (2006). "Absolute Magnitudes of Be Stars Based on Hipparcos Parallaxes". Astrophysics and Space Science 306 (3): 113. Bibcode:2006Ap&SS.306..113Z. doi:10.1007/s10509-006-9173-1. 
  7. ^ Zorec, J.; Frémat, Y.; Cidale, L. (2005). "On the evolutionary status of Be stars. I. Field Be stars near the Sun". Astronomy and Astrophysics 441: 235. arXiv:astro-ph/0509119. Bibcode:2005A&A...441..235Z. doi:10.1051/0004-6361:20053051. 
  8. ^ 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 (3): 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601 
  9. ^ Harmanec, P. (2000). "Physical Properties and Evolutionary Stage of Be Stars". The Be Phenomenon in Early-Type Stars 214: 13. Bibcode:2000ASPC..214...13H. 
  10. ^ Gebran, M.; Monier, R. (2008). "Chemical composition of a and F dwarfs members of the Pleiades open cluster". Astronomy and Astrophysics 483 (2): 567. arXiv:0802.3148. Bibcode:2008A&A...483..567G. doi:10.1051/0004-6361:20079271. 
  11. ^ Dommanget, J.; Nys, O. (1994). "Catalogue of the Components of Double and Multiple stars (CCDM). First edition". Obs. R. Belg 115. Bibcode:1994CoORB.115.....D. 
  12. ^ Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally published in: 2009yCat....102025S 1. Bibcode:2009yCat....102025S. 
  13. ^ Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920. 
  14. ^ Tokovinin, A. A. (1997). "MSC - a catalogue of physical multiple stars". A&A Supplement Series 124: 75. Bibcode:1997A&AS..124...75T. doi:10.1051/aas:1997181. 

External links[edit]