Alcyone (star)

Alcyone /ælˈsaɪəniː/,[10] designated η Tauri (Eta Tauri, abbreviated Eta Tau, η Tau), is a multiple star system in the constellation of Taurus. Approximately 440 light years from the Sun, it is the brightest star in the Pleiades open cluster, which is a young cluster, around 100 million years old. There are a number of fainter stars very close to Alcyone, all likely members of the same cluster.

This article is about the star. For other uses, see Alcyone (disambiguation).
Alcyone
Alcyone in the Pleiades cluster (circled)
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]
Characteristics
Spectral type B5IIIe[3]
U−B color index −0.34[2]
B−V color index −0.09[2]
Astrometry
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
Distance136[5] pc
Absolute magnitude (MV)-2.62[6]
Details
Mass5.9-6.1[7] M☉
Radius9.3±0.7[8] R☉
Luminosity2,030[9] L☉
Surface gravity (log g)3.047[3] cgs
Temperature12,258[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
SIMBADdata

Nomenclature

Eta Tauri is the star's Bayer designation. The name Alcyone originates with Greek mythology; she is one of the seven daughters of Atlas and Pleione known as the Pleiades. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[11] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[12] included a table of the first two batches of names approved by the WGSN; which included Alcyone for this star. It is now so entered in the IAU Catalog of Star Names.[13]

In Chinese, 昴宿 (Mǎo Xiù), meaning Hairy Head, refers to an asterism consisting Alcyone, Electra, Taygeta, Asterope, Maia, Merope and Atlas.[14] Consequently, the Chinese name for Alcyone itself is 昴宿六 (Mǎo Xiù liù), "the Sixth Star of Hairy Head".[15]

Star system

The Catalog of Components of Double and Multiple Stars lists three companions: B is 24 Tauri, a magnitude 6.28 A0 main sequence star 117" away; C is V647 Tauri, a δ Sct variable star;[16] and D is a magnitude 9.15 F3 main sequence star.[17] V647 Tau varies from magnitude +8.25 to +8.30 over 1.13 hours.[18]

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".[19]

The main star, Alcyone A, consists of three components, the brightest being 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.

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.[20]

See also

References
  1. 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. S2CID 18759600. Vizier catalog entry
  2. 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. 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. S2CID 9488327.
  4. Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
  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. S2CID 34750246.
  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. S2CID 122897957.
  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 (1): 235–248. arXiv:astro-ph/0509119. Bibcode:2005A&A...441..235Z. doi:10.1051/0004-6361:20053051. S2CID 17592657.
  8. White, T. R.; et al. (2017). "Beyond the Kepler/K2 bright limit: Variability in the seven brightest members of the Pleiades". Monthly Notices of the Royal Astronomical Society. 471 (3): 2882–2901. arXiv:1708.07462. Bibcode:2017MNRAS.471.2882W. doi:10.1093/mnras/stx1050. S2CID 119221178.
  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. "Alcyone". Merriam-Webster Dictionary.
  11. "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  12. "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
  13. "IAU Catalog of Star Names". Retrieved 28 July 2016.
  14. (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  15. (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2008-10-25 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  16. 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. S2CID 18923359.
  17. 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.
  18. 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.
  19. 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.
  20. Tokovinin, A. A. (1997). "MSC - a catalogue of physical multiple stars". Astronomy and Astrophysics Supplement Series. 124: 75–84. Bibcode:1997A&AS..124...75T. doi:10.1051/aas:1997181.
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