Astronomy:Alcyone (star)

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Short description: Star system in the constellation Taurus


Alcyone
Image of the Pleiades star cluster
Red circle.svg
Alcyone in the Pleiades cluster (circled)
Observation data
Equinox J2000.0]] (ICRS)
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
Age70[10] Myr
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

Coordinates: Sky map 03h 47m 29.0765s, +24° 06′ 18.494″ Alcyone /ælˈsaɪəniː/,[11] designated η Tauri (Eta Tauri, abbreviated Eta Tau, η Tau), is a star 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, some of which are members of the same cluster.[citation needed]

Nomenclature

Eta Tauri is the star's Bayer designation. The name Alcyone originates in Greek mythology; she is one of the seven daughters of Atlas and Pleione known as the Pleiades. In 2016, the International Astronomical Union (IAU) organized a Working Group on Star Names (WGSN)[12] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[13] 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.[14]

In Chinese, 昴宿 (Mǎo Xiù), meaning Hairy Head, refers to an asterism consisting Alcyone, Electra, Taygeta, Asterope, Maia, Merope, and Atlas.[15] Consequently, the Chinese name for Alcyone itself is 昴宿六 (Mǎo Xiù liù), "the Sixth Star of Hairy Head".[16]

Physical properties

Alcyone Is a blue-white B-type giant, similar the other bright B-type stars in the Pleiades cluster. With an apparent magnitude of +2.87 (absolute magnitude = −2.39), it is the brightest and most luminous star in the Pleiades. The spectral type of B7IIIe indicates that emission lines are present in its spectrum. Like many Be stars, Alcyone has created a gaseous disk flung into orbit around the star from its equator.

Alcyone has a high rotational velocity, which causes it to have an ellipsoidal shape. Its effective radius is almost ten times that of the Sun, but the actual radius is lesser at poles and greater at the equator. Its effective temperature is approximately 12,300 K, with the actual temperature being greater at the poles and lesser at the equator. Its bolometric luminosity is 2,030 times solar.

The age of the Pleiades is typically calculated to be around 130 million years, but Alcyone itself appears to be younger, less than 100 million years. Alcyone may be a blue straggler or models may not be deriving an accurate age for stars of this type.[10]

Companions

A light curve for Alcyone, adapted from White et al. (2017)[8]

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;[17] and D is a magnitude 9.15 F3 main-sequence star.[18] V647 Tau varies from magnitude +8.25 to +8.30 over 1.13 hours.[19]

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".[20]

Some previous lunar occultation studies found evidence of sub-arcsound companions, but more recently, a 2021 interferometric study concluded that Alcyone is a single star system.[21]

See also

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. doi:10.1051/0004-6361:20078357. Bibcode: 2007A&A...474..653V. https://www.aanda.org/articles/aa/full/2007/41/aa8357-07/aa8357-07.html.  Vizier catalog entry
  2. ↑ 2.0 2.1 2.2 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. ↑ 3.0 3.1 3.2 3.3 Touhami, Y.; Gies, D. R.; Schaefer, G. H.; McAlister, H. A.; Ridgway, S. T.; Richardson, N. D.; Matson, R.; Grundstrom, E. D. et al. (2013). "A CHARA Array Survey of Circumstellar Disks around Nearby Be-type Stars". The Astrophysical Journal 768 (2): 128. doi:10.1088/0004-637X/768/2/128. Bibcode: 2013ApJ...768..128T. 
  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. doi:10.1134/S1063773706110065. Bibcode: 2006AstL...32..759G. 
  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. doi:10.1126/science.1256101. PMID 25170147. Bibcode: 2014Sci...345.1029M. 
  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. doi:10.1007/s10509-006-9173-1. Bibcode: 2006Ap&SS.306..113Z. 
  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. doi:10.1051/0004-6361:20053051. Bibcode: 2005A&A...441..235Z. 
  8. ↑ 8.0 8.1 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. doi:10.1093/mnras/stx1050. Bibcode: 2017MNRAS.471.2882W. 
  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. ↑ 10.0 10.1 Brandt, Timothy D.; Huang, Chelsea X. (2015). "Bayesian Ages for Early-type Stars from Isochrones Including Rotation, and a Possible Old Age for the Hyades". The Astrophysical Journal 807 (1): 58. doi:10.1088/0004-637X/807/1/58. Bibcode: 2015ApJ...807...58B. 
  11. ↑ "Alcyone". Merriam-Webster Dictionary. https://www.merriam-webster.com/dictionary/Alcyone. 
  12. ↑ "IAU Working Group on Star Names (WGSN)". https://www.iau.org/science/scientific_bodies/working_groups/280/. Retrieved 22 May 2016. 
  13. ↑ "Bulletin of the IAU Working Group on Star Names, No. 1". http://www.pas.rochester.edu/~emamajek/WGSN/WGSN_bulletin1.pdf. Retrieved 28 July 2016. 
  14. ↑ "IAU Catalog of Star Names". http://www.pas.rochester.edu/~emamajek/WGSN/IAU-CSN.txt. Retrieved 28 July 2016. 
  15. ↑ (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.
  16. ↑ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 , Hong Kong Space Museum. Accessed on line November 23, 2010.
  17. ↑ Gebran, M.; Monier, R. (2008). "Chemical composition of a and F dwarfs members of the Pleiades open cluster". Astronomy and Astrophysics 483 (2): 567. doi:10.1051/0004-6361:20079271. Bibcode: 2008A&A...483..567G. 
  18. ↑ 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. 
  19. ↑ Samus, N. N. 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. 
  20. ↑ 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. doi:10.1086/323920. Bibcode: 2001AJ....122.3466M. 
  21. ↑ Hutter, D. J.; Tycner, C.; Zavala, R. T.; Benson, J. A.; Hummel, C. A.; Zirm, H. (2021-12-01). "Surveying the Bright Stars by Optical Interferometry III: A Magnitude-Limited Multiplicity Survey of Classical Be-Stars". The Astrophysical Journal Supplement Series 257 (2): 69. doi:10.3847/1538-4365/ac23cb. ISSN 0067-0049. Bibcode: 2021ApJS..257...69H. 

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