Alcyone (star)

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This article is about the star. For other uses, see Alcyone (disambiguation).
Alcyone, η Tau
M45map.jpg
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]
Characteristics
Spectral type B7IIIe[3]
U−B color index -0.35[4]
B−V color index -0.09[4]
Variable type suspected
Astrometry
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
Details
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
SIMBAD data

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.

Overview[edit]

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]

References[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]