Alpha Tucanae

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Alpha Tucanae
Diagram showing star positions and boundaries of the Tucana constellation and its surroundings
Cercle rouge 100%.svg

Location of α Tucanae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Tucana
Right ascension 22h 18m 30.09478s[1]
Declination –60° 15′ 34.5263″[1]
Apparent magnitude (V) 2.86[2]
Characteristics
Spectral type K3 III[3]
U−B color index +1.54[2]
B−V color index +1.39[2]
Astrometry
Radial velocity (Rv) +45.8[4] km/s
Proper motion (μ) RA: −70.72[1] mas/yr
Dec.: −39.44[1] mas/yr
Parallax (π) 16.33 ± 0.59[1] mas
Distance 200 ± 7 ly
(61 ± 2 pc)
Orbit[5]
Period (P) 4197.7 days
Eccentricity (e) 0.39
Periastron epoch (T) 18666.4
Argument of periastron (ω)
(secondary)
48.5°
Semi-amplitude (K1)
(primary)
7.2 km/s
Other designations
CP−60 7561, FK5 841, HD 211416, HIP 110130, HR 8502, SAO 255193.[6]

Alpha Tucanae (α Tuc, α Tucanae) is a binary star system in the southern circumpolar constellation of Tucana. With an apparent visual magnitude of 2.86,[2] it can be seen with the naked eye from the southern hemisphere. Using parallax measurements, the distance to this system can be estimated as 200 light-years (61 parsecs).[1] A cool star with a surface temperature of 4300 K, it is 424 times as luminous as the sun and 37 times its diameter. It is 2.5 to 3 times as massive. It is unclear what stage of evolution the star is in.[7]

This is a spectroscopic binary, which means that the two stars have not been individually resolved using a telescope, but the presence of the companion has been inferred from measuring changes in the spectrum of the primary. The orbital period of the binary system is 4197.7 days (11.5 years).[5] The primary component has a stellar classification of K3 III,[3] which indicates it is a giant star that has exhausted the supply of hydrogen at its core and evolved away from the main sequence. It has the characteristic orange hue of a K-type star.

References[edit]

  1. ^ a b c d e f van Leeuwen, F. (November 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 
  2. ^ a b c d Johnson, H. L. et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory 4 (99), Bibcode:1966CoLPL...4...99J 
  3. ^ a b Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars 1, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1975mcts.book.....H 
  4. ^ Buscombe, W.; Kennedy, P. M. (1968), "Stellar radial velocities from coudé spectrograms", Monthly Notices of the Royal Astronomical Society 139: 341, Bibcode:1968MNRAS.139..341B, doi:10.1093/mnras/139.3.341 
  5. ^ a b Pourbaix, D. et al. (2004), "SB9: The Ninth Catalogue of Spectroscopic Binary Orbits", Astronomy & Astrophysics 424, Bibcode:2009yCat....102020P 
  6. ^ "alf Tuc -- Spectroscopic binary", SIMBAD (Centre de Données astronomiques de Strasbourg), retrieved 2012-01-20 
  7. ^ Kaler, Jim. "Alpha Tucanae". Stars. University of Illinois. Retrieved 19 October 2013.