Tau2 Capricorni

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Tau2 Capricorni
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Capricornus
Right ascension 20h 39m 16.31779s[1]
Declination +14° 57′ 17.1352″[1]
Apparent magnitude (V) 5.20 (5.77 + 9.5 + 6.19)[2]
Spectral type B6III + ? + B6IV[2]
Proper motion (μ) RA: +2.62[1] mas/yr
Dec.: −19.46[1] mas/yr
Parallax (π)2.87 ± 0.65[1] mas
Distanceapprox. 1,100 ly
(approx. 350 pc)
Primaryτ2 Cap A
Companionτ2 Cap B
Period (P)420 yr
Semi-major axis (a)0.48″
Eccentricity (e)0.73
Inclination (i)75°
Longitude of the node (Ω)93.0°
Periastron epoch (T)1915.0
Argument of periastron (ω)
Other designations
τ2 Cap, 14 Cap, BD−15° 5743, GC 28748, HD 196662, HIP 101923, HR 7889, SAO 163771, ADS 14099, CCDM J20392-1457[4]
Database references

Tau2 Capricorni2 Capricorni) is a triple star[2] system in the constellation Capricornus. It is approximately 1,100 light years from Earth. The system has a combined apparent magnitude of +5.20.[2] Because it is near the ecliptic, τ2 Capricorni can be occulted by the Moon, and also (rarely) by planets.

The primary component, τ2 Capricorni A, is a blue-white B-type giant with an apparent magnitude of +5.8. At a distance of only 0.34 arcseconds is the second component, τ2 Capricorni B, a blue-white B-type subgiant with an apparent magnitude of +6.3. These two stars orbit around their common centre of mass once every 420 years.[3] A possible third component with an apparent magnitude of +9.5,[2] detected by studying the star during occultation, is located 0.052 arcseconds away from the A component.


  1. ^ a b c d e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d e Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878Freely accessible, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x. 
  3. ^ a b Hartkopf, W. I.; et al. (June 30, 2006), Sixth Catalog of Orbits of Visual Binary Stars, United States Naval Observatory, retrieved 2017-06-02. 
  4. ^ "tau Cap". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-08-30.