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] |
Characteristics | |
Spectral type | B6III + ? + B6IV[2] |
Astrometry | |
Radial velocity (Rv) | −4.1±2.1[3] km/s |
Proper motion (μ) | RA: +2.62[1] mas/yr Dec.: −19.46[1] mas/yr |
Parallax (π) | 2.87 ± 0.65 mas[1] |
Distance | approx. 1,100 ly (approx. 350 pc) |
Orbit[4] | |
Primary | τ2 Cap A |
Companion | τ2 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) (secondary) | 270° |
Details | |
A | |
Mass | 5.01±0.35[5] M☉ |
Luminosity (bolometric) | 1,893[5] L☉ |
Surface gravity (log g) | 3.90[6] cgs |
Temperature | 15,439[6] K |
Metallicity [Fe/H] | 0.14[6] dex |
Rotational velocity (v sin i) | 170[7] km/s |
Other designations | |
Database references | |
SIMBAD | data |
Tau2 Capricorni, Latinized from τ2 Capricorni, is a triple star[2] system in the constellation Capricornus. It is approximately 1,100 light years from Earth based on parallax. The system has a blue-white hue and a combined apparent visual magnitude of +5.20.[2] Because it is positioned near the ecliptic, τ2 Capricorni can be occulted by the Moon.[9]
The primary, component A, is a B-type giant with a stellar classification of B6III and an apparent magnitude of +5.8.[2] It has five[5] times the mass of the Sun and is spinning rapidly with a projected rotational velocity of 170 km/s.[7] The star is radiating 1,893[5] times the luminosity of the Sun from its photosphere at an effective temperature of 15,439 K.[6]
At an angular separation of only 0.34 arcseconds is the companion, component B, a B-type subgiant star with a class of B6IV[2] and an apparent magnitude of +6.3. These two stars orbit around their common centre of mass once every 420 years.[4] 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.[10]
vanLeeuwen2007
was invoked but never defined (see the help page).Eggleton2008
was invoked but never defined (see the help page).Kharchenko2007
was invoked but never defined (see the help page).Hartkopf2006
was invoked but never defined (see the help page).Hohle2010
was invoked but never defined (see the help page).Koleva2012
was invoked but never defined (see the help page).Abt2002
was invoked but never defined (see the help page).SIMBAD
was invoked but never defined (see the help page).Radick1980
was invoked but never defined (see the help page).bsc
was invoked but never defined (see the help page).