Tau2 Capricorni
Star in the constellation Capricornus / From Wikipedia, the free encyclopedia
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]
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 |
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]