Tau2 Capricorni
Star in the constellation Capricornus
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Tau2 Capricorni is a triple star[2] system in the constellation Capricornus. Its name is a Bayer designation that is Latinized from Ï2 Capricorni, and abbreviated Tau2 Cap or Ï2 Cap. This system is located at a distance of approximately 1,100 light years from Earth based on parallax. It has a blue-white hue and a combined apparent visual magnitude of +5.20.[2] Because it is positioned near the ecliptic, Ï2 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 | â14° 57â² 17.1352â³[1] |
| Apparent magnitude (V) | 5.20 (5.77 + 9.5 + 6.19)[2] |
| Characteristics | |
| Spectral type | B6III + ? + B6IV[2] |
| Astrometry | |
| Radial velocity (Rv) | â4.1±2.1[3] km/s |
| Proper motion (μ) | RA: +2.62[1] mas/yr Dec.: â19.46[1] mas/yr |
| Parallax (Ï) | 2.87±0.65 mas[1] |
| Distance | approx. 1,100 ly (approx. 350 pc) |
| Orbit[4] | |
| Primary | Ï2 Cap A |
| Name | Ï2 Cap B |
| Period (P) | 420 yr |
| Semi-major axis (a) | 0.48â³ |
| Eccentricity (e) | 0.73 |
| Inclination (i) | 75° |
| Longitude of the node (Ω) | 93.0° |
| Periastron epoch (T) | 1915.0 |
| Argument of periastron (Ï) (secondary) | 270° |
| Details | |
| A | |
| Mass | 5.01±0.35[5] Mâ |
| Luminosity (bolometric) | 1,893[5] Lâ |
| 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 | |
| Ï2 Cap, 14 Capricorni, BDâ15°5743, GC 28748, HD 196662, HIP 101923, HR 7889, SAO 163771, ADS 14099, CCDM J20392-1457, WDS J20393-1457[8] | |
| 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]