Tau2 Capricorni

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]

For other stars with this Bayer designation, see τ Capricorni.

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]
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
τ2 Cap, 14 Capricorni, BD−15°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]