Tau2 Hydrae

Tau² Hydrae is a probable astrometric binary^[10] star system in the equatorial constellation of Hydra. Based upon an annual parallax shift of 6.30 mas as seen from Earth, it is located around 520 light years from the Sun. The brighter component is visible to the naked eye with an apparent visual magnitude of +4.56.^[2]

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

Tau² Hydrae

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Hydra
Right ascension	09h 31m 58.92729s[1]
Declination	−01° 11′ 04.7899″[1]
Apparent magnitude (V)	+4.56[2]
Characteristics
Spectral type	A3 V[3]
U−B color index	+0.06[2]
B−V color index	+0.11[2]
Variable type	Suspected[4]
Astrometry
Radial velocity (Rv)	+3.9±0.4[5] km/s
Proper motion (μ)	RA: −12.60[1] mas/yr Dec.: −3.99[1] mas/yr
Parallax (π)	6.30±0.72 mas[1]
Distance	approx. 520 ly (approx. 160 pc)
Absolute magnitude (MV)	−1.43[6]
Details
Radius	4.5[7] R☉
Luminosity	285[8] L☉
Temperature	7,918[8] K
Rotational velocity (v sin i)	54.0±0.6[3] km/s
Other designations
Ukdah, τ2 Hya, 32 Hydrae, BD−00°2211, HD 82446, HIP 46776, HR 3787, SAO 136932.[9]
Database references
SIMBAD	data

The primary member, component A, is an A-type main sequence star with a stellar classification of A3 V.^[3] It is a suspected variable of unknown type, with an amplitude of 0.06 in visual magnitude.^[4] The star has around 4.5^[7] times the radius of the Sun and is radiating about 285 times the solar luminosity from its photosphere at an effective temperature of 7,918 K.^[8]