Chi1 Hydrae

For other stars with this Bayer designation, see χ Hydrae

Chi¹ Hydrae (χ¹ Hydrae) is a binary star^[4] in the equatorial constellation of Hydra. It originally received the Flamsteed designation of 9 Crateris before being placed in the Hydra constellation.^[11] Based upon an annual parallax shift of 22.8 mas as seen from Earth, it is located about 143 light years from the Sun. It is visible to the naked eye with a combined apparent visual magnitude of 4.94.^[3]

Chi¹ Hydrae

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Hydra[1]
Right ascension	11h 05m 19.90766s[2]
Declination	−27° 17′ 36.9957″[2]
Apparent magnitude (V)	4.94[3]
Characteristics
Spectral type	F4 V + F7 V[4]
U−B color index	+0.04[3]
B−V color index	+0.36[3]
Astrometry
Radial velocity (Rv)	+19.1±1.6[5] km/s
Proper motion (μ)	RA: −190.728[6] mas/yr Dec.: −6.273[6] mas/yr
Parallax (π)	22.8323±0.1828 mas[6]
Distance	143 ± 1 ly (43.8 ± 0.4 pc)
Absolute magnitude (MV)	1.74[7]
Orbit[8]
Period (P)	7.5535±0.0064 yr
Semi-major axis (a)	0.1388±0.0016″
Eccentricity (e)	0.349±0.015
Inclination (i)	96.50±0.84°
Longitude of the node (Ω)	224.00±0.59°
Periastron epoch (T)	1983.455 ± 0.084
Argument of periastron (ω) (secondary)	343.0±4.3°
Details
χ1 Hya A
Mass	1.93[9] M☉
Radius	3.19[6] R☉
Luminosity	17.798[6] L☉
Temperature	6,637[6] K
Metallicity [Fe/H]	−0.10[7] dex
Age	1.3[7] Gyr
χ1 Hya B
Mass	1.93[9] M☉
Other designations
χ1 Hya, CD−26°8338, FK5 419, GJ 3642, HD 96202, HIP 54204, HR 4314, SAO 179514[10]
Database references
SIMBAD	data

The two components of this system appear to have equal masses of 1.93 times the mass of the Sun.^[8] The pair circle each other with an orbital period of 7.55 years with an eccentricity of 0.35.^[8]