6 Hydrae

This article is about a Hydrae and is not to be confused with A Hydrae or α Hydrae.

6 Hydrae is a single^[7] star in the equatorial constellation of Hydra,^[6] located 373 light-years away from the Sun.^[1] It has the Bayer designation a Hydrae; 6 Hydrae is the Flamsteed designation. This object is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.98.^[2] It is moving closer to the Earth with a heliocentric radial velocity of −8 km/s.^[4] Eggen (1995) listed it as a proper motion candidate for membership in the IC 2391 supercluster.^[8]

6 Hydrae

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Hydra
Right ascension	08h 40m 01.47182s[1]
Declination	−12° 28′ 31.3433″[1]
Apparent magnitude (V)	4.98[2]
Characteristics
Evolutionary stage	giant
Spectral type	K3 III[3]
B−V color index	1.415±0.001[2]
Astrometry
Radial velocity (Rv)	−7.8±0.6[4] km/s
Proper motion (μ)	RA: −81.619[1] mas/yr Dec.: −1.646[1] mas/yr
Parallax (π)	8.7394±0.1769 mas[1]
Distance	373 ± 8 ly (114 ± 2 pc)
Absolute magnitude (MV)	−0.40[2]
Details
Radius	32.7+0.5 −2.6[1] R☉
Luminosity	267±6[1] L☉
Surface gravity (log g)	1.91[5] cgs
Temperature	4,080+173 −30[1] K
Metallicity [Fe/H]	−0.21[5] dex
Other designations
a Hya, 6 Hya, BD−11°2420, HD 73840, HIP 42509, HR 3431, SAO 154515[6]
Database references
SIMBAD	data

This is an aging giant star with a stellar classification of K3 III,^[3] which indicates it has exhausted the hydrogen at its core and evolved away from the main sequence. As a consequence, it has expanded to 33^[1] times the radius of the Sun. The star is radiating 267^[1] times the luminosity of the Sun from its swollen photosphere at an effective temperature of 4,080 K.^[1]