Mu Hydrae

μ Hydrae, Latinised as Mu Hydrae, is a solitary,^[8] orange-hued star in the equatorial constellation of Hydra. It is visible to the naked eye with an apparent visual magnitude of 3.83.^[2] Positioned just 1.8° to the south-southwest is the planetary nebula NGC 3242.^[9] Mu Hydrae has an annual parallax shift of 13.93 mas,^[1] which yields a distance estimate of 234 light years.

μ Hydrae

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Hydra
Right ascension	10h 26m 05.42630s[1]
Declination	−14° 19′ 56.2675″[1]
Apparent magnitude (V)	3.83[2]
Characteristics
Spectral type	K4 III[3]
U−B color index	+1.83[2]
B−V color index	+1.47[2]
Variable type	Suspected[4]
Astrometry
Radial velocity (Rv)	+40.81±0.36[5] km/s
Proper motion (μ)	RA: −129.17[1] mas/yr Dec.: −79.76[1] mas/yr
Parallax (π)	13.93±0.18 mas[1]
Distance	234 ± 3 ly (71.8 ± 0.9 pc)
Absolute magnitude (MV)	−0.45[6]
Details[5]
Radius	45 R☉
Luminosity	332[6] L☉
Surface gravity (log g)	1.5 cgs
Temperature	3,999±8 K
Metallicity [Fe/H]	−0.12 dex
Rotational velocity (v sin i)	6.0 km/s
Other designations
μ Hya, 42 Hydrae, BD−16° 3052, FK5 389, HD 90432, HIP 51069, HR 4094, SAO 155980.[7]
Database references
SIMBAD	data

This is an evolved K-type giant star with a stellar classification of K4 III,^[3] having used up its core hydrogen and has expanded to around 45 times the radius of the Sun.^[5] It is a suspected variable star, with a brightness that varies about 0.03 in magnitude.^[4] The relatively cool outer atmosphere has an effective temperature of 3999 K.^[5]