HD 39194

HD 39194 (Gliese 217.2; LHS 210) is a star located in the southern circumpolar constellation Mensa. It has an apparent magnitude of 8.07,^[2] making it readily visible in binoculars but not to the naked eye. The object is relatively close at a distance of 86 light years^[1] but is receding with a heliocentric radial velocity of 13.9 km/s.^[6]

HD 39194

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Mensa
Right ascension	05h 44m 31.9180s[1]
Declination	−70° 08′ 36.858″[1]
Apparent magnitude (V)	8.07±0.01[2]
Characteristics
Spectral type	K0 V[3]
U−B color index	+0.26[4][5]
B−V color index	+0.76[4][5]
Astrometry
Radial velocity (Rv)	13.90±0.10[6] km/s
Proper motion (μ)	RA: −309.273 mas/yr[1] Dec.: +1238.862 mas/yr[1]
Parallax (π)	37.8235±0.0206 mas[1]
Distance	86.23 ± 0.05 ly (26.44 ± 0.01 pc)
Absolute magnitude (MV)	+6.02[7]
Details
Mass	0.71[8] M☉
Luminosity	0.389[9] L☉
Surface gravity (log g)	4.61±0.05[10] cgs
Temperature	5,205±23[10] K
Metallicity [Fe/H]	−0.61±0.02[10] dex
Rotational velocity (v sin i)	2[11] km/s
Age	11.7[8] Gyr
Other designations
CD−70°340, CPD−70°447, GJ 217.2, HD 39194, HIP 27080, SAO 256232, LHS 210
Database references
SIMBAD	data

Characteristics

HD 39194 has a general stellar classification of K0 V,^[3] indicating that it is a K-type main-sequence star. Houk & Cowley found a slightly warmer class of G8 V,^[12] instead making it a G-type main-sequence star. Nevertheless, it has 71% the mass of the Sun^[8] and an effective temperature of 5,205 K,^[10] giving an orange hue. Its photosphere radiates a luminosity only 38% that of the Sun.^[9] HD 39194 is estimated to be 11.7 billion years old^[8] and is extremely chromospherically inactive.^[3] Despite being a planetary host, it has an iron abundance only 24% that of the Sun.^[10] HD 39194's projected rotational velocity is similar to the Sun's, with the value being 2 km/s.^[11]

Planetary system

Three planet candidates around this star were first reported in a 2011 preprint.^[13] After 10 years of observations, a team of astronomers confirmed 3 super-Earths circling HD 39194 in eccentric orbits;^[9] none of the planets are in the habitable zone. HD 39194 b and d have similar masses.

The HD 39194 planetary system^[9]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	≥4.13±0.20 M🜨	0.056±0.001	5.6368±0.0004	<0.207	—	—
c	≥6.29±0.51 M🜨	0.103±0.002	14.030±0.003	<0.154	—	—
d	≥4.13±0.60 M🜨	0.185±0.003	33.91±0.03	<0.333	—	—

See also

• List of multiplanetary systems
• Pi Mensae, another exoplanet-hosting star in the same constellation.