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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]
| 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☉ |
| Radius | 0.74[9] R☉ |
| Luminosity | 0.389[10] L☉ |
| Surface gravity (log g) | 4.61±0.05[11] cgs |
| Temperature | 5,205±23[11] K |
| Metallicity [Fe/H] | −0.61±0.02[11] dex |
| Rotational velocity (v sin i) | 2[12] km/s |
| Age | 11.7[8] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
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,[13] 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,[11] giving an orange hue. It radius of 0.74 R☉[9] yields a luminosity only 38% that of the Sun.[10] 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.[11] HD 39194's projected rotational velocity is similar to the Sun's, with the value being 2 km/s.[12]
Three planet candidates around this star were first reported in a 2011 preprint.[14] After 10 years of observations, a team of astronomers confirmed 3 super-Earths circling HD 39194 in eccentric orbits;[10] none of the planets are in the habitable zone. HD 39194 b and d have similar masses.
This star was selected as a potential candidate for future exoplanet imaging missions in 2015.[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 | — | — |
- List of multiplanetary systems
- Pi Mensae, another exoplanet-hosting star in the same constellation.
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