| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Taurus |
| Right ascension | 05h 37m 02.4867s[1] |
| Declination | +20° 43′ 50.8346″[1] |
| Apparent magnitude (V) | 7.68[2] |
| Characteristics | |
| Spectral type | G4IV-V[3] |
| B−Vcolor index | 0.667±0.008[2] |
| Astrometry | |
| Radial velocity (Rv) | −23.02±0.09[2] km/s |
| Proper motion (μ) | RA: −79.607±0.184[1]mas/yr Dec.: −420.161±0.166[1]mas/yr |
| Parallax (π) | 31.5536±0.0751 mas[1] |
| Distance | 103.4 ± 0.2 ly (31.69 ± 0.08 pc) |
| Absolute magnitude (MV) | 5.05[2] |
| Details[4] | |
| Mass | 0.81±0.01 M☉[4] 0.92±0.01[5] M☉ |
| Radius | 0.92±0.02 R☉ 0.91+0.01 −0.04[1] R☉ |
| Luminosity | 0.839±0.003 L☉[4] 0.772+0.003 −0.002[1] L☉ |
| Surface gravity (log g) | 4.41±0.01 cgs |
| Temperature | 5,763±22 K |
| Metallicity [Fe/H] | −0.38±0.01 dex[2] −0.45[6] dex |
| Rotational velocity (v sin i) | 3.6[5] km/s |
| Age | 11.8±1.2 Gyr[4] 10.62±1.74[5] Gyr |
| Other designations | |
| BD+20°1018,GJ 209,HD 37124,HIP 26381,SAO 77323,G 100-27[3] | |
| Database references | |
| SIMBAD | data |
HD 37124 is astar in theequatorialconstellation ofTaurus (the Bull), positioned about a half degree to the SSW of the bright starZeta Tauri.[7] Theapparent visual magnitude of this star is 7.68,[2] which is too dim to be visible to the naked eye. It is located at a distance of 103 light years from theSun based onparallax, but is drifting closer with aradial velocity of −23 km/s.[2] Threeextrasolar planets have been found to orbit the star.
Thestellar classification of HD 37124 is G4IV-V, showing a spectrum with blended traits of amain sequence star and a moreevolvedsubgiant star. It is aquiet star with a lowactivity index.[8] This star is smaller than the Sun, with 81–92% of themass of the Sun and around 92% of theSun's radius. It is an older,thick disk[9] star with an age of around 11 billion years, and is spinning with aprojected rotational velocity of 3.6 km/s.[5] Themetallicity of the star, what astronomers term the abundance of heavier elements, is much lower than in the Sun with an iron abundance of 35–41%. It is radiating 77–84% of theSun's luminosity from itsphotosphere at aneffective temperature of 5,763 K.
As of 2011, threeextrasolar planets have been found to orbit the star. Announced on the first of November 1999, the first planet (HD 37124 b)[10][11] was discovered orbiting its parent star around the inner edge of the habitable zone, causing the planet to have a somewhat similarinsolation to that ofVenus. A second planet became apparent by 2003, thought to orbit in a 1940 days on an eccentric orbit,[12] but this was subsequently found to be unstable.[13] Solving this, a three-planet solution was announced in 2005:[14] this contained a second planet (HD 37124 c) orbiting at the outer edge of the habitable zone with an insolation similar to that ofMars, and a third planet, (HD 37124 d). While not obviously in anyorbital resonances in 2005, an updated solution announced in 2011 found planets 'c' and 'd' to likely be in a 2:1 resonance.[15]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | ≥0.675±0.017 MJ | 0.53364±0.00020 | 154.378±0.089 | 0.054±0.028 | — | — |
| c | ≥0.652±0.052 MJ | 1.7100±0.0065 | 885.5±5.1 | 0.125±0.055 | — | — |
| d | ≥0.69±0.059 MJ | 2.807±0.038 | 1,862±38 | 0.16±0.14 | — | — |
