HD 37124 d
Astrophysical Synthesis & Habitability Characterization
HD 37124 d is a confirmed gas giant exoplanet orbiting the star HD 37124, located approximately 103.3 light-years (31.66 parsecs) from the Solar System. First announced in 2005 by W. M. Keck Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 14 Earth radii (1.25 Jupiter radii) and has a measured mass of 221.21 Earth masses (0.7 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.44 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.13 g⊕ (11.08 m/s²), and an escape velocity of 44.5 km/s.
In its orbital architecture around HD 37124, HD 37124 d completes one full revolution every 1862 Earth days (5.1Julian years) at a semi-major axis of 2.807 AU (corresponding to the middle-system regime between Mars at 1.52 AU and Jupiter at 5.20 AU). Its mean orbital velocity is approximately 16.4 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.16 carries the world between 2.3579 AU at periapsis and 3.2561 AU at apoapsis, driving measurable seasonal insolation cycles.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 160 K (-113°C / -171°F) and an incident flux of 0.10 S⊕ (~133 W/m²), surface water and volatile species on HD 37124 d would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 37124 is classified as a solar-type yellow star of spectral type G4 V with an effective photospheric temperature of 5,699 K, a radius of 0.9492 R☉, a mass of 0.85 M☉, an estimated bolometric luminosity of 0.853 L☉. Stellar evolution modeling indicates an estimated stellar age of 4 Gyr and a metallicity of [Fe/H] = -0.44 dex (metal-poor relative to the Sun). From Earth, HD 37124 shines at apparent V-band magnitude 7.68 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 37124 system is a multi-planet architecture hosting 3 confirmed worlds, with HD 37124 d sharing its stellar neighborhood alongside HD 37124 b, HD 37124 c.
Methodology: Computed using the Schulze-Makuch et al. (2011) weighted metric comparing physical interior (radius, estimated density) and surface thermal regime (escape velocity, equilibrium temperature).
Discovery Facility: W. M. Keck Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 37124 |
| Spectral Type | G4 V |
| Effective Temp (Teff) | 5,699 K |
| Stellar Radius | 0.9492 R☉ |
| Stellar Mass | 0.8500 M☉ |
| Bolometric Luminosity | 0.853 L☉ |
| Metallicity [Fe/H] | -0.440 dex |
| Stellar Age | 4.000 Gyr |
| Apparent Magnitude | V: 7.680 · G: 7.472 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.807000 AU |
| Orbital Period | 1862 days |
| Mean Orbital Velocity | 16.4 km/s |
| Orbital Eccentricity (e) | 0.16000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.44 g/cm³ (44.5 km/s vesc) |
| Insolation Flux | 0.0980 S⊕ (~133 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 103.300 LY (31.663 pc) |