HD 3167 d
Astrophysical Synthesis & Habitability Characterization
HD 3167 d is a confirmed sub-neptune exoplanet orbiting the star HD 3167, located approximately 154.2 light-years (47.29 parsecs) from the Solar System. First announced in 2017 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 2.61 Earth radii and has a measured mass of 7.3 Earth masses. Combining its mass and radius yields a mean bulk density of 2.26 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.07 g⊕ (10.49 m/s²), and an escape velocity of 18.7 km/s.
In its orbital architecture around HD 3167, HD 3167 d completes one full revolution every 8.397 Earth days at a semi-major axis of 0.077 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 99.8 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.35, swinging from 0.0501 AU at periapsis out to 0.104 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 865 K (+592°C / +1098°F) and receiving 88.90 S⊕ (~120,993 W/m²), HD 3167 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 3167 is classified as an orange K-type star of spectral type K0 V with an effective photospheric temperature of 5,338 K, a radius of 0.871 R☉, a mass of 0.864 M☉, an estimated bolometric luminosity of 0.553 L☉. Stellar evolution modeling indicates an estimated stellar age of 8.4 Gyr and a metallicity of [Fe/H] = 0.037 dex (near-solar heavy-element abundance). From Earth, HD 3167 shines at apparent V-band magnitude 8.97 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 3167 system is a multi-planet architecture hosting 4 confirmed worlds, with HD 3167 d sharing its stellar neighborhood alongside HD 3167 b, HD 3167 c, HD 3167 e.
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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 3167 |
| Spectral Type | K0 V |
| Effective Temp (Teff) | 5,338 K |
| Stellar Radius | 0.8710 R☉ |
| Stellar Mass | 0.8640 M☉ |
| Bolometric Luminosity | 0.553 L☉ |
| Metallicity [Fe/H] | 0.037 dex |
| Stellar Age | 8.400 Gyr |
| Apparent Magnitude | V: 8.970 · G: 8.762 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.077000 AU |
| Orbital Period | 8.397 days |
| Mean Orbital Velocity | 99.8 km/s |
| Orbital Eccentricity (e) | 0.35000 |
| Orbital Inclination (i) | 39.0000° |
| Mean Bulk Density | 2.26 g/cm³ (18.7 km/s vesc) |
| Insolation Flux | 88.9000 S⊕ (~120,993 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 154.200 LY (47.290 pc) |