HD 27894 d
Astrophysical Synthesis & Habitability Characterization
HD 27894 d is a confirmed gas giant exoplanet orbiting the star HD 27894, located approximately 142.9 light-years (43.82 parsecs) from the Solar System. First announced in 2017 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.7 Earth radii (1.13 Jupiter radii) and has a measured mass of 2063.66 Earth masses (6.49 Jupiter masses). Combining its mass and radius yields a mean bulk density of 5.56 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 12.79 g⊕ (125.43 m/s²), and an escape velocity of 142.6 km/s.
In its orbital architecture around HD 27894, HD 27894 d completes one full revolution every 5019.542 Earth days (13.74Julian years) at a semi-major axis of 5.362 AU (a wide outer-system orbit beyond Jupiter's 5.20 AU distance in our Solar System). Its mean orbital velocity is approximately 11.6 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.343, swinging from 3.5228 AU at periapsis out to 7.2012 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 96 K (-177°C / -287°F) and an incident flux of 0.01 S⊕ (~17 W/m²), surface water and volatile species on HD 27894 d would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 27894 is classified as an orange K-type star of spectral type K2 V with an effective photospheric temperature of 4,875 K, a radius of 0.8918 R☉, a mass of 0.81 M☉, an estimated bolometric luminosity of 0.403 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.9 Gyr and a metallicity of [Fe/H] = 0.3 dex (metal-rich relative to the Sun). From Earth, HD 27894 shines at apparent V-band magnitude 9.36 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 27894 system is a multi-planet architecture hosting 3 confirmed worlds, with HD 27894 d sharing its stellar neighborhood alongside HD 27894 b, HD 27894 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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 27894 |
| Spectral Type | K2 V |
| Effective Temp (Teff) | 4,875 K |
| Stellar Radius | 0.8918 R☉ |
| Stellar Mass | 0.8100 M☉ |
| Bolometric Luminosity | 0.403 L☉ |
| Metallicity [Fe/H] | 0.300 dex |
| Stellar Age | 3.900 Gyr |
| Apparent Magnitude | V: 9.360 · G: 9.066 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 5.362000 AU |
| Orbital Period | 5019.542 days |
| Mean Orbital Velocity | 11.6 km/s |
| Orbital Eccentricity (e) | 0.34300 |
| Orbital Inclination (i) | 101.5240° |
| Mean Bulk Density | 5.56 g/cm³ (142.6 km/s vesc) |
| Insolation Flux | 0.0124 S⊕ (~17 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 142.900 LY (43.821 pc) |