HD 27894 c
Astrophysical Synthesis & Habitability Characterization
HD 27894 c 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 8.24 Earth radii (0.74 Jupiter radii) and has a measured mass of 51.488 Earth masses (0.16 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.51 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.76 g⊕ (7.45 m/s²), and an escape velocity of 28 km/s.
In its orbital architecture around HD 27894, HD 27894 c completes one full revolution every 36.07 Earth days at a semi-major axis of 0.198 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 59.7 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.015 (ranging from 0.195 AU at periapsis to 0.201 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 499 K (+226°C / +439°F) and receiving 9.07 S⊕ (~12,346 W/m²), HD 27894 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
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 0.8 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 c sharing its stellar neighborhood alongside HD 27894 b, HD 27894 d.
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 | 0.8000 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) | 0.198000 AU |
| Orbital Period | 36.07 days |
| Mean Orbital Velocity | 59.7 km/s |
| Orbital Eccentricity (e) | 0.01500 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.51 g/cm³ (28 km/s vesc) |
| Insolation Flux | 9.0713 S⊕ (~12,346 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 142.900 LY (43.821 pc) |