HD 13908 c
Astrophysical Synthesis & Habitability Characterization
HD 13908 c is a confirmed gas giant exoplanet orbiting the star HD 13908, located approximately 259.5 light-years (79.55 parsecs) from the Solar System. First announced in 2013 by Haute-Provence Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.8 Earth radii (1.14 Jupiter radii) and has a measured mass of 1630.4 Earth masses (5.13 Jupiter masses). Combining its mass and radius yields a mean bulk density of 4.29 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 9.95 g⊕ (97.58 m/s²), and an escape velocity of 126.2 km/s.
In its orbital architecture around HD 13908, HD 13908 c completes one full revolution every 931 Earth days (2.55Julian years) at a semi-major axis of 2.03 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 23.7 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.12 carries the world between 1.7864 AU at periapsis and 2.2736 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 12.800 R⊕, HD 13908 c exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star HD 13908 is classified as a warm F-type star of spectral type F8 V with an effective photospheric temperature of 6,255 K, a radius of 1.67 R☉, a mass of 1.29 M☉, an estimated bolometric luminosity of 3.83 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.9 Gyr and a metallicity of [Fe/H] = 0.01 dex (near-solar heavy-element abundance). From Earth, HD 13908 shines at apparent V-band magnitude 7.52 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 13908 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 13908 c sharing its stellar neighborhood alongside HD 13908 b.
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: Haute-Provence Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 13908 |
| Spectral Type | F8 V |
| Effective Temp (Teff) | 6,255 K |
| Stellar Radius | 1.6700 R☉ |
| Stellar Mass | 1.2900 M☉ |
| Bolometric Luminosity | 3.83 L☉ |
| Metallicity [Fe/H] | 0.010 dex |
| Stellar Age | 2.900 Gyr |
| Apparent Magnitude | V: 7.520 · G: 7.385 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.030000 AU |
| Orbital Period | 931 days |
| Mean Orbital Velocity | 23.7 km/s |
| Orbital Eccentricity (e) | 0.12000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 4.29 g/cm³ (126.2 km/s vesc) |
| Insolation Flux | 0.9705 S⊕ (~1,321 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 259.500 LY (79.552 pc) |