GJ 1148 c
Astrophysical Synthesis & Habitability Characterization
GJ 1148 c is a confirmed gas giant exoplanet orbiting the star GJ 1148, located approximately 35.9 light-years (11.01 parsecs) from the Solar System. First announced in 2017 by Calar Alto Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 9.71 Earth radii (0.87 Jupiter radii) and has a measured mass of 68.06 Earth masses (0.21 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.41 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.72 g⊕ (7.06 m/s²), and an escape velocity of 29.6 km/s.
In its orbital architecture around GJ 1148, GJ 1148 c completes one full revolution every 532.58 Earth days (1.46Julian years) at a semi-major axis of 0.912 AU (comparable to the inner terrestrial zone between Venus, Earth at 1.00 AU, and Mars at 1.52 AU). Its mean orbital velocity is approximately 18.6 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.342, swinging from 0.6001 AU at periapsis out to 1.2239 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 99 K (-174°C / -281°F) and an incident flux of 0.02 S⊕ (~22 W/m²), surface water and volatile species on GJ 1148 c would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star GJ 1148 is classified as a low-mass red dwarf of spectral type M5 with an effective photospheric temperature of 3,287 K, a radius of 0.3585 R☉, a mass of 0.344 M☉, an estimated bolometric luminosity of 0.013 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.16 dex (metal-rich relative to the Sun). From Earth, GJ 1148 shines at apparent V-band magnitude 11.939 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The GJ 1148 system is a multi-planet architecture hosting 2 confirmed worlds, with GJ 1148 c sharing its stellar neighborhood alongside GJ 1148 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: Calar Alto Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | GJ 1148 |
| Spectral Type | M5 |
| Effective Temp (Teff) | 3,287 K |
| Stellar Radius | 0.3585 R☉ |
| Stellar Mass | 0.3440 M☉ |
| Bolometric Luminosity | 0.013 L☉ |
| Metallicity [Fe/H] | 0.160 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 11.939 · G: 10.577 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.912000 AU |
| Orbital Period | 532.58 days |
| Mean Orbital Velocity | 18.6 km/s |
| Orbital Eccentricity (e) | 0.34200 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.41 g/cm³ (29.6 km/s vesc) |
| Insolation Flux | 0.0163 S⊕ (~22 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 35.900 LY (11.014 pc) |