GJ 1148 b
Astrophysical Synthesis & Habitability Characterization
GJ 1148 b 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 2010 by W. M. Keck Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 11.9 Earth radii (1.06 Jupiter radii) and has a measured mass of 96.7 Earth masses (0.3 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.32 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.68 g⊕ (6.67 m/s²), and an escape velocity of 31.9 km/s.
In its orbital architecture around GJ 1148, GJ 1148 b completes one full revolution every 41.38 Earth days at a semi-major axis of 0.166 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 43.6 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.38, swinging from 0.1029 AU at periapsis out to 0.2291 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 11.900 R⊕, GJ 1148 b 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 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 b sharing its stellar neighborhood alongside GJ 1148 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: W. M. Keck 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) | 0.166000 AU |
| Orbital Period | 41.38 days |
| Mean Orbital Velocity | 43.6 km/s |
| Orbital Eccentricity (e) | 0.38000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.32 g/cm³ (31.9 km/s vesc) |
| Insolation Flux | 0.4906 S⊕ (~668 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 35.900 LY (11.014 pc) |