GJ 251 b
Astrophysical Synthesis & Habitability Characterization
GJ 251 b is a confirmed super-earth exoplanet orbiting the star GJ 251, located approximately 18.2 light-years (5.58 parsecs) from the Solar System. First announced in 2020 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 1.79 Earth radii and has a measured mass of 3.85 Earth masses. Combining its mass and radius yields a mean bulk density of 3.7 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.2 g⊕ (11.77 m/s²), and an escape velocity of 16.4 km/s.
In its orbital architecture around GJ 251, GJ 251 b completes one full revolution every 14.237 Earth days at a semi-major axis of 0.0808 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 61.7 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
ℹ️ Thermal & Atmospheric Regime: Current photometric and spectroscopic constraints for GJ 251 b place it outside the conservative habitable zone definition pending further atmospheric characterization.
The host star GJ 251 is classified as a low-mass red dwarf of spectral type M3.0 V with an effective photospheric temperature of 3,342 K, a radius of 0.36 R☉, a mass of 0.35 M☉, an estimated bolometric luminosity of 0.015 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.8 Gyr and a metallicity of [Fe/H] = 0.07 dex (metal-rich relative to the Sun). From Earth, GJ 251 shines at apparent V-band magnitude 9.89 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The GJ 251 system is a multi-planet architecture hosting 2 confirmed worlds, with GJ 251 b sharing its stellar neighborhood alongside GJ 251 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 251 |
| Spectral Type | M3.0 V |
| Effective Temp (Teff) | 3,342 K |
| Stellar Radius | 0.3600 R☉ |
| Stellar Mass | 0.3500 M☉ |
| Bolometric Luminosity | 0.015 L☉ |
| Metallicity [Fe/H] | 0.070 dex |
| Stellar Age | 6.800 Gyr |
| Apparent Magnitude | V: 9.890 · G: 8.855 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.080800 AU |
| Orbital Period | 14.237 days |
| Mean Orbital Velocity | 61.7 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 3.7 g/cm³ (16.4 km/s vesc) |
| Insolation Flux | 2.3700 S⊕ (~3,226 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 18.200 LY (5.581 pc) |