GJ 682 c
Astrophysical Synthesis & Habitability Characterization
GJ 682 c is a confirmed sub-neptune exoplanet orbiting the star GJ 682, located approximately 16.3 light-years (5.01 parsecs) from the Solar System. First announced in 2014 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 2.89 Earth radii and has a measured mass of 8.7 Earth masses. Combining its mass and radius yields a mean bulk density of 1.99 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.04 g⊕ (10.2 m/s²), and an escape velocity of 19.4 km/s.
In its orbital architecture around GJ 682, GJ 682 c completes one full revolution every 57.32 Earth days at a semi-major axis of 0.176 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 33.4 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.1 carries the world between 0.1584 AU at periapsis and 0.1936 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 2.890 R⊕, GJ 682 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 GJ 682 is classified as a low-mass red dwarf of spectral type M3.5 V with an effective photospheric temperature of 3,028 K, a radius of 0.2983 R☉, a mass of 0.27 M☉, an estimated bolometric luminosity of 0.00671 L☉. From Earth, GJ 682 shines at apparent V-band magnitude 10.94 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The GJ 682 system is a multi-planet architecture hosting 2 confirmed worlds, with GJ 682 c sharing its stellar neighborhood alongside GJ 682 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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | GJ 682 |
| Spectral Type | M3.5 V |
| Effective Temp (Teff) | 3,028 K |
| Stellar Radius | 0.2983 R☉ |
| Stellar Mass | 0.2700 M☉ |
| Bolometric Luminosity | 0.00671 L☉ |
| Metallicity [Fe/H] | — |
| Stellar Age | — |
| Apparent Magnitude | V: 10.940 · G: 9.570 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.176000 AU |
| Orbital Period | 57.32 days |
| Mean Orbital Velocity | 33.4 km/s |
| Orbital Eccentricity (e) | 0.10000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.99 g/cm³ (19.4 km/s vesc) |
| Insolation Flux | 0.0646 S⊕ (~88 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 16.300 LY (5.007 pc) |