Gl 686 b

Astrophysical Synthesis & Habitability Characterization

Gl 686 b is a confirmed sub-neptune exoplanet orbiting the star Gl 686, located approximately 26.6 light-years (8.16 parsecs) from the Solar System. First announced in 2018 by Roque de los Muchachos Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 2.46 Earth radii and has a measured mass of 6.624 Earth masses. Combining its mass and radius yields a mean bulk density of 2.45 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.09 g⊕ (10.69 m/s²), and an escape velocity of 18.4 km/s.

In its orbital architecture around Gl 686, Gl 686 b completes one full revolution every 15.53 Earth days at a semi-major axis of 0.091 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 63.7 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.05 carries the world between 0.0865 AU at periapsis and 0.0956 AU at apoapsis, driving measurable seasonal insolation cycles.

⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 379 K (+106°C / +223°F) and receiving 3.56 S⊕ (~4,850 W/m²), Gl 686 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Gl 686 is classified as a low-mass red dwarf of spectral type M1.0 V with an effective photospheric temperature of 3,656 K, a radius of 0.427 R☉, a mass of 0.426 M☉, an estimated bolometric luminosity of 0.029 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.23 dex (metal-poor relative to the Sun). From Earth, Gl 686 shines at apparent V-band magnitude 9.62 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere.

Discovery Facility: Roque de los Muchachos Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).