GJ 15 A c
Astrophysical Synthesis & Habitability Characterization
GJ 15 A c is a confirmed gas giant exoplanet orbiting the star GJ 15 A, located approximately 11.6 light-years (3.56 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 6.67 Earth radii (0.6 Jupiter radii) and has a measured mass of 36 Earth masses (0.11 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.67 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.81 g⊕ (7.94 m/s²), and an escape velocity of 26 km/s.
In its orbital architecture around GJ 15 A, GJ 15 A c completes one full revolution every 7600 Earth days (20.81Julian years) at a semi-major axis of 5.4 AU (a wide outer-system orbit beyond Jupiter's 5.20 AU distance in our Solar System). Its mean orbital velocity is approximately 7.7 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.27, swinging from 3.942 AU at periapsis out to 6.858 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 46 K (-227°C / -377°F) and an incident flux of 0.00 S⊕ (~1 W/m²), surface water and volatile species on GJ 15 A c would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star GJ 15 A is classified as a low-mass red dwarf of spectral type M1 with an effective photospheric temperature of 3,607 K, a radius of 0.38 R☉, a mass of 0.38 M☉, an estimated bolometric luminosity of 0.022 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.34 dex (metal-poor relative to the Sun). From Earth, GJ 15 A shines at apparent V-band magnitude 8.09 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The GJ 15 A system is a multi-planet architecture hosting 2 confirmed worlds, with GJ 15 A c sharing its stellar neighborhood alongside GJ 15 A 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: Roque de los Muchachos Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | GJ 15 A |
| Spectral Type | M1 |
| Effective Temp (Teff) | 3,607 K |
| Stellar Radius | 0.3800 R☉ |
| Stellar Mass | 0.3800 M☉ |
| Bolometric Luminosity | 0.022 L☉ |
| Metallicity [Fe/H] | -0.340 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 8.090 · G: 7.216 |
| System Architecture | 2 Stars, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 5.400000 AU |
| Orbital Period | 7600 days |
| Mean Orbital Velocity | 7.7 km/s |
| Orbital Eccentricity (e) | 0.27000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.67 g/cm³ (26 km/s vesc) |
| Insolation Flux | 0.0008 S⊕ (~1 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 11.600 LY (3.562 pc) |