GJ 15 A b
Astrophysical Synthesis & Habitability Characterization
GJ 15 A b is a confirmed super-earth exoplanet orbiting the star GJ 15 A, located approximately 11.6 light-years (3.56 parsecs) from the Solar System. First announced in 2014 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 1.55 Earth radii and has a measured mass of 3.03 Earth masses. Combining its mass and radius yields a mean bulk density of 4.49 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.26 g⊕ (12.36 m/s²), and an escape velocity of 15.6 km/s.
In its orbital architecture around GJ 15 A, GJ 15 A b completes one full revolution every 11.441 Earth days at a semi-major axis of 0.072 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 68.5 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.094 carries the world between 0.0652 AU at periapsis and 0.0788 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 550 K (+277°C / +531°F) and receiving 4.27 S⊕ (~5,810 W/m²), GJ 15 A b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
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 b sharing its stellar neighborhood alongside GJ 15 A 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 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) | 0.072000 AU |
| Orbital Period | 11.441 days |
| Mean Orbital Velocity | 68.5 km/s |
| Orbital Eccentricity (e) | 0.09400 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 4.49 g/cm³ (15.6 km/s vesc) |
| Insolation Flux | 4.2691 S⊕ (~5,810 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 11.600 LY (3.562 pc) |