GJ 676 A b
Astrophysical Synthesis & Habitability Characterization
GJ 676 A b is a confirmed gas giant exoplanet orbiting the star GJ 676 A, located approximately 52.3 light-years (16.03 parsecs) from the Solar System. First announced in 2010 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.8 Earth radii (1.14 Jupiter radii) and has a measured mass of 1840.862 Earth masses (5.79 Jupiter masses). Combining its mass and radius yields a mean bulk density of 4.84 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 11.24 g⊕ (110.23 m/s²), and an escape velocity of 134.1 km/s.
In its orbital architecture around GJ 676 A, GJ 676 A b completes one full revolution every 1051.445 Earth days (2.88Julian years) at a semi-major axis of 1.735 AU (corresponding to the middle-system regime between Mars at 1.52 AU and Jupiter at 5.20 AU). Its mean orbital velocity is approximately 18 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.319, swinging from 1.1815 AU at periapsis out to 2.2885 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 114 K (-159°C / -254°F) and an incident flux of 0.03 S⊕ (~41 W/m²), surface water and volatile species on GJ 676 A b would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star GJ 676 A is classified as a low-mass red dwarf of spectral type M0 with an effective photospheric temperature of 3,734 K, a radius of 0.69 R☉, a mass of 0.626 M☉, an estimated bolometric luminosity of 0.083 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.23 dex (metal-rich relative to the Sun). From Earth, GJ 676 A shines at apparent V-band magnitude 9.58 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The GJ 676 A system is a multi-planet architecture hosting 4 confirmed worlds, with GJ 676 A b sharing its stellar neighborhood alongside GJ 676 A d, GJ 676 A e, GJ 676 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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | GJ 676 A |
| Spectral Type | M0 |
| Effective Temp (Teff) | 3,734 K |
| Stellar Radius | 0.6900 R☉ |
| Stellar Mass | 0.6260 M☉ |
| Bolometric Luminosity | 0.083 L☉ |
| Metallicity [Fe/H] | 0.230 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 9.580 · G: 8.865 |
| System Architecture | 2 Stars, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.735000 AU |
| Orbital Period | 1051.445 days |
| Mean Orbital Velocity | 18 km/s |
| Orbital Eccentricity (e) | 0.31900 |
| Orbital Inclination (i) | 48.9190° |
| Mean Bulk Density | 4.84 g/cm³ (134.1 km/s vesc) |
| Insolation Flux | 0.0301 S⊕ (~41 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 52.300 LY (16.027 pc) |