GJ 676 A d
Astrophysical Synthesis & Habitability Characterization
GJ 676 A d is a confirmed super-earth exoplanet orbiting the star GJ 676 A, located approximately 52.3 light-years (16.03 parsecs) from the Solar System. First announced in 2012 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 1.78 Earth radii and has a measured mass of 3.814 Earth masses. Combining its mass and radius yields a mean bulk density of 3.73 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.2 g⊕ (11.77 m/s²), and an escape velocity of 16.4 km/s.
In its orbital architecture around GJ 676 A, GJ 676 A d completes one full revolution every 3.601 Earth days at a semi-major axis of 0.039 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 117.8 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.192 carries the world between 0.0315 AU at periapsis and 0.0465 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 757 K (+484°C / +903°F) and receiving 59.62 S⊕ (~81,137 W/m²), GJ 676 A d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
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 d sharing its stellar neighborhood alongside GJ 676 A e, GJ 676 A b, 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) | 0.039000 AU |
| Orbital Period | 3.601 days |
| Mean Orbital Velocity | 117.8 km/s |
| Orbital Eccentricity (e) | 0.19200 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 3.73 g/cm³ (16.4 km/s vesc) |
| Insolation Flux | 59.6154 S⊕ (~81,137 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 52.300 LY (16.027 pc) |