GJ 674 b
Astrophysical Synthesis & Habitability Characterization
GJ 674 b is a confirmed sub-neptune exoplanet orbiting the star GJ 674, located approximately 14.8 light-years (4.55 parsecs) from the Solar System. First announced in 2007 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 3.33 Earth radii (0.3 Jupiter radii) and has a measured mass of 11.09 Earth masses. Combining its mass and radius yields a mean bulk density of 1.66 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1 g⊕ (9.81 m/s²), and an escape velocity of 20.4 km/s.
In its orbital architecture around GJ 674, GJ 674 b completes one full revolution every 4.694 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 90.4 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.2 carries the world between 0.0312 AU at periapsis and 0.0468 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 531 K (+258°C / +496°F) and receiving 10.52 S⊕ (~14,313 W/m²), GJ 674 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star GJ 674 is classified as a low-mass red dwarf of spectral type M2.5 with an effective photospheric temperature of 3,600 K, a radius of 0.3646 R☉, a mass of 0.35 M☉, an estimated bolometric luminosity of 0.02 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.55 Gyr and a metallicity of [Fe/H] = -0.28 dex (metal-poor relative to the Sun). From Earth, GJ 674 shines at apparent V-band magnitude 9.38 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere.
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 674 |
| Spectral Type | M2.5 |
| Effective Temp (Teff) | 3,600 K |
| Stellar Radius | 0.3646 R☉ |
| Stellar Mass | 0.3500 M☉ |
| Bolometric Luminosity | 0.02 L☉ |
| Metallicity [Fe/H] | -0.280 dex |
| Stellar Age | 0.550 Gyr |
| Apparent Magnitude | V: 9.380 · G: 8.331 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.039000 AU |
| Orbital Period | 4.694 days |
| Mean Orbital Velocity | 90.4 km/s |
| Orbital Eccentricity (e) | 0.20000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.66 g/cm³ (20.4 km/s vesc) |
| Insolation Flux | 10.5165 S⊕ (~14,313 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 14.800 LY (4.549 pc) |