GJ 3929 c
Astrophysical Synthesis & Habitability Characterization
GJ 3929 c is a confirmed sub-neptune exoplanet orbiting the star GJ 3929, located approximately 51.6 light-years (15.81 parsecs) from the Solar System. First announced in 2022 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 2.26 Earth radii and has a measured mass of 5.71 Earth masses. Combining its mass and radius yields a mean bulk density of 2.73 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.12 g⊕ (10.98 m/s²), and an escape velocity of 17.8 km/s.
In its orbital architecture around GJ 3929, GJ 3929 c completes one full revolution every 15.04 Earth days at a semi-major axis of 0.081 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 58.6 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 2.260 R⊕, GJ 3929 c exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star GJ 3929 is classified as a low-mass red dwarf of spectral type M3.5 V with an effective photospheric temperature of 3,384 K, a radius of 0.32 R☉, a mass of 0.313 M☉, an estimated bolometric luminosity of 0.012 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.1 Gyr and a metallicity of [Fe/H] = -0.02 dex (near-solar heavy-element abundance). From Earth, GJ 3929 shines at apparent V-band magnitude 12.675 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The GJ 3929 system is a multi-planet architecture hosting 2 confirmed worlds, with GJ 3929 c sharing its stellar neighborhood alongside GJ 3929 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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | GJ 3929 |
| Spectral Type | M3.5 V |
| Effective Temp (Teff) | 3,384 K |
| Stellar Radius | 0.3200 R☉ |
| Stellar Mass | 0.3130 M☉ |
| Bolometric Luminosity | 0.012 L☉ |
| Metallicity [Fe/H] | -0.020 dex |
| Stellar Age | 7.100 Gyr |
| Apparent Magnitude | V: 12.675 · G: 11.511 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.081000 AU |
| Orbital Period | 15.04 days |
| Mean Orbital Velocity | 58.6 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.73 g/cm³ (17.8 km/s vesc) |
| Insolation Flux | 1.6800 S⊕ (~2,286 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 51.600 LY (15.810 pc) |