GJ 3929 b
Astrophysical Synthesis & Habitability Characterization
GJ 3929 b is a confirmed terrestrial exoplanet orbiting the star GJ 3929, located approximately 51.6 light-years (15.81 parsecs) from the Solar System. First announced in 2022 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.0975% across the stellar disk), this world measures 1.09 Earth radii and has a measured mass of 1.75 Earth masses. Combining its mass and radius yields a mean bulk density of 7.45 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 1.47 g⊕ (14.42 m/s²), and an escape velocity of 14.2 km/s.
In its orbital architecture around GJ 3929, GJ 3929 b completes one full revolution every 2.616 Earth days at a semi-major axis of 0.0252 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 104.8 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.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 568 K (+295°C / +563°F) and receiving 17.30 S⊕ (~23,545 W/m²), GJ 3929 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
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 b sharing its stellar neighborhood alongside GJ 3929 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: Transiting Exoplanet Survey Satellite (TESS) · 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) | 0.025200 AU |
| Orbital Period | 2.616 days |
| Mean Orbital Velocity | 104.8 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.4420° |
| Mean Bulk Density | 7.45 g/cm³ (14.2 km/s vesc) |
| Insolation Flux | 17.3000 S⊕ (~23,545 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 51.600 LY (15.810 pc) |