GJ 393 b
Astrophysical Synthesis & Habitability Characterization
GJ 393 b is a confirmed terrestrial exoplanet orbiting the star GJ 393, located approximately 22.9 light-years (7.03 parsecs) from the Solar System. First announced in 2021 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 1.17 Earth radii and has a measured mass of 1.71 Earth masses. Combining its mass and radius yields a mean bulk density of 5.89 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.25 g⊕ (12.26 m/s²), and an escape velocity of 13.5 km/s.
In its orbital architecture around GJ 393, GJ 393 b completes one full revolution every 7.027 Earth days at a semi-major axis of 0.05402 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 83.6 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 485 K (+212°C / +414°F) and receiving 9.21 S⊕ (~12,535 W/m²), GJ 393 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star GJ 393 is classified as a low-mass red dwarf of spectral type M2.0 V with an effective photospheric temperature of 3,579 K, a radius of 0.426 R☉, a mass of 0.426 M☉, an estimated bolometric luminosity of 0.027 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.09 dex (near-solar heavy-element abundance). From Earth, GJ 393 shines at apparent V-band magnitude 9.65 (accessible to binoculars and small amateur telescopes) in the Northern 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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | GJ 393 |
| Spectral Type | M2.0 V |
| Effective Temp (Teff) | 3,579 K |
| Stellar Radius | 0.4260 R☉ |
| Stellar Mass | 0.4260 M☉ |
| Bolometric Luminosity | 0.027 L☉ |
| Metallicity [Fe/H] | -0.090 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 9.650 · G: 8.674 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.054020 AU |
| Orbital Period | 7.027 days |
| Mean Orbital Velocity | 83.6 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 5.89 g/cm³ (13.5 km/s vesc) |
| Insolation Flux | 9.2100 S⊕ (~12,535 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 22.900 LY (7.031 pc) |