GJ 357 c
Astrophysical Synthesis & Habitability Characterization
GJ 357 c is a confirmed super-earth exoplanet orbiting the star GJ 357, located approximately 30.8 light-years (9.44 parsecs) from the Solar System. First announced in 2019 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 1.66 Earth radii and has a measured mass of 3.4 Earth masses. Combining its mass and radius yields a mean bulk density of 4.1 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.23 g⊕ (12.06 m/s²), and an escape velocity of 16 km/s.
In its orbital architecture around GJ 357, GJ 357 c completes one full revolution every 9.125 Earth days at a semi-major axis of 0.061 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 72.7 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 401 K (+128°C / +262°F) and receiving 4.45 S⊕ (~6,056 W/m²), GJ 357 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star GJ 357 is classified as a low-mass red dwarf of spectral type M2.5 V with an effective photospheric temperature of 3,505 K, a radius of 0.337 R☉, a mass of 0.342 M☉, an estimated bolometric luminosity of 0.015 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.12 dex (metal-poor relative to the Sun). From Earth, GJ 357 shines at apparent V-band magnitude 10.91 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The GJ 357 system is a multi-planet architecture hosting 3 confirmed worlds, with GJ 357 c sharing its stellar neighborhood alongside GJ 357 b, GJ 357 d.
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 357 |
| Spectral Type | M2.5 V |
| Effective Temp (Teff) | 3,505 K |
| Stellar Radius | 0.3370 R☉ |
| Stellar Mass | 0.3420 M☉ |
| Bolometric Luminosity | 0.015 L☉ |
| Metallicity [Fe/H] | -0.120 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 10.910 · G: 9.880 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.061000 AU |
| Orbital Period | 9.125 days |
| Mean Orbital Velocity | 72.7 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 4.1 g/cm³ (16 km/s vesc) |
| Insolation Flux | 4.4500 S⊕ (~6,056 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 30.800 LY (9.442 pc) |