Kepler-57 c
Astrophysical Synthesis & Habitability Characterization
Kepler-57 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-57, located approximately 2100.9 light-years (644.14 parsecs) from the Solar System. First announced in 2012 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0594% across the stellar disk), this world measures 2.196 Earth radii and has a measured mass of 6.86 Earth masses. Combining its mass and radius yields a mean bulk density of 3.57 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.42 g⊕ (13.93 m/s²), and an escape velocity of 19.8 km/s.
In its orbital architecture around Kepler-57, Kepler-57 c completes one full revolution every 11.6 Earth days at a semi-major axis of 0.09588 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 89.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.0725 carries the world between 0.0889 AU at periapsis and 0.1028 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 671 K (+398°C / +748°F) and receiving 48.57 S⊕ (~66,109 W/m²), Kepler-57 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-57 is classified as a stellar host with an effective photospheric temperature of 5,188 K, a radius of 0.826 R☉, a mass of 0.859 M☉, an estimated bolometric luminosity of 0.443 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.31 Gyr and a metallicity of [Fe/H] = 0.117 dex (metal-rich relative to the Sun). From Earth, Kepler-57 shines at apparent V-band magnitude 15.017 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-57 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-57 c sharing its stellar neighborhood alongside Kepler-57 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: Kepler · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | Kepler-57 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,188 K |
| Stellar Radius | 0.8260 R☉ |
| Stellar Mass | 0.8590 M☉ |
| Bolometric Luminosity | 0.443 L☉ |
| Metallicity [Fe/H] | 0.117 dex |
| Stellar Age | 3.310 Gyr |
| Apparent Magnitude | V: 15.017 · G: 14.774 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.095880 AU |
| Orbital Period | 11.6 days |
| Mean Orbital Velocity | 89.9 km/s |
| Orbital Eccentricity (e) | 0.07250 |
| Orbital Inclination (i) | 89.9600° |
| Mean Bulk Density | 3.57 g/cm³ (19.8 km/s vesc) |
| Insolation Flux | 48.5740 S⊕ (~66,109 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2100.900 LY (644.140 pc) |