Kepler-57 b
Astrophysical Synthesis & Habitability Characterization
Kepler-57 b 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 0.1211% across the stellar disk), this world measures 3.135 Earth radii (0.28 Jupiter radii) and has a measured mass of 25.06 Earth masses. Combining its mass and radius yields a mean bulk density of 4.48 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 2.55 g⊕ (25.01 m/s²), and an escape velocity of 31.6 km/s.
In its orbital architecture around Kepler-57, Kepler-57 b completes one full revolution every 5.72 Earth days at a semi-major axis of 0.05988 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 113.9 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.0162 (ranging from 0.0589 AU at periapsis to 0.0609 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 850 K (+577°C / +1071°F) and receiving 124.35 S⊕ (~169,239 W/m²), Kepler-57 b 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 b sharing its stellar neighborhood alongside Kepler-57 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: 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) | 0.059880 AU |
| Orbital Period | 5.72 days |
| Mean Orbital Velocity | 113.9 km/s |
| Orbital Eccentricity (e) | 0.01620 |
| Orbital Inclination (i) | 88.9000° |
| Mean Bulk Density | 4.48 g/cm³ (31.6 km/s vesc) |
| Insolation Flux | 124.3490 S⊕ (~169,239 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2100.900 LY (644.140 pc) |