Kepler-1257 b
Astrophysical Synthesis & Habitability Characterization
Kepler-1257 b is a confirmed super-earth exoplanet orbiting the star Kepler-1257, located approximately 3607.1 light-years (1105.95 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0257% across the stellar disk), this world measures 1.52 Earth radii and has a measured mass of 2.92 Earth masses. Combining its mass and radius yields a mean bulk density of 4.58 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.26 g⊕ (12.36 m/s²), and an escape velocity of 15.5 km/s.
In its orbital architecture around Kepler-1257, Kepler-1257 b completes one full revolution every 2.668 Earth days at a semi-major axis of 0.0376 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 153.3 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 1252 K (+979°C / +1794°F) and receiving 546.91 S⊕ (~744,342 W/m²), Kepler-1257 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-1257 is classified as a stellar host with an effective photospheric temperature of 5,502 K, a radius of 0.87 R☉, a mass of 0.9 M☉, an estimated bolometric luminosity of 0.622 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.37 Gyr and a metallicity of [Fe/H] = -0.09 dex (near-solar heavy-element abundance). From Earth, Kepler-1257 shines at apparent V-band magnitude 15.644 (faint and requiring research-grade or CCD telescopic photometry) 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: Kepler · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | Kepler-1257 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,502 K |
| Stellar Radius | 0.8700 R☉ |
| Stellar Mass | 0.9000 M☉ |
| Bolometric Luminosity | 0.622 L☉ |
| Metallicity [Fe/H] | -0.090 dex |
| Stellar Age | 4.370 Gyr |
| Apparent Magnitude | V: 15.644 · G: 15.512 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.037600 AU |
| Orbital Period | 2.668 days |
| Mean Orbital Velocity | 153.3 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 87.6500° |
| Mean Bulk Density | 4.58 g/cm³ (15.5 km/s vesc) |
| Insolation Flux | 546.9080 S⊕ (~744,342 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 3607.100 LY (1105.950 pc) |