Kepler-157 d
Astrophysical Synthesis & Habitability Characterization
Kepler-157 d is a confirmed super-earth exoplanet orbiting the star Kepler-157, located approximately 2523.5 light-years (773.71 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0169% across the stellar disk), this world measures 1.46 Earth radii and has a measured mass of 2.73 Earth masses. Combining its mass and radius yields a mean bulk density of 4.84 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.28 g⊕ (12.55 m/s²), and an escape velocity of 15.3 km/s.
In its orbital architecture around Kepler-157, Kepler-157 d completes one full revolution every 7.026 Earth days at a semi-major axis of 0.0706 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 109.3 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 969 K (+696°C / +1285°F) and receiving 244.06 S⊕ (~332,163 W/m²), Kepler-157 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-157 is classified as a stellar host with an effective photospheric temperature of 5,866 K, a radius of 1.03 R☉, a mass of 1.02 M☉, an estimated bolometric luminosity of 1.127 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.07 Gyr and a metallicity of [Fe/H] = -0.01 dex (near-solar heavy-element abundance). From Earth, Kepler-157 shines at apparent V-band magnitude 14.206 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-157 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-157 d sharing its stellar neighborhood alongside Kepler-157 b, Kepler-157 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-157 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,866 K |
| Stellar Radius | 1.0300 R☉ |
| Stellar Mass | 1.0200 M☉ |
| Bolometric Luminosity | 1.127 L☉ |
| Metallicity [Fe/H] | -0.010 dex |
| Stellar Age | 4.070 Gyr |
| Apparent Magnitude | V: 14.206 · G: 14.037 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.070600 AU |
| Orbital Period | 7.026 days |
| Mean Orbital Velocity | 109.3 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 86.8000° |
| Mean Bulk Density | 4.84 g/cm³ (15.3 km/s vesc) |
| Insolation Flux | 244.0580 S⊕ (~332,163 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2523.500 LY (773.713 pc) |