Kepler-1656 b
Astrophysical Synthesis & Habitability Characterization
Kepler-1656 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-1656, located approximately 606.2 light-years (185.88 parsecs) from the Solar System. First announced in 2018 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1453% across the stellar disk), this world measures 4.574 Earth radii (0.41 Jupiter radii) and has a measured mass of 47.8 Earth masses (0.15 Jupiter masses). Combining its mass and radius yields a mean bulk density of 2.75 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 2.28 g⊕ (22.36 m/s²), and an escape velocity of 36.2 km/s.
In its orbital architecture around Kepler-1656, Kepler-1656 b completes one full revolution every 31.562 Earth days at a semi-major axis of 0.1974 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 68 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.838, swinging from 0.032 AU at periapsis out to 0.3628 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 651 K (+378°C / +712°F) and receiving 24.60 S⊕ (~33,481 W/m²), Kepler-1656 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-1656 is classified as a stellar host with an effective photospheric temperature of 5,569 K, a radius of 1.1 R☉, a mass of 1.03 M☉, an estimated bolometric luminosity of 1.044 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.31 Gyr and a metallicity of [Fe/H] = 0.19 dex (metal-rich relative to the Sun). From Earth, Kepler-1656 shines at apparent V-band magnitude 11.64 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-1656 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-1656 b sharing its stellar neighborhood alongside Kepler-1656 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-1656 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,569 K |
| Stellar Radius | 1.1000 R☉ |
| Stellar Mass | 1.0300 M☉ |
| Bolometric Luminosity | 1.044 L☉ |
| Metallicity [Fe/H] | 0.190 dex |
| Stellar Age | 6.310 Gyr |
| Apparent Magnitude | V: 11.640 · G: 11.062 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.197400 AU |
| Orbital Period | 31.562 days |
| Mean Orbital Velocity | 68 km/s |
| Orbital Eccentricity (e) | 0.83800 |
| Orbital Inclination (i) | 89.3100° |
| Mean Bulk Density | 2.75 g/cm³ (36.2 km/s vesc) |
| Insolation Flux | 24.6000 S⊕ (~33,481 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 606.200 LY (185.875 pc) |