Kepler-1681 b
Astrophysical Synthesis & Habitability Characterization
Kepler-1681 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-1681, located approximately 2473.2 light-years (758.3 parsecs) from the Solar System. First announced in 2020 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0951% across the stellar disk), this world measures 2.553 Earth radii and has a measured mass of 7.05 Earth masses. Combining its mass and radius yields a mean bulk density of 2.34 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.08 g⊕ (10.59 m/s²), and an escape velocity of 18.6 km/s.
In its orbital architecture around Kepler-1681, Kepler-1681 b completes one full revolution every 69.896 Earth days at a semi-major axis of 0.32 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 49.8 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 442 K (+169°C / +336°F) and receiving 5.33 S⊕ (~7,254 W/m²), Kepler-1681 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-1681 is classified as a stellar host with an effective photospheric temperature of 5,756 K, a radius of 0.759 R☉, a mass of 0.893 M☉, an estimated bolometric luminosity of 0.567 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.3 Gyr and a metallicity of [Fe/H] = 0.106 dex (metal-rich relative to the Sun). From Earth, Kepler-1681 shines at apparent V-band magnitude 14.646 (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-1681 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,756 K |
| Stellar Radius | 0.7590 R☉ |
| Stellar Mass | 0.8930 M☉ |
| Bolometric Luminosity | 0.567 L☉ |
| Metallicity [Fe/H] | 0.106 dex |
| Stellar Age | 3.300 Gyr |
| Apparent Magnitude | V: 14.646 · G: 14.557 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.320000 AU |
| Orbital Period | 69.896 days |
| Mean Orbital Velocity | 49.8 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.0800° |
| Mean Bulk Density | 2.34 g/cm³ (18.6 km/s vesc) |
| Insolation Flux | 5.3300 S⊕ (~7,254 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2473.200 LY (758.300 pc) |