Kepler-1781 b
Astrophysical Synthesis & Habitability Characterization
Kepler-1781 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-1781, located approximately 3139.7 light-years (962.63 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.052% across the stellar disk), this world measures 2.381 Earth radii and has a measured mass of 6.26 Earth masses. Combining its mass and radius yields a mean bulk density of 2.56 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.1 g⊕ (10.79 m/s²), and an escape velocity of 18.1 km/s.
In its orbital architecture around Kepler-1781, Kepler-1781 b completes one full revolution every 4.888 Earth days at a semi-major axis of 0.0574 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 127.8 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 1003 K (+730°C / +1346°F) and receiving 239.11 S⊕ (~325,429 W/m²), Kepler-1781 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-1781 is classified as a stellar host with an effective photospheric temperature of 5,568 K, a radius of 0.957 R☉, a mass of 1.053 M☉, an estimated bolometric luminosity of 0.79 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.9 Gyr and a metallicity of [Fe/H] = 0.44 dex (metal-rich relative to the Sun). From Earth, Kepler-1781 shines at apparent V-band magnitude 15.713 (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-1781 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,568 K |
| Stellar Radius | 0.9570 R☉ |
| Stellar Mass | 1.0530 M☉ |
| Bolometric Luminosity | 0.79 L☉ |
| Metallicity [Fe/H] | 0.440 dex |
| Stellar Age | 0.900 Gyr |
| Apparent Magnitude | V: 15.713 · G: 15.735 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.057400 AU |
| Orbital Period | 4.888 days |
| Mean Orbital Velocity | 127.8 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.5500° |
| Mean Bulk Density | 2.56 g/cm³ (18.1 km/s vesc) |
| Insolation Flux | 239.1100 S⊕ (~325,429 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 3139.700 LY (962.630 pc) |