Kepler-1801 c
Astrophysical Synthesis & Habitability Characterization
Kepler-1801 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-1801, located approximately 2737.5 light-years (839.33 parsecs) from the Solar System. First announced in 2023 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.074% across the stellar disk), this world measures 2.91 Earth radii and has a measured mass of 8.8 Earth masses. Combining its mass and radius yields a mean bulk density of 1.97 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.04 g⊕ (10.2 m/s²), and an escape velocity of 19.5 km/s.
In its orbital architecture around Kepler-1801, Kepler-1801 c completes one full revolution every 116.583 Earth days at a semi-major axis of 0.4572 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 42.7 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 371 K (+98°C / +208°F) and receiving 4.47 S⊕ (~6,084 W/m²), Kepler-1801 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-1801 is classified as a stellar host with an effective photospheric temperature of 5,738 K, a radius of 0.981 R☉, a mass of 0.936 M☉, an estimated bolometric luminosity of 0.936 L☉. Stellar evolution modeling indicates an estimated stellar age of 8.1 Gyr and a metallicity of [Fe/H] = -0.06 dex (near-solar heavy-element abundance). From Earth, Kepler-1801 shines at apparent V-band magnitude 15.28 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-1801 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-1801 c sharing its stellar neighborhood alongside Kepler-1801 b.
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-1801 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,738 K |
| Stellar Radius | 0.9810 R☉ |
| Stellar Mass | 0.9360 M☉ |
| Bolometric Luminosity | 0.936 L☉ |
| Metallicity [Fe/H] | -0.060 dex |
| Stellar Age | 8.100 Gyr |
| Apparent Magnitude | V: 15.280 · G: 15.072 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.457200 AU |
| Orbital Period | 116.583 days |
| Mean Orbital Velocity | 42.7 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.7400° |
| Mean Bulk Density | 1.97 g/cm³ (19.5 km/s vesc) |
| Insolation Flux | 4.4700 S⊕ (~6,084 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2737.500 LY (839.332 pc) |