Kepler-181 c
Astrophysical Synthesis & Habitability Characterization
Kepler-181 c is a confirmed super-earth exoplanet orbiting the star Kepler-181, located approximately 1987.2 light-years (609.28 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0593% across the stellar disk), this world measures 1.99 Earth radii and has a measured mass of 4.62 Earth masses. Combining its mass and radius yields a mean bulk density of 3.23 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.17 g⊕ (11.47 m/s²), and an escape velocity of 17 km/s.
In its orbital architecture around Kepler-181, Kepler-181 c completes one full revolution every 4.302 Earth days at a semi-major axis of 0.049 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 123.9 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 937 K (+664°C / +1227°F) and receiving 168.19 S⊕ (~228,904 W/m²), Kepler-181 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-181 is classified as a stellar host with an effective photospheric temperature of 5,333 K, a radius of 0.749 R☉, a mass of 0.81 M☉, an estimated bolometric luminosity of 0.407 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.46 Gyr and a metallicity of [Fe/H] = -0.04 dex (near-solar heavy-element abundance). From Earth, Kepler-181 shines at apparent V-band magnitude 14.854 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-181 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-181 c sharing its stellar neighborhood alongside Kepler-181 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-181 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,333 K |
| Stellar Radius | 0.7490 R☉ |
| Stellar Mass | 0.8100 M☉ |
| Bolometric Luminosity | 0.407 L☉ |
| Metallicity [Fe/H] | -0.040 dex |
| Stellar Age | 6.460 Gyr |
| Apparent Magnitude | V: 14.854 · G: 14.714 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.049000 AU |
| Orbital Period | 4.302 days |
| Mean Orbital Velocity | 123.9 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 87.0900° |
| Mean Bulk Density | 3.23 g/cm³ (17 km/s vesc) |
| Insolation Flux | 168.1880 S⊕ (~228,904 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1987.200 LY (609.283 pc) |