Kepler-203 c
Astrophysical Synthesis & Habitability Characterization
Kepler-203 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-203, located approximately 2293.9 light-years (703.3 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0413% across the stellar disk), this world measures 2.47 Earth radii and has a measured mass of 749.9 Earth masses (2.36 Jupiter masses). Combining its mass and radius yields a mean bulk density of 274.4 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 122.92 g⊕ (1205.43 m/s²), and an escape velocity of 194.9 km/s.
In its orbital architecture around Kepler-203, Kepler-203 c completes one full revolution every 5.371 Earth days at a semi-major axis of 0.061 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 123.6 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 1096 K (+823°C / +1513°F) and receiving 329.79 S⊕ (~448,841 W/m²), Kepler-203 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-203 is classified as a stellar host with an effective photospheric temperature of 5,821 K, a radius of 1.114 R☉, a mass of 1.06 M☉, an estimated bolometric luminosity of 1.278 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.78 Gyr and a metallicity of [Fe/H] = 0.08 dex (metal-rich relative to the Sun). From Earth, Kepler-203 shines at apparent V-band magnitude 14.14 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-203 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-203 c sharing its stellar neighborhood alongside Kepler-203 b, Kepler-203 d.
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-203 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,821 K |
| Stellar Radius | 1.1140 R☉ |
| Stellar Mass | 1.0600 M☉ |
| Bolometric Luminosity | 1.278 L☉ |
| Metallicity [Fe/H] | 0.080 dex |
| Stellar Age | 1.780 Gyr |
| Apparent Magnitude | V: 14.140 · G: 13.942 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.061000 AU |
| Orbital Period | 5.371 days |
| Mean Orbital Velocity | 123.6 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 87.4600° |
| Mean Bulk Density | 274.4 g/cm³ (194.9 km/s vesc) |
| Insolation Flux | 329.7880 S⊕ (~448,841 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2293.900 LY (703.302 pc) |