Kepler-33 c
Astrophysical Synthesis & Habitability Characterization
Kepler-33 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-33, located approximately 3943.7 light-years (1209.16 parsecs) from the Solar System. First announced in 2011 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.026% across the stellar disk), this world measures 3.2 Earth radii (0.29 Jupiter radii) and has a measured mass of 0.39 Earth masses. Combining its mass and radius yields a mean bulk density of 0.07 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.04 g⊕ (0.39 m/s²), and an escape velocity of 3.9 km/s.
In its orbital architecture around Kepler-33, Kepler-33 c completes one full revolution every 13.176 Earth days at a semi-major axis of 0.1189 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 98.2 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 1009 K (+736°C / +1357°F) and receiving 241.76 S⊕ (~329,034 W/m²), Kepler-33 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-33 is classified as a stellar host with an effective photospheric temperature of 5,904 K, a radius of 1.82 R☉, a mass of 1.291 M☉, an estimated bolometric luminosity of 3.611 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.27 Gyr and a metallicity of [Fe/H] = 0.025 dex (near-solar heavy-element abundance). From Earth, Kepler-33 shines at apparent V-band magnitude 14.099 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-33 system is a multi-planet architecture hosting 5 confirmed worlds, with Kepler-33 c sharing its stellar neighborhood alongside Kepler-33 b, Kepler-33 d, Kepler-33 e, Kepler-33 f.
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-33 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,904 K |
| Stellar Radius | 1.8200 R☉ |
| Stellar Mass | 1.2910 M☉ |
| Bolometric Luminosity | 3.611 L☉ |
| Metallicity [Fe/H] | 0.025 dex |
| Stellar Age | 4.270 Gyr |
| Apparent Magnitude | V: 14.099 · G: 13.951 |
| System Architecture | 1 Star, 5 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.118900 AU |
| Orbital Period | 13.176 days |
| Mean Orbital Velocity | 98.2 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.1900° |
| Mean Bulk Density | 0.07 g/cm³ (3.9 km/s vesc) |
| Insolation Flux | 241.7590 S⊕ (~329,034 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 3943.700 LY (1209.160 pc) |