Kepler-633 c
Astrophysical Synthesis & Habitability Characterization
Kepler-633 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-633, located approximately 2219.6 light-years (680.54 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0277% across the stellar disk), this world measures 2.296 Earth radii and has a measured mass of 5.89 Earth masses. Combining its mass and radius yields a mean bulk density of 2.68 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.12 g⊕ (10.98 m/s²), and an escape velocity of 17.9 km/s.
In its orbital architecture around Kepler-633, Kepler-633 c completes one full revolution every 23.783 Earth days at a semi-major axis of 0.16246 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 74.3 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 725 K (+452°C / +846°F) and receiving 115.40 S⊕ (~157,059 W/m²), Kepler-633 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-633 is classified as a stellar host with an effective photospheric temperature of 5,877 K, a radius of 1.265 R☉, a mass of 0.997 M☉, an estimated bolometric luminosity of 1.713 L☉. Stellar evolution modeling indicates an estimated stellar age of 8.13 Gyr and a metallicity of [Fe/H] = -0.04 dex (near-solar heavy-element abundance). From Earth, Kepler-633 shines at apparent V-band magnitude 13.812 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-633 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-633 c sharing its stellar neighborhood alongside Kepler-633 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-633 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,877 K |
| Stellar Radius | 1.2650 R☉ |
| Stellar Mass | 0.9970 M☉ |
| Bolometric Luminosity | 1.713 L☉ |
| Metallicity [Fe/H] | -0.040 dex |
| Stellar Age | 8.130 Gyr |
| Apparent Magnitude | V: 13.812 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.162460 AU |
| Orbital Period | 23.783 days |
| Mean Orbital Velocity | 74.3 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.9800° |
| Mean Bulk Density | 2.68 g/cm³ (17.9 km/s vesc) |
| Insolation Flux | 115.4000 S⊕ (~157,059 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2219.600 LY (680.540 pc) |