K2-133 c
Astrophysical Synthesis & Habitability Characterization
K2-133 c is a confirmed super-earth exoplanet orbiting the star K2-133, located approximately 245.2 light-years (75.17 parsecs) from the Solar System. First announced in 2017 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.1043% across the stellar disk), this world measures 1.603 Earth radii and has a measured mass of 3.2 Earth masses. Combining its mass and radius yields a mean bulk density of 4.28 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.25 g⊕ (12.26 m/s²), and an escape velocity of 15.8 km/s.
In its orbital architecture around K2-133, K2-133 c completes one full revolution every 4.868 Earth days at a semi-major axis of 0.04341 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 97 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 571 K (+298°C / +568°F) and receiving 17.62 S⊕ (~23,978 W/m²), K2-133 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-133 is classified as a low-mass red dwarf of spectral type M1.5 V with an effective photospheric temperature of 3,655 K, a radius of 0.455 R☉, a mass of 0.461 M☉, an estimated bolometric luminosity of 0.033 L☉. From Earth, K2-133 shines at apparent V-band magnitude 14.073 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The K2-133 system is a multi-planet architecture hosting 4 confirmed worlds, with K2-133 c sharing its stellar neighborhood alongside K2-133 b, K2-133 d, K2-133 e.
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: K2 · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | K2-133 |
| Spectral Type | M1.5 V |
| Effective Temp (Teff) | 3,655 K |
| Stellar Radius | 0.4550 R☉ |
| Stellar Mass | 0.4610 M☉ |
| Bolometric Luminosity | 0.033 L☉ |
| Metallicity [Fe/H] | — |
| Stellar Age | — |
| Apparent Magnitude | V: 14.073 · G: 13.325 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.043410 AU |
| Orbital Period | 4.868 days |
| Mean Orbital Velocity | 97 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 88.2100° |
| Mean Bulk Density | 4.28 g/cm³ (15.8 km/s vesc) |
| Insolation Flux | 17.6181 S⊕ (~23,978 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 245.200 LY (75.170 pc) |