K2-36 c
Astrophysical Synthesis & Habitability Characterization
K2-36 c is a confirmed sub-neptune exoplanet orbiting the star K2-36, located approximately 358 light-years (109.75 parsecs) from the Solar System. First announced in 2016 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.167% across the stellar disk), this world measures 3.2 Earth radii (0.29 Jupiter radii) and has a measured mass of 7.9 Earth masses. Combining its mass and radius yields a mean bulk density of 1.33 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.77 g⊕ (7.55 m/s²), and an escape velocity of 17.6 km/s.
In its orbital architecture around K2-36, K2-36 c completes one full revolution every 5.341 Earth days at a semi-major axis of 0.05528 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 112.6 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.089 carries the world between 0.0504 AU at periapsis and 0.0602 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 854 K (+581°C / +1078°F) and receiving 89.00 S⊕ (~121,129 W/m²), K2-36 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-36 is classified as an orange K-type star of spectral type K2 V with an effective photospheric temperature of 4,916 K, a radius of 0.718 R☉, a mass of 0.79 M☉, an estimated bolometric luminosity of 0.27 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.4 Gyr and a metallicity of [Fe/H] = -0.047 dex (near-solar heavy-element abundance). From Earth, K2-36 shines at apparent V-band magnitude 11.726 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The K2-36 system is a multi-planet architecture hosting 2 confirmed worlds, with K2-36 c sharing its stellar neighborhood alongside K2-36 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: K2 · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | K2-36 |
| Spectral Type | K2 V |
| Effective Temp (Teff) | 4,916 K |
| Stellar Radius | 0.7180 R☉ |
| Stellar Mass | 0.7900 M☉ |
| Bolometric Luminosity | 0.27 L☉ |
| Metallicity [Fe/H] | -0.047 dex |
| Stellar Age | 1.400 Gyr |
| Apparent Magnitude | V: 11.726 · G: 11.527 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.055280 AU |
| Orbital Period | 5.341 days |
| Mean Orbital Velocity | 112.6 km/s |
| Orbital Eccentricity (e) | 0.08900 |
| Orbital Inclination (i) | 86.9170° |
| Mean Bulk Density | 1.33 g/cm³ (17.6 km/s vesc) |
| Insolation Flux | 89.0000 S⊕ (~121,129 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 358.000 LY (109.749 pc) |