K2-240 c
Astrophysical Synthesis & Habitability Characterization
K2-240 c is a confirmed super-earth exoplanet orbiting the star K2-240, located approximately 237.8 light-years (72.91 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0934% across the stellar disk), this world measures 1.8 Earth radii and has a measured mass of 3.89 Earth masses. Combining its mass and radius yields a mean bulk density of 3.68 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.2 g⊕ (11.77 m/s²), and an escape velocity of 16.4 km/s.
In its orbital architecture around K2-240, K2-240 c completes one full revolution every 20.523 Earth days at a semi-major axis of 0.1159 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 61.4 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 389 K (+116°C / +241°F) and receiving 3.95 S⊕ (~5,370 W/m²), K2-240 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-240 is classified as a low-mass red dwarf of spectral type M0.5 V with an effective photospheric temperature of 3,810 K, a radius of 0.54 R☉, a mass of 0.58 M☉, an estimated bolometric luminosity of 0.055 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.1 dex (near-solar heavy-element abundance). From Earth, K2-240 shines at apparent V-band magnitude 13.372 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The K2-240 system is a multi-planet architecture hosting 2 confirmed worlds, with K2-240 c sharing its stellar neighborhood alongside K2-240 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 | K2-240 |
| Spectral Type | M0.5 V |
| Effective Temp (Teff) | 3,810 K |
| Stellar Radius | 0.5400 R☉ |
| Stellar Mass | 0.5800 M☉ |
| Bolometric Luminosity | 0.055 L☉ |
| Metallicity [Fe/H] | -0.100 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 13.372 · G: 12.621 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.115900 AU |
| Orbital Period | 20.523 days |
| Mean Orbital Velocity | 61.4 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 89.6600° |
| Mean Bulk Density | 3.68 g/cm³ (16.4 km/s vesc) |
| Insolation Flux | 3.9456 S⊕ (~5,370 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 237.800 LY (72.911 pc) |