K2-242 b
Astrophysical Synthesis & Habitability Characterization
K2-242 b is a confirmed sub-neptune exoplanet orbiting the star K2-242, located approximately 356.3 light-years (109.24 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.3961% across the stellar disk), this world measures 2.54 Earth radii and has a measured mass of 6.99 Earth masses. Combining its mass and radius yields a mean bulk density of 2.35 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.08 g⊕ (10.59 m/s²), and an escape velocity of 18.6 km/s.
In its orbital architecture around K2-242, K2-242 b completes one full revolution every 6.514 Earth days at a semi-major axis of 0.0494 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 82.5 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 416 K (+143°C / +289°F) and receiving 6.38 S⊕ (~8,678 W/m²), K2-242 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-242 is classified as a stellar host with an effective photospheric temperature of 3,459 K, a radius of 0.37 R☉, a mass of 0.38 M☉, an estimated bolometric luminosity of 0.018 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.01 dex (near-solar heavy-element abundance). From Earth, K2-242 shines at apparent V-band magnitude 16.414 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere.
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 | K2-242 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 3,459 K |
| Stellar Radius | 0.3700 R☉ |
| Stellar Mass | 0.3800 M☉ |
| Bolometric Luminosity | 0.018 L☉ |
| Metallicity [Fe/H] | -0.010 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 16.414 · G: 15.382 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.049400 AU |
| Orbital Period | 6.514 days |
| Mean Orbital Velocity | 82.5 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.35 g/cm³ (18.6 km/s vesc) |
| Insolation Flux | 6.3759 S⊕ (~8,678 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 356.300 LY (109.237 pc) |