K2-63 c
Astrophysical Synthesis & Habitability Characterization
K2-63 c is a confirmed sub-neptune exoplanet orbiting the star K2-63, located approximately 1688 light-years (517.53 parsecs) from the Solar System. First announced in 2016 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0481% across the stellar disk), this world measures 3.9 Earth radii (0.35 Jupiter radii) and has a measured mass of 14.5 Earth masses. Combining its mass and radius yields a mean bulk density of 1.35 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.95 g⊕ (9.32 m/s²), and an escape velocity of 21.6 km/s.
In its orbital architecture around K2-63, K2-63 c completes one full revolution every 25.456 Earth days at a semi-major axis of 0.189 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 80.8 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 959 K (+686°C / +1267°F) and receiving 139.00 S⊕ (~189,179 W/m²), K2-63 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-63 is classified as a stellar host with an effective photospheric temperature of 6,771 K, a radius of 1.63 R☉, a mass of 1.4 M☉, an estimated bolometric luminosity of 5.01 L☉. From Earth, K2-63 shines at apparent V-band magnitude 12.98 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The K2-63 system is a multi-planet architecture hosting 2 confirmed worlds, with K2-63 c sharing its stellar neighborhood alongside K2-63 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 | K2-63 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,771 K |
| Stellar Radius | 1.6300 R☉ |
| Stellar Mass | 1.4000 M☉ |
| Bolometric Luminosity | 5.01 L☉ |
| Metallicity [Fe/H] | — |
| Stellar Age | — |
| Apparent Magnitude | V: 12.980 · G: 12.727 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.189000 AU |
| Orbital Period | 25.456 days |
| Mean Orbital Velocity | 80.8 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.35 g/cm³ (21.6 km/s vesc) |
| Insolation Flux | 139.0000 S⊕ (~189,179 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1688.000 LY (517.534 pc) |