K2-247 b
Astrophysical Synthesis & Habitability Characterization
K2-247 b is a confirmed sub-neptune exoplanet orbiting the star K2-247, located approximately 841.9 light-years (258.11 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0793% across the stellar disk), this world measures 2.12 Earth radii and has a measured mass of 5.14 Earth masses. Combining its mass and radius yields a mean bulk density of 2.97 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.14 g⊕ (11.18 m/s²), and an escape velocity of 17.4 km/s.
In its orbital architecture around K2-247, K2-247 b completes one full revolution every 2.25 Earth days at a semi-major axis of 0.0304 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 147 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 979 K (+706°C / +1303°F) and receiving 142.14 S⊕ (~193,451 W/m²), K2-247 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-247 is classified as a stellar host with an effective photospheric temperature of 4,667 K, a radius of 0.69 R☉, a mass of 0.74 M☉, an estimated bolometric luminosity of 0.203 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.08 dex (near-solar heavy-element abundance). From Earth, K2-247 shines at apparent V-band magnitude 14.857 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The K2-247 system is a multi-planet architecture hosting 2 confirmed worlds, with K2-247 b sharing its stellar neighborhood alongside K2-247 c.
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 | K2-247 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,667 K |
| Stellar Radius | 0.6900 R☉ |
| Stellar Mass | 0.7400 M☉ |
| Bolometric Luminosity | 0.203 L☉ |
| Metallicity [Fe/H] | -0.080 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 14.857 · G: 14.358 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.030400 AU |
| Orbital Period | 2.25 days |
| Mean Orbital Velocity | 147 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.97 g/cm³ (17.4 km/s vesc) |
| Insolation Flux | 142.1387 S⊕ (~193,451 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 841.900 LY (258.113 pc) |