K2-54 b
Astrophysical Synthesis & Habitability Characterization
K2-54 b is a confirmed sub-neptune exoplanet orbiting the star K2-54, located approximately 570.6 light-years (174.96 parsecs) from the Solar System. First announced in 2016 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.1387% across the stellar disk), this world measures 2.612 Earth radii and has a measured mass of 7.33 Earth masses. Combining its mass and radius yields a mean bulk density of 2.27 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.07 g⊕ (10.49 m/s²), and an escape velocity of 18.7 km/s.
In its orbital architecture around K2-54, K2-54 b completes one full revolution every 9.783 Earth days at a semi-major axis of 0.0761 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 84.6 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.24 carries the world between 0.0578 AU at periapsis and 0.0944 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 560 K (+287°C / +549°F) and receiving 6.10 S⊕ (~8,302 W/m²), K2-54 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-54 is classified as a stellar host with an effective photospheric temperature of 3,990 K, a radius of 0.643 R☉, a mass of 0.615 M☉, an estimated bolometric luminosity of 0.094 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.02 dex (near-solar heavy-element abundance). From Earth, K2-54 shines at apparent V-band magnitude 14.542 (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 | K2-54 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 3,990 K |
| Stellar Radius | 0.6430 R☉ |
| Stellar Mass | 0.6150 M☉ |
| Bolometric Luminosity | 0.094 L☉ |
| Metallicity [Fe/H] | -0.020 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 14.542 · G: 13.945 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.076100 AU |
| Orbital Period | 9.783 days |
| Mean Orbital Velocity | 84.6 km/s |
| Orbital Eccentricity (e) | 0.24000 |
| Orbital Inclination (i) | 89.0800° |
| Mean Bulk Density | 2.27 g/cm³ (18.7 km/s vesc) |
| Insolation Flux | 6.1000 S⊕ (~8,302 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 570.600 LY (174.955 pc) |