K2-53 b
Astrophysical Synthesis & Habitability Characterization
K2-53 b is a confirmed sub-neptune exoplanet orbiting the star K2-53, located approximately 450.2 light-years (138.02 parsecs) from the Solar System. First announced in 2016 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0872% across the stellar disk), this world measures 2.6 Earth radii and has a measured mass of 7.27 Earth masses. Combining its mass and radius yields a mean bulk density of 2.28 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 18.7 km/s.
In its orbital architecture around K2-53, K2-53 b completes one full revolution every 12.208 Earth days at a semi-major axis of 0.098 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 87.3 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 665 K (+392°C / +738°F) and receiving 52.50 S⊕ (~71,453 W/m²), K2-53 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-53 is classified as a stellar host with an effective photospheric temperature of 5,263 K, a radius of 0.807 R☉, a mass of 0.851 M☉, an estimated bolometric luminosity of 0.448 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.037 dex (near-solar heavy-element abundance). From Earth, K2-53 shines at apparent V-band magnitude 12.634 (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 | K2-53 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,263 K |
| Stellar Radius | 0.8070 R☉ |
| Stellar Mass | 0.8510 M☉ |
| Bolometric Luminosity | 0.448 L☉ |
| Metallicity [Fe/H] | -0.037 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 12.634 · G: 12.148 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.098000 AU |
| Orbital Period | 12.208 days |
| Mean Orbital Velocity | 87.3 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 89.3200° |
| Mean Bulk Density | 2.28 g/cm³ (18.7 km/s vesc) |
| Insolation Flux | 52.5000 S⊕ (~71,453 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 450.200 LY (138.018 pc) |