K2-353 b
Astrophysical Synthesis & Habitability Characterization
K2-353 b is a confirmed sub-neptune exoplanet orbiting the star K2-353, located approximately 875.8 light-years (268.52 parsecs) from the Solar System. First announced in 2021 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.2642% across the stellar disk), this world measures 5.55 Earth radii (0.5 Jupiter radii) and has a measured mass of 26.3 Earth masses. Combining its mass and radius yields a mean bulk density of 0.85 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.85 g⊕ (8.34 m/s²), and an escape velocity of 24.4 km/s.
In its orbital architecture around K2-353, K2-353 b completes one full revolution every 15.467 Earth days.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 735 K (+462°C / +864°F) and receiving 33.06 S⊕ (~45,001 W/m²), K2-353 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-353 is classified as a stellar host with an effective photospheric temperature of 5,698 K, a radius of 0.99 R☉, a mass of 0.87 M☉, an estimated bolometric luminosity of 0.927 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.21 dex (metal-poor relative to the Sun). From Earth, K2-353 shines at apparent V-band magnitude 12.337 (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 | K2-353 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,698 K |
| Stellar Radius | 0.9900 R☉ |
| Stellar Mass | 0.8700 M☉ |
| Bolometric Luminosity | 0.927 L☉ |
| Metallicity [Fe/H] | -0.210 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 12.337 · G: 12.099 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 15.467 days |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.85 g/cm³ (24.4 km/s vesc) |
| Insolation Flux | 33.0649 S⊕ (~45,001 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 875.800 LY (268.515 pc) |