K2-396 c
Astrophysical Synthesis & Habitability Characterization
K2-396 c is a confirmed sub-neptune exoplanet orbiting the star K2-396, located approximately 896.5 light-years (274.86 parsecs) from the Solar System. First announced in 2022 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0969% across the stellar disk), this world measures 3.124 Earth radii (0.28 Jupiter radii) and has a measured mass of 9.93 Earth masses. Combining its mass and radius yields a mean bulk density of 1.8 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.02 g⊕ (10 m/s²), and an escape velocity of 19.9 km/s.
In its orbital architecture around K2-396, K2-396 c completes one full revolution every 25.761 Earth days.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 3.124 R⊕, K2-396 c exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star K2-396 is classified as a solar-type yellow star of spectral type G9 with an effective photospheric temperature of 5,236 K, a radius of 0.92 R☉, a mass of 0.954 M☉, an estimated bolometric luminosity of 0.571 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.237 dex (metal-rich relative to the Sun). From Earth, K2-396 shines at apparent V-band magnitude 13.32 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The K2-396 system is a multi-planet architecture hosting 2 confirmed worlds, with K2-396 c sharing its stellar neighborhood alongside K2-396 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 | K2-396 |
| Spectral Type | G9 |
| Effective Temp (Teff) | 5,236 K |
| Stellar Radius | 0.9200 R☉ |
| Stellar Mass | 0.9540 M☉ |
| Bolometric Luminosity | 0.571 L☉ |
| Metallicity [Fe/H] | 0.237 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 13.320 · G: 12.935 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 25.761 days |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.8 g/cm³ (19.9 km/s vesc) |
| Insolation Flux | — |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 896.500 LY (274.864 pc) |