K2-402 b
Astrophysical Synthesis & Habitability Characterization
K2-402 b is a confirmed sub-neptune exoplanet orbiting the star K2-402, located approximately 1706 light-years (523.06 parsecs) from the Solar System. First announced in 2022 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0368% across the stellar disk), this world measures 2.678 Earth radii and has a measured mass of 7.65 Earth masses. Combining its mass and radius yields a mean bulk density of 2.2 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 18.9 km/s.
In its orbital architecture around K2-402, K2-402 b completes one full revolution every 17.275 Earth days.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 2.678 R⊕, K2-402 b 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 K2-402 is classified as a solar-type yellow star of spectral type G2 with an effective photospheric temperature of 5,716 K, a radius of 1.28 R☉, a mass of 0.944 M☉, an estimated bolometric luminosity of 1.569 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.378 dex (metal-poor relative to the Sun). From Earth, K2-402 shines at apparent V-band magnitude 13.032 (faint and requiring research-grade or CCD telescopic photometry) in the Northern 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 | K2-402 |
| Spectral Type | G2 |
| Effective Temp (Teff) | 5,716 K |
| Stellar Radius | 1.2800 R☉ |
| Stellar Mass | 0.9440 M☉ |
| Bolometric Luminosity | 1.569 L☉ |
| Metallicity [Fe/H] | -0.378 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 13.032 · G: 12.836 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 17.275 days |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.2 g/cm³ (18.9 km/s vesc) |
| Insolation Flux | — |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1706.000 LY (523.055 pc) |