K2-404 b
Astrophysical Synthesis & Habitability Characterization
K2-404 b is a confirmed sub-neptune exoplanet orbiting the star K2-404, located approximately 396.7 light-years (121.63 parsecs) from the Solar System. First announced in 2022 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.1766% across the stellar disk), this world measures 2.53 Earth radii and has a measured mass of 6.94 Earth masses. Combining its mass and radius yields a mean bulk density of 2.36 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 18.5 km/s.
In its orbital architecture around K2-404, K2-404 b completes one full revolution every 13.115 Earth days.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 2.530 R⊕, K2-404 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 K2-404 is classified as a low-mass red dwarf of spectral type M1 with an effective photospheric temperature of 3,748 K, a radius of 0.552 R☉, a mass of 0.552 M☉, an estimated bolometric luminosity of 0.054 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.005 dex (near-solar heavy-element abundance). From Earth, K2-404 shines at apparent V-band magnitude 14.622 (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 | K2-404 |
| Spectral Type | M1 |
| Effective Temp (Teff) | 3,748 K |
| Stellar Radius | 0.5520 R☉ |
| Stellar Mass | 0.5520 M☉ |
| Bolometric Luminosity | 0.054 L☉ |
| Metallicity [Fe/H] | 0.005 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 14.622 · G: 13.843 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 13.115 days |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.36 g/cm³ (18.5 km/s vesc) |
| Insolation Flux | — |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 396.700 LY (121.630 pc) |