K2-340 b
Astrophysical Synthesis & Habitability Characterization
K2-340 b is a confirmed sub-neptune exoplanet orbiting the star K2-340, located approximately 2407.5 light-years (738.14 parsecs) from the Solar System. First announced in 2021 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0743% across the stellar disk), this world measures 3.36 Earth radii (0.3 Jupiter radii) and has a measured mass of 11.2 Earth masses. Combining its mass and radius yields a mean bulk density of 1.63 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.99 g⊕ (9.71 m/s²), and an escape velocity of 20.4 km/s.
In its orbital architecture around K2-340, K2-340 b completes one full revolution every 29.74 Earth days.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 606 K (+333°C / +631°F), K2-340 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-340 is classified as a stellar host with an effective photospheric temperature of 5,532 K, a radius of 1.13 R☉, a mass of 0.93 M☉, an estimated bolometric luminosity of 1.073 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.08 dex (metal-rich relative to the Sun). From Earth, K2-340 shines at apparent V-band magnitude 14.428 (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 | K2-340 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,532 K |
| Stellar Radius | 1.1300 R☉ |
| Stellar Mass | 0.9300 M☉ |
| Bolometric Luminosity | 1.073 L☉ |
| Metallicity [Fe/H] | 0.080 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 14.428 · G: 14.133 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 29.74 days |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.63 g/cm³ (20.4 km/s vesc) |
| Insolation Flux | — |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2407.500 LY (738.136 pc) |