K2-325 b
Astrophysical Synthesis & Habitability Characterization
K2-325 b is a confirmed sub-neptune exoplanet orbiting the star K2-325, located approximately 364.1 light-years (111.64 parsecs) from the Solar System. First announced in 2020 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.4581% across the stellar disk), this world measures 2.2 Earth radii and has a measured mass of 5.48 Earth masses. Combining its mass and radius yields a mean bulk density of 2.84 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.13 g⊕ (11.08 m/s²), and an escape velocity of 17.7 km/s.
In its orbital architecture around K2-325, K2-325 b completes one full revolution every 6.93 Earth days at a semi-major axis of 0.0419 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 65.8 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 423 K (+150°C / +302°F) and receiving 5.10 S⊕ (~6,941 W/m²), K2-325 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-325 is classified as a stellar host with an effective photospheric temperature of 3,287 K, a radius of 0.298 R☉, a mass of 0.274 M☉, an estimated bolometric luminosity of 0.00930 L☉. From Earth, K2-325 shines at apparent V-band magnitude 17.77 (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 | K2-325 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 3,287 K |
| Stellar Radius | 0.2980 R☉ |
| Stellar Mass | 0.2740 M☉ |
| Bolometric Luminosity | 0.00930 L☉ |
| Metallicity [Fe/H] | — |
| Stellar Age | — |
| Apparent Magnitude | V: 17.770 · G: 16.137 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.041900 AU |
| Orbital Period | 6.93 days |
| Mean Orbital Velocity | 65.8 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 89.3700° |
| Mean Bulk Density | 2.84 g/cm³ (17.7 km/s vesc) |
| Insolation Flux | 5.0999 S⊕ (~6,941 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 364.100 LY (111.638 pc) |