K2-58 b
Astrophysical Synthesis & Habitability Characterization
K2-58 b is a confirmed sub-neptune exoplanet orbiting the star K2-58, located approximately 592.8 light-years (181.75 parsecs) from the Solar System. First announced in 2016 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0816% across the stellar disk), this world measures 2.68 Earth radii and has a measured mass of 7.65 Earth masses. Combining its mass and radius yields a mean bulk density of 2.19 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 K2-58, K2-58 b completes one full revolution every 7.053 Earth days at a semi-major axis of 0.0692 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 106.7 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 920 K (+647°C / +1197°F) and receiving 118.00 S⊕ (~160,598 W/m²), K2-58 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-58 is classified as a stellar host with an effective photospheric temperature of 5,413 K, a radius of 0.86 R☉, a mass of 0.89 M☉, an estimated bolometric luminosity of 0.57 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.11 dex (metal-rich relative to the Sun). From Earth, K2-58 shines at apparent V-band magnitude 12.415 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The K2-58 system is a multi-planet architecture hosting 3 confirmed worlds, with K2-58 b sharing its stellar neighborhood alongside K2-58 c, K2-58 d.
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 | K2-58 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,413 K |
| Stellar Radius | 0.8600 R☉ |
| Stellar Mass | 0.8900 M☉ |
| Bolometric Luminosity | 0.57 L☉ |
| Metallicity [Fe/H] | 0.110 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 12.415 · G: 12.132 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.069200 AU |
| Orbital Period | 7.053 days |
| Mean Orbital Velocity | 106.7 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 88.8546° |
| Mean Bulk Density | 2.19 g/cm³ (18.9 km/s vesc) |
| Insolation Flux | 118.0000 S⊕ (~160,598 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 592.800 LY (181.746 pc) |