K2-151 b
Astrophysical Synthesis & Habitability Characterization
K2-151 b is a confirmed super-earth exoplanet orbiting the star K2-151, located approximately 226.6 light-years (69.48 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0921% across the stellar disk), this world measures 1.49 Earth radii and has a measured mass of 2.83 Earth masses. Combining its mass and radius yields a mean bulk density of 4.72 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.27 g⊕ (12.45 m/s²), and an escape velocity of 15.4 km/s.
In its orbital architecture around K2-151, K2-151 b completes one full revolution every 3.835 Earth days at a semi-major axis of 0.0373 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 105.8 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 566 K (+293°C / +559°F) and receiving 20.80 S⊕ (~28,309 W/m²), K2-151 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-151 is classified as a low-mass red dwarf of spectral type M1.5 V with an effective photospheric temperature of 3,695 K, a radius of 0.45 R☉, a mass of 0.47 M☉, an estimated bolometric luminosity of 0.034 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.19 dex (metal-poor relative to the Sun). From Earth, K2-151 shines at apparent V-band magnitude 14.175 (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 | K2-151 |
| Spectral Type | M1.5 V |
| Effective Temp (Teff) | 3,695 K |
| Stellar Radius | 0.4500 R☉ |
| Stellar Mass | 0.4700 M☉ |
| Bolometric Luminosity | 0.034 L☉ |
| Metallicity [Fe/H] | -0.190 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 14.175 · G: 13.312 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.037300 AU |
| Orbital Period | 3.835 days |
| Mean Orbital Velocity | 105.8 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 4.72 g/cm³ (15.4 km/s vesc) |
| Insolation Flux | 20.8000 S⊕ (~28,309 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 226.600 LY (69.480 pc) |