K2-154 b
Astrophysical Synthesis & Habitability Characterization
K2-154 b is a confirmed super-earth exoplanet orbiting the star K2-154, located approximately 421.9 light-years (129.36 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0839% across the stellar disk), this world measures 1.99 Earth radii and has a measured mass of 4.62 Earth masses. Combining its mass and radius yields a mean bulk density of 3.23 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.17 g⊕ (11.47 m/s²), and an escape velocity of 17 km/s.
In its orbital architecture around K2-154, K2-154 b completes one full revolution every 3.676 Earth days at a semi-major axis of 0.0405 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 119.9 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 715 K (+442°C / +828°F) and receiving 57.50 S⊕ (~78,258 W/m²), K2-154 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-154 is classified as a low-mass red dwarf of spectral type M0.0 V with an effective photospheric temperature of 4,097 K, a radius of 0.63 R☉, a mass of 0.65 M☉, an estimated bolometric luminosity of 0.1 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.21 dex (metal-rich relative to the Sun). From Earth, K2-154 shines at apparent V-band magnitude 13.861 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The K2-154 system is a multi-planet architecture hosting 2 confirmed worlds, with K2-154 b sharing its stellar neighborhood alongside K2-154 c.
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 | K2-154 |
| Spectral Type | M0.0 V |
| Effective Temp (Teff) | 4,097 K |
| Stellar Radius | 0.6300 R☉ |
| Stellar Mass | 0.6500 M☉ |
| Bolometric Luminosity | 0.1 L☉ |
| Metallicity [Fe/H] | 0.210 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 13.861 · G: 13.317 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.040500 AU |
| Orbital Period | 3.676 days |
| Mean Orbital Velocity | 119.9 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 3.23 g/cm³ (17 km/s vesc) |
| Insolation Flux | 57.5000 S⊕ (~78,258 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 421.900 LY (129.356 pc) |