Kepler-120 b
Astrophysical Synthesis & Habitability Characterization
Kepler-120 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-120, located approximately 1267.5 light-years (388.63 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1362% across the stellar disk), this world measures 2.15 Earth radii and has a measured mass of 8.5 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 1.84 g⊕ (18.04 m/s²), and an escape velocity of 22.2 km/s.
In its orbital architecture around Kepler-120, Kepler-120 b completes one full revolution every 6.313 Earth days at a semi-major axis of 0.055 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 94.8 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 575 K (+302°C / +576°F) and receiving 42.69 S⊕ (~58,104 W/m²), Kepler-120 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-120 is classified as a low-mass red dwarf of spectral type M0 V with an effective photospheric temperature of 4,096 K, a radius of 0.534 R☉, a mass of 0.654 M☉, an estimated bolometric luminosity of 0.072 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.63 Gyr and a metallicity of [Fe/H] = -0.12 dex (metal-poor relative to the Sun). From Earth, Kepler-120 shines at apparent V-band magnitude 14.995 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-120 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-120 b sharing its stellar neighborhood alongside Kepler-120 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: Kepler · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | Kepler-120 |
| Spectral Type | M0 V |
| Effective Temp (Teff) | 4,096 K |
| Stellar Radius | 0.5340 R☉ |
| Stellar Mass | 0.6540 M☉ |
| Bolometric Luminosity | 0.072 L☉ |
| Metallicity [Fe/H] | -0.120 dex |
| Stellar Age | 3.630 Gyr |
| Apparent Magnitude | V: 14.995 · G: 14.719 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.055000 AU |
| Orbital Period | 6.313 days |
| Mean Orbital Velocity | 94.8 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.9100° |
| Mean Bulk Density | 4.72 g/cm³ (22.2 km/s vesc) |
| Insolation Flux | 42.6920 S⊕ (~58,104 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1267.500 LY (388.630 pc) |