Kepler-123 b
Astrophysical Synthesis & Habitability Characterization
Kepler-123 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-123, located approximately 3332.2 light-years (1021.66 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0455% across the stellar disk), this world measures 2.94 Earth radii and has a measured mass of 55.3 Earth masses (0.17 Jupiter masses). Combining its mass and radius yields a mean bulk density of 12 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 6.4 g⊕ (62.76 m/s²), and an escape velocity of 48.5 km/s.
In its orbital architecture around Kepler-123, Kepler-123 b completes one full revolution every 17.232 Earth days at a semi-major axis of 0.135 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 85.2 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 817 K (+544°C / +1011°F) and receiving 138.81 S⊕ (~188,916 W/m²), Kepler-123 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-123 is classified as a stellar host with an effective photospheric temperature of 6,089 K, a radius of 1.264 R☉, a mass of 1.079 M☉, an estimated bolometric luminosity of 1.97 L☉. Stellar evolution modeling indicates an estimated stellar age of 5.01 Gyr and a metallicity of [Fe/H] = -0.08 dex (near-solar heavy-element abundance). From Earth, Kepler-123 shines at apparent V-band magnitude 14.129 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-123 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-123 b sharing its stellar neighborhood alongside Kepler-123 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-123 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,089 K |
| Stellar Radius | 1.2640 R☉ |
| Stellar Mass | 1.0790 M☉ |
| Bolometric Luminosity | 1.97 L☉ |
| Metallicity [Fe/H] | -0.080 dex |
| Stellar Age | 5.010 Gyr |
| Apparent Magnitude | V: 14.129 · G: 14.021 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.135000 AU |
| Orbital Period | 17.232 days |
| Mean Orbital Velocity | 85.2 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.1700° |
| Mean Bulk Density | 12 g/cm³ (48.5 km/s vesc) |
| Insolation Flux | 138.8070 S⊕ (~188,916 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 3332.200 LY (1021.660 pc) |