Kepler-373 c
Astrophysical Synthesis & Habitability Characterization
Kepler-373 c is a confirmed terrestrial exoplanet orbiting the star Kepler-373, located approximately 3556.6 light-years (1090.45 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0181% across the stellar disk), this world measures 1.24 Earth radii and has a measured mass of 2.07 Earth masses. Combining its mass and radius yields a mean bulk density of 5.99 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.35 g⊕ (13.24 m/s²), and an escape velocity of 14.5 km/s.
In its orbital architecture around Kepler-373, Kepler-373 c completes one full revolution every 16.726 Earth days at a semi-major axis of 0.126 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 82 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 729 K (+456°C / +853°F) and receiving 103.76 S⊕ (~141,212 W/m²), Kepler-373 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-373 is classified as a stellar host with an effective photospheric temperature of 5,787 K, a radius of 0.845 R☉, a mass of 0.981 M☉, an estimated bolometric luminosity of 0.718 L☉. Stellar evolution modeling indicates an estimated stellar age of 10.96 Gyr and a metallicity of [Fe/H] = 0.14 dex (metal-rich relative to the Sun). From Earth, Kepler-373 shines at apparent V-band magnitude 14.596 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-373 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-373 c sharing its stellar neighborhood alongside Kepler-373 b.
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-373 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,787 K |
| Stellar Radius | 0.8450 R☉ |
| Stellar Mass | 0.9810 M☉ |
| Bolometric Luminosity | 0.718 L☉ |
| Metallicity [Fe/H] | 0.140 dex |
| Stellar Age | 10.960 Gyr |
| Apparent Magnitude | V: 14.596 · G: 14.486 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.126000 AU |
| Orbital Period | 16.726 days |
| Mean Orbital Velocity | 82 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.3200° |
| Mean Bulk Density | 5.99 g/cm³ (14.5 km/s vesc) |
| Insolation Flux | 103.7560 S⊕ (~141,212 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 3556.600 LY (1090.450 pc) |