Kepler-210 c
Astrophysical Synthesis & Habitability Characterization
Kepler-210 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-210, located approximately 759.1 light-years (232.75 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.2607% across the stellar disk), this world measures 3.62 Earth radii (0.32 Jupiter radii) and has a measured mass of 12.8 Earth masses. Combining its mass and radius yields a mean bulk density of 1.49 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.98 g⊕ (9.61 m/s²), and an escape velocity of 21 km/s.
In its orbital architecture around Kepler-210, Kepler-210 c completes one full revolution every 7.973 Earth days at a semi-major axis of 0.07 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 95.5 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 497 K (+224°C / +435°F) and receiving 25.44 S⊕ (~34,624 W/m²), Kepler-210 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-210 is classified as a low-mass red dwarf of spectral type M0 V with an effective photospheric temperature of 4,559 K, a radius of 0.65 R☉, a mass of 0.77 M☉, an estimated bolometric luminosity of 0.164 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.78 Gyr and a metallicity of [Fe/H] = 0.277 dex (metal-rich relative to the Sun). From Earth, Kepler-210 shines at apparent V-band magnitude 14.126 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-210 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-210 c sharing its stellar neighborhood alongside Kepler-210 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-210 |
| Spectral Type | M0 V |
| Effective Temp (Teff) | 4,559 K |
| Stellar Radius | 0.6500 R☉ |
| Stellar Mass | 0.7700 M☉ |
| Bolometric Luminosity | 0.164 L☉ |
| Metallicity [Fe/H] | 0.277 dex |
| Stellar Age | 1.780 Gyr |
| Apparent Magnitude | V: 14.126 · G: 13.804 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.070000 AU |
| Orbital Period | 7.973 days |
| Mean Orbital Velocity | 95.5 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 85.7300° |
| Mean Bulk Density | 1.49 g/cm³ (21 km/s vesc) |
| Insolation Flux | 25.4400 S⊕ (~34,624 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 759.100 LY (232.750 pc) |