Kepler-210 b
Astrophysical Synthesis & Habitability Characterization
Kepler-210 b 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 0.172% across the stellar disk), this world measures 2.94 Earth radii and has a measured mass of 8.96 Earth masses. Combining its mass and radius yields a mean bulk density of 1.94 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.04 g⊕ (10.2 m/s²), and an escape velocity of 19.5 km/s.
In its orbital architecture around Kepler-210, Kepler-210 b completes one full revolution every 2.453 Earth days at a semi-major axis of 0.032 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 141.9 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 737 K (+464°C / +867°F) and receiving 122.14 S⊕ (~166,231 W/m²), Kepler-210 b 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 b sharing its stellar neighborhood alongside Kepler-210 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-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) | 0.032000 AU |
| Orbital Period | 2.453 days |
| Mean Orbital Velocity | 141.9 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 77.8600° |
| Mean Bulk Density | 1.94 g/cm³ (19.5 km/s vesc) |
| Insolation Flux | 122.1390 S⊕ (~166,231 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 759.100 LY (232.750 pc) |