Kepler-22 b
Astrophysical Synthesis & Habitability Characterization
Kepler-22 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-22, located approximately 634.8 light-years (194.64 parsecs) from the Solar System. First announced in 2011 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0491% across the stellar disk), this world measures 2.1 Earth radii and has a measured mass of 9.1 Earth masses. Combining its mass and radius yields a mean bulk density of 5.42 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 2.06 g⊕ (20.2 m/s²), and an escape velocity of 23.3 km/s.
In its orbital architecture around Kepler-22, Kepler-22 b completes one full revolution every 289.864 Earth days at a semi-major axis of 0.812 AU (comparable to the inner terrestrial zone between Venus, Earth at 1.00 AU, and Mars at 1.52 AU). Its mean orbital velocity is approximately 30.5 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.72, swinging from 0.2274 AU at periapsis out to 1.3966 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
✓ Classified as a Temperate Habitable Zone Candidate.
With an estimated equilibrium temperature of 279 K (+6°C / +43°F) and an incident stellar irradiance of 1.01 S⊕ (~1,379 W/m²), Kepler-22 b orbits within the empirical circumstellar habitable zone where a rocky surface under sufficient atmospheric pressure can maintain liquid surface water.
The host star Kepler-22 is classified as a solar-type yellow star of spectral type G5 V with an effective photospheric temperature of 5,596 K, a radius of 0.869 R☉, a mass of 0.857 M☉, an estimated bolometric luminosity of 0.664 L☉. Stellar evolution modeling indicates an estimated stellar age of 7 Gyr and a metallicity of [Fe/H] = -0.255 dex (metal-poor relative to the Sun). From Earth, Kepler-22 shines at apparent V-band magnitude 11.751 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.
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-22 |
| Spectral Type | G5 V |
| Effective Temp (Teff) | 5,596 K |
| Stellar Radius | 0.8690 R☉ |
| Stellar Mass | 0.8570 M☉ |
| Bolometric Luminosity | 0.664 L☉ |
| Metallicity [Fe/H] | -0.255 dex |
| Stellar Age | 7.000 Gyr |
| Apparent Magnitude | V: 11.751 · G: 11.644 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.812000 AU |
| Orbital Period | 289.864 days |
| Mean Orbital Velocity | 30.5 km/s |
| Orbital Eccentricity (e) | 0.72000 |
| Orbital Inclination (i) | 89.7640° |
| Mean Bulk Density | 5.42 g/cm³ (23.3 km/s vesc) |
| Insolation Flux | 1.0130 S⊕ (~1,379 W/m²) |
| Habitable Zone Status | ★ Temperate Zone |
| Celestial Distance | 634.800 LY (194.642 pc) |