Kepler-438 b
Astrophysical Synthesis & Habitability Characterization
Kepler-438 b is a confirmed terrestrial exoplanet orbiting the star Kepler-438, located approximately 639.1 light-years (195.94 parsecs) from the Solar System. First announced in 2015 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.039% across the stellar disk), this world measures 1.12 Earth radii and has a measured mass of 1.46 Earth masses. Combining its mass and radius yields a mean bulk density of 5.73 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.16 g⊕ (11.38 m/s²), and an escape velocity of 12.8 km/s.
In its orbital architecture around Kepler-438, Kepler-438 b completes one full revolution every 35.233 Earth days at a semi-major axis of 0.166 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 51.3 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.03 (ranging from 0.161 AU at periapsis to 0.171 AU at apoapsis), the planet experiences minimal orbital distance variation.
✓ Classified as a Temperate Habitable Zone Candidate.
With an estimated equilibrium temperature of 288 K (+15°C / +59°F) and an incident stellar irradiance of 1.40 S⊕ (~1,905 W/m²), Kepler-438 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-438 is classified as a stellar host with an effective photospheric temperature of 3,748 K, a radius of 0.52 R☉, a mass of 0.544 M☉, an estimated bolometric luminosity of 0.048 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.4 Gyr and a metallicity of [Fe/H] = 0.16 dex (metal-rich relative to the Sun). From Earth, Kepler-438 shines at apparent V-band magnitude 15.104 (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-438 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 3,748 K |
| Stellar Radius | 0.5200 R☉ |
| Stellar Mass | 0.5440 M☉ |
| Bolometric Luminosity | 0.048 L☉ |
| Metallicity [Fe/H] | 0.160 dex |
| Stellar Age | 4.400 Gyr |
| Apparent Magnitude | V: 15.104 · G: 14.485 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.166000 AU |
| Orbital Period | 35.233 days |
| Mean Orbital Velocity | 51.3 km/s |
| Orbital Eccentricity (e) | 0.03000 |
| Orbital Inclination (i) | 89.8600° |
| Mean Bulk Density | 5.73 g/cm³ (12.8 km/s vesc) |
| Insolation Flux | 1.4000 S⊕ (~1,905 W/m²) |
| Habitable Zone Status | ★ Temperate Zone |
| Celestial Distance | 639.100 LY (195.943 pc) |