Kepler-38 b
Astrophysical Synthesis & Habitability Characterization
Kepler-38 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-38, located approximately 3831 light-years (1174.59 parsecs) from the Solar System. First announced in 2012 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0506% across the stellar disk), this world measures 4.3 Earth radii (0.38 Jupiter radii) and has a measured mass of 122 Earth masses (0.38 Jupiter masses). Combining its mass and radius yields a mean bulk density of 8.46 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 6.6 g⊕ (64.72 m/s²), and an escape velocity of 59.6 km/s.
In its orbital architecture around Kepler-38, Kepler-38 b completes one full revolution every 105.599 Earth days at a semi-major axis of 0.4632 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 47.7 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.032 (ranging from 0.4484 AU at periapsis to 0.478 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 475 K (+202°C / +396°F) and receiving 14.46 S⊕ (~19,676 W/m²), Kepler-38 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-38 is classified as a solar-type yellow star of spectral type G4 V with an effective photospheric temperature of 5,623 K, a radius of 1.752 R☉, a mass of 0.941 M☉, an estimated bolometric luminosity of 2.753 L☉. Stellar evolution modeling indicates an estimated stellar age of 10 Gyr and a metallicity of [Fe/H] = -0.11 dex (metal-poor relative to the Sun). From Earth, Kepler-38 shines at apparent V-band magnitude 14.015 (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-38 |
| Spectral Type | G4 V |
| Effective Temp (Teff) | 5,623 K |
| Stellar Radius | 1.7520 R☉ |
| Stellar Mass | 0.9410 M☉ |
| Bolometric Luminosity | 2.753 L☉ |
| Metallicity [Fe/H] | -0.110 dex |
| Stellar Age | 10.000 Gyr |
| Apparent Magnitude | V: 14.015 · G: 13.907 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.463200 AU |
| Orbital Period | 105.599 days |
| Mean Orbital Velocity | 47.7 km/s |
| Orbital Eccentricity (e) | 0.03200 |
| Orbital Inclination (i) | 89.4420° |
| Mean Bulk Density | 8.46 g/cm³ (59.6 km/s vesc) |
| Insolation Flux | 14.4568 S⊕ (~19,676 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 3831.000 LY (1174.590 pc) |