Kepler-8 b
Astrophysical Synthesis & Habitability Characterization
Kepler-8 b is a confirmed gas giant exoplanet orbiting the star Kepler-8, located approximately 3332.9 light-years (1021.87 parsecs) from the Solar System. First announced in 2010 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.9589% across the stellar disk), this world measures 15.872 Earth radii (1.42 Jupiter radii) and has a measured mass of 187.52 Earth masses (0.59 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.26 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.74 g⊕ (7.26 m/s²), and an escape velocity of 38.4 km/s.
In its orbital architecture around Kepler-8, Kepler-8 b completes one full revolution every 3.522 Earth days at a semi-major axis of 0.0474 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 146.4 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 1680 K (+1407°C / +2565°F) and receiving 1,444.88 S⊕ (~1,966,483 W/m²), Kepler-8 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-8 is classified as a stellar host with an effective photospheric temperature of 6,213 K, a radius of 1.486 R☉, a mass of 1.213 M☉, an estimated bolometric luminosity of 2.952 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.47 Gyr and a metallicity of [Fe/H] = -0.055 dex (near-solar heavy-element abundance). From Earth, Kepler-8 shines at apparent V-band magnitude 13.598 (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-8 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,213 K |
| Stellar Radius | 1.4860 R☉ |
| Stellar Mass | 1.2130 M☉ |
| Bolometric Luminosity | 2.952 L☉ |
| Metallicity [Fe/H] | -0.055 dex |
| Stellar Age | 3.470 Gyr |
| Apparent Magnitude | V: 13.598 · G: 13.530 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.047400 AU |
| Orbital Period | 3.522 days |
| Mean Orbital Velocity | 146.4 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 83.9780° |
| Mean Bulk Density | 0.26 g/cm³ (38.4 km/s vesc) |
| Insolation Flux | 1444.8810 S⊕ (~1,966,483 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 3332.900 LY (1021.870 pc) |