Kepler-17 b
Astrophysical Synthesis & Habitability Characterization
Kepler-17 b is a confirmed gas giant exoplanet orbiting the star Kepler-17, located approximately 2350.8 light-years (720.75 parsecs) from the Solar System. First announced in 2011 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 1.7746% across the stellar disk), this world measures 14.68 Earth radii (1.31 Jupiter radii) and has a measured mass of 778.65 Earth masses (2.45 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.36 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 3.61 g⊕ (35.4 m/s²), and an escape velocity of 81.5 km/s.
In its orbital architecture around Kepler-17, Kepler-17 b completes one full revolution every 1.486 Earth days at a semi-major axis of 0.02591 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 189.7 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.011 (ranging from 0.0256 AU at periapsis to 0.0262 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1570 K (+1297°C / +2367°F) and receiving 1,481.77 S⊕ (~2,016,684 W/m²), Kepler-17 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-17 is classified as a solar-type yellow star of spectral type G2 V with an effective photospheric temperature of 5,781 K, a radius of 1.0103 R☉, a mass of 1.04 M☉, an estimated bolometric luminosity of 1.023 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.8 Gyr and a metallicity of [Fe/H] = 0.26 dex (metal-rich relative to the Sun). From Earth, Kepler-17 shines at apparent V-band magnitude 14.314 (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-17 |
| Spectral Type | G2 V |
| Effective Temp (Teff) | 5,781 K |
| Stellar Radius | 1.0103 R☉ |
| Stellar Mass | 1.0400 M☉ |
| Bolometric Luminosity | 1.023 L☉ |
| Metallicity [Fe/H] | 0.260 dex |
| Stellar Age | 1.800 Gyr |
| Apparent Magnitude | V: 14.314 · G: 14.131 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.025910 AU |
| Orbital Period | 1.486 days |
| Mean Orbital Velocity | 189.7 km/s |
| Orbital Eccentricity (e) | 0.01100 |
| Orbital Inclination (i) | 87.2000° |
| Mean Bulk Density | 1.36 g/cm³ (81.5 km/s vesc) |
| Insolation Flux | 1481.7660 S⊕ (~2,016,684 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2350.800 LY (720.753 pc) |