Kepler-91 b
Astrophysical Synthesis & Habitability Characterization
Kepler-91 b is a confirmed gas giant exoplanet orbiting the star Kepler-91, located approximately 4222.7 light-years (1294.69 parsecs) from the Solar System. First announced in 2013 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0497% across the stellar disk), this world measures 15.323 Earth radii (1.37 Jupiter radii) and has a measured mass of 257.442 Earth masses (0.81 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.39 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.1 g⊕ (10.79 m/s²), and an escape velocity of 45.9 km/s.
In its orbital architecture around Kepler-91, Kepler-91 b completes one full revolution every 6.247 Earth days at a semi-major axis of 0.0731 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 127.3 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.0519 carries the world between 0.0693 AU at periapsis and 0.0769 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 2040 K (+1767°C / +3213°F) and receiving 3,273.32 S⊕ (~4,454,994 W/m²), Kepler-91 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-91 is classified as an orange K-type star of spectral type K3 with an effective photospheric temperature of 4,550 K, a radius of 6.3 R☉, a mass of 1.31 M☉, an estimated bolometric luminosity of 15.262 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.47 Gyr and a metallicity of [Fe/H] = 0.11 dex (metal-rich relative to the Sun). From Earth, Kepler-91 shines at apparent V-band magnitude 12.712 (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-91 |
| Spectral Type | K3 |
| Effective Temp (Teff) | 4,550 K |
| Stellar Radius | 6.3000 R☉ |
| Stellar Mass | 1.3100 M☉ |
| Bolometric Luminosity | 15.262 L☉ |
| Metallicity [Fe/H] | 0.110 dex |
| Stellar Age | 4.470 Gyr |
| Apparent Magnitude | V: 12.712 · G: 12.476 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.073100 AU |
| Orbital Period | 6.247 days |
| Mean Orbital Velocity | 127.3 km/s |
| Orbital Eccentricity (e) | 0.05190 |
| Orbital Inclination (i) | 69.6800° |
| Mean Bulk Density | 0.39 g/cm³ (45.9 km/s vesc) |
| Insolation Flux | 3273.3240 S⊕ (~4,454,994 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 4222.700 LY (1294.690 pc) |