Kepler-77 b
Astrophysical Synthesis & Habitability Characterization
Kepler-77 b is a confirmed gas giant exoplanet orbiting the star Kepler-77, located approximately 2085.5 light-years (639.41 parsecs) from the Solar System. First announced in 2013 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.9931% across the stellar disk), this world measures 10.761 Earth radii (0.96 Jupiter radii) and has a measured mass of 136.661 Earth masses (0.43 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.6 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.18 g⊕ (11.57 m/s²), and an escape velocity of 39.9 km/s.
In its orbital architecture around Kepler-77, Kepler-77 b completes one full revolution every 3.579 Earth days at a semi-major axis of 0.04501 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 136.8 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 1440 K (+1167°C / +2133°F) and receiving 432.87 S⊕ (~589,137 W/m²), Kepler-77 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-77 is classified as a solar-type yellow star of spectral type G5 V with an effective photospheric temperature of 5,520 K, a radius of 0.99 R☉, a mass of 0.95 M☉, an estimated bolometric luminosity of 0.816 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.5 Gyr and a metallicity of [Fe/H] = 0.2 dex (metal-rich relative to the Sun). From Earth, Kepler-77 shines at apparent V-band magnitude 14.152 (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-77 |
| Spectral Type | G5 V |
| Effective Temp (Teff) | 5,520 K |
| Stellar Radius | 0.9900 R☉ |
| Stellar Mass | 0.9500 M☉ |
| Bolometric Luminosity | 0.816 L☉ |
| Metallicity [Fe/H] | 0.200 dex |
| Stellar Age | 7.500 Gyr |
| Apparent Magnitude | V: 14.152 · G: 13.917 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.045010 AU |
| Orbital Period | 3.579 days |
| Mean Orbital Velocity | 136.8 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.0000° |
| Mean Bulk Density | 0.6 g/cm³ (39.9 km/s vesc) |
| Insolation Flux | 432.8710 S⊕ (~589,137 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2085.500 LY (639.411 pc) |