Kepler-177 b
Astrophysical Synthesis & Habitability Characterization
Kepler-177 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-177, located approximately 4681.8 light-years (1435.44 parsecs) from the Solar System. First announced in 2013 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0587% across the stellar disk), this world measures 3.5 Earth radii (0.31 Jupiter radii) and has a measured mass of 5.84 Earth masses. Combining its mass and radius yields a mean bulk density of 0.75 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.48 g⊕ (4.71 m/s²), and an escape velocity of 14.4 km/s.
In its orbital architecture around Kepler-177, Kepler-177 b completes one full revolution every 36.86 Earth days at a semi-major axis of 0.21101 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 62.3 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 549 K (+276°C / +529°F) and receiving 30.40 S⊕ (~41,374 W/m²), Kepler-177 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-177 is classified as a stellar host with an effective photospheric temperature of 5,732 K, a radius of 1.324 R☉, a mass of 0.921 M☉, an estimated bolometric luminosity of 1.698 L☉. Stellar evolution modeling indicates an estimated stellar age of 11.75 Gyr and a metallicity of [Fe/H] = -0.11 dex (metal-poor relative to the Sun). From Earth, Kepler-177 shines at apparent V-band magnitude 15.171 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-177 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-177 b sharing its stellar neighborhood alongside Kepler-177 c.
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-177 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,732 K |
| Stellar Radius | 1.3240 R☉ |
| Stellar Mass | 0.9210 M☉ |
| Bolometric Luminosity | 1.698 L☉ |
| Metallicity [Fe/H] | -0.110 dex |
| Stellar Age | 11.750 Gyr |
| Apparent Magnitude | V: 15.171 · G: 14.941 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.211010 AU |
| Orbital Period | 36.86 days |
| Mean Orbital Velocity | 62.3 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.9300° |
| Mean Bulk Density | 0.75 g/cm³ (14.4 km/s vesc) |
| Insolation Flux | 30.4000 S⊕ (~41,374 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 4681.800 LY (1435.440 pc) |