Kepler-1877 b
Astrophysical Synthesis & Habitability Characterization
Kepler-1877 b is a confirmed sub-earth exoplanet orbiting the star Kepler-1877, located approximately 930.6 light-years (285.31 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0037% across the stellar disk), this world measures 0.624 Earth radii and has a measured mass of 0.179 Earth masses. Combining its mass and radius yields a mean bulk density of 4.06 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 0.46 g⊕ (4.51 m/s²), and an escape velocity of 6 km/s.
In its orbital architecture around Kepler-1877, Kepler-1877 b completes one full revolution every 2.378 Earth days at a semi-major axis of 0.03472 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 158.9 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 1278 K (+1005°C / +1841°F) and receiving 691.10 S⊕ (~940,587 W/m²), Kepler-1877 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-1877 is classified as a stellar host with an effective photospheric temperature of 5,615 K, a radius of 0.936 R☉, a mass of 1.022 M☉, an estimated bolometric luminosity of 0.781 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.9 Gyr and a metallicity of [Fe/H] = 0.24 dex (metal-rich relative to the Sun). From Earth, Kepler-1877 shines at apparent V-band magnitude 12.29 (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-1877 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,615 K |
| Stellar Radius | 0.9360 R☉ |
| Stellar Mass | 1.0220 M☉ |
| Bolometric Luminosity | 0.781 L☉ |
| Metallicity [Fe/H] | 0.240 dex |
| Stellar Age | 4.900 Gyr |
| Apparent Magnitude | V: 12.290 · G: 12.229 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.034720 AU |
| Orbital Period | 2.378 days |
| Mean Orbital Velocity | 158.9 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.0900° |
| Mean Bulk Density | 4.06 g/cm³ (6 km/s vesc) |
| Insolation Flux | 691.1000 S⊕ (~940,587 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 930.600 LY (285.312 pc) |