Kepler-1891 b
Astrophysical Synthesis & Habitability Characterization
Kepler-1891 b is a confirmed super-earth exoplanet orbiting the star Kepler-1891, located approximately 1944.7 light-years (596.24 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0284% across the stellar disk), this world measures 1.521 Earth radii and has a measured mass of 2.93 Earth masses. Combining its mass and radius yields a mean bulk density of 4.59 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.27 g⊕ (12.45 m/s²), and an escape velocity of 15.5 km/s.
In its orbital architecture around Kepler-1891, Kepler-1891 b completes one full revolution every 4.022 Earth days at a semi-major axis of 0.0473 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 127.9 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 1017 K (+744°C / +1371°F) and receiving 253.28 S⊕ (~344,714 W/m²), Kepler-1891 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-1891 is classified as a stellar host with an effective photospheric temperature of 5,516 K, a radius of 0.827 R☉, a mass of 0.873 M☉, an estimated bolometric luminosity of 0.568 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.7 Gyr and a metallicity of [Fe/H] = -0.14 dex (metal-poor relative to the Sun). From Earth, Kepler-1891 shines at apparent V-band magnitude 14.412 (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-1891 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,516 K |
| Stellar Radius | 0.8270 R☉ |
| Stellar Mass | 0.8730 M☉ |
| Bolometric Luminosity | 0.568 L☉ |
| Metallicity [Fe/H] | -0.140 dex |
| Stellar Age | 3.700 Gyr |
| Apparent Magnitude | V: 14.412 · G: 14.275 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.047300 AU |
| Orbital Period | 4.022 days |
| Mean Orbital Velocity | 127.9 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.3000° |
| Mean Bulk Density | 4.59 g/cm³ (15.5 km/s vesc) |
| Insolation Flux | 253.2800 S⊕ (~344,714 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1944.700 LY (596.240 pc) |