Kepler-457 d
Astrophysical Synthesis & Habitability Characterization
Kepler-457 d is a confirmed sub-neptune exoplanet orbiting the star KOI-7892, located approximately 3497.4 light-years (1072.3 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0485% across the stellar disk), this world measures 2.985 Earth radii and has a measured mass of 9.19 Earth masses. Combining its mass and radius yields a mean bulk density of 1.91 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.03 g⊕ (10.1 m/s²), and an escape velocity of 19.6 km/s.
In its orbital architecture around KOI-7892, Kepler-457 d completes one full revolution every 10.691 Earth days at a semi-major axis of 0.0996 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 101.4 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 1008 K (+735°C / +1355°F) and receiving 244.47 S⊕ (~332,724 W/m²), Kepler-457 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star KOI-7892 is classified as a stellar host with an effective photospheric temperature of 6,474 K, a radius of 1.242 R☉, a mass of 1.148 M☉, an estimated bolometric luminosity of 2.431 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.16 dex (metal-poor relative to the Sun). From Earth, KOI-7892 shines at apparent V-band magnitude 14.411 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The KOI-7892 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-457 d sharing its stellar neighborhood alongside KIC 8540376 b, KIC 8540376 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 | KOI-7892 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,474 K |
| Stellar Radius | 1.2420 R☉ |
| Stellar Mass | 1.1480 M☉ |
| Bolometric Luminosity | 2.431 L☉ |
| Metallicity [Fe/H] | -0.160 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 14.411 · G: 14.217 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.099600 AU |
| Orbital Period | 10.691 days |
| Mean Orbital Velocity | 101.4 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 86.6200° |
| Mean Bulk Density | 1.91 g/cm³ (19.6 km/s vesc) |
| Insolation Flux | 244.4700 S⊕ (~332,724 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 3497.400 LY (1072.300 pc) |