Kepler-250 d
Astrophysical Synthesis & Habitability Characterization
Kepler-250 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-250, located approximately 2480.7 light-years (760.59 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0616% across the stellar disk), this world measures 2.18 Earth radii and has a measured mass of 5.39 Earth masses. Combining its mass and radius yields a mean bulk density of 2.87 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.13 g⊕ (11.08 m/s²), and an escape velocity of 17.6 km/s.
In its orbital architecture around Kepler-250, Kepler-250 d completes one full revolution every 17.648 Earth days at a semi-major axis of 0.127 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 78.3 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 579 K (+306°C / +583°F) and receiving 21.46 S⊕ (~29,211 W/m²), Kepler-250 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-250 is classified as a stellar host with an effective photospheric temperature of 5,160 K, a radius of 0.805 R☉, a mass of 0.806 M☉, an estimated bolometric luminosity of 0.412 L☉. Stellar evolution modeling indicates an estimated stellar age of 13.2 Gyr and a metallicity of [Fe/H] = 0.01 dex (near-solar heavy-element abundance). From Earth, Kepler-250 shines at apparent V-band magnitude 15.819 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-250 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-250 d sharing its stellar neighborhood alongside Kepler-250 b, Kepler-250 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-250 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,160 K |
| Stellar Radius | 0.8050 R☉ |
| Stellar Mass | 0.8060 M☉ |
| Bolometric Luminosity | 0.412 L☉ |
| Metallicity [Fe/H] | 0.010 dex |
| Stellar Age | 13.200 Gyr |
| Apparent Magnitude | V: 15.819 · G: 15.414 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.127000 AU |
| Orbital Period | 17.648 days |
| Mean Orbital Velocity | 78.3 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.2700° |
| Mean Bulk Density | 2.87 g/cm³ (17.6 km/s vesc) |
| Insolation Flux | 21.4630 S⊕ (~29,211 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2480.700 LY (760.585 pc) |