Kepler-207 d
Astrophysical Synthesis & Habitability Characterization
Kepler-207 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-207, located approximately 2855.6 light-years (875.52 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0365% across the stellar disk), this world measures 3.31 Earth radii (0.3 Jupiter radii) and has a measured mass of 11 Earth masses. Combining its mass and radius yields a mean bulk density of 1.67 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1 g⊕ (9.81 m/s²), and an escape velocity of 20.4 km/s.
In its orbital architecture around Kepler-207, Kepler-207 d completes one full revolution every 5.868 Earth days at a semi-major axis of 0.068 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 126.1 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 1254 K (+981°C / +1798°F) and receiving 732.60 S⊕ (~997,074 W/m²), Kepler-207 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-207 is classified as a stellar host with an effective photospheric temperature of 5,920 K, a radius of 1.588 R☉, a mass of 1.313 M☉, an estimated bolometric luminosity of 2.779 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.63 Gyr and a metallicity of [Fe/H] = 0.29 dex (metal-rich relative to the Sun). From Earth, Kepler-207 shines at apparent V-band magnitude 13.164 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-207 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-207 d sharing its stellar neighborhood alongside Kepler-207 b, Kepler-207 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-207 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,920 K |
| Stellar Radius | 1.5880 R☉ |
| Stellar Mass | 1.3130 M☉ |
| Bolometric Luminosity | 2.779 L☉ |
| Metallicity [Fe/H] | 0.290 dex |
| Stellar Age | 3.630 Gyr |
| Apparent Magnitude | V: 13.164 · G: 13.167 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.068000 AU |
| Orbital Period | 5.868 days |
| Mean Orbital Velocity | 126.1 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 83.3800° |
| Mean Bulk Density | 1.67 g/cm³ (20.4 km/s vesc) |
| Insolation Flux | 732.6040 S⊕ (~997,074 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2855.600 LY (875.519 pc) |