Kepler-9 d
Astrophysical Synthesis & Habitability Characterization
Kepler-9 d is a confirmed super-earth exoplanet orbiting the star Kepler-9, located approximately 2049.1 light-years (628.26 parsecs) from the Solar System. First announced in 2010 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0217% across the stellar disk), this world measures 1.64 Earth radii and has a measured mass of 8.415 Earth masses. Combining its mass and radius yields a mean bulk density of 10.52 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 3.13 g⊕ (30.69 m/s²), and an escape velocity of 25.3 km/s.
In its orbital architecture around Kepler-9, Kepler-9 d completes one full revolution every 1.593 Earth days at a semi-major axis of 0.0273 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 186.5 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 2026 K (+1753°C / +3187°F) and receiving 1,339.66 S⊕ (~1,823,275 W/m²), Kepler-9 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-9 is classified as a stellar host with an effective photospheric temperature of 5,777 K, a radius of 1.02 R☉, a mass of 1.07 M☉, an estimated bolometric luminosity of 1.04 L☉. Stellar evolution modeling indicates an estimated stellar age of 1 Gyr and a metallicity of [Fe/H] = 0.12 dex (metal-rich relative to the Sun). From Earth, Kepler-9 shines at apparent V-band magnitude 13.922 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-9 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-9 d sharing its stellar neighborhood alongside Kepler-9 b, Kepler-9 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-9 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,777 K |
| Stellar Radius | 1.0200 R☉ |
| Stellar Mass | 1.0700 M☉ |
| Bolometric Luminosity | 1.04 L☉ |
| Metallicity [Fe/H] | 0.120 dex |
| Stellar Age | 1.000 Gyr |
| Apparent Magnitude | V: 13.922 · G: 13.781 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.027300 AU |
| Orbital Period | 1.593 days |
| Mean Orbital Velocity | 186.5 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.3800° |
| Mean Bulk Density | 10.52 g/cm³ (25.3 km/s vesc) |
| Insolation Flux | 1339.6580 S⊕ (~1,823,275 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2049.100 LY (628.257 pc) |