Kepler-224 d
Astrophysical Synthesis & Habitability Characterization
Kepler-224 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-224, located approximately 2550.8 light-years (782.09 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0973% across the stellar disk), this world measures 2.3 Earth radii and has a measured mass of 5.9 Earth masses. Combining its mass and radius yields a mean bulk density of 2.67 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.12 g⊕ (10.98 m/s²), and an escape velocity of 17.9 km/s.
In its orbital architecture around Kepler-224, Kepler-224 d completes one full revolution every 11.349 Earth days at a semi-major axis of 0.089 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 85.3 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 610 K (+337°C / +639°F) and receiving 36.29 S⊕ (~49,395 W/m²), Kepler-224 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-224 is classified as a stellar host with an effective photospheric temperature of 5,018 K, a radius of 0.676 R☉, a mass of 0.777 M☉, an estimated bolometric luminosity of 0.26 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.29 Gyr and a metallicity of [Fe/H] = -0.06 dex (near-solar heavy-element abundance). From Earth, Kepler-224 shines at apparent V-band magnitude 15.801 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-224 system is a multi-planet architecture hosting 4 confirmed worlds, with Kepler-224 d sharing its stellar neighborhood alongside Kepler-224 b, Kepler-224 c, Kepler-224 e.
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-224 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,018 K |
| Stellar Radius | 0.6760 R☉ |
| Stellar Mass | 0.7770 M☉ |
| Bolometric Luminosity | 0.26 L☉ |
| Metallicity [Fe/H] | -0.060 dex |
| Stellar Age | 2.290 Gyr |
| Apparent Magnitude | V: 15.801 · G: 15.636 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.089000 AU |
| Orbital Period | 11.349 days |
| Mean Orbital Velocity | 85.3 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.1400° |
| Mean Bulk Density | 2.67 g/cm³ (17.9 km/s vesc) |
| Insolation Flux | 36.2930 S⊕ (~49,395 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2550.800 LY (782.088 pc) |