Kepler-223 d
Astrophysical Synthesis & Habitability Characterization
Kepler-223 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-223, located approximately 6065.6 light-years (1859.71 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.078% across the stellar disk), this world measures 5.24 Earth radii (0.47 Jupiter radii) and has a measured mass of 8 Earth masses. Combining its mass and radius yields a mean bulk density of 0.31 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.29 g⊕ (2.84 m/s²), and an escape velocity of 13.8 km/s.
In its orbital architecture around Kepler-223, Kepler-223 d completes one full revolution every 14.789 Earth days at a semi-major axis of 0.11956 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 88 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.037 (ranging from 0.1151 AU at periapsis to 0.124 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 827 K (+554°C / +1029°F) and receiving 175.95 S⊕ (~239,469 W/m²), Kepler-223 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-223 is classified as a stellar host with an effective photospheric temperature of 5,803 K, a radius of 1.72 R☉, a mass of 1.125 M☉, an estimated bolometric luminosity of 3.01 L☉. Stellar evolution modeling indicates an estimated stellar age of 8.91 Gyr and a metallicity of [Fe/H] = 0.1 dex (metal-rich relative to the Sun). From Earth, Kepler-223 shines at apparent V-band magnitude 15.69 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-223 system is a multi-planet architecture hosting 4 confirmed worlds, with Kepler-223 d sharing its stellar neighborhood alongside Kepler-223 b, Kepler-223 c, Kepler-223 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-223 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,803 K |
| Stellar Radius | 1.7200 R☉ |
| Stellar Mass | 1.1250 M☉ |
| Bolometric Luminosity | 3.01 L☉ |
| Metallicity [Fe/H] | 0.100 dex |
| Stellar Age | 8.910 Gyr |
| Apparent Magnitude | V: 15.690 · G: 15.395 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.119560 AU |
| Orbital Period | 14.789 days |
| Mean Orbital Velocity | 88 km/s |
| Orbital Eccentricity (e) | 0.03700 |
| Orbital Inclination (i) | 87.9400° |
| Mean Bulk Density | 0.31 g/cm³ (13.8 km/s vesc) |
| Insolation Flux | 175.9510 S⊕ (~239,469 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 6065.600 LY (1859.710 pc) |