Kepler-23 d
Astrophysical Synthesis & Habitability Characterization
Kepler-23 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-23, located approximately 2725.9 light-years (835.76 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0171% across the stellar disk), this world measures 2.206 Earth radii and has a measured mass of 4.44 Earth masses. Combining its mass and radius yields a mean bulk density of 2.28 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 0.91 g⊕ (8.92 m/s²), and an escape velocity of 15.9 km/s.
In its orbital architecture around Kepler-23, Kepler-23 d completes one full revolution every 15.27 Earth days at a semi-major axis of 0.12012 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 85.6 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.01 (ranging from 0.1189 AU at periapsis to 0.1213 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 896 K (+623°C / +1153°F) and receiving 161.04 S⊕ (~219,173 W/m²), Kepler-23 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-23 is classified as a stellar host with an effective photospheric temperature of 5,828 K, a radius of 1.548 R☉, a mass of 1.078 M☉, an estimated bolometric luminosity of 2.48 L☉. Stellar evolution modeling indicates an estimated stellar age of 9.12 Gyr and a metallicity of [Fe/H] = -0.112 dex (metal-poor relative to the Sun). From Earth, Kepler-23 shines at apparent V-band magnitude 13.567 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-23 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-23 d sharing its stellar neighborhood alongside Kepler-23 b, Kepler-23 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-23 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,828 K |
| Stellar Radius | 1.5480 R☉ |
| Stellar Mass | 1.0780 M☉ |
| Bolometric Luminosity | 2.48 L☉ |
| Metallicity [Fe/H] | -0.112 dex |
| Stellar Age | 9.120 Gyr |
| Apparent Magnitude | V: 13.567 · G: 13.402 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.120120 AU |
| Orbital Period | 15.27 days |
| Mean Orbital Velocity | 85.6 km/s |
| Orbital Eccentricity (e) | 0.01000 |
| Orbital Inclination (i) | 89.5400° |
| Mean Bulk Density | 2.28 g/cm³ (15.9 km/s vesc) |
| Insolation Flux | 161.0380 S⊕ (~219,173 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2725.900 LY (835.756 pc) |