Kepler-336 d
Astrophysical Synthesis & Habitability Characterization
Kepler-336 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-336, located approximately 2507.7 light-years (768.86 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0278% across the stellar disk), this world measures 2.37 Earth radii and has a measured mass of 6.21 Earth masses. Combining its mass and radius yields a mean bulk density of 2.57 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.11 g⊕ (10.89 m/s²), and an escape velocity of 18.1 km/s.
In its orbital architecture around Kepler-336, Kepler-336 d completes one full revolution every 20.679 Earth days at a semi-major axis of 0.154 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 81 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 749 K (+476°C / +889°F) and receiving 74.36 S⊕ (~101,204 W/m²), Kepler-336 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-336 is classified as a stellar host with an effective photospheric temperature of 5,867 K, a radius of 1.304 R☉, a mass of 1.09 M☉, an estimated bolometric luminosity of 1.808 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.9 Gyr and a metallicity of [Fe/H] = 0.337 dex (metal-rich relative to the Sun). From Earth, Kepler-336 shines at apparent V-band magnitude 13.677 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-336 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-336 d sharing its stellar neighborhood alongside Kepler-336 b, Kepler-336 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-336 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,867 K |
| Stellar Radius | 1.3040 R☉ |
| Stellar Mass | 1.0900 M☉ |
| Bolometric Luminosity | 1.808 L☉ |
| Metallicity [Fe/H] | 0.337 dex |
| Stellar Age | 4.900 Gyr |
| Apparent Magnitude | V: 13.677 · G: 13.584 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.154000 AU |
| Orbital Period | 20.679 days |
| Mean Orbital Velocity | 81 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.5500° |
| Mean Bulk Density | 2.57 g/cm³ (18.1 km/s vesc) |
| Insolation Flux | 74.3600 S⊕ (~101,204 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2507.700 LY (768.860 pc) |