Kepler-56 d
Astrophysical Synthesis & Habitability Characterization
Kepler-56 d is a confirmed gas giant exoplanet orbiting the star Kepler-56, located approximately 2977.8 light-years (912.99 parsecs) from the Solar System. First announced in 2016 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.8 Earth radii (1.14 Jupiter radii) and has a measured mass of 1784 Earth masses (5.61 Jupiter masses). Combining its mass and radius yields a mean bulk density of 4.69 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 10.89 g⊕ (106.79 m/s²), and an escape velocity of 132.1 km/s.
In its orbital architecture around Kepler-56, Kepler-56 d completes one full revolution every 1002 Earth days (2.74Julian years) at a semi-major axis of 2.16 AU (corresponding to the middle-system regime between Mars at 1.52 AU and Jupiter at 5.20 AU). Its mean orbital velocity is approximately 23.5 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.2 carries the world between 1.728 AU at periapsis and 2.592 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 12.800 R⊕, Kepler-56 d exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star Kepler-56 is classified as a stellar host with an effective photospheric temperature of 4,819 K, a radius of 4.218 R☉, a mass of 1.29 M☉, an estimated bolometric luminosity of 8.609 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.37 Gyr and a metallicity of [Fe/H] = 0.363 dex (metal-rich relative to the Sun). From Earth, Kepler-56 shines at apparent V-band magnitude 12.598 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-56 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-56 d sharing its stellar neighborhood alongside Kepler-56 b, Kepler-56 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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | Kepler-56 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,819 K |
| Stellar Radius | 4.2180 R☉ |
| Stellar Mass | 1.2900 M☉ |
| Bolometric Luminosity | 8.609 L☉ |
| Metallicity [Fe/H] | 0.363 dex |
| Stellar Age | 4.370 Gyr |
| Apparent Magnitude | V: 12.598 · G: 12.430 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.160000 AU |
| Orbital Period | 1002 days |
| Mean Orbital Velocity | 23.5 km/s |
| Orbital Eccentricity (e) | 0.20000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 4.69 g/cm³ (132.1 km/s vesc) |
| Insolation Flux | 1.7204 S⊕ (~2,341 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2977.800 LY (912.994 pc) |