Kepler-1311 d
Astrophysical Synthesis & Habitability Characterization
Kepler-1311 d is a confirmed gas giant exoplanet orbiting the star Kepler-1311, located approximately 2825.6 light-years (866.33 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.2798% across the stellar disk), this world measures 9.658 Earth radii (0.86 Jupiter radii) and has a measured mass of 67.5 Earth masses (0.21 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.41 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.72 g⊕ (7.06 m/s²), and an escape velocity of 29.6 km/s.
In its orbital architecture around Kepler-1311, Kepler-1311 d completes one full revolution every 197.511 Earth days at a semi-major axis of 0.68434 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 37.7 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 391 K (+118°C / +244°F) and receiving 6.00 S⊕ (~8,166 W/m²), Kepler-1311 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-1311 is classified as a stellar host with an effective photospheric temperature of 5,616 K, a radius of 1.674 R☉, a mass of 1.032 M☉, an estimated bolometric luminosity of 2.501 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.59 Gyr and a metallicity of [Fe/H] = 0.04 dex (near-solar heavy-element abundance). From Earth, Kepler-1311 shines at apparent V-band magnitude 13.528 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-1311 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-1311 d sharing its stellar neighborhood alongside Kepler-1311 c, Kepler-1311 b.
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-1311 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,616 K |
| Stellar Radius | 1.6740 R☉ |
| Stellar Mass | 1.0320 M☉ |
| Bolometric Luminosity | 2.501 L☉ |
| Metallicity [Fe/H] | 0.040 dex |
| Stellar Age | 7.590 Gyr |
| Apparent Magnitude | V: 13.528 · G: 13.318 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.684340 AU |
| Orbital Period | 197.511 days |
| Mean Orbital Velocity | 37.7 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.4900° |
| Mean Bulk Density | 0.41 g/cm³ (29.6 km/s vesc) |
| Insolation Flux | 6.0000 S⊕ (~8,166 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2825.600 LY (866.331 pc) |