Kepler-411 d
Astrophysical Synthesis & Habitability Characterization
Kepler-411 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-411, located approximately 501.2 light-years (153.68 parsecs) from the Solar System. First announced in 2018 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1377% across the stellar disk), this world measures 3.319 Earth radii (0.3 Jupiter radii) and has a measured mass of 15.2 Earth masses. Combining its mass and radius yields a mean bulk density of 2.29 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.38 g⊕ (13.53 m/s²), and an escape velocity of 23.9 km/s.
In its orbital architecture around Kepler-411, Kepler-411 d completes one full revolution every 58.02 Earth days at a semi-major axis of 0.279 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 52.3 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.128 carries the world between 0.2433 AU at periapsis and 0.3147 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 410 K (+137°C / +279°F) and receiving 3.90 S⊕ (~5,308 W/m²), Kepler-411 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-411 is classified as an orange K-type star of spectral type K2 V with an effective photospheric temperature of 4,974 K, a radius of 0.82 R☉, a mass of 0.87 M☉, an estimated bolometric luminosity of 0.369 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.212 Gyr and a metallicity of [Fe/H] = 0.21 dex (metal-rich relative to the Sun). From Earth, Kepler-411 shines at apparent V-band magnitude 12.448 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-411 system is a multi-planet architecture hosting 4 confirmed worlds, with Kepler-411 d sharing its stellar neighborhood alongside Kepler-411 b, Kepler-411 c, Kepler-411 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-411 |
| Spectral Type | K2 V |
| Effective Temp (Teff) | 4,974 K |
| Stellar Radius | 0.8200 R☉ |
| Stellar Mass | 0.8700 M☉ |
| Bolometric Luminosity | 0.369 L☉ |
| Metallicity [Fe/H] | 0.210 dex |
| Stellar Age | 0.212 Gyr |
| Apparent Magnitude | V: 12.448 · G: 12.233 |
| System Architecture | 2 Stars, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.279000 AU |
| Orbital Period | 58.02 days |
| Mean Orbital Velocity | 52.3 km/s |
| Orbital Eccentricity (e) | 0.12800 |
| Orbital Inclination (i) | 89.4300° |
| Mean Bulk Density | 2.29 g/cm³ (23.9 km/s vesc) |
| Insolation Flux | 3.9000 S⊕ (~5,308 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 501.200 LY (153.676 pc) |