Kepler-347 d
Astrophysical Synthesis & Habitability Characterization
Kepler-347 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-347, located approximately 4236.4 light-years (1298.88 parsecs) from the Solar System. First announced in 2023 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0369% across the stellar disk), this world measures 3.04 Earth radii (0.27 Jupiter radii) and has a measured mass of 9.48 Earth masses. Combining its mass and radius yields a mean bulk density of 1.86 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.03 g⊕ (10.1 m/s²), and an escape velocity of 19.8 km/s.
In its orbital architecture around Kepler-347, Kepler-347 d completes one full revolution every 85.517 Earth days at a semi-major axis of 0.3802 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 48.4 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 482 K (+209°C / +408°F) and receiving 12.75 S⊕ (~17,353 W/m²), Kepler-347 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-347 is classified as a stellar host with an effective photospheric temperature of 5,592 K, a radius of 1.451 R☉, a mass of 1 M☉, an estimated bolometric luminosity of 1.847 L☉. Stellar evolution modeling indicates an estimated stellar age of 11.75 Gyr and a metallicity of [Fe/H] = 0.16 dex (metal-rich relative to the Sun). From Earth, Kepler-347 shines at apparent V-band magnitude 14.567 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-347 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-347 d sharing its stellar neighborhood alongside Kepler-347 b, Kepler-347 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-347 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,592 K |
| Stellar Radius | 1.4510 R☉ |
| Stellar Mass | 1.0000 M☉ |
| Bolometric Luminosity | 1.847 L☉ |
| Metallicity [Fe/H] | 0.160 dex |
| Stellar Age | 11.750 Gyr |
| Apparent Magnitude | V: 14.567 · G: 14.489 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.380200 AU |
| Orbital Period | 85.517 days |
| Mean Orbital Velocity | 48.4 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.0000° |
| Mean Bulk Density | 1.86 g/cm³ (19.8 km/s vesc) |
| Insolation Flux | 12.7500 S⊕ (~17,353 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 4236.400 LY (1298.880 pc) |