Kepler-758 d
Astrophysical Synthesis & Habitability Characterization
Kepler-758 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-758, located approximately 4899.9 light-years (1502.32 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0187% across the stellar disk), this world measures 2.12 Earth radii and has a measured mass of 5.14 Earth masses. Combining its mass and radius yields a mean bulk density of 2.97 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.14 g⊕ (11.18 m/s²), and an escape velocity of 17.4 km/s.
In its orbital architecture around Kepler-758, Kepler-758 d completes one full revolution every 20.497 Earth days at a semi-major axis of 0.1527 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 843 K (+570°C / +1058°F) and receiving 173.17 S⊕ (~235,686 W/m²), Kepler-758 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-758 is classified as a stellar host with an effective photospheric temperature of 6,228 K, a radius of 1.42 R☉, a mass of 1.16 M☉, an estimated bolometric luminosity of 2.722 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.8 Gyr and a metallicity of [Fe/H] = -0.1 dex (near-solar heavy-element abundance). From Earth, Kepler-758 shines at apparent V-band magnitude 14.379 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-758 system is a multi-planet architecture hosting 4 confirmed worlds, with Kepler-758 d sharing its stellar neighborhood alongside Kepler-758 c, Kepler-758 e, Kepler-758 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-758 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,228 K |
| Stellar Radius | 1.4200 R☉ |
| Stellar Mass | 1.1600 M☉ |
| Bolometric Luminosity | 2.722 L☉ |
| Metallicity [Fe/H] | -0.100 dex |
| Stellar Age | 3.800 Gyr |
| Apparent Magnitude | V: 14.379 · G: 14.327 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.152700 AU |
| Orbital Period | 20.497 days |
| Mean Orbital Velocity | 81 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 80.7300° |
| Mean Bulk Density | 2.97 g/cm³ (17.4 km/s vesc) |
| Insolation Flux | 173.1710 S⊕ (~235,686 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 4899.900 LY (1502.320 pc) |