Kepler-265 d
Astrophysical Synthesis & Habitability Characterization
Kepler-265 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-265, located approximately 4175.6 light-years (1280.25 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0428% across the stellar disk), this world measures 2.49 Earth radii and has a measured mass of 6.76 Earth masses. Combining its mass and radius yields a mean bulk density of 2.41 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.09 g⊕ (10.69 m/s²), and an escape velocity of 18.4 km/s.
In its orbital architecture around Kepler-265, Kepler-265 d completes one full revolution every 43.131 Earth days at a semi-major axis of 0.236 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 59.5 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 554 K (+281°C / +538°F) and receiving 18.94 S⊕ (~25,779 W/m²), Kepler-265 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-265 is classified as a stellar host with an effective photospheric temperature of 5,835 K, a radius of 1.103 R☉, a mass of 0.97 M☉, an estimated bolometric luminosity of 1.265 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.28 Gyr and a metallicity of [Fe/H] = -0.11 dex (metal-poor relative to the Sun). From Earth, Kepler-265 shines at apparent V-band magnitude 15.47 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-265 system is a multi-planet architecture hosting 4 confirmed worlds, with Kepler-265 d sharing its stellar neighborhood alongside Kepler-265 b, Kepler-265 c, Kepler-265 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-265 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,835 K |
| Stellar Radius | 1.1030 R☉ |
| Stellar Mass | 0.9700 M☉ |
| Bolometric Luminosity | 1.265 L☉ |
| Metallicity [Fe/H] | -0.110 dex |
| Stellar Age | 0.280 Gyr |
| Apparent Magnitude | V: 15.470 · G: 15.352 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.236000 AU |
| Orbital Period | 43.131 days |
| Mean Orbital Velocity | 59.5 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.5200° |
| Mean Bulk Density | 2.41 g/cm³ (18.4 km/s vesc) |
| Insolation Flux | 18.9410 S⊕ (~25,779 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 4175.600 LY (1280.250 pc) |