Kepler-325 d
Astrophysical Synthesis & Habitability Characterization
Kepler-325 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-325, located approximately 2685.1 light-years (823.24 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.065% across the stellar disk), this world measures 2.79 Earth radii and has a measured mass of 8.2 Earth masses. Combining its mass and radius yields a mean bulk density of 2.08 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.05 g⊕ (10.3 m/s²), and an escape velocity of 19.2 km/s.
In its orbital architecture around Kepler-325, Kepler-325 d completes one full revolution every 38.715 Earth days at a semi-major axis of 0.22 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 61.8 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 498 K (+225°C / +437°F) and receiving 12.08 S⊕ (~16,445 W/m²), Kepler-325 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-325 is classified as a stellar host with an effective photospheric temperature of 5,752 K, a radius of 1.003 R☉, a mass of 0.914 M☉, an estimated bolometric luminosity of 0.988 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.93 Gyr and a metallicity of [Fe/H] = 0.02 dex (near-solar heavy-element abundance). From Earth, Kepler-325 shines at apparent V-band magnitude 15.175 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-325 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-325 d sharing its stellar neighborhood alongside Kepler-325 b, Kepler-325 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-325 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,752 K |
| Stellar Radius | 1.0030 R☉ |
| Stellar Mass | 0.9140 M☉ |
| Bolometric Luminosity | 0.988 L☉ |
| Metallicity [Fe/H] | 0.020 dex |
| Stellar Age | 0.930 Gyr |
| Apparent Magnitude | V: 15.175 · G: 15.005 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.220000 AU |
| Orbital Period | 38.715 days |
| Mean Orbital Velocity | 61.8 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.3900° |
| Mean Bulk Density | 2.08 g/cm³ (19.2 km/s vesc) |
| Insolation Flux | 12.0830 S⊕ (~16,445 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2685.100 LY (823.242 pc) |