KOI-1831 d
Astrophysical Synthesis & Habitability Characterization
KOI-1831 d is a confirmed terrestrial exoplanet orbiting the star Kepler-324, located approximately 1635.9 light-years (501.57 parsecs) from the Solar System. First announced in 2018 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0154% across the stellar disk), this world measures 1.13 Earth radii and has a measured mass of 2.23 Earth masses. Combining its mass and radius yields a mean bulk density of 8.52 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 1.75 g⊕ (17.16 m/s²), and an escape velocity of 15.7 km/s.
In its orbital architecture around Kepler-324, KOI-1831 d completes one full revolution every 34.169 Earth days at a semi-major axis of 0.19924 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 63.4 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 475 K (+202°C / +396°F) and receiving 11.80 S⊕ (~16,060 W/m²), KOI-1831 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-324 is classified as a stellar host with an effective photospheric temperature of 5,233 K, a radius of 0.835 R☉, a mass of 0.901 M☉, an estimated bolometric luminosity of 0.469 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.39 Gyr and a metallicity of [Fe/H] = 0.18 dex (metal-rich relative to the Sun). From Earth, Kepler-324 shines at apparent V-band magnitude 14.222 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-324 system is a multi-planet architecture hosting 4 confirmed worlds, with KOI-1831 d sharing its stellar neighborhood alongside Kepler-324 b, Kepler-324 e, Kepler-324 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-324 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,233 K |
| Stellar Radius | 0.8350 R☉ |
| Stellar Mass | 0.9010 M☉ |
| Bolometric Luminosity | 0.469 L☉ |
| Metallicity [Fe/H] | 0.180 dex |
| Stellar Age | 3.390 Gyr |
| Apparent Magnitude | V: 14.222 · G: 14.091 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.199240 AU |
| Orbital Period | 34.169 days |
| Mean Orbital Velocity | 63.4 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.6200° |
| Mean Bulk Density | 8.52 g/cm³ (15.7 km/s vesc) |
| Insolation Flux | 11.8000 S⊕ (~16,060 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1635.900 LY (501.574 pc) |