KOI-1843.03
Astrophysical Synthesis & Habitability Characterization
KOI-1843.03 is a confirmed sub-earth exoplanet orbiting the star Kepler-974, located approximately 438.1 light-years (134.31 parsecs) from the Solar System. First announced in 2013 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0154% across the stellar disk), this world measures 0.61 Earth radii and has a measured mass of 8 Earth masses. Combining its mass and radius yields a mean bulk density of 194.34 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 21.5 g⊕ (210.84 m/s²), and an escape velocity of 40.5 km/s.
In its orbital architecture around Kepler-974, KOI-1843.03 completes one full revolution every 0.177 Earth days at a semi-major axis of 0.005 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 307.5 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1654 K (+1381°C / +2518°F) and receiving 1,769.29 S⊕ (~2,408,006 W/m²), KOI-1843.03 orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-974 is classified as a stellar host with an effective photospheric temperature of 3,584 K, a radius of 0.45 R☉, a mass of 0.46 M☉, an estimated bolometric luminosity of 0.03 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.79 Gyr and a metallicity of [Fe/H] = 0 dex (near-solar heavy-element abundance). From Earth, Kepler-974 shines at apparent V-band magnitude 15.295 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-974 system is a multi-planet architecture hosting 2 confirmed worlds, with KOI-1843.03 sharing its stellar neighborhood alongside Kepler-974 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-974 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 3,584 K |
| Stellar Radius | 0.4500 R☉ |
| Stellar Mass | 0.4600 M☉ |
| Bolometric Luminosity | 0.03 L☉ |
| Metallicity [Fe/H] | 0.000 dex |
| Stellar Age | 4.790 Gyr |
| Apparent Magnitude | V: 15.295 · G: 14.413 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.005000 AU |
| Orbital Period | 0.177 days |
| Mean Orbital Velocity | 307.5 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 72.0000° |
| Mean Bulk Density | 194.34 g/cm³ (40.5 km/s vesc) |
| Insolation Flux | 1769.2920 S⊕ (~2,408,006 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 438.100 LY (134.311 pc) |