KOI-3503 c
Astrophysical Synthesis & Habitability Characterization
KOI-3503 c is a confirmed terrestrial exoplanet orbiting the star KOI-3503, located approximately 2893.2 light-years (887.06 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0078% across the stellar disk), this world measures 1.21 Earth radii and has a measured mass of 10.36 Earth masses. Combining its mass and radius yields a mean bulk density of 32.25 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 7.08 g⊕ (69.43 m/s²), and an escape velocity of 32.7 km/s.
In its orbital architecture around KOI-3503, KOI-3503 c completes one full revolution every 31.828 Earth days at a semi-major axis of 0.18688 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 63.9 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 686 K (+413°C / +775°F) and receiving 52.50 S⊕ (~71,453 W/m²), KOI-3503 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star KOI-3503 is classified as a stellar host with an effective photospheric temperature of 6,001 K, a radius of 1.255 R☉, a mass of 0.858 M☉, an estimated bolometric luminosity of 1.833 L☉. Stellar evolution modeling indicates an estimated stellar age of 11.48 Gyr and a metallicity of [Fe/H] = -0.543 dex (metal-poor relative to the Sun). From Earth, KOI-3503 shines at apparent V-band magnitude 13.831 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The KOI-3503 system is a multi-planet architecture hosting 2 confirmed worlds, with KOI-3503 c sharing its stellar neighborhood alongside KOI-3503 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 | KOI-3503 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,001 K |
| Stellar Radius | 1.2550 R☉ |
| Stellar Mass | 0.8580 M☉ |
| Bolometric Luminosity | 1.833 L☉ |
| Metallicity [Fe/H] | -0.543 dex |
| Stellar Age | 11.480 Gyr |
| Apparent Magnitude | V: 13.831 · G: 13.774 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.186880 AU |
| Orbital Period | 31.828 days |
| Mean Orbital Velocity | 63.9 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.3800° |
| Mean Bulk Density | 32.25 g/cm³ (32.7 km/s vesc) |
| Insolation Flux | 52.5000 S⊕ (~71,453 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2893.200 LY (887.064 pc) |