TOI-1803 c
Astrophysical Synthesis & Habitability Characterization
TOI-1803 c is a confirmed sub-neptune exoplanet orbiting the star TOI-1803, located approximately 388.9 light-years (119.24 parsecs) from the Solar System. First announced in 2025 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.3026% across the stellar disk), this world measures 4.29 Earth radii (0.38 Jupiter radii) and has a measured mass of 8 Earth masses. Combining its mass and radius yields a mean bulk density of 0.56 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.43 g⊕ (4.22 m/s²), and an escape velocity of 15.3 km/s.
In its orbital architecture around TOI-1803, TOI-1803 c completes one full revolution every 12.886 Earth days at a semi-major axis of 0.097 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 81.9 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 588 K (+315°C / +599°F) and receiving 22.00 S⊕ (~29,942 W/m²), TOI-1803 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-1803 is classified as a stellar host with an effective photospheric temperature of 4,687 K, a radius of 0.715 R☉, a mass of 0.756 M☉, an estimated bolometric luminosity of 0.221 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.4 Gyr and a metallicity of [Fe/H] = 0.014 dex (near-solar heavy-element abundance). From Earth, TOI-1803 shines at apparent V-band magnitude 11.871 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The TOI-1803 system is a multi-planet architecture hosting 2 confirmed worlds, with TOI-1803 c sharing its stellar neighborhood alongside TOI-1803 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: Transiting Exoplanet Survey Satellite (TESS) · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | TOI-1803 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,687 K |
| Stellar Radius | 0.7150 R☉ |
| Stellar Mass | 0.7560 M☉ |
| Bolometric Luminosity | 0.221 L☉ |
| Metallicity [Fe/H] | 0.014 dex |
| Stellar Age | 1.400 Gyr |
| Apparent Magnitude | V: 11.871 · G: 11.771 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.097000 AU |
| Orbital Period | 12.886 days |
| Mean Orbital Velocity | 81.9 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.4800° |
| Mean Bulk Density | 0.56 g/cm³ (15.3 km/s vesc) |
| Insolation Flux | 22.0000 S⊕ (~29,942 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 388.900 LY (119.240 pc) |