TOI-1203.01
Astrophysical Synthesis & Habitability Characterization
TOI-1203.01 is a confirmed sub-neptune exoplanet orbiting the star TOI-1203, located approximately 212 light-years (64.99 parsecs) from the Solar System. First announced in 2021 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.0515% across the stellar disk), this world measures 2.918 Earth radii and has a measured mass of 7.39 Earth masses. Combining its mass and radius yields a mean bulk density of 1.64 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.87 g⊕ (8.53 m/s²), and an escape velocity of 17.8 km/s.
In its orbital architecture around TOI-1203, TOI-1203.01 completes one full revolution every 25.503 Earth days at a semi-major axis of 0.1632 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 69.6 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.032 (ranging from 0.158 AU at periapsis to 0.1684 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 744 K (+471°C / +880°F) and receiving 51.00 S⊕ (~69,411 W/m²), TOI-1203.01 orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-1203 is classified as a solar-type yellow star of spectral type G3 V with an effective photospheric temperature of 5,737 K, a radius of 1.179 R☉, a mass of 0.886 M☉, an estimated bolometric luminosity of 1.351 L☉. Stellar evolution modeling indicates an estimated stellar age of 12.5 Gyr and a metallicity of [Fe/H] = -0.39 dex (metal-poor relative to the Sun). From Earth, TOI-1203 shines at apparent V-band magnitude 8.59 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The TOI-1203 system is a multi-planet architecture hosting 4 confirmed worlds, with TOI-1203.01 sharing its stellar neighborhood alongside TOI-1203 b, TOI-1203 c, TOI-1203 e.
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-1203 |
| Spectral Type | G3 V |
| Effective Temp (Teff) | 5,737 K |
| Stellar Radius | 1.1790 R☉ |
| Stellar Mass | 0.8860 M☉ |
| Bolometric Luminosity | 1.351 L☉ |
| Metallicity [Fe/H] | -0.390 dex |
| Stellar Age | 12.500 Gyr |
| Apparent Magnitude | V: 8.590 · G: 8.422 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.163200 AU |
| Orbital Period | 25.503 days |
| Mean Orbital Velocity | 69.6 km/s |
| Orbital Eccentricity (e) | 0.03200 |
| Orbital Inclination (i) | 89.2200° |
| Mean Bulk Density | 1.64 g/cm³ (17.8 km/s vesc) |
| Insolation Flux | 51.0000 S⊕ (~69,411 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 212.000 LY (64.994 pc) |