TOI-1203 b
Astrophysical Synthesis & Habitability Characterization
TOI-1203 b is a confirmed super-earth exoplanet orbiting the star TOI-1203, located approximately 212 light-years (64.99 parsecs) from the Solar System. First announced in 2025 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 1.52 Earth radii and has a measured mass of 3.51 Earth masses. Combining its mass and radius yields a mean bulk density of 5.51 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.52 g⊕ (14.91 m/s²), and an escape velocity of 17 km/s.
In its orbital architecture around TOI-1203, TOI-1203 b completes one full revolution every 4.157 Earth days at a semi-major axis of 0.04869 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 127.4 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.067 carries the world between 0.0454 AU at periapsis and 0.052 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1361 K (+1088°C / +1990°F) and receiving 572.20 S⊕ (~778,764 W/m²), TOI-1203 b 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 b sharing its stellar neighborhood alongside TOI-1203 c, TOI-1203.01, 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: La Silla Observatory · 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) | 0.048690 AU |
| Orbital Period | 4.157 days |
| Mean Orbital Velocity | 127.4 km/s |
| Orbital Eccentricity (e) | 0.06700 |
| Orbital Inclination (i) | 84.2900° |
| Mean Bulk Density | 5.51 g/cm³ (17 km/s vesc) |
| Insolation Flux | 572.2000 S⊕ (~778,764 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 212.000 LY (64.994 pc) |