TOI-198 b
Astrophysical Synthesis & Habitability Characterization
TOI-198 b is a confirmed super-earth exoplanet orbiting the star TOI-198, located approximately 77.4 light-years (23.73 parsecs) from the Solar System. First announced in 2023 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.089% across the stellar disk), this world measures 1.36 Earth radii and has a measured mass of 3.17 Earth masses. Combining its mass and radius yields a mean bulk density of 6.95 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 1.71 g⊕ (16.77 m/s²), and an escape velocity of 17.1 km/s.
In its orbital architecture around TOI-198, TOI-198 b completes one full revolution every 10.215 Earth days at a semi-major axis of 0.0675 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 71.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.15 carries the world between 0.0574 AU at periapsis and 0.0776 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 456 K (+183°C / +361°F) and receiving 7.20 S⊕ (~9,799 W/m²), TOI-198 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-198 is classified as a low-mass red dwarf of spectral type M0 V with an effective photospheric temperature of 3,801 K, a radius of 0.418 R☉, a mass of 0.417 M☉, an estimated bolometric luminosity of 0.033 L☉. Stellar evolution modeling indicates an estimated stellar age of 1 Gyr and a metallicity of [Fe/H] = -0.66 dex (metal-poor relative to the Sun). From Earth, TOI-198 shines at apparent V-band magnitude 11.688 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere.
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-198 |
| Spectral Type | M0 V |
| Effective Temp (Teff) | 3,801 K |
| Stellar Radius | 0.4180 R☉ |
| Stellar Mass | 0.4170 M☉ |
| Bolometric Luminosity | 0.033 L☉ |
| Metallicity [Fe/H] | -0.660 dex |
| Stellar Age | 1.000 Gyr |
| Apparent Magnitude | V: 11.688 · G: 10.919 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.067500 AU |
| Orbital Period | 10.215 days |
| Mean Orbital Velocity | 71.9 km/s |
| Orbital Eccentricity (e) | 0.15000 |
| Orbital Inclination (i) | 89.6300° |
| Mean Bulk Density | 6.95 g/cm³ (17.1 km/s vesc) |
| Insolation Flux | 7.2000 S⊕ (~9,799 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 77.400 LY (23.726 pc) |