TOI-181 b
Astrophysical Synthesis & Habitability Characterization
TOI-181 b is a confirmed gas giant exoplanet orbiting the star TOI-181, located approximately 313.9 light-years (96.23 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 0.7327% across the stellar disk), this world measures 6.956 Earth radii (0.62 Jupiter radii) and has a measured mass of 46.169 Earth masses (0.15 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.76 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.95 g⊕ (9.32 m/s²), and an escape velocity of 28.8 km/s.
In its orbital architecture around TOI-181, TOI-181 b completes one full revolution every 4.532 Earth days at a semi-major axis of 0.0539 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 129.4 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.1543 carries the world between 0.0456 AU at periapsis and 0.0622 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 895 K (+622°C / +1152°F) and receiving 102.43 S⊕ (~139,407 W/m²), TOI-181 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-181 is classified as an orange K-type star of spectral type K with an effective photospheric temperature of 4,994 K, a radius of 0.745 R☉, a mass of 0.822 M☉, an estimated bolometric luminosity of 0.31 L☉. Stellar evolution modeling indicates an estimated stellar age of 5.4 Gyr and a metallicity of [Fe/H] = 0.272 dex (metal-rich relative to the Sun). From Earth, TOI-181 shines at apparent V-band magnitude 11.191 (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-181 |
| Spectral Type | K |
| Effective Temp (Teff) | 4,994 K |
| Stellar Radius | 0.7450 R☉ |
| Stellar Mass | 0.8220 M☉ |
| Bolometric Luminosity | 0.31 L☉ |
| Metallicity [Fe/H] | 0.272 dex |
| Stellar Age | 5.400 Gyr |
| Apparent Magnitude | V: 11.191 · G: 11.086 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.053900 AU |
| Orbital Period | 4.532 days |
| Mean Orbital Velocity | 129.4 km/s |
| Orbital Eccentricity (e) | 0.15430 |
| Orbital Inclination (i) | 88.2800° |
| Mean Bulk Density | 0.76 g/cm³ (28.8 km/s vesc) |
| Insolation Flux | 102.4300 S⊕ (~139,407 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 313.900 LY (96.234 pc) |