TOI-172 b
Astrophysical Synthesis & Habitability Characterization
TOI-172 b is a confirmed gas giant exoplanet orbiting the star TOI-172, located approximately 1118.2 light-years (342.83 parsecs) from the Solar System. First announced in 2019 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.3114% across the stellar disk), this world measures 10.817 Earth radii (0.97 Jupiter radii) and has a measured mass of 1722.639 Earth masses (5.42 Jupiter masses). Combining its mass and radius yields a mean bulk density of 7.5 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 14.72 g⊕ (144.35 m/s²), and an escape velocity of 141.2 km/s.
In its orbital architecture around TOI-172, TOI-172 b completes one full revolution every 9.477 Earth days at a semi-major axis of 0.0914 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 104.9 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.3806, swinging from 0.0566 AU at periapsis out to 0.1262 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1198 K (+925°C / +1697°F) and receiving 299.00 S⊕ (~406,939 W/m²), TOI-172 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-172 is classified as a stellar host with an effective photospheric temperature of 5,645 K, a radius of 1.777 R☉, a mass of 1.128 M☉, an estimated bolometric luminosity of 2.877 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.4 Gyr and a metallicity of [Fe/H] = 0.148 dex (metal-rich relative to the Sun). From Earth, TOI-172 shines at apparent V-band magnitude 11.299 (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-172 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,645 K |
| Stellar Radius | 1.7770 R☉ |
| Stellar Mass | 1.1280 M☉ |
| Bolometric Luminosity | 2.877 L☉ |
| Metallicity [Fe/H] | 0.148 dex |
| Stellar Age | 7.400 Gyr |
| Apparent Magnitude | V: 11.299 · G: 11.193 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.091400 AU |
| Orbital Period | 9.477 days |
| Mean Orbital Velocity | 104.9 km/s |
| Orbital Eccentricity (e) | 0.38060 |
| Orbital Inclination (i) | 88.2000° |
| Mean Bulk Density | 7.5 g/cm³ (141.2 km/s vesc) |
| Insolation Flux | 299.0000 S⊕ (~406,939 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1118.200 LY (342.831 pc) |