TOI-1173 b
Astrophysical Synthesis & Habitability Characterization
TOI-1173 b is a confirmed gas giant exoplanet orbiting the star TOI-1173, located approximately 431.7 light-years (132.35 parsecs) from the Solar System. First announced in 2024 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.7422% across the stellar disk), this world measures 8.777 Earth radii (0.78 Jupiter radii) and has a measured mass of 28.287 Earth masses. Combining its mass and radius yields a mean bulk density of 0.23 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.37 g⊕ (3.63 m/s²), and an escape velocity of 20.1 km/s.
In its orbital architecture around TOI-1173, TOI-1173 b completes one full revolution every 7.064 Earth days at a semi-major axis of 0.071 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 109.3 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.037 (ranging from 0.0684 AU at periapsis to 0.0736 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 868 K (+595°C / +1103°F) and receiving 132.00 S⊕ (~179,652 W/m²), TOI-1173 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-1173 is classified as a solar-type yellow star of spectral type G9 with an effective photospheric temperature of 5,350 K, a radius of 0.934 R☉, a mass of 0.911 M☉, an estimated bolometric luminosity of 0.641 L☉. Stellar evolution modeling indicates an estimated stellar age of 8.7 Gyr and a metallicity of [Fe/H] = 0.191 dex (metal-rich relative to the Sun). From Earth, TOI-1173 shines at apparent V-band magnitude 11.038 (faint and requiring research-grade or CCD telescopic photometry) in the Northern 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-1173 |
| Spectral Type | G9 |
| Effective Temp (Teff) | 5,350 K |
| Stellar Radius | 0.9340 R☉ |
| Stellar Mass | 0.9110 M☉ |
| Bolometric Luminosity | 0.641 L☉ |
| Metallicity [Fe/H] | 0.191 dex |
| Stellar Age | 8.700 Gyr |
| Apparent Magnitude | V: 11.038 · G: 10.804 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.071000 AU |
| Orbital Period | 7.064 days |
| Mean Orbital Velocity | 109.3 km/s |
| Orbital Eccentricity (e) | 0.03700 |
| Orbital Inclination (i) | 87.2280° |
| Mean Bulk Density | 0.23 g/cm³ (20.1 km/s vesc) |
| Insolation Flux | 132.0000 S⊕ (~179,652 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 431.700 LY (132.353 pc) |