TOI-3321 b
Astrophysical Synthesis & Habitability Characterization
TOI-3321 b is a confirmed gas giant exoplanet orbiting the star TOI-3321, located approximately 932.5 light-years (285.9 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 0.8479% across the stellar disk), this world measures 15.558 Earth radii (1.39 Jupiter radii) and has a measured mass of 176.077 Earth masses (0.55 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.26 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.73 g⊕ (7.16 m/s²), and an escape velocity of 37.6 km/s.
In its orbital architecture around TOI-3321, TOI-3321 b completes one full revolution every 3.653 Earth days at a semi-major axis of 0.047 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 140 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.054 carries the world between 0.0445 AU at periapsis and 0.0495 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1616 K (+1343°C / +2449°F) and receiving 967.92 S⊕ (~1,317,338 W/m²), TOI-3321 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-3321 is classified as a stellar host with an effective photospheric temperature of 5,850 K, a radius of 1.549 R☉, a mass of 1.041 M☉, an estimated bolometric luminosity of 2.521 L☉. Stellar evolution modeling indicates an estimated stellar age of 8.1 Gyr and a metallicity of [Fe/H] = -0.103 dex (metal-poor relative to the Sun). From Earth, TOI-3321 shines at apparent V-band magnitude 11.076 (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-3321 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,850 K |
| Stellar Radius | 1.5490 R☉ |
| Stellar Mass | 1.0410 M☉ |
| Bolometric Luminosity | 2.521 L☉ |
| Metallicity [Fe/H] | -0.103 dex |
| Stellar Age | 8.100 Gyr |
| Apparent Magnitude | V: 11.076 · G: 11.093 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.047000 AU |
| Orbital Period | 3.653 days |
| Mean Orbital Velocity | 140 km/s |
| Orbital Eccentricity (e) | 0.05400 |
| Orbital Inclination (i) | 86.3300° |
| Mean Bulk Density | 0.26 g/cm³ (37.6 km/s vesc) |
| Insolation Flux | 967.9190 S⊕ (~1,317,338 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 932.500 LY (285.895 pc) |