TOI-5646 b
Astrophysical Synthesis & Habitability Characterization
TOI-5646 b is a confirmed gas giant exoplanet orbiting the star TOI-5646, located approximately 1399.9 light-years (429.22 parsecs) from the Solar System. First announced in 2026 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.1088% across the stellar disk), this world measures 6.61 Earth radii (0.59 Jupiter radii) and has a measured mass of 45.93 Earth masses (0.14 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.88 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.05 g⊕ (10.3 m/s²), and an escape velocity of 29.5 km/s.
In its orbital architecture around TOI-5646, TOI-5646 b completes one full revolution every 2.428 Earth days at a semi-major axis of 0.0427 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 191.3 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.12 carries the world between 0.0376 AU at periapsis and 0.0478 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1935 K (+1662°C / +3024°F) and receiving 2,340.00 S⊕ (~3,184,740 W/m²), TOI-5646 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-5646 is classified as a warm F-type star of spectral type F8 IV-V with an effective photospheric temperature of 6,136 K, a radius of 1.837 R☉, a mass of 1.418 M☉, an estimated bolometric luminosity of 4.292 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.82 Gyr and a metallicity of [Fe/H] = 0.32 dex (metal-rich relative to the Sun). From Earth, TOI-5646 shines at apparent V-band magnitude 11.382 (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-5646 |
| Spectral Type | F8 IV-V |
| Effective Temp (Teff) | 6,136 K |
| Stellar Radius | 1.8370 R☉ |
| Stellar Mass | 1.4180 M☉ |
| Bolometric Luminosity | 4.292 L☉ |
| Metallicity [Fe/H] | 0.320 dex |
| Stellar Age | 2.820 Gyr |
| Apparent Magnitude | V: 11.382 · G: 11.292 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.042700 AU |
| Orbital Period | 2.428 days |
| Mean Orbital Velocity | 191.3 km/s |
| Orbital Eccentricity (e) | 0.12000 |
| Orbital Inclination (i) | 84.7700° |
| Mean Bulk Density | 0.88 g/cm³ (29.5 km/s vesc) |
| Insolation Flux | 2340.0000 S⊕ (~3,184,740 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1399.900 LY (429.221 pc) |