TOI-5205 b
Astrophysical Synthesis & Habitability Characterization
TOI-5205 b is a confirmed gas giant exoplanet orbiting the star TOI-5205, located approximately 282 light-years (86.45 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 7.2856% across the stellar disk), this world measures 11.6 Earth radii (1.03 Jupiter radii) and has a measured mass of 343 Earth masses (1.08 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.21 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.55 g⊕ (25.01 m/s²), and an escape velocity of 60.8 km/s.
In its orbital architecture around TOI-5205, TOI-5205 b completes one full revolution every 1.631 Earth days at a semi-major axis of 0.0199 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 132.8 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.02 (ranging from 0.0195 AU at periapsis to 0.0203 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 737 K (+464°C / +867°F) and receiving 49.00 S⊕ (~66,689 W/m²), TOI-5205 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-5205 is classified as a low-mass red dwarf of spectral type M4.0 with an effective photospheric temperature of 3,430 K, a radius of 0.394 R☉, a mass of 0.392 M☉, an estimated bolometric luminosity of 0.019 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0 dex (near-solar heavy-element abundance). From Earth, TOI-5205 shines at apparent V-band magnitude 15.899 (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-5205 |
| Spectral Type | M4.0 |
| Effective Temp (Teff) | 3,430 K |
| Stellar Radius | 0.3940 R☉ |
| Stellar Mass | 0.3920 M☉ |
| Bolometric Luminosity | 0.019 L☉ |
| Metallicity [Fe/H] | 0.000 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 15.899 · G: 14.932 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.019900 AU |
| Orbital Period | 1.631 days |
| Mean Orbital Velocity | 132.8 km/s |
| Orbital Eccentricity (e) | 0.02000 |
| Orbital Inclination (i) | 88.2100° |
| Mean Bulk Density | 1.21 g/cm³ (60.8 km/s vesc) |
| Insolation Flux | 49.0000 S⊕ (~66,689 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 282.000 LY (86.449 pc) |