TOI-205 b
Astrophysical Synthesis & Habitability Characterization
TOI-205 b is a confirmed sub-neptune exoplanet orbiting the star TOI-205, located approximately 579.8 light-years (177.76 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 0.0249% across the stellar disk), this world measures 2.501 Earth radii and has a measured mass of 6.81 Earth masses. Combining its mass and radius yields a mean bulk density of 2.4 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.09 g⊕ (10.69 m/s²), and an escape velocity of 18.5 km/s.
In its orbital architecture around TOI-205, TOI-205 b completes one full revolution every 4.253 Earth days.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1800 K (+1527°C / +2781°F) and receiving 1,740.92 S⊕ (~2,369,395 W/m²), TOI-205 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-205 is classified as a stellar host with an effective photospheric temperature of 6,303 K, a radius of 1.4538 R☉, a mass of 1.2 M☉, an estimated bolometric luminosity of 2.993 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.13 dex (metal-rich relative to the Sun). From Earth, TOI-205 shines at apparent V-band magnitude 9.921 (accessible to binoculars and small amateur telescopes) 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-205 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,303 K |
| Stellar Radius | 1.4538 R☉ |
| Stellar Mass | 1.2000 M☉ |
| Bolometric Luminosity | 2.993 L☉ |
| Metallicity [Fe/H] | 0.130 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 9.921 · G: 9.794 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 4.253 days |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 86.6259° |
| Mean Bulk Density | 2.4 g/cm³ (18.5 km/s vesc) |
| Insolation Flux | 1740.9224 S⊕ (~2,369,395 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 579.800 LY (177.759 pc) |