TOI-908 b
Astrophysical Synthesis & Habitability Characterization
TOI-908 b is a confirmed sub-neptune exoplanet orbiting the star TOI-908, located approximately 573.2 light-years (175.75 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 0.0807% across the stellar disk), this world measures 3.186 Earth radii (0.28 Jupiter radii) and has a measured mass of 16.137 Earth masses. Combining its mass and radius yields a mean bulk density of 2.75 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.59 g⊕ (15.59 m/s²), and an escape velocity of 25.2 km/s.
In its orbital architecture around TOI-908, TOI-908 b completes one full revolution every 3.184 Earth days at a semi-major axis of 0.041657 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 142.3 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.132 carries the world between 0.0362 AU at periapsis and 0.0472 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1317 K (+1044°C / +1911°F) and receiving 80.88 S⊕ (~110,083 W/m²), TOI-908 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-908 is classified as a solar-type yellow star of spectral type G V with an effective photospheric temperature of 5,626 K, a radius of 1.028 R☉, a mass of 0.95 M☉, an estimated bolometric luminosity of 0.95 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.6 Gyr and a metallicity of [Fe/H] = 0.08 dex (metal-rich relative to the Sun). From Earth, TOI-908 shines at apparent V-band magnitude 11.316 (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-908 |
| Spectral Type | G V |
| Effective Temp (Teff) | 5,626 K |
| Stellar Radius | 1.0280 R☉ |
| Stellar Mass | 0.9500 M☉ |
| Bolometric Luminosity | 0.95 L☉ |
| Metallicity [Fe/H] | 0.080 dex |
| Stellar Age | 4.600 Gyr |
| Apparent Magnitude | V: 11.316 · G: 11.106 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.041657 AU |
| Orbital Period | 3.184 days |
| Mean Orbital Velocity | 142.3 km/s |
| Orbital Eccentricity (e) | 0.13200 |
| Orbital Inclination (i) | 86.4750° |
| Mean Bulk Density | 2.75 g/cm³ (25.2 km/s vesc) |
| Insolation Flux | 80.8840 S⊕ (~110,083 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 573.200 LY (175.748 pc) |