TOI-1231 b
Astrophysical Synthesis & Habitability Characterization
TOI-1231 b is a confirmed sub-neptune exoplanet orbiting the star TOI-1231, located approximately 90.1 light-years (27.62 parsecs) from the Solar System. First announced in 2021 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.4942% across the stellar disk), this world measures 3.65 Earth radii (0.33 Jupiter radii) and has a measured mass of 15.4 Earth masses. Combining its mass and radius yields a mean bulk density of 1.75 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.16 g⊕ (11.38 m/s²), and an escape velocity of 23 km/s.
In its orbital architecture around TOI-1231, TOI-1231 b completes one full revolution every 24.246 Earth days at a semi-major axis of 0.1288 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 57.8 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.087 carries the world between 0.1176 AU at periapsis and 0.14 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 3.650 R⊕, TOI-1231 b exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star TOI-1231 is classified as a low-mass red dwarf of spectral type M3 V with an effective photospheric temperature of 3,553 K, a radius of 0.476 R☉, a mass of 0.485 M☉, an estimated bolometric luminosity of 0.032 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.041 dex (near-solar heavy-element abundance). From Earth, TOI-1231 shines at apparent V-band magnitude 12.36 (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-1231 |
| Spectral Type | M3 V |
| Effective Temp (Teff) | 3,553 K |
| Stellar Radius | 0.4760 R☉ |
| Stellar Mass | 0.4850 M☉ |
| Bolometric Luminosity | 0.032 L☉ |
| Metallicity [Fe/H] | 0.041 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 12.360 · G: 11.360 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.128800 AU |
| Orbital Period | 24.246 days |
| Mean Orbital Velocity | 57.8 km/s |
| Orbital Eccentricity (e) | 0.08700 |
| Orbital Inclination (i) | 89.7300° |
| Mean Bulk Density | 1.75 g/cm³ (23 km/s vesc) |
| Insolation Flux | 1.9300 S⊕ (~2,627 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 90.100 LY (27.623 pc) |