TOI-406.01
Astrophysical Synthesis & Habitability Characterization
TOI-406.01 is a confirmed sub-neptune exoplanet orbiting the star TOI-406, located approximately 101.3 light-years (31.06 parsecs) from the Solar System. First announced in 2024 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.2163% across the stellar disk), this world measures 2.08 Earth radii and has a measured mass of 6.57 Earth masses. Combining its mass and radius yields a mean bulk density of 4.03 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.52 g⊕ (14.91 m/s²), and an escape velocity of 19.9 km/s.
In its orbital architecture around TOI-406, TOI-406.01 completes one full revolution every 13.176 Earth days at a semi-major axis of 0.0809 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 66.8 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.056 carries the world between 0.0764 AU at periapsis and 0.0854 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 368 K (+95°C / +203°F) and receiving 3.00 S⊕ (~4,083 W/m²), TOI-406.01 orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-406 is classified as a low-mass red dwarf of spectral type M3 with an effective photospheric temperature of 3,392 K, a radius of 0.41 R☉, a mass of 0.408 M☉, an estimated bolometric luminosity of 0.02 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.02 dex (near-solar heavy-element abundance). From Earth, TOI-406 shines at apparent V-band magnitude 13.773 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The TOI-406 system is a multi-planet architecture hosting 2 confirmed worlds, with TOI-406.01 sharing its stellar neighborhood alongside TOI-406 c.
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-406 |
| Spectral Type | M3 |
| Effective Temp (Teff) | 3,392 K |
| Stellar Radius | 0.4100 R☉ |
| Stellar Mass | 0.4080 M☉ |
| Bolometric Luminosity | 0.02 L☉ |
| Metallicity [Fe/H] | -0.020 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 13.773 · G: 12.553 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.080900 AU |
| Orbital Period | 13.176 days |
| Mean Orbital Velocity | 66.8 km/s |
| Orbital Eccentricity (e) | 0.05600 |
| Orbital Inclination (i) | 89.4000° |
| Mean Bulk Density | 4.03 g/cm³ (19.9 km/s vesc) |
| Insolation Flux | 3.0000 S⊕ (~4,083 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 101.300 LY (31.060 pc) |