TOI-1806 d
Astrophysical Synthesis & Habitability Characterization
TOI-1806 d is a confirmed sub-neptune exoplanet orbiting the star TOI-1806, located approximately 181.1 light-years (55.52 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 0.4323% across the stellar disk), this world measures 2.88 Earth radii and has a measured mass of 8.65 Earth masses. Combining its mass and radius yields a mean bulk density of 2 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.04 g⊕ (10.2 m/s²), and an escape velocity of 19.4 km/s.
In its orbital architecture around TOI-1806, TOI-1806 d completes one full revolution every 8.196 Earth days. The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 379 K (+106°C / +223°F) and receiving 4.87 S⊕ (~6,627 W/m²), TOI-1806 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-1806 is classified as a stellar host with an effective photospheric temperature of 3,272 K, a radius of 0.4016 R☉, a mass of 0.3933 M☉, an estimated bolometric luminosity of 0.017 L☉. From Earth, TOI-1806 shines at apparent V-band magnitude 15.193 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The TOI-1806 system is a multi-planet architecture hosting 3 confirmed worlds, with TOI-1806 d sharing its stellar neighborhood alongside TOI-1806 c, TOI-1806.01.
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-1806 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 3,272 K |
| Stellar Radius | 0.4016 R☉ |
| Stellar Mass | 0.3933 M☉ |
| Bolometric Luminosity | 0.017 L☉ |
| Metallicity [Fe/H] | — |
| Stellar Age | — |
| Apparent Magnitude | V: 15.193 · G: 13.927 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 8.196 days |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2 g/cm³ (19.4 km/s vesc) |
| Insolation Flux | 4.8692 S⊕ (~6,627 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 181.100 LY (55.521 pc) |