TOI-1801 b
Astrophysical Synthesis & Habitability Characterization
TOI-1801 b is a confirmed sub-neptune exoplanet orbiting the star TOI-1801, located approximately 100.1 light-years (30.68 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 0.1214% across the stellar disk), this world measures 2.079 Earth radii and has a measured mass of 5.738 Earth masses. Combining its mass and radius yields a mean bulk density of 3.52 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.33 g⊕ (13.04 m/s²), and an escape velocity of 18.6 km/s.
In its orbital architecture around TOI-1801, TOI-1801 b completes one full revolution every 10.644 Earth days at a semi-major axis of 0.075 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 76.7 km/s (compared to Earth's 29.8 km/s). 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 494 K (+221°C / +430°F) and receiving 10.73 S⊕ (~14,600 W/m²), TOI-1801 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-1801 is classified as a low-mass red dwarf of spectral type M0.5+/-0.5 V with an effective photospheric temperature of 3,863 K, a radius of 0.547 R☉, a mass of 0.556 M☉, an estimated bolometric luminosity of 0.06 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.7 Gyr and a metallicity of [Fe/H] = -0.19 dex (metal-poor relative to the Sun). From Earth, TOI-1801 shines at apparent V-band magnitude 11.58 (faint and requiring research-grade or CCD telescopic photometry) in the Northern 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-1801 |
| Spectral Type | M0.5+/-0.5 V |
| Effective Temp (Teff) | 3,863 K |
| Stellar Radius | 0.5470 R☉ |
| Stellar Mass | 0.5560 M☉ |
| Bolometric Luminosity | 0.06 L☉ |
| Metallicity [Fe/H] | -0.190 dex |
| Stellar Age | 0.700 Gyr |
| Apparent Magnitude | V: 11.580 · G: 10.827 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.075000 AU |
| Orbital Period | 10.644 days |
| Mean Orbital Velocity | 76.7 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.5070° |
| Mean Bulk Density | 3.52 g/cm³ (18.6 km/s vesc) |
| Insolation Flux | 10.7276 S⊕ (~14,600 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 100.100 LY (30.680 pc) |