TOI-1859 b
Astrophysical Synthesis & Habitability Characterization
TOI-1859 b is a confirmed gas giant exoplanet orbiting the star TOI-1859, located approximately 731.8 light-years (224.39 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 0.4322% across the stellar disk), this world measures 9.752 Earth radii (0.87 Jupiter radii) and has a measured mass of 68.6 Earth masses (0.22 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.41 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.72 g⊕ (7.06 m/s²), and an escape velocity of 29.7 km/s.
In its orbital architecture around TOI-1859, TOI-1859 b completes one full revolution every 63.483 Earth days at a semi-major axis of 0.337 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). The planet follows a highly eccentric trajectory (e = 0.57, swinging from 0.1449 AU at periapsis out to 0.5291 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 615 K (+342°C / +648°F) and receiving 23.79 S⊕ (~32,373 W/m²), TOI-1859 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-1859 is classified as a stellar host with an effective photospheric temperature of 6,341 K, a radius of 1.36 R☉, a mass of 1.287 M☉, an estimated bolometric luminosity of 2.683 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.41 Gyr and a metallicity of [Fe/H] = 0.12 dex (metal-rich relative to the Sun). From Earth, TOI-1859 shines at apparent V-band magnitude 10.33 (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-1859 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,341 K |
| Stellar Radius | 1.3600 R☉ |
| Stellar Mass | 1.2870 M☉ |
| Bolometric Luminosity | 2.683 L☉ |
| Metallicity [Fe/H] | 0.120 dex |
| Stellar Age | 1.410 Gyr |
| Apparent Magnitude | V: 10.330 · G: 10.284 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.337000 AU |
| Orbital Period | 63.483 days |
| Mean Orbital Velocity | 57.8 km/s |
| Orbital Eccentricity (e) | 0.57000 |
| Orbital Inclination (i) | 88.6400° |
| Mean Bulk Density | 0.41 g/cm³ (29.7 km/s vesc) |
| Insolation Flux | 23.7860 S⊕ (~32,373 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 731.800 LY (224.385 pc) |