TOI-3856 b
Astrophysical Synthesis & Habitability Characterization
TOI-3856 b is a confirmed gas giant exoplanet orbiting the star TOI-3856, located approximately 1025.6 light-years (314.44 parsecs) from the Solar System. First announced in 2025 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 1.3959% across the stellar disk), this world measures 13.596 Earth radii (1.21 Jupiter radii) and has a measured mass of 171.627 Earth masses (0.54 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.38 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.93 g⊕ (9.12 m/s²), and an escape velocity of 39.7 km/s.
In its orbital architecture around TOI-3856, TOI-3856 b completes one full revolution every 2.044 Earth days at a semi-major axis of 0.0325 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 173 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.083 carries the world between 0.0298 AU at periapsis and 0.0352 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1544 K (+1271°C / +2320°F) and receiving 949.00 S⊕ (~1,291,589 W/m²), TOI-3856 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-3856 is classified as a stellar host with an effective photospheric temperature of 5,622 K, a radius of 1.055 R☉, a mass of 1.096 M☉, an estimated bolometric luminosity of 0.998 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.6 Gyr and a metallicity of [Fe/H] = 0.454 dex (metal-rich relative to the Sun). From Earth, TOI-3856 shines at apparent V-band magnitude 12.292 (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-3856 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,622 K |
| Stellar Radius | 1.0550 R☉ |
| Stellar Mass | 1.0960 M☉ |
| Bolometric Luminosity | 0.998 L☉ |
| Metallicity [Fe/H] | 0.454 dex |
| Stellar Age | 2.600 Gyr |
| Apparent Magnitude | V: 12.292 · G: 12.132 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.032500 AU |
| Orbital Period | 2.044 days |
| Mean Orbital Velocity | 173 km/s |
| Orbital Eccentricity (e) | 0.08300 |
| Orbital Inclination (i) | 82.9400° |
| Mean Bulk Density | 0.38 g/cm³ (39.7 km/s vesc) |
| Insolation Flux | 949.0000 S⊕ (~1,291,589 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1025.600 LY (314.443 pc) |