TOI-778 b
Astrophysical Synthesis & Habitability Characterization
TOI-778 b is a confirmed gas giant exoplanet orbiting the star TOI-778, located approximately 527.5 light-years (161.74 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 0.6817% across the stellar disk), this world measures 15.4 Earth radii (1.37 Jupiter radii) and has a measured mass of 878 Earth masses (2.76 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.33 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 3.7 g⊕ (36.28 m/s²), and an escape velocity of 84.5 km/s.
In its orbital architecture around TOI-778, TOI-778 b completes one full revolution every 4.634 Earth days at a semi-major axis of 0.06 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 140.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.21 carries the world between 0.0474 AU at periapsis and 0.0726 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1561 K (+1288°C / +2350°F) and receiving 734.67 S⊕ (~999,889 W/m²), TOI-778 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-778 is classified as a warm F-type star of spectral type F3 V with an effective photospheric temperature of 6,643 K, a radius of 1.71 R☉, a mass of 1.4 M☉, an estimated bolometric luminosity of 5.109 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.95 Gyr and a metallicity of [Fe/H] = 0 dex (near-solar heavy-element abundance). From Earth, TOI-778 shines at apparent V-band magnitude 9.109 (accessible to binoculars and small amateur telescopes) in the Southern 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-778 |
| Spectral Type | F3 V |
| Effective Temp (Teff) | 6,643 K |
| Stellar Radius | 1.7100 R☉ |
| Stellar Mass | 1.4000 M☉ |
| Bolometric Luminosity | 5.109 L☉ |
| Metallicity [Fe/H] | 0.000 dex |
| Stellar Age | 1.950 Gyr |
| Apparent Magnitude | V: 9.109 · G: 8.994 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.060000 AU |
| Orbital Period | 4.634 days |
| Mean Orbital Velocity | 140.9 km/s |
| Orbital Eccentricity (e) | 0.21000 |
| Orbital Inclination (i) | 84.7000° |
| Mean Bulk Density | 1.33 g/cm³ (84.5 km/s vesc) |
| Insolation Flux | 734.6720 S⊕ (~999,889 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 527.500 LY (161.743 pc) |