TOI-1338 b
Astrophysical Synthesis & Habitability Characterization
TOI-1338 b is a confirmed gas giant exoplanet orbiting the star TOI-1338 A, located approximately 1301.4 light-years (399.02 parsecs) from the Solar System. First announced in 2020 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.2861% across the stellar disk), this world measures 7.661 Earth radii (0.68 Jupiter radii) and has a measured mass of 11.3 Earth masses. Combining its mass and radius yields a mean bulk density of 0.14 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.19 g⊕ (1.86 m/s²), and an escape velocity of 13.6 km/s.
In its orbital architecture around TOI-1338 A, TOI-1338 b completes one full revolution every 95.4 Earth days at a semi-major axis of 0.4607 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 52.5 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.0331 (ranging from 0.4455 AU at periapsis to 0.4759 AU at apoapsis), the planet experiences minimal orbital distance variation.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 7.661 R⊕, TOI-1338 b exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star TOI-1338 A is classified as a warm F-type star of spectral type F8 with an effective photospheric temperature of 5,723 K, a radius of 1.313 R☉, a mass of 1.0936 M☉, an estimated bolometric luminosity of 1.659 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.4 Gyr and a metallicity of [Fe/H] = 0.01 dex (near-solar heavy-element abundance). From Earth, TOI-1338 A shines at apparent V-band magnitude 11.722 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The TOI-1338 A system is a multi-planet architecture hosting 2 confirmed worlds, with TOI-1338 b sharing its stellar neighborhood alongside TOI-1338 c.
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-1338 A |
| Spectral Type | F8 |
| Effective Temp (Teff) | 5,723 K |
| Stellar Radius | 1.3130 R☉ |
| Stellar Mass | 1.0936 M☉ |
| Bolometric Luminosity | 1.659 L☉ |
| Metallicity [Fe/H] | 0.010 dex |
| Stellar Age | 4.400 Gyr |
| Apparent Magnitude | V: 11.722 · G: 11.876 |
| System Architecture | 2 Stars, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.460700 AU |
| Orbital Period | 95.4 days |
| Mean Orbital Velocity | 52.5 km/s |
| Orbital Eccentricity (e) | 0.03310 |
| Orbital Inclination (i) | 90.4940° |
| Mean Bulk Density | 0.14 g/cm³ (13.6 km/s vesc) |
| Insolation Flux | 0.9938 S⊕ (~1,353 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1301.400 LY (399.017 pc) |