TOI-3984 A b
Astrophysical Synthesis & Habitability Characterization
TOI-3984 A b is a confirmed gas giant exoplanet orbiting the star TOI-3984 A, located approximately 355.1 light-years (108.88 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 2.3747% across the stellar disk), this world measures 7.9 Earth radii (0.7 Jupiter radii) and has a measured mass of 44 Earth masses (0.14 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.49 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.71 g⊕ (6.96 m/s²), and an escape velocity of 26.4 km/s.
In its orbital architecture around TOI-3984 A, TOI-3984 A b completes one full revolution every 4.353 Earth days at a semi-major axis of 0.041 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 102.5 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.23 carries the world between 0.0316 AU at periapsis and 0.0504 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 563 K (+290°C / +554°F) and receiving 16.70 S⊕ (~22,729 W/m²), TOI-3984 A b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-3984 A is classified as a low-mass red dwarf of spectral type M4+/-0.5 with an effective photospheric temperature of 3,476 K, a radius of 0.47 R☉, a mass of 0.49 M☉, an estimated bolometric luminosity of 0.029 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.9 Gyr and a metallicity of [Fe/H] = 0.18 dex (metal-rich relative to the Sun). From Earth, TOI-3984 A shines at apparent V-band magnitude 15.694 (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-3984 A |
| Spectral Type | M4+/-0.5 |
| Effective Temp (Teff) | 3,476 K |
| Stellar Radius | 0.4700 R☉ |
| Stellar Mass | 0.4900 M☉ |
| Bolometric Luminosity | 0.029 L☉ |
| Metallicity [Fe/H] | 0.180 dex |
| Stellar Age | 2.900 Gyr |
| Apparent Magnitude | V: 15.694 · G: 14.672 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.041000 AU |
| Orbital Period | 4.353 days |
| Mean Orbital Velocity | 102.5 km/s |
| Orbital Eccentricity (e) | 0.23000 |
| Orbital Inclination (i) | 89.5000° |
| Mean Bulk Density | 0.49 g/cm³ (26.4 km/s vesc) |
| Insolation Flux | 16.7000 S⊕ (~22,729 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 355.100 LY (108.883 pc) |