NGTS-39 b
Astrophysical Synthesis & Habitability Characterization
NGTS-39 b is a confirmed gas giant exoplanet orbiting the star NGTS-39, located approximately 908 light-years (278.4 parsecs) from the Solar System. First announced in 2026 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.9289% across the stellar disk), this world measures 12.195 Earth radii (1.09 Jupiter radii) and has a measured mass of 466.254 Earth masses (1.47 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.42 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 3.14 g⊕ (30.79 m/s²), and an escape velocity of 69.2 km/s.
In its orbital architecture around NGTS-39, NGTS-39 b completes one full revolution every 58.205 Earth days at a semi-major axis of 0.3077 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 57.5 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.386, swinging from 0.1889 AU at periapsis out to 0.4265 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 519 K (+246°C / +475°F) and receiving 16.71 S⊕ (~22,736 W/m²), NGTS-39 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star NGTS-39 is classified as a warm F-type star of spectral type F9 V with an effective photospheric temperature of 6,053 K, a radius of 1.16 R☉, a mass of 1.16 M☉, an estimated bolometric luminosity of 1.621 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.2 Gyr and a metallicity of [Fe/H] = 0.196 dex (metal-rich relative to the Sun). From Earth, NGTS-39 shines at apparent V-band magnitude 11.568 (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 | NGTS-39 |
| Spectral Type | F9 V |
| Effective Temp (Teff) | 6,053 K |
| Stellar Radius | 1.1600 R☉ |
| Stellar Mass | 1.1600 M☉ |
| Bolometric Luminosity | 1.621 L☉ |
| Metallicity [Fe/H] | 0.196 dex |
| Stellar Age | 2.200 Gyr |
| Apparent Magnitude | V: 11.568 · G: 11.427 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.307700 AU |
| Orbital Period | 58.205 days |
| Mean Orbital Velocity | 57.5 km/s |
| Orbital Eccentricity (e) | 0.38600 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.42 g/cm³ (69.2 km/s vesc) |
| Insolation Flux | 16.7057 S⊕ (~22,736 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 908.000 LY (278.402 pc) |