NGTS-38 b
Astrophysical Synthesis & Habitability Characterization
NGTS-38 b is a confirmed gas giant exoplanet orbiting the star NGTS-38, located approximately 876.2 light-years (268.64 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 0.3492% across the stellar disk), this world measures 12.117 Earth radii (1.08 Jupiter radii) and has a measured mass of 1516.042 Earth masses (4.77 Jupiter masses). Combining its mass and radius yields a mean bulk density of 4.7 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 10.33 g⊕ (101.3 m/s²), and an escape velocity of 125.1 km/s.
In its orbital architecture around NGTS-38, NGTS-38 b completes one full revolution every 180.528 Earth days at a semi-major axis of 0.697 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 42 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.3086, swinging from 0.4819 AU at periapsis out to 0.9121 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 457 K (+184°C / +363°F) and receiving 10.13 S⊕ (~13,789 W/m²), NGTS-38 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star NGTS-38 is classified as a stellar host with an effective photospheric temperature of 6,310 K, a radius of 1.88 R☉, a mass of 1.46 M☉, an estimated bolometric luminosity of 5.027 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.2 Gyr and a metallicity of [Fe/H] = 0.33 dex (metal-rich relative to the Sun). From Earth, NGTS-38 shines at apparent V-band magnitude 10.225 (faint and requiring research-grade or CCD telescopic photometry) 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 | NGTS-38 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,310 K |
| Stellar Radius | 1.8800 R☉ |
| Stellar Mass | 1.4600 M☉ |
| Bolometric Luminosity | 5.027 L☉ |
| Metallicity [Fe/H] | 0.330 dex |
| Stellar Age | 2.200 Gyr |
| Apparent Magnitude | V: 10.225 · G: 10.106 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.697000 AU |
| Orbital Period | 180.528 days |
| Mean Orbital Velocity | 42 km/s |
| Orbital Eccentricity (e) | 0.30860 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 4.7 g/cm³ (125.1 km/s vesc) |
| Insolation Flux | 10.1316 S⊕ (~13,789 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 876.200 LY (268.637 pc) |