NGTS-3 A b
Astrophysical Synthesis & Habitability Characterization
NGTS-3 A b is a confirmed gas giant exoplanet orbiting the star NGTS-3 A, located approximately 2426.5 light-years (743.97 parsecs) from the Solar System. First announced in 2018 by Next-Generation Transit Survey (NGTS) using the Transit detection technique (producing an estimated primary transit depth of 2.6743% across the stellar disk), this world measures 16.589 Earth radii (1.48 Jupiter radii) and has a measured mass of 756.435 Earth masses (2.38 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.91 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.75 g⊕ (26.97 m/s²), and an escape velocity of 75.5 km/s.
In its orbital architecture around NGTS-3 A, NGTS-3 A b completes one full revolution every 1.675 Earth days at a semi-major axis of 0.023 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 149.4 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1434 K (+1161°C / +2122°F) and receiving 1,000.57 S⊕ (~1,361,773 W/m²), NGTS-3 A b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star NGTS-3 A is classified as a solar-type yellow star of spectral type G6 V with an effective photospheric temperature of 5,600 K, a radius of 0.93 R☉, a mass of 1.017 M☉, an estimated bolometric luminosity of 0.763 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.12 dex (metal-rich relative to the Sun). From Earth, NGTS-3 A shines at apparent V-band magnitude 14.669 (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: Next-Generation Transit Survey (NGTS) · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | NGTS-3 A |
| Spectral Type | G6 V |
| Effective Temp (Teff) | 5,600 K |
| Stellar Radius | 0.9300 R☉ |
| Stellar Mass | 1.0170 M☉ |
| Bolometric Luminosity | 0.763 L☉ |
| Metallicity [Fe/H] | 0.120 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 14.669 · G: 14.488 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.023000 AU |
| Orbital Period | 1.675 days |
| Mean Orbital Velocity | 149.4 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 89.5600° |
| Mean Bulk Density | 0.91 g/cm³ (75.5 km/s vesc) |
| Insolation Flux | 1000.5679 S⊕ (~1,361,773 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2426.500 LY (743.972 pc) |