NGTS-9 b
Astrophysical Synthesis & Habitability Characterization
NGTS-9 b is a confirmed gas giant exoplanet orbiting the star NGTS-9, located approximately 1986.7 light-years (609.13 parsecs) from the Solar System. First announced in 2019 by Next-Generation Transit Survey (NGTS) using the Transit detection technique (producing an estimated primary transit depth of 0.6349% across the stellar disk), this world measures 11.994 Earth radii (1.07 Jupiter radii) and has a measured mass of 921.707 Earth masses (2.9 Jupiter masses). Combining its mass and radius yields a mean bulk density of 2.95 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 6.41 g⊕ (62.86 m/s²), and an escape velocity of 98.1 km/s.
In its orbital architecture around NGTS-9, NGTS-9 b completes one full revolution every 4.435 Earth days at a semi-major axis of 0.058 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 142.3 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.06 carries the world between 0.0545 AU at periapsis and 0.0615 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1448 K (+1175°C / +2147°F) and receiving 729.00 S⊕ (~992,169 W/m²), NGTS-9 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star NGTS-9 is classified as a warm F-type star of spectral type F8 V with an effective photospheric temperature of 6,330 K, a radius of 1.38 R☉, a mass of 1.34 M☉, an estimated bolometric luminosity of 2.743 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.96 Gyr and a metallicity of [Fe/H] = 0.31 dex (metal-rich relative to the Sun). From Earth, NGTS-9 shines at apparent V-band magnitude 12.868 (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-9 |
| Spectral Type | F8 V |
| Effective Temp (Teff) | 6,330 K |
| Stellar Radius | 1.3800 R☉ |
| Stellar Mass | 1.3400 M☉ |
| Bolometric Luminosity | 2.743 L☉ |
| Metallicity [Fe/H] | 0.310 dex |
| Stellar Age | 0.960 Gyr |
| Apparent Magnitude | V: 12.868 · G: 12.655 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.058000 AU |
| Orbital Period | 4.435 days |
| Mean Orbital Velocity | 142.3 km/s |
| Orbital Eccentricity (e) | 0.06000 |
| Orbital Inclination (i) | 84.1000° |
| Mean Bulk Density | 2.95 g/cm³ (98.1 km/s vesc) |
| Insolation Flux | 729.0000 S⊕ (~992,169 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1986.700 LY (609.128 pc) |