NGTS-25 b
Astrophysical Synthesis & Habitability Characterization
NGTS-25 b is a confirmed gas giant exoplanet orbiting the star NGTS-25, located approximately 1700 light-years (521.23 parsecs) from the Solar System. First announced in 2022 by Next-Generation Transit Survey (NGTS) using the Transit detection technique (producing an estimated primary transit depth of 1.4943% across the stellar disk), this world measures 11.467 Earth radii (1.02 Jupiter radii) and has a measured mass of 203.092 Earth masses (0.64 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.74 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.54 g⊕ (15.1 m/s²), and an escape velocity of 47.1 km/s.
In its orbital architecture around NGTS-25, NGTS-25 b completes one full revolution every 2.823 Earth days at a semi-major axis of 0.0388 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 149.5 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1101 K (+828°C / +1522°F) and receiving 339.44 S⊕ (~461,972 W/m²), NGTS-25 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star NGTS-25 is classified as an orange K-type star of spectral type K0 V with an effective photospheric temperature of 5,321 K, a radius of 0.86 R☉, a mass of 0.91 M☉, an estimated bolometric luminosity of 0.532 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.49 Gyr and a metallicity of [Fe/H] = 0.12 dex (metal-rich relative to the Sun). From Earth, NGTS-25 shines at apparent V-band magnitude 14.333 (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-25 |
| Spectral Type | K0 V |
| Effective Temp (Teff) | 5,321 K |
| Stellar Radius | 0.8600 R☉ |
| Stellar Mass | 0.9100 M☉ |
| Bolometric Luminosity | 0.532 L☉ |
| Metallicity [Fe/H] | 0.120 dex |
| Stellar Age | 3.490 Gyr |
| Apparent Magnitude | V: 14.333 · G: 14.086 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.038800 AU |
| Orbital Period | 2.823 days |
| Mean Orbital Velocity | 149.5 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.3400° |
| Mean Bulk Density | 0.74 g/cm³ (47.1 km/s vesc) |
| Insolation Flux | 339.4356 S⊕ (~461,972 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1700.000 LY (521.233 pc) |