Qatar-9 b
Astrophysical Synthesis & Habitability Characterization
Qatar-9 b is a confirmed gas giant exoplanet orbiting the star Qatar-9, located approximately 697.2 light-years (213.77 parsecs) from the Solar System. First announced in 2019 by Qatar using the Transit detection technique (producing an estimated primary transit depth of 2.2195% across the stellar disk), this world measures 11.31 Earth radii (1.01 Jupiter radii) and has a measured mass of 378.218 Earth masses (1.19 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.44 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.96 g⊕ (29.03 m/s²), and an escape velocity of 64.7 km/s.
In its orbital architecture around Qatar-9, Qatar-9 b completes one full revolution every 1.541 Earth days at a semi-major axis of 0.0234 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 165.2 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 1134 K (+861°C / +1582°F) and receiving 210.67 S⊕ (~286,721 W/m²), Qatar-9 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Qatar-9 is classified as an orange K-type star of spectral type K5 V with an effective photospheric temperature of 4,309 K, a radius of 0.696 R☉, a mass of 0.719 M☉, an estimated bolometric luminosity of 0.15 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.5 Gyr and a metallicity of [Fe/H] = 0.252 dex (metal-rich relative to the Sun). From Earth, Qatar-9 shines at apparent V-band magnitude 14.023 (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: Qatar · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | Qatar-9 |
| Spectral Type | K5 V |
| Effective Temp (Teff) | 4,309 K |
| Stellar Radius | 0.6960 R☉ |
| Stellar Mass | 0.7190 M☉ |
| Bolometric Luminosity | 0.15 L☉ |
| Metallicity [Fe/H] | 0.252 dex |
| Stellar Age | 7.500 Gyr |
| Apparent Magnitude | V: 14.023 · G: 13.687 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.023400 AU |
| Orbital Period | 1.541 days |
| Mean Orbital Velocity | 165.2 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.2300° |
| Mean Bulk Density | 1.44 g/cm³ (64.7 km/s vesc) |
| Insolation Flux | 210.6690 S⊕ (~286,721 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 697.200 LY (213.771 pc) |