xi Aql b
Astrophysical Synthesis & Habitability Characterization
xi Aql b is a confirmed gas giant exoplanet orbiting the star xi Aql, located approximately 183.3 light-years (56.19 parsecs) from the Solar System. First announced in 2007 by Okayama Astrophysical Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.4 Earth radii (1.2 Jupiter radii) and has a measured mass of 616.905 Earth masses (1.94 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.41 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 3.44 g⊕ (33.73 m/s²), and an escape velocity of 75.9 km/s.
In its orbital architecture around xi Aql, xi Aql b completes one full revolution every 136.97 Earth days at a semi-major axis of 0.625 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 49.6 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.059 carries the world between 0.5881 AU at periapsis and 0.6619 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 973 K (+700°C / +1292°F) and receiving 149.86 S⊕ (~203,963 W/m²), xi Aql b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star xi Aql is classified as an orange K-type star of spectral type K0 III with an effective photospheric temperature of 4,841 K, a radius of 10.86 R☉, a mass of 1.74 M☉, an estimated bolometric luminosity of 58.115 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.1 Gyr and a metallicity of [Fe/H] = -0.11 dex (metal-poor relative to the Sun). From Earth, xi Aql shines at apparent V-band magnitude 4.71 (visible to the unaided human eye under dark skies) 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: Okayama Astrophysical Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | xi Aql |
| Spectral Type | K0 III |
| Effective Temp (Teff) | 4,841 K |
| Stellar Radius | 10.8600 R☉ |
| Stellar Mass | 1.7400 M☉ |
| Bolometric Luminosity | 58.115 L☉ |
| Metallicity [Fe/H] | -0.110 dex |
| Stellar Age | 7.100 Gyr |
| Apparent Magnitude | V: 4.710 · G: 4.425 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.625000 AU |
| Orbital Period | 136.97 days |
| Mean Orbital Velocity | 49.6 km/s |
| Orbital Eccentricity (e) | 0.05900 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.41 g/cm³ (75.9 km/s vesc) |
| Insolation Flux | 149.8624 S⊕ (~203,963 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 183.300 LY (56.186 pc) |