XO-1 b
Astrophysical Synthesis & Habitability Characterization
XO-1 b is a confirmed gas giant exoplanet orbiting the star XO-1, located approximately 533.4 light-years (163.55 parsecs) from the Solar System. First announced in 2006 by XO using the Transit detection technique (producing an estimated primary transit depth of 1.7722% across the stellar disk), this world measures 12.778 Earth radii (1.14 Jupiter radii) and has a measured mass of 263.799 Earth masses (0.83 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.7 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.62 g⊕ (15.89 m/s²), and an escape velocity of 50.8 km/s.
In its orbital architecture around XO-1, XO-1 b completes one full revolution every 3.942 Earth days at a semi-major axis of 0.0488 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 134.7 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 1210 K (+937°C / +1719°F) and receiving 321.85 S⊕ (~438,038 W/m²), XO-1 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star XO-1 is classified as a solar-type yellow star of spectral type G1 V with an effective photospheric temperature of 5,750 K, a radius of 0.88 R☉, a mass of 0.88 M☉, an estimated bolometric luminosity of 0.759 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.9 Gyr and a metallicity of [Fe/H] = 0.02 dex (near-solar heavy-element abundance). From Earth, XO-1 shines at apparent V-band magnitude 11.251 (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: XO · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | XO-1 |
| Spectral Type | G1 V |
| Effective Temp (Teff) | 5,750 K |
| Stellar Radius | 0.8800 R☉ |
| Stellar Mass | 0.8800 M☉ |
| Bolometric Luminosity | 0.759 L☉ |
| Metallicity [Fe/H] | 0.020 dex |
| Stellar Age | 0.900 Gyr |
| Apparent Magnitude | V: 11.251 · G: 11.004 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.048800 AU |
| Orbital Period | 3.942 days |
| Mean Orbital Velocity | 134.7 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.8100° |
| Mean Bulk Density | 0.7 g/cm³ (50.8 km/s vesc) |
| Insolation Flux | 321.8500 S⊕ (~438,038 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 533.400 LY (163.553 pc) |