XO-2 N b
Astrophysical Synthesis & Habitability Characterization
XO-2 N b is a confirmed gas giant exoplanet orbiting the star XO-2 N, located approximately 503.2 light-years (154.27 parsecs) from the Solar System. First announced in 2007 by XO using the Transit detection technique (producing an estimated primary transit depth of 1.0456% across the stellar disk), this world measures 11.131 Earth radii (0.99 Jupiter radii) and has a measured mass of 199.915 Earth masses (0.63 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.8 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.61 g⊕ (15.79 m/s²), and an escape velocity of 47.4 km/s.
In its orbital architecture around XO-2 N, XO-2 N b completes one full revolution every 2.616 Earth days at a semi-major axis of 0.03666 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 152.5 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 1328 K (+1055°C / +1931°F) and receiving 428.04 S⊕ (~582,557 W/m²), XO-2 N b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star XO-2 N is classified as a solar-type yellow star of spectral type G8 V with an effective photospheric temperature of 5,290 K, a radius of 0.998 R☉, a mass of 0.96 M☉, an estimated bolometric luminosity of 0.7 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.8 Gyr and a metallicity of [Fe/H] = 0.37 dex (metal-rich relative to the Sun). From Earth, XO-2 N shines at apparent V-band magnitude 11.246 (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-2 N |
| Spectral Type | G8 V |
| Effective Temp (Teff) | 5,290 K |
| Stellar Radius | 0.9980 R☉ |
| Stellar Mass | 0.9600 M☉ |
| Bolometric Luminosity | 0.7 L☉ |
| Metallicity [Fe/H] | 0.370 dex |
| Stellar Age | 7.800 Gyr |
| Apparent Magnitude | V: 11.246 · G: 10.972 |
| System Architecture | 2 Stars, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.036660 AU |
| Orbital Period | 2.616 days |
| Mean Orbital Velocity | 152.5 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.0100° |
| Mean Bulk Density | 0.8 g/cm³ (47.4 km/s vesc) |
| Insolation Flux | 428.0360 S⊕ (~582,557 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 503.200 LY (154.273 pc) |