HD 222155 b
Astrophysical Synthesis & Habitability Characterization
HD 222155 b is a confirmed gas giant exoplanet orbiting the star HD 222155, located approximately 165.1 light-years (50.61 parsecs) from the Solar System. First announced in 2011 by Haute-Provence 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 581.626 Earth masses (1.83 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.33 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 3.24 g⊕ (31.77 m/s²), and an escape velocity of 73.7 km/s.
In its orbital architecture around HD 222155, HD 222155 b completes one full revolution every 3999 Earth days (10.95Julian years) at a semi-major axis of 5.14 AU (corresponding to the middle-system regime between Mars at 1.52 AU and Jupiter at 5.20 AU). Its mean orbital velocity is approximately 14 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.16 carries the world between 4.3176 AU at periapsis and 5.9624 AU at apoapsis, driving measurable seasonal insolation cycles.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 165 K (-108°C / -162°F) and an incident flux of 0.12 S⊕ (~166 W/m²), surface water and volatile species on HD 222155 b would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 222155 is classified as a solar-type yellow star of spectral type G2 V with an effective photospheric temperature of 5,701 K, a radius of 1.85 R☉, a mass of 1.21 M☉, an estimated bolometric luminosity of 3.244 L☉. Stellar evolution modeling indicates an estimated stellar age of 8.2 Gyr and a metallicity of [Fe/H] = -0.18 dex (metal-poor relative to the Sun). From Earth, HD 222155 shines at apparent V-band magnitude 7.117 (accessible to binoculars and small amateur telescopes) 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: Haute-Provence Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 222155 |
| Spectral Type | G2 V |
| Effective Temp (Teff) | 5,701 K |
| Stellar Radius | 1.8500 R☉ |
| Stellar Mass | 1.2100 M☉ |
| Bolometric Luminosity | 3.244 L☉ |
| Metallicity [Fe/H] | -0.180 dex |
| Stellar Age | 8.200 Gyr |
| Apparent Magnitude | V: 7.117 · G: 6.936 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 5.140000 AU |
| Orbital Period | 3999 days |
| Mean Orbital Velocity | 14 km/s |
| Orbital Eccentricity (e) | 0.16000 |
| Orbital Inclination (i) | 68.0000° |
| Mean Bulk Density | 1.33 g/cm³ (73.7 km/s vesc) |
| Insolation Flux | 0.1222 S⊕ (~166 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 165.100 LY (50.608 pc) |