HD 220197 b
Astrophysical Synthesis & Habitability Characterization
HD 220197 b is a confirmed gas giant exoplanet orbiting the star HD 220197, located approximately 210.1 light-years (64.41 parsecs) from the Solar System. First announced in 2018 by Roque de los Muchachos Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 9.32 Earth radii (0.83 Jupiter radii) and has a measured mass of 63.566 Earth masses (0.2 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.43 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.73 g⊕ (7.16 m/s²), and an escape velocity of 29.2 km/s.
In its orbital architecture around HD 220197, HD 220197 b completes one full revolution every 1728 Earth days (4.73Julian years) at a semi-major axis of 2.729 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 17.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.187 carries the world between 2.2187 AU at periapsis and 3.2393 AU at apoapsis, driving measurable seasonal insolation cycles.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 164 K (-109°C / -164°F) and an incident flux of 0.13 S⊕ (~181 W/m²), surface water and volatile species on HD 220197 b would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 220197 is classified as a solar-type yellow star of spectral type G5 with an effective photospheric temperature of 5,683 K, a radius of 0.98 R☉, a mass of 0.91 M☉, an estimated bolometric luminosity of 0.899 L☉. Stellar evolution modeling indicates an estimated stellar age of 10.165 Gyr and a metallicity of [Fe/H] = -0.55 dex (metal-poor relative to the Sun). From Earth, HD 220197 shines at apparent V-band magnitude 8.92 (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: Roque de los Muchachos Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 220197 |
| Spectral Type | G5 |
| Effective Temp (Teff) | 5,683 K |
| Stellar Radius | 0.9800 R☉ |
| Stellar Mass | 0.9100 M☉ |
| Bolometric Luminosity | 0.899 L☉ |
| Metallicity [Fe/H] | -0.550 dex |
| Stellar Age | 10.165 Gyr |
| Apparent Magnitude | V: 8.920 · G: 8.745 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.729000 AU |
| Orbital Period | 1728 days |
| Mean Orbital Velocity | 17.2 km/s |
| Orbital Eccentricity (e) | 0.18700 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.43 g/cm³ (29.2 km/s vesc) |
| Insolation Flux | 0.1332 S⊕ (~181 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 210.100 LY (64.411 pc) |