HD 206255 b

Astrophysical Synthesis & Habitability Characterization

HD 206255 b is a confirmed gas giant exoplanet orbiting the star HD 206255, located approximately 245.4 light-years (75.24 parsecs) from the Solar System. First announced in 2019 by Las Campanas Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 6.47 Earth radii (0.58 Jupiter radii) and has a measured mass of 34.2 Earth masses (0.11 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 0.82 g⊕ (8.04 m/s²), and an escape velocity of 25.7 km/s.

In its orbital architecture around HD 206255, HD 206255 b completes one full revolution every 96.045 Earth days at a semi-major axis of 0.461 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 52.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.23 carries the world between 0.355 AU at periapsis and 0.567 AU at apoapsis, driving measurable seasonal insolation cycles.

⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 596 K (+323°C / +613°F) and receiving 21.09 S⊕ (~28,709 W/m²), HD 206255 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star HD 206255 is classified as a solar-type yellow star of spectral type G5 IV/V with an effective photospheric temperature of 5,635 K, a radius of 2.2215 R☉, a mass of 1.42 M☉, an estimated bolometric luminosity of 4.464 L☉. From Earth, HD 206255 shines at apparent V-band magnitude 7.62 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere.

Discovery Facility: Las Campanas Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).