HD 216770 b
Astrophysical Synthesis & Habitability Characterization
HD 216770 b is a confirmed gas giant exoplanet orbiting the star HD 216770, located approximately 119.6 light-years (36.66 parsecs) from the Solar System. First announced in 2003 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 14.1 Earth radii (1.26 Jupiter radii) and has a measured mass of 181.163 Earth masses (0.57 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.36 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.91 g⊕ (8.92 m/s²), and an escape velocity of 40.1 km/s.
In its orbital architecture around HD 216770, HD 216770 b completes one full revolution every 118.45 Earth days at a semi-major axis of 0.46 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 42.2 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.37, swinging from 0.2898 AU at periapsis out to 0.6302 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 370 K (+97°C / +207°F) and receiving 3.75 S⊕ (~5,109 W/m²), HD 216770 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 216770 is classified as a solar-type yellow star of spectral type G9 V CN+1 with an effective photospheric temperature of 5,399 K, a radius of 0.93 R☉, a mass of 0.74 M☉, an estimated bolometric luminosity of 0.659 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.1 Gyr and a metallicity of [Fe/H] = 0.27 dex (metal-rich relative to the Sun). From Earth, HD 216770 shines at apparent V-band magnitude 8.11 (accessible to binoculars and small amateur telescopes) in the Southern 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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 216770 |
| Spectral Type | G9 V CN+1 |
| Effective Temp (Teff) | 5,399 K |
| Stellar Radius | 0.9300 R☉ |
| Stellar Mass | 0.7400 M☉ |
| Bolometric Luminosity | 0.659 L☉ |
| Metallicity [Fe/H] | 0.270 dex |
| Stellar Age | 3.100 Gyr |
| Apparent Magnitude | V: 8.110 · G: 7.916 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.460000 AU |
| Orbital Period | 118.45 days |
| Mean Orbital Velocity | 42.2 km/s |
| Orbital Eccentricity (e) | 0.37000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.36 g/cm³ (40.1 km/s vesc) |
| Insolation Flux | 3.7539 S⊕ (~5,109 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 119.600 LY (36.663 pc) |