HD 216536 b
Astrophysical Synthesis & Habitability Characterization
HD 216536 b is a confirmed gas giant exoplanet orbiting the star HD 216536, located approximately 1227.1 light-years (376.23 parsecs) from the Solar System. First announced in 2015 by McDonald Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.8 Earth radii (1.23 Jupiter radii) and has a measured mass of 333.722 Earth masses (1.05 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 1.75 g⊕ (17.16 m/s²), and an escape velocity of 55 km/s.
In its orbital architecture around HD 216536, HD 216536 b completes one full revolution every 148.6 Earth days at a semi-major axis of 0.61 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 44.7 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.38, swinging from 0.3782 AU at periapsis out to 0.8418 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 898 K (+625°C / +1157°F) and receiving 169.57 S⊕ (~230,780 W/m²), HD 216536 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 216536 is classified as an orange K-type star of spectral type K0 with an effective photospheric temperature of 4,639 K, a radius of 9.83 R☉, a mass of 0.81 M☉, an estimated bolometric luminosity of 40.151 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.8 Gyr and a metallicity of [Fe/H] = -0.17 dex (metal-poor relative to the Sun). From Earth, HD 216536 shines at apparent V-band magnitude 9.229 (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: McDonald Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 216536 |
| Spectral Type | K0 |
| Effective Temp (Teff) | 4,639 K |
| Stellar Radius | 9.8300 R☉ |
| Stellar Mass | 0.8100 M☉ |
| Bolometric Luminosity | 40.151 L☉ |
| Metallicity [Fe/H] | -0.170 dex |
| Stellar Age | 3.800 Gyr |
| Apparent Magnitude | V: 9.229 · G: 8.883 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.610000 AU |
| Orbital Period | 148.6 days |
| Mean Orbital Velocity | 44.7 km/s |
| Orbital Eccentricity (e) | 0.38000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.7 g/cm³ (55 km/s vesc) |
| Insolation Flux | 169.5666 S⊕ (~230,780 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1227.100 LY (376.233 pc) |