HD 87816 b
Astrophysical Synthesis & Habitability Characterization
HD 87816 b is a confirmed gas giant exoplanet orbiting the star HD 87816, located approximately 434.5 light-years (133.23 parsecs) from the Solar System. First announced in 2025 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.7 Earth radii (1.13 Jupiter radii) and has a measured mass of 2142.163 Earth masses (6.74 Jupiter masses). Combining its mass and radius yields a mean bulk density of 5.77 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 13.28 g⊕ (130.23 m/s²), and an escape velocity of 145.3 km/s.
In its orbital architecture around HD 87816, HD 87816 b completes one full revolution every 484.17 Earth days (1.33Julian years) at a semi-major axis of 1.618 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 36.4 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.78, swinging from 0.356 AU at periapsis out to 2.88 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 567 K (+294°C / +561°F) and receiving 17.27 S⊕ (~23,498 W/m²), HD 87816 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 87816 is classified as an orange K-type star of spectral type K0 III with an effective photospheric temperature of 4,989 K, a radius of 9 R☉, a mass of 2.41 M☉, an estimated bolometric luminosity of 45.022 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.14 dex (metal-rich relative to the Sun). From Earth, HD 87816 shines at apparent V-band magnitude 6.5 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 87816 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 87816 b sharing its stellar neighborhood alongside HD 87816 c.
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 87816 |
| Spectral Type | K0 III |
| Effective Temp (Teff) | 4,989 K |
| Stellar Radius | 9.0000 R☉ |
| Stellar Mass | 2.4100 M☉ |
| Bolometric Luminosity | 45.022 L☉ |
| Metallicity [Fe/H] | 0.140 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 6.500 · G: 6.242 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.618000 AU |
| Orbital Period | 484.17 days |
| Mean Orbital Velocity | 36.4 km/s |
| Orbital Eccentricity (e) | 0.78000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 5.77 g/cm³ (145.3 km/s vesc) |
| Insolation Flux | 17.2656 S⊕ (~23,498 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 434.500 LY (133.233 pc) |