HIP 18606 b

Astrophysical Synthesis & Habitability Characterization

HIP 18606 b is a confirmed gas giant exoplanet orbiting the star HIP 18606, located approximately 153.4 light-years (47.03 parsecs) from the Solar System. First announced in 2025 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 14 Earth radii (1.25 Jupiter radii) and has a measured mass of 244.728 Earth masses (0.77 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.49 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.25 g⊕ (12.26 m/s²), and an escape velocity of 46.8 km/s.

In its orbital architecture around HIP 18606, HIP 18606 b completes one full revolution every 674.94 Earth days (1.85Julian years) at a semi-major axis of 1.61 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 26 km/s (compared to Earth's 29.8 km/s).

⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 406 K (+133°C / +271°F) and receiving 4.43 S⊕ (~6,028 W/m²), HIP 18606 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star HIP 18606 is classified as an orange K-type star of spectral type K0/1 III with an effective photospheric temperature of 4,860 K, a radius of 4.83 R☉, a mass of 1.21 M☉, an estimated bolometric luminosity of 11.677 L☉. Stellar evolution modeling indicates an estimated stellar age of 5.29 Gyr and a metallicity of [Fe/H] = -0.01 dex (near-solar heavy-element abundance). From Earth, HIP 18606 shines at apparent V-band magnitude 5.833 (visible to the unaided human eye under dark skies) in the Southern celestial hemisphere.

Discovery Facility: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).