HIP 98599 b
Astrophysical Synthesis & Habitability Characterization
HIP 98599 b is a confirmed gas giant exoplanet orbiting the star HIP 98599, located approximately 247.7 light-years (75.94 parsecs) from the Solar System. First announced in 2026 by Multiple Facilities 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 2177.125 Earth masses (6.85 Jupiter masses). Combining its mass and radius yields a mean bulk density of 5.86 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 13.5 g⊕ (132.39 m/s²), and an escape velocity of 146.5 km/s.
In its orbital architecture around HIP 98599, HIP 98599 b completes one full revolution every 2656 Earth days (7.27Julian years) at a semi-major axis of 3.96 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 16.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.169 carries the world between 3.2908 AU at periapsis and 4.6292 AU at apoapsis, driving measurable seasonal insolation cycles.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 171 K (-102°C / -152°F) and an incident flux of 0.17 S⊕ (~235 W/m²), surface water and volatile species on HIP 98599 b would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HIP 98599 is classified as a warm F-type star of spectral type F7 V with an effective photospheric temperature of 5,978 K, a radius of 1.3948 R☉, a mass of 1.19 M☉, an estimated bolometric luminosity of 2.229 L☉. Stellar evolution modeling indicates an estimated stellar age of 5.23 Gyr and a metallicity of [Fe/H] = -0.12 dex (metal-poor relative to the Sun). From Earth, HIP 98599 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: Multiple Facilities · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HIP 98599 |
| Spectral Type | F7 V |
| Effective Temp (Teff) | 5,978 K |
| Stellar Radius | 1.3948 R☉ |
| Stellar Mass | 1.1900 M☉ |
| Bolometric Luminosity | 2.229 L☉ |
| Metallicity [Fe/H] | -0.120 dex |
| Stellar Age | 5.230 Gyr |
| Apparent Magnitude | V: 8.110 · G: 7.982 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 3.960000 AU |
| Orbital Period | 2656 days |
| Mean Orbital Velocity | 16.2 km/s |
| Orbital Eccentricity (e) | 0.16900 |
| Orbital Inclination (i) | 29.7000° |
| Mean Bulk Density | 5.86 g/cm³ (146.5 km/s vesc) |
| Insolation Flux | 0.1724 S⊕ (~235 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 247.700 LY (75.943 pc) |