HIP 90988 b
Astrophysical Synthesis & Habitability Characterization
HIP 90988 b is a confirmed gas giant exoplanet orbiting the star HIP 90988, located approximately 306.7 light-years (94.04 parsecs) from the Solar System. First announced in 2021 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.4 Earth radii (1.2 Jupiter radii) and has a measured mass of 668.075 Earth masses (2.1 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.53 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 3.72 g⊕ (36.48 m/s²), and an escape velocity of 79 km/s.
In its orbital architecture around HIP 90988, HIP 90988 b completes one full revolution every 455.738 Earth days (1.25Julian years) at a semi-major axis of 1.36 AU (comparable to the inner terrestrial zone between Venus, Earth at 1.00 AU, and Mars at 1.52 AU). Its mean orbital velocity is approximately 32.5 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.081 carries the world between 1.2498 AU at periapsis and 1.4702 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 401 K (+128°C / +262°F) and receiving 4.20 S⊕ (~5,710 W/m²), HIP 90988 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HIP 90988 is classified as an orange K-type star of spectral type K1 III with an effective photospheric temperature of 4,883 K, a radius of 3.94 R☉, a mass of 1.613 M☉, an estimated bolometric luminosity of 7.918 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.55 Gyr and a metallicity of [Fe/H] = 0.17 dex (metal-rich relative to the Sun). From Earth, HIP 90988 shines at apparent V-band magnitude 7.75 (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 Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HIP 90988 |
| Spectral Type | K1 III |
| Effective Temp (Teff) | 4,883 K |
| Stellar Radius | 3.9400 R☉ |
| Stellar Mass | 1.6130 M☉ |
| Bolometric Luminosity | 7.918 L☉ |
| Metallicity [Fe/H] | 0.170 dex |
| Stellar Age | 4.550 Gyr |
| Apparent Magnitude | V: 7.750 · G: 7.466 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.360000 AU |
| Orbital Period | 455.738 days |
| Mean Orbital Velocity | 32.5 km/s |
| Orbital Eccentricity (e) | 0.08100 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.53 g/cm³ (79 km/s vesc) |
| Insolation Flux | 4.1955 S⊕ (~5,710 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 306.700 LY (94.035 pc) |