HD 98736 b
Astrophysical Synthesis & Habitability Characterization
HD 98736 b is a confirmed gas giant exoplanet orbiting the star HD 98736, located approximately 105.8 light-years (32.45 parsecs) from the Solar System. First announced in 2018 by W. M. Keck Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.3 Earth radii (1.19 Jupiter radii) and has a measured mass of 740.544 Earth masses (2.33 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.74 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 4.19 g⊕ (41.09 m/s²), and an escape velocity of 83.5 km/s.
In its orbital architecture around HD 98736, HD 98736 b completes one full revolution every 968.8 Earth days (2.65Julian years) at a semi-major axis of 1.864 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 20.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.226 carries the world between 1.4427 AU at periapsis and 2.2853 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 13.300 R⊕, HD 98736 b exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star HD 98736 is classified as a solar-type yellow star of spectral type G5 with an effective photospheric temperature of 5,271 K, a radius of 0.93 R☉, a mass of 0.92 M☉, an estimated bolometric luminosity of 0.599 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.39 Gyr and a metallicity of [Fe/H] = 0.36 dex (metal-rich relative to the Sun). From Earth, HD 98736 shines at apparent V-band magnitude 7.93 (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: W. M. Keck Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 98736 |
| Spectral Type | G5 |
| Effective Temp (Teff) | 5,271 K |
| Stellar Radius | 0.9300 R☉ |
| Stellar Mass | 0.9200 M☉ |
| Bolometric Luminosity | 0.599 L☉ |
| Metallicity [Fe/H] | 0.360 dex |
| Stellar Age | 7.390 Gyr |
| Apparent Magnitude | V: 7.930 · G: 7.754 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.864000 AU |
| Orbital Period | 968.8 days |
| Mean Orbital Velocity | 20.9 km/s |
| Orbital Eccentricity (e) | 0.22600 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.74 g/cm³ (83.5 km/s vesc) |
| Insolation Flux | 0.1734 S⊕ (~236 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 105.800 LY (32.446 pc) |