HD 99283 b
Astrophysical Synthesis & Habitability Characterization
HD 99283 b is a confirmed gas giant exoplanet orbiting the star HD 99283, located approximately 362.3 light-years (111.09 parsecs) from the Solar System. First announced in 2021 by Okayama Astrophysical Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.8 Earth radii (1.23 Jupiter radii) and has a measured mass of 308.294 Earth masses (0.97 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.65 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.62 g⊕ (15.89 m/s²), and an escape velocity of 52.9 km/s.
In its orbital architecture around HD 99283, HD 99283 b completes one full revolution every 310.4 Earth days at a semi-major axis of 1.08 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 37.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.2 carries the world between 0.864 AU at periapsis and 1.296 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 759 K (+486°C / +907°F) and receiving 55.31 S⊕ (~75,273 W/m²), HD 99283 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 99283 is classified as an orange K-type star of spectral type K0 III with an effective photospheric temperature of 4,886 K, a radius of 11.21 R☉, a mass of 1.76 M☉, an estimated bolometric luminosity of 64.256 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.16 dex (metal-poor relative to the Sun). From Earth, HD 99283 shines at apparent V-band magnitude 5.729 (visible to the unaided human eye under dark skies) 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: Okayama Astrophysical Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 99283 |
| Spectral Type | K0 III |
| Effective Temp (Teff) | 4,886 K |
| Stellar Radius | 11.2100 R☉ |
| Stellar Mass | 1.7600 M☉ |
| Bolometric Luminosity | 64.256 L☉ |
| Metallicity [Fe/H] | -0.160 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 5.729 · G: 5.464 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.080000 AU |
| Orbital Period | 310.4 days |
| Mean Orbital Velocity | 37.9 km/s |
| Orbital Eccentricity (e) | 0.20000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.65 g/cm³ (52.9 km/s vesc) |
| Insolation Flux | 55.3069 S⊕ (~75,273 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 362.300 LY (111.093 pc) |