HD 190228 b
Astrophysical Synthesis & Habitability Characterization
HD 190228 b is a confirmed gas giant exoplanet orbiting the star HD 190228, located approximately 204.5 light-years (62.72 parsecs) from the Solar System. First announced in 2022 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.9 Earth radii (1.15 Jupiter radii) and has a measured mass of 1598.677 Earth masses (5.03 Jupiter masses). Combining its mass and radius yields a mean bulk density of 4.11 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 9.61 g⊕ (94.24 m/s²), and an escape velocity of 124.5 km/s.
In its orbital architecture around HD 190228, HD 190228 b completes one full revolution every 1143.599 Earth days (3.13Julian years) at a semi-major axis of 2.406 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 22.9 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.559, swinging from 1.061 AU at periapsis out to 3.751 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 12.900 R⊕, HD 190228 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 190228 is classified as a solar-type yellow star of spectral type G5 IV with an effective photospheric temperature of 5,360 K, a radius of 2.5866 R☉, a mass of 1.415 M☉, an estimated bolometric luminosity of 4.955 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.24 dex (metal-poor relative to the Sun). From Earth, HD 190228 shines at apparent V-band magnitude 7.3 (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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 190228 |
| Spectral Type | G5 IV |
| Effective Temp (Teff) | 5,360 K |
| Stellar Radius | 2.5866 R☉ |
| Stellar Mass | 1.4150 M☉ |
| Bolometric Luminosity | 4.955 L☉ |
| Metallicity [Fe/H] | -0.240 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 7.300 · G: 7.085 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.406000 AU |
| Orbital Period | 1143.599 days |
| Mean Orbital Velocity | 22.9 km/s |
| Orbital Eccentricity (e) | 0.55900 |
| Orbital Inclination (i) | 94.9870° |
| Mean Bulk Density | 4.11 g/cm³ (124.5 km/s vesc) |
| Insolation Flux | 0.8598 S⊕ (~1,170 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 204.500 LY (62.715 pc) |