HD 28254 b
Astrophysical Synthesis & Habitability Characterization
HD 28254 b is a confirmed gas giant exoplanet orbiting the star HD 28254, located approximately 180.3 light-years (55.29 parsecs) from the Solar System. First announced in 2010 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13 Earth radii (1.16 Jupiter radii) and has a measured mass of 1207.748 Earth masses (3.8 Jupiter masses). Combining its mass and radius yields a mean bulk density of 3.03 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 7.15 g⊕ (70.12 m/s²), and an escape velocity of 107.8 km/s.
In its orbital architecture around HD 28254, HD 28254 b completes one full revolution every 1333 Earth days (3.65Julian years) at a semi-major axis of 2.45 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 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.95, swinging from 0.1225 AU at periapsis out to 4.7775 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 13.000 R⊕, HD 28254 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 28254 is classified as a solar-type yellow star of spectral type G5 V with an effective photospheric temperature of 5,664 K, a radius of 1.48 R☉, a mass of 1.1 M☉, an estimated bolometric luminosity of 2.023 L☉. Stellar evolution modeling indicates an estimated stellar age of 6 Gyr and a metallicity of [Fe/H] = 0.06 dex (metal-rich relative to the Sun). From Earth, HD 28254 shines at apparent V-band magnitude 7.69 (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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 28254 |
| Spectral Type | G5 V |
| Effective Temp (Teff) | 5,664 K |
| Stellar Radius | 1.4800 R☉ |
| Stellar Mass | 1.1000 M☉ |
| Bolometric Luminosity | 2.023 L☉ |
| Metallicity [Fe/H] | 0.060 dex |
| Stellar Age | 6.000 Gyr |
| Apparent Magnitude | V: 7.690 · G: 7.500 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.450000 AU |
| Orbital Period | 1333 days |
| Mean Orbital Velocity | 20 km/s |
| Orbital Eccentricity (e) | 0.95000 |
| Orbital Inclination (i) | 162.0000° |
| Mean Bulk Density | 3.03 g/cm³ (107.8 km/s vesc) |
| Insolation Flux | 0.3645 S⊕ (~496 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 180.300 LY (55.288 pc) |