HD 171028 b
Astrophysical Synthesis & Habitability Characterization
HD 171028 b is a confirmed gas giant exoplanet orbiting the star HD 171028, located approximately 364.2 light-years (111.66 parsecs) from the Solar System. First announced in 2007 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.2 Earth radii (1.18 Jupiter radii) and has a measured mass of 832.715 Earth masses (2.62 Jupiter masses). Combining its mass and radius yields a mean bulk density of 2 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 4.78 g⊕ (46.88 m/s²), and an escape velocity of 88.8 km/s.
In its orbital architecture around HD 171028, HD 171028 b completes one full revolution every 550 Earth days (1.51Julian years) at a semi-major axis of 1.32 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 26.1 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.59, swinging from 0.5412 AU at periapsis out to 2.0988 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 374 K (+101°C / +214°F) and receiving 3.10 S⊕ (~4,223 W/m²), HD 171028 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 171028 is classified as a solar-type yellow star of spectral type G0 with an effective photospheric temperature of 5,671 K, a radius of 2.47 R☉, a mass of 1.53 M☉, an estimated bolometric luminosity of 5.661 L☉. Stellar evolution modeling indicates an estimated stellar age of 8.59 Gyr and a metallicity of [Fe/H] = -0.48 dex (metal-poor relative to the Sun). From Earth, HD 171028 shines at apparent V-band magnitude 8.292 (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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 171028 |
| Spectral Type | G0 |
| Effective Temp (Teff) | 5,671 K |
| Stellar Radius | 2.4700 R☉ |
| Stellar Mass | 1.5300 M☉ |
| Bolometric Luminosity | 5.661 L☉ |
| Metallicity [Fe/H] | -0.480 dex |
| Stellar Age | 8.590 Gyr |
| Apparent Magnitude | V: 8.292 · G: 8.102 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.320000 AU |
| Orbital Period | 550 days |
| Mean Orbital Velocity | 26.1 km/s |
| Orbital Eccentricity (e) | 0.59000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2 g/cm³ (88.8 km/s vesc) |
| Insolation Flux | 3.1028 S⊕ (~4,223 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 364.200 LY (111.659 pc) |