HN Peg b
Astrophysical Synthesis & Habitability Characterization
HN Peg b is a confirmed gas giant exoplanet orbiting the star HN Peg, located approximately 59.1 light-years (18.12 parsecs) from the Solar System. First announced in 2006 by Spitzer Space Telescope using the Imaging detection technique (resolved directly via high-contrast coronagraphic or interferometric imaging), this world measures 11.777 Earth radii (1.05 Jupiter radii) and has a measured mass of 6991.57 Earth masses (22 Jupiter masses). Combining its mass and radius yields a mean bulk density of 23.6 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 50.41 g⊕ (494.35 m/s²), and an escape velocity of 272.5 km/s.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 11 K (-262°C / -440°F), surface water and volatile species on HN Peg b would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HN Peg is classified as a solar-type yellow star of spectral type G0 V with an effective photospheric temperature of 6,186 K, a radius of 1.007 R☉, a mass of 1.08 M☉, an estimated bolometric luminosity of 1.332 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.3 Gyr and a metallicity of [Fe/H] = -0.036 dex (near-solar heavy-element abundance). From Earth, HN Peg shines at apparent V-band magnitude 5.977 (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: Spitzer Space Telescope · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HN Peg |
| Spectral Type | G0 V |
| Effective Temp (Teff) | 6,186 K |
| Stellar Radius | 1.0070 R☉ |
| Stellar Mass | 1.0800 M☉ |
| Bolometric Luminosity | 1.332 L☉ |
| Metallicity [Fe/H] | -0.036 dex |
| Stellar Age | 0.300 Gyr |
| Apparent Magnitude | V: 5.977 · G: 5.824 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 773.000000 AU |
| Orbital Period | — |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 23.6 g/cm³ (272.5 km/s vesc) |
| Insolation Flux | 0.0000 S⊕ |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 59.100 LY (18.119 pc) |