HD 175541 b
Astrophysical Synthesis & Habitability Characterization
HD 175541 b is a confirmed gas giant exoplanet orbiting the star HD 175541, located approximately 422.7 light-years (129.6 parsecs) from the Solar System. First announced in 2007 by W. M. Keck Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 14.1 Earth radii (1.26 Jupiter radii) and has a measured mass of 190.062 Earth masses (0.6 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.37 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.96 g⊕ (9.41 m/s²), and an escape velocity of 41.1 km/s.
In its orbital architecture around HD 175541, HD 175541 b completes one full revolution every 298.43 Earth days at a semi-major axis of 0.975 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 35.5 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.11 carries the world between 0.8678 AU at periapsis and 1.0823 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 501 K (+228°C / +442°F) and receiving 9.04 S⊕ (~12,298 W/m²), HD 175541 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 175541 is classified as a solar-type yellow star of spectral type G8 IV with an effective photospheric temperature of 5,013 K, a radius of 4.19 R☉, a mass of 1.39 M☉, an estimated bolometric luminosity of 9.947 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.9 Gyr and a metallicity of [Fe/H] = -0.07 dex (near-solar heavy-element abundance). From Earth, HD 175541 shines at apparent V-band magnitude 8.02 (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: W. M. Keck Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 175541 |
| Spectral Type | G8 IV |
| Effective Temp (Teff) | 5,013 K |
| Stellar Radius | 4.1900 R☉ |
| Stellar Mass | 1.3900 M☉ |
| Bolometric Luminosity | 9.947 L☉ |
| Metallicity [Fe/H] | -0.070 dex |
| Stellar Age | 1.900 Gyr |
| Apparent Magnitude | V: 8.020 · G: 7.759 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.975000 AU |
| Orbital Period | 298.43 days |
| Mean Orbital Velocity | 35.5 km/s |
| Orbital Eccentricity (e) | 0.11000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.37 g/cm³ (41.1 km/s vesc) |
| Insolation Flux | 9.0363 S⊕ (~12,298 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 422.700 LY (129.603 pc) |