HD 126105 b
Astrophysical Synthesis & Habitability Characterization
HD 126105 b is a confirmed gas giant exoplanet orbiting the star HD 126105, located approximately 270.3 light-years (82.88 parsecs) from the Solar System. First announced in 2026 by Multiple Facilities using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.5 Earth radii (1.2 Jupiter radii) and has a measured mass of 530.773 Earth masses (1.67 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.19 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.91 g⊕ (28.54 m/s²), and an escape velocity of 70.1 km/s.
In its orbital architecture around HD 126105, HD 126105 b completes one full revolution every 524 Earth days (1.43Julian years) at a semi-major axis of 1.36 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 28.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.103 carries the world between 1.2199 AU at periapsis and 1.5001 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 414 K (+141°C / +286°F) and receiving 4.87 S⊕ (~6,622 W/m²), HD 126105 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 126105 is classified as an orange K-type star of spectral type K1 III with an effective photospheric temperature of 4,875 K, a radius of 4.21 R☉, a mass of 1.2 M☉, an estimated bolometric luminosity of 8.982 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.9 Gyr and a metallicity of [Fe/H] = 0 dex (near-solar heavy-element abundance). From Earth, HD 126105 shines at apparent V-band magnitude 7.32 (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: Multiple Facilities · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 126105 |
| Spectral Type | K1 III |
| Effective Temp (Teff) | 4,875 K |
| Stellar Radius | 4.2100 R☉ |
| Stellar Mass | 1.2000 M☉ |
| Bolometric Luminosity | 8.982 L☉ |
| Metallicity [Fe/H] | 0.000 dex |
| Stellar Age | 4.900 Gyr |
| Apparent Magnitude | V: 7.320 · G: 7.051 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.360000 AU |
| Orbital Period | 524 days |
| Mean Orbital Velocity | 28.2 km/s |
| Orbital Eccentricity (e) | 0.10300 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.19 g/cm³ (70.1 km/s vesc) |
| Insolation Flux | 4.8659 S⊕ (~6,622 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 270.300 LY (82.881 pc) |