HD 100655 b
Astrophysical Synthesis & Habitability Characterization
HD 100655 b is a confirmed gas giant exoplanet orbiting the star HD 100655, located approximately 447.4 light-years (137.18 parsecs) from the Solar System. First announced in 2011 by Bohyunsan Optical Astronomical Observatory 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 511.706 Earth masses (1.61 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.15 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.81 g⊕ (27.56 m/s²), and an escape velocity of 68.9 km/s.
In its orbital architecture around HD 100655, HD 100655 b completes one full revolution every 157.57 Earth days at a semi-major axis of 0.68 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 46.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.09 carries the world between 0.6188 AU at periapsis and 0.7412 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 907 K (+634°C / +1173°F) and receiving 92.99 S⊕ (~126,564 W/m²), HD 100655 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 100655 is classified as a solar-type yellow star of spectral type G9 III with an effective photospheric temperature of 4,891 K, a radius of 10.06 R☉, a mass of 2.28 M☉, an estimated bolometric luminosity of 51.961 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.309 Gyr and a metallicity of [Fe/H] = 0.07 dex (metal-rich relative to the Sun). From Earth, HD 100655 shines at apparent V-band magnitude 6.442 (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: Bohyunsan Optical Astronomical Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 100655 |
| Spectral Type | G9 III |
| Effective Temp (Teff) | 4,891 K |
| Stellar Radius | 10.0600 R☉ |
| Stellar Mass | 2.2800 M☉ |
| Bolometric Luminosity | 51.961 L☉ |
| Metallicity [Fe/H] | 0.070 dex |
| Stellar Age | 1.309 Gyr |
| Apparent Magnitude | V: 6.442 · G: 6.179 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.680000 AU |
| Orbital Period | 157.57 days |
| Mean Orbital Velocity | 46.9 km/s |
| Orbital Eccentricity (e) | 0.09000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.15 g/cm³ (68.9 km/s vesc) |
| Insolation Flux | 92.9931 S⊕ (~126,564 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 447.400 LY (137.178 pc) |