HD 177830 b
Astrophysical Synthesis & Habitability Characterization
HD 177830 b is a confirmed gas giant exoplanet orbiting the star HD 177830, located approximately 204.7 light-years (62.77 parsecs) from the Solar System. First announced in 1999 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 13.5 Earth radii (1.2 Jupiter radii) and has a measured mass of 537.133 Earth masses (1.69 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.2 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.95 g⊕ (28.93 m/s²), and an escape velocity of 70.6 km/s.
In its orbital architecture around HD 177830, HD 177830 b completes one full revolution every 410.1 Earth days (1.12Julian years) at a semi-major axis of 1.14 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 30.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.1 carries the world between 1.026 AU at periapsis and 1.254 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 400 K (+127°C / +261°F) and receiving 3.73 S⊕ (~5,071 W/m²), HD 177830 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 177830 is classified as an orange K-type star of spectral type K0 with an effective photospheric temperature of 4,901 K, a radius of 3.26 R☉, a mass of 1.7 M☉, an estimated bolometric luminosity of 5.501 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.4 Gyr and a metallicity of [Fe/H] = 0.42 dex (metal-rich relative to the Sun). From Earth, HD 177830 shines at apparent V-band magnitude 7.18 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 177830 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 177830 b sharing its stellar neighborhood alongside HD 177830 c.
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 177830 |
| Spectral Type | K0 |
| Effective Temp (Teff) | 4,901 K |
| Stellar Radius | 3.2600 R☉ |
| Stellar Mass | 1.7000 M☉ |
| Bolometric Luminosity | 5.501 L☉ |
| Metallicity [Fe/H] | 0.420 dex |
| Stellar Age | 4.400 Gyr |
| Apparent Magnitude | V: 7.180 · G: 6.887 |
| System Architecture | 2 Stars, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.140000 AU |
| Orbital Period | 410.1 days |
| Mean Orbital Velocity | 30.2 km/s |
| Orbital Eccentricity (e) | 0.10000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.2 g/cm³ (70.6 km/s vesc) |
| Insolation Flux | 3.7258 S⊕ (~5,071 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 204.700 LY (62.767 pc) |