HD 177830 c
Astrophysical Synthesis & Habitability Characterization
HD 177830 c 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 2010 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 7.87 Earth radii (0.7 Jupiter radii) and has a measured mass of 47.673 Earth masses (0.15 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.54 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.77 g⊕ (7.55 m/s²), and an escape velocity of 27.5 km/s.
In its orbital architecture around HD 177830, HD 177830 c completes one full revolution every 110.9 Earth days at a semi-major axis of 0.5137 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 50.4 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.3, swinging from 0.3596 AU at periapsis out to 0.6678 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 539 K (+266°C / +511°F) and receiving 18.35 S⊕ (~24,973 W/m²), HD 177830 c 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 4,949 K, a radius of 2.62 R☉, a mass of 1.47 M☉, an estimated bolometric luminosity of 3.695 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.4 Gyr and a metallicity of [Fe/H] = 0.545 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 c sharing its stellar neighborhood alongside HD 177830 b.
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) | 4,949 K |
| Stellar Radius | 2.6200 R☉ |
| Stellar Mass | 1.4700 M☉ |
| Bolometric Luminosity | 3.695 L☉ |
| Metallicity [Fe/H] | 0.545 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) | 0.513700 AU |
| Orbital Period | 110.9 days |
| Mean Orbital Velocity | 50.4 km/s |
| Orbital Eccentricity (e) | 0.30000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.54 g/cm³ (27.5 km/s vesc) |
| Insolation Flux | 18.3487 S⊕ (~24,973 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 204.700 LY (62.767 pc) |