HD 11977 b
Astrophysical Synthesis & Habitability Characterization
HD 11977 b is a confirmed gas giant exoplanet orbiting the star HD 11977, located approximately 221.6 light-years (67.93 parsecs) from the Solar System. First announced in 2005 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.7 Earth radii (1.13 Jupiter radii) and has a measured mass of 2080 Earth masses (6.54 Jupiter masses). Combining its mass and radius yields a mean bulk density of 5.6 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 12.9 g⊕ (126.51 m/s²), and an escape velocity of 143.2 km/s.
In its orbital architecture around HD 11977, HD 11977 b completes one full revolution every 711 Earth days (1.95Julian years) at a semi-major axis of 1.93 AU (corresponding to the middle-system regime between Mars at 1.52 AU and Jupiter at 5.20 AU). Its mean orbital velocity is approximately 29.5 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.4, swinging from 1.158 AU at periapsis out to 2.702 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 548 K (+275°C / +527°F) and receiving 18.51 S⊕ (~25,196 W/m²), HD 11977 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 11977 is classified as a solar-type yellow star of spectral type G8 III/IV with an effective photospheric temperature of 4,970 K, a radius of 10.09 R☉, a mass of 1.91 M☉, an estimated bolometric luminosity of 55.731 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.2 Gyr and a metallicity of [Fe/H] = -0.21 dex (metal-poor relative to the Sun). From Earth, HD 11977 shines at apparent V-band magnitude 4.68 (visible to the unaided human eye under dark skies) 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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 11977 |
| Spectral Type | G8 III/IV |
| Effective Temp (Teff) | 4,970 K |
| Stellar Radius | 10.0900 R☉ |
| Stellar Mass | 1.9100 M☉ |
| Bolometric Luminosity | 55.731 L☉ |
| Metallicity [Fe/H] | -0.210 dex |
| Stellar Age | 1.200 Gyr |
| Apparent Magnitude | V: 4.680 · G: 4.439 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.930000 AU |
| Orbital Period | 711 days |
| Mean Orbital Velocity | 29.5 km/s |
| Orbital Eccentricity (e) | 0.40000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 5.6 g/cm³ (143.2 km/s vesc) |
| Insolation Flux | 18.5126 S⊕ (~25,196 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 221.600 LY (67.933 pc) |