HD 191939 f
Astrophysical Synthesis & Habitability Characterization
HD 191939 f is a confirmed gas giant exoplanet orbiting the star HD 191939, located approximately 174.8 light-years (53.61 parsecs) from the Solar System. First announced in 2022 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 13.2 Earth radii (1.18 Jupiter radii) and has a measured mass of 915.346 Earth masses (2.88 Jupiter masses). Combining its mass and radius yields a mean bulk density of 2.19 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 5.25 g⊕ (51.48 m/s²), and an escape velocity of 93.1 km/s.
In its orbital architecture around HD 191939, HD 191939 f completes one full revolution every 2898 Earth days (7.93Julian years) at a semi-major axis of 3.71 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 13.9 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 125 K (-148°C / -234°F) and an incident flux of 0.05 S⊕ (~64 W/m²), surface water and volatile species on HD 191939 f would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 191939 is classified as a solar-type yellow star of spectral type G9 V with an effective photospheric temperature of 5,348 K, a radius of 0.94 R☉, a mass of 0.81 M☉, an estimated bolometric luminosity of 0.649 L☉. Stellar evolution modeling indicates an estimated stellar age of 8.7 Gyr and a metallicity of [Fe/H] = -0.15 dex (metal-poor relative to the Sun). From Earth, HD 191939 shines at apparent V-band magnitude 8.97 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 191939 system is a multi-planet architecture hosting 6 confirmed worlds, with HD 191939 f sharing its stellar neighborhood alongside HD 191939 b, HD 191939 c, HD 191939 d, HD 191939 e, HD 191939 g.
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 191939 |
| Spectral Type | G9 V |
| Effective Temp (Teff) | 5,348 K |
| Stellar Radius | 0.9400 R☉ |
| Stellar Mass | 0.8100 M☉ |
| Bolometric Luminosity | 0.649 L☉ |
| Metallicity [Fe/H] | -0.150 dex |
| Stellar Age | 8.700 Gyr |
| Apparent Magnitude | V: 8.970 · G: 8.775 |
| System Architecture | 1 Star, 6 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 3.710000 AU |
| Orbital Period | 2898 days |
| Mean Orbital Velocity | 13.9 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.19 g/cm³ (93.1 km/s vesc) |
| Insolation Flux | 0.0472 S⊕ (~64 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 174.800 LY (53.609 pc) |