HD 139357 b
Astrophysical Synthesis & Habitability Characterization
HD 139357 b is a confirmed gas giant exoplanet orbiting the star HD 139357, located approximately 365.6 light-years (112.09 parsecs) from the Solar System. First announced in 2008 by Thueringer Landessternwarte Tautenburg using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.1 Earth radii (1.08 Jupiter radii) and has a measured mass of 6315.568 Earth masses (19.87 Jupiter masses). Combining its mass and radius yields a mean bulk density of 19.66 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 43.14 g⊕ (423.06 m/s²), and an escape velocity of 255.6 km/s.
In its orbital architecture around HD 139357, HD 139357 b completes one full revolution every 1124.791 Earth days (3.08Julian years) at a semi-major axis of 2.949 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 28.5 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.099 carries the world between 2.657 AU at periapsis and 3.241 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 447 K (+174°C / +345°F) and receiving 7.65 S⊕ (~10,410 W/m²), HD 139357 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 139357 is classified as an orange K-type star of spectral type K4 III with an effective photospheric temperature of 4,700 K, a radius of 11.47 R☉, a mass of 2.69 M☉, an estimated bolometric luminosity of 57.598 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.07 Gyr and a metallicity of [Fe/H] = -0.13 dex (metal-poor relative to the Sun). From Earth, HD 139357 shines at apparent V-band magnitude 5.973 (visible to the unaided human eye under dark skies) 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: Thueringer Landessternwarte Tautenburg · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 139357 |
| Spectral Type | K4 III |
| Effective Temp (Teff) | 4,700 K |
| Stellar Radius | 11.4700 R☉ |
| Stellar Mass | 2.6900 M☉ |
| Bolometric Luminosity | 57.598 L☉ |
| Metallicity [Fe/H] | -0.130 dex |
| Stellar Age | 3.070 Gyr |
| Apparent Magnitude | V: 5.973 · G: 5.630 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.949000 AU |
| Orbital Period | 1124.791 days |
| Mean Orbital Velocity | 28.5 km/s |
| Orbital Eccentricity (e) | 0.09900 |
| Orbital Inclination (i) | 103.2350° |
| Mean Bulk Density | 19.66 g/cm³ (255.6 km/s vesc) |
| Insolation Flux | 7.6490 S⊕ (~10,410 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 365.600 LY (112.090 pc) |