HR 8799 e
Astrophysical Synthesis & Habitability Characterization
HR 8799 e is a confirmed gas giant exoplanet orbiting the star HR 8799, located approximately 134.5 light-years (41.24 parsecs) from the Solar System. First announced in 2010 by W. M. Keck Observatory using the Imaging detection technique (resolved directly via high-contrast coronagraphic or interferometric imaging), this world measures 13.115 Earth radii (1.17 Jupiter radii) and has a measured mass of 3178.3 Earth masses (10 Jupiter masses). Combining its mass and radius yields a mean bulk density of 7.77 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 18.48 g⊕ (181.23 m/s²), and an escape velocity of 174.1 km/s.
In its orbital architecture around HR 8799, HR 8799 e completes one full revolution every 20815.6 Earth days (56.99Julian years) at a semi-major axis of 16.4 AU (a wide outer-system orbit beyond Jupiter's 5.20 AU distance in our Solar System). Its mean orbital velocity is approximately 8.6 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.15 carries the world between 13.94 AU at periapsis and 18.86 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1150 K (+877°C / +1611°F) and receiving 0.02 S⊕ (~27 W/m²), HR 8799 e orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HR 8799 is classified as a luminous A-type star of spectral type A5 with an effective photospheric temperature of 7,400 K, a radius of 1.4934 R☉, a mass of 1.51 M☉, an estimated bolometric luminosity of 6 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.03 Gyr and a metallicity of [Fe/H] = -0.5 dex (metal-poor relative to the Sun). From Earth, HR 8799 shines at apparent V-band magnitude 5.98 (visible to the unaided human eye under dark skies) in the Northern celestial hemisphere. The HR 8799 system is a multi-planet architecture hosting 4 confirmed worlds, with HR 8799 e sharing its stellar neighborhood alongside HR 8799 d, HR 8799 c, HR 8799 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 | HR 8799 |
| Spectral Type | A5 |
| Effective Temp (Teff) | 7,400 K |
| Stellar Radius | 1.4934 R☉ |
| Stellar Mass | 1.5100 M☉ |
| Bolometric Luminosity | 6 L☉ |
| Metallicity [Fe/H] | -0.500 dex |
| Stellar Age | 0.030 Gyr |
| Apparent Magnitude | V: 5.980 · G: 5.909 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 16.400000 AU |
| Orbital Period | 20815.6 days |
| Mean Orbital Velocity | 8.6 km/s |
| Orbital Eccentricity (e) | 0.15000 |
| Orbital Inclination (i) | 25.0000° |
| Mean Bulk Density | 7.77 g/cm³ (174.1 km/s vesc) |
| Insolation Flux | 0.0201 S⊕ (~27 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 134.500 LY (41.244 pc) |