HR 8799 e
Reference data for HR 8799 e: 16.2 AU orbit, 7.4 Jupiter masses, VLTI/GRAVITY interferometric spectrum, and resonant four-planet dynamics.
Provenance-Backed Scientific Measurements
Every measurement below preserves its unit, uncertainty interval, observational method, reference epoch, quality status, and primary catalog source. See Uncertainty & Provenance for how competing measurements are handled.
| Parameter | Value | Uncertainty | Method & Epoch | Quality Status | Source Archive |
|---|---|---|---|---|---|
| Distance | 133.3 ly | ± 0.3 ly | Gaia DR3 trigonometric parallax of host star | definitive | ESA Gaia Archive — Data Release 3 |
| Orbital Period | 17532 d | ± 900 d | Equivalent to ~48.0 ± 2.5 years in a 1:2:4:8 resonant chain. | high-confidence | NASA Exoplanet Archive |
| Semi-Major Axis | 16.2 AU | ± 0.5 AU | Keplerian third-law solution from stellar mass and orbital period | high-confidence | NASA Exoplanet Archive |
| Planetary Mass | 2350 M⊕ | ± 380 M⊕ | Equivalent to 7.4 ± 1.2 Jupiter masses from dynamical stability and evolutionary cooling models. | high-confidence | NASA Exoplanet Archive |
| Planetary Radius | 13.1 R⊕ | ± 0.8 R⊕ | Equivalent to 1.17 ± 0.07 Jupiter radii. | high-confidence | NASA Exoplanet Archive |
| Effective Temperature | 1150 K | ± 50 K | Internal heat of a ~30 Myr young gas giant measured via VLTI/GRAVITY K-band spectroscopy. | definitive | NASA Exoplanet Archive |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots HR 8799 e — Directly Imaged Super-Jupiter at RA 23h 07m 28.72s, Dec +21° 08′ 03.3″ within Pegasus, alongside peak meridian transit altitudes for 40°N and 30°S observers. Use the RA/Dec Coordinate Converter to compute exact culmination altitude for your latitude.
Astrophysical Context & Structure
Discovered in November 2010 by Christian Marois and collaborators using the Keck II adaptive optics system, HR 8799 e is the fourth and innermost known super-Jupiter orbiting the 30-million-year-old Lambda Bootis star HR 8799 in Pegasus. While its three outer siblings (planets d, c, and b, announced in 2008) orbit at roughly 26, 41, and 71 astronomical units, HR 8799 e circles at 16.2 astronomical units—between the distances of Saturn and Uranus in our Solar System—completing a circuit every ~48 years.
Because all four planets pack between 5 and 9 Jupiter masses into adjacent orbits, uncoordinated trajectories would rapidly scatter the system apart through mutual gravitational kicks. Long-term astrometric tracking over more than 15 years demonstrates that the four worlds survive by marching in a grand 1:2:4:8 mean-motion resonance chain, making the HR 8799 system a scaled-up, giant-planet analog of Jupiter's Galilean moons.
In 2019, the GRAVITY collaboration combined light from all four 8.2-meter Unit Telescopes of the Very Large Telescope to observe HR 8799 e via long-baseline optical interferometry—a historic first for exoplanet science. The resulting K-band spectrum and 50-microarcsecond astrometry revealed an effective temperature near 1,150 K, vigorous vertical mixing driving carbon monoxide over methane disequilibrium chemistry, and thick clouds of iron and silicate dust.
Practical Visual Observing Guide
- Host star HR 8799 (V342 Pegasi) shines at visual magnitude V = 5.96 in Pegasus, visible in binoculars and to the unaided eye under dark skies.
- Separated by ~0.39 arcseconds from its host star, requiring extreme adaptive optics or long-baseline infrared interferometry.
- Multi-year time-lapse movies from Keck and Gemini directly show the four planets revolving counterclockwise in a nearly face-on plane.
Catalog Cross-Identifications & Aliases
Common Aliases: HR 8799e · HD 218396 e · V342 Pegasi e
| Catalog Authority | Identifier |
|---|---|
| NASAEXOPLANET | HR 8799 e |
| SIMBAD | HR 8799 e |
Related Objects, Comparisons & Guides
Beta Pictoris b — Directly Imaged Gas Giant
Reference data for Beta Pictoris b: 11.9 Jupiter masses, 9.9 AU orbit inside an edge-on debris disk, rapid 8.1-hour rotation, and interferometry.
51 Pegasi b (Dimidium First Hot Jupiter)
Coordinates, Gaia DR3 distance (15.46 pc), 4.2308-day orbital period, Nobel-winning radial-velocity discovery, and observing guide for 51 Pegasi b.
Fomalhaut (Alpha Piscis Austrini Debris Disk)
Coordinates, Hipparcos distance (25.13 ly), magnitude 1.16, JWST triple debris-belt system, and observing guide for Fomalhaut.
Angular Size, Separation & Field of View
How angular diameter (degrees, arcminutes, arcseconds), spherical angular separation, and small-angle physical diameter relate to telescope field of view.
Measurement Uncertainty & Optics in Astronomy
How random vs systematic errors, asymmetric error bars, model dependencies, and optical aperture/exit-pupil limits shape astronomical measurements.
Scientific Sources & Dataset Provenance
- NASA Exoplanet Archive (2026-10-01 snapshot): Akeson, R. L., et al. 2013, PASP, 125, 989; NASA Exoplanet Archive (IPAC/Caltech) — NASA Exoplanet Science Institute (NExScI / Caltech / IPAC)
- ESA Gaia Archive — Data Release 3 (DR3 (2022-06-13)): Gaia Collaboration, Vallenari, A., et al. 2023, A&A, 674, A1 (Gaia Data Release 3) — European Space Agency / Gaia DPAC