Astronomical evidence
HR 8799 e is one of the directly imaged giant planets around the young star HR 8799. Unlike a transit measurement, direct imaging separates planetary light from the much brighter host. A young giant can be bright in the infrared because it is still releasing internal heat. [1,2] The GRAVITY instrument combined light from the Very Large Telescope Interferometer to obtain precise position measurements and a K-band spectrum. Atmospheric modeling indicated substantial carbon monoxide and cloud opacity associated with iron and silicate particles. The interpretation connects observed light to temperature, composition and vertical mixing. [2] Direct detection does not mean a detailed photograph of the planetary disk. The planet’s radius, gravity and mass depend on model interpretation; the saved catalog mass estimate has a particularly broad uncertainty. The observations constrain a distant luminous atmosphere, not mountains or moon surfaces. [1,2]
The illustrated viewpoint
Nonhumanoid / crescent-crowned umbral being. An invented moon of HR 8799 e, rendered as an interpretive infrared-to-visible scene. The planet’s self-luminosity is translated from infrared into visible rose and wine tones. The patchy atmospheric texture is imagined and deliberately differs from Jupiter’s familiar bands. This is not a calibrated human-eye sky. The satellite, ice, organism and its survival are fictional.
The planet’s self-luminosity is translated from infrared into visible rose and wine tones. The patchy atmospheric texture is imagined and deliberately differs from Jupiter’s familiar bands. This is not a calibrated human-eye sky. The satellite, ice, organism and its survival are fictional. All beings, civilizations and technology are fictional. No motives, moral alignment or character history is asserted.
Catalog measurements & sources
Host: HR 8799. Snapshot: 25 September 2026. Errors, limits and source provenance are retained. Calculated values and model estimates are not direct measurements. Unknown is not zero; equilibrium temperature is not surface temperature.
| Quantity / unit | Value / reported errors | Source |
|---|---|---|
| Radius · Earth radii | 13.1145 (+1.45717 / -1.23299) | Gravity Collaboration et al. 2019 |
| Mass · Earth masses | 3178.3 (+2224.81 / -1271.32) | Gravity Collaboration et al. 2019 |
| Density · g/cm³ | 7.74 | Calculated Value |
| Orbital period · days | 20815.6 (+1128.62 / -1128.62) | Zurlo et al. 2016 |
| Orbital semimajor axis · AU | 16.4 (+2.1 / -1.1) | Gravity Collaboration et al. 2019 |
| Eccentricity | 0.15 (+0.08 / -0.08) | Gravity Collaboration et al. 2019 |
| Inclination · degrees | 25 (+8 / -8) | Gravity Collaboration et al. 2019 |
| Irradiation · Earth flux | 0.0201 (+0.004 / -0.004) | Calculated Value |
| Equilibrium temperature · K | 1150 (+50 / -50) | Gravity Collaboration et al. 2019 |
| Stellar effective temperature · K | 7400 | Gravity Collaboration et al. 2019 |
| Stellar radius · Solar | 1.49338 (+0.049341 / -0.050935) | Konopacky et al. 2016 |
| Stellar mass · Solar | 1.51 (+0.038 / -0.024) | Zurlo et al. 2016 |
| Stellar luminosity · log Solar | 0.73347 (+0.01645 / -0.01535) | Konopacky et al. 2016 |
| Stellar age · Gyr | 0.03 | Gravity Collaboration et al. 2019 |
| Stellar metallicity · dex | -0.5 | Gravity Collaboration et al. 2019 |
| Distance · pc | 41.2441 (+0.1515 / -0.1505) | TICv8 |