Astronomical evidence
HD 128311 c was discovered through stellar radial-velocity measurements. A later study combined those measurements with Hubble astrometry to constrain orbital inclination and derive a true mass of 3.789 Jupiter masses, with reported errors of +0.924/−0.432. [2] The saved catalog gives an orbital period of 921.538 ± 1.150 days and records this mass as Mass rather than Msini. [1] These constraints motivate a giant-planet setting without providing a resolved atmospheric portrait. The blue color and pale cloud veils are invented. The foreground is explicitly an imagined moon; neither that moon nor its local environment is a reported discovery.
The illustrated viewpoint
Pale four-armed humanoid with an elongated cranial crest in meditation. An open cliff sanctuary on an invented rocky moon of HD 128311 c. The rocky moon, atmosphere, blue cloud colors, cliff sanctuary, mosaic and warrior are fictional. The setting is on solid ground with an open view across terrain. The giant's mass is constrained through stellar motion; its cloud colors, weather and apparent size in this scene are not measured. No orbit or moon-stability calculation is claimed.
The rocky moon, atmosphere, blue cloud colors, cliff sanctuary, mosaic and warrior are fictional. The setting is on solid ground with an open view across terrain. The giant's mass is constrained through stellar motion; its cloud colors, weather and apparent size in this scene are not measured. No orbit or moon-stability calculation is claimed. All beings and cultures are fictional. Apparent sizes, phases and exposure are artistic, not a calibrated sky simulation. Cosmic connection is a visual theme, not an observed biological mechanism.
Catalog measurements & sources
Host: HD 128311. 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 | Calculated Value |
| Mass · Earth masses | 1204.26 (+293.675 / -137.303) | McArthur et al. 2014 |
| Density · g/cm³ | 3.01 | Calculated Value |
| Orbital period · days | 921.538 (+1.15 / -1.15) | McArthur et al. 2014 |
| Orbital semimajor axis · AU | 1.74 (+0.01 / -0.01) | McArthur et al. 2014 |
| Eccentricity | 0.159 (+0.006 / -0.006) | McArthur et al. 2014 |
| Inclination · degrees | 55.95 (+14.553 / -14.553) | McArthur et al. 2014 |
| Irradiation · Earth flux | 0.1017 (+0.0012 / -0.0012) | Calculated Value |
| Equilibrium temperature · K | 158.23 (+2.55 / -2.55) | Calculated Value |
| Stellar effective temperature · K | 4965 (+44 / -44) | Wittenmyer et al. 2009 |
| Stellar radius · Solar | 0.76 (+0.02 / -0.02) | McArthur et al. 2014 |
| Stellar mass · Solar | 0.828 (+0.008 / -0.012) | McArthur et al. 2014 |
| Stellar luminosity · log Solar | -0.5116 (+0.0007 / -0.0007) | Gaia DR2 |
| Stellar age · Gyr | ≤ 0.96 | McArthur et al. 2014 |
| Stellar metallicity · dex | 0.08 (+0.03 / -0.03) | Wittenmyer et al. 2009 |
| Distance · pc | 16.3292 (+0.0199 / -0.0198) | TICv8 |