The James Webb Space Telescope may have detected a previously unknown faint source in the inner region of the famous HR 8799 planetary system. Located about 130 light-years away, HR 8799 is already known for four directly imaged giant planets.
In a preprint submitted on 9 September 2026, researchers report a weak source in JWST NIRISS Aperture Masking Interferometry data at an angular separation of roughly 150 milliarcseconds. At the distance of the system, that corresponds to an orbital scale of about 7 astronomical units.
Brightness models suggest a mass of a few Jupiters. The candidate also lies near a dynamically interesting configuration, potentially close to a 3:1 mean-motion resonance with HR 8799 e.
The scientific caveat is important: this is not yet a confirmed planet. The signal is only just above the reported ~3σ contrast threshold, and the study is currently a preprint. Follow-up observations must recover the source and show that it shares the star’s proper motion.
If confirmed, HR 8799 could become the first system with five directly imaged planets.
Source: Nguyen et al., A Candidate Innermost Fifth Planet In the HR 8799 System Revealed By JWST NIRISS Aperture Masking Interferometry, arXiv:2609.10507 (2026).