A Candidate Innermost Fifth Planet In the HR 8799 System Revealed By JWST NIRISS Aperture Masking Interferometry
Abstract
We detect a candidate fifth planet in the HR 8799 system, directly imaged with the JWST/NIRISS Aperture Masking Interferometer (AMI). The detected source lies just above a 3σ contrast curve at a contrast of ∼2×10−4 in the F380M filter at a projected separation of ∼150 mas, corresponding to a few-to-several Jupiter mass planet at an orbital radius of ∼ 7au. The separation of the candidate is compatible with absolute proper-motion constraints from Gaia and Hipparcos assuming it is bound, while its orbital position lies near a stable orbital solution of a fifth planet in a 3:1 mean motion resonance with planet e. This detection was made possible by a new JWST/NIRISS AMI data pipeline that reaches the photon noise limited potential of AMI by accounting for the optical and electronic systematics that limited sensitivity in prior analyses. Confirmation of this candidate would make HR 8799 the first directly imaged five-planet system and provide insight into the orbital dynamics and the dynamical evolution of planetary systems with widely-separated gas giants.
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BibTeX
@misc{nguyen2026candidate,
title = {{A Candidate Innermost Fifth Planet In the HR 8799 System Revealed By JWST NIRISS Aperture Masking Interferometry}},
author = {Jayke S. Nguyen and Louis Desdoigts and Alexandra Z. Greenbaum and Benjamin J. S. Pope and Max Charles and Quinn M. Konopacky and Kaitlyn Hessel and Dori Blakely and Matthew De Furio and Clarissa R. Do Ó and René Doyon and Doug Johnstone and Jens Kammerer and David Lafrenière and Bruce A. Macintosh and Michael R. Meyer and Eric L. Nielsen and Anne E. Peck and William Roberson and Anand Sivaramakrishnan and Peter Tuthill and Thomas Vandal and Marie Ygouf},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.10507},
eprint = {2609.10507},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.10507},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A Candidate Innermost Fifth Planet In the HR 8799 System Revealed By JWST NIRISS Aperture Masking Interferometry
AU - Jayke S. Nguyen
AU - Louis Desdoigts
AU - Alexandra Z. Greenbaum
AU - Benjamin J. S. Pope
AU - Max Charles
AU - Quinn M. Konopacky
AU - Kaitlyn Hessel
AU - Dori Blakely
AU - Matthew De Furio
AU - Clarissa R. Do Ó
AU - René Doyon
AU - Doug Johnstone
AU - Jens Kammerer
AU - David Lafrenière
AU - Bruce A. Macintosh
AU - Michael R. Meyer
AU - Eric L. Nielsen
AU - Anne E. Peck
AU - William Roberson
AU - Anand Sivaramakrishnan
AU - Peter Tuthill
AU - Thomas Vandal
AU - Marie Ygouf
PY - 2026
DA - 2026/09/09
PB - arXiv
DO - 10.48550/arxiv.2609.10507
UR - https://arxiv.org/abs/2609.10507
AB - We detect a candidate fifth planet in the HR 8799 system, directly imaged with the JWST/NIRISS Aperture Masking Interferometer (AMI). The detected source lies just above a 3σ contrast curve at a contrast of ∼2×10^−4 in the F380M filter at a projected separation of ∼150 mas, corresponding to a few-to-several Jupiter mass planet at an orbital radius of ∼ 7au. The separation of the candidate is compatible with absolute proper-motion constraints from Gaia and Hipparcos assuming it is bound, while its orbital position lies near a stable orbital solution of a fifth planet in a 3:1 mean motion resonance with planet e. This detection was made possible by a new JWST/NIRISS AMI data pipeline that reaches the photon noise limited potential of AMI by accounting for the optical and electronic systematics that limited sensitivity in prior analyses. Confirmation of this candidate would make HR 8799 the first directly imaged five-planet system and provide insight into the orbital dynamics and the dynamical evolution of planetary systems with widely-separated gas giants.
ER -