The anomalously large transiting planet around Boyajian's star: evidence for a circumplanetary ring
Abstract
A recent study reported a transiting giant-planet candidate with a mass of 9.4+4.9−4.1 MJ and a radius of 1.7±0.1 RJ on a wide orbit around Boyajian's star (KIC 8462852, also called Tabby's star), which is well known for its irregular, deep flux dips. The reported radius is puzzling, because cool giant planets of ∼10\,MJup are expected to have radii close to Jupiter's, so the companion appears ∼60--70\% larger than standard models allow. Here we explore the solution that the planet is actually ringed. We develop a fast and accurate code to compute the transit light curve due to a ringed planet, and apply it to the TESS light curve. The ring model is marginally favoured by the data by Δχ2>10 and a difference in Bayesian information criterion (BIC) of <2. The preferred configuration is a Jupiter-sized (1.1 RJ) planet surrounded by an opaque, highly flattened ring extending to $3.1−−4.4$ planetary radii with a nearly polar obliquity. While the ring geometry is uncertain, simple estimates suggest that a debris annulus extending out to the planet's Roche limit is needed to explain the large transit depth. The ring thus removes the radius anomaly altogether and is qualitatively consistent with the dusty, comet-shepherding environment inferred from the star's historic dimmings.
Related
- Hot Rocks Survey VI: An anomalously hot dayside for the rocky planet GJ 357 b
- Planetesimal Delivery to Giant Planet Circumplanetary Disks: Bulk Ice Enrichment and an Ice-rich Iapetus
- Marginalized planet-to-star radius ratio posteriors for low-SNR transiting planets via dimensionality reduction
- Hidden worlds: A non-transiting candidate planet in the Neptunian desert around the solar-type pulsator KIC 9139163
- A JWST Transiting Survey of FGK Stellar Limb Darkening: Empirical Evidence for Quadratic Laws and Atmospheric Model Comparisons
BibTeX
@misc{zhu2026anomalously,
title = {{The anomalously large transiting planet around Boyajian's star: evidence for a circumplanetary ring}},
author = {Wei Zhu and Quanyi Liu},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.34806},
eprint = {2610.34806},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.34806},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The anomalously large transiting planet around Boyajian's star: evidence for a circumplanetary ring
AU - Wei Zhu
AU - Quanyi Liu
PY - 2026
DA - 2026/10/26
PB - arXiv
DO - 10.48550/arxiv.2610.34806
UR - https://arxiv.org/abs/2610.34806
AB - A recent study reported a transiting giant-planet candidate with a mass of 9.4^+4.9_−4.1 M_J and a radius of 1.7±0.1 R_J on a wide orbit around Boyajian's star (KIC 8462852, also called Tabby's star), which is well known for its irregular, deep flux dips. The reported radius is puzzling, because cool giant planets of ∼10\,M_Jup are expected to have radii close to Jupiter's, so the companion appears ∼60--70\% larger than standard models allow. Here we explore the solution that the planet is actually ringed. We develop a fast and accurate code to compute the transit light curve due to a ringed planet, and apply it to the TESS light curve. The ring model is marginally favoured by the data by Δχ^2>10 and a difference in Bayesian information criterion (BIC) of <2. The preferred configuration is a Jupiter-sized (1.1 R_J) planet surrounded by an opaque, highly flattened ring extending to $3.1−−4.4$ planetary radii with a nearly polar obliquity. While the ring geometry is uncertain, simple estimates suggest that a debris annulus extending out to the planet's Roche limit is needed to explain the large transit depth. The ring thus removes the radius anomaly altogether and is qualitatively consistent with the dusty, comet-shepherding environment inferred from the star's historic dimmings.
ER -