Two inner dust clumps in PDS 70. A third protoplanet traced by trojan material or a substructured inner disk?
Abstract
The PDS 70 cavity hosts two confirmed directly imaged protoplanets and a third inner planet candidate at 13au, labeled PDS 70 d. Despite its Keplerian motion, its unusually blue spectrum challenges a planetary interpretation. We further investigate the presence and nature of a third inner planet using new SPHERE and GRAVITY+ observations. Using the star-hopping strategy, we obtained coronagraphic IRDIS polarimetric observations in the H-band, and non-coronagraphic observations with IRDIFS in the YJHK-bands. We also searched for a planetary signal with GRAVITY in the 4UT configuration. We consistently detect two elongated inner emissions with SPHERE: the previously proposed planet candidate and another feature that appears to share the same orbit while leading it by ~120∘. Both features show dust-scattered-light spectra but different colors, possibly indicating different grain sizes. Such configuration is consistent with co-orbital dust accumulated at the stable Lagrangian regions of a distinct and yet undetected planet. GRAVITY yields a marginal (3σ) detection at the predicted location along the same orbit (ρ=76.2±0.29mas, PA=226.50±0.21∘), and consistent with a ~3MJup planet. This planet-like signal is aligned with a narrow shadow that we detect in the outer disk. We also detect polarized emission very close to the star likely arising from the inner disk. The apparent embedding of the two dust clumps within it motivates an inner-disk origin as an alternative scenario. We conclude that the previously reported third planet candidate traces a dust clump either trailing an unseen planet on the same orbit or a rotating substructure within the inner disk. Further observations are needed to test these scenarios. Confirming the new GRAVITY planet-like signal would support co-orbital substructures as indirect tracers of protoplanets.
Versions
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BibTeX
@misc{balsalobreruza2026inner,
title = {{Two inner dust clumps in PDS 70. A third protoplanet traced by trojan material or a substructured inner disk?}},
author = {O. Balsalobre-Ruza and V. Christiaens and N. Huélamo and I. Hammond and M. Benisty and S. Lacour and D. Blakely and R. G. van Holstein and J. Latour and J. Lillo-Box and Z. Wahhaj and D. Trevascus and O. Absil and J. Bae and C. Charalambous and I. de Gregorio-Monsalvo and A. Leleu and I. Mendigutía and C. Petrovich and Á. Ribas and S. Juillard},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2606.26381},
eprint = {2606.26381},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.26381},
note = {CC BY-NC-SA 4.0},
}
RIS
TY - UNPB
TI - Two inner dust clumps in PDS 70. A third protoplanet traced by trojan material or a substructured inner disk?
AU - O. Balsalobre-Ruza
AU - V. Christiaens
AU - N. Huélamo
AU - I. Hammond
AU - M. Benisty
AU - S. Lacour
AU - D. Blakely
AU - R. G. van Holstein
AU - J. Latour
AU - J. Lillo-Box
AU - Z. Wahhaj
AU - D. Trevascus
AU - O. Absil
AU - J. Bae
AU - C. Charalambous
AU - I. de Gregorio-Monsalvo
AU - A. Leleu
AU - I. Mendigutía
AU - C. Petrovich
AU - Á. Ribas
AU - S. Juillard
PY - 2026
DA - 2026/08/06
PB - arXiv
DO - 10.48550/arxiv.2606.26381
UR - https://arxiv.org/abs/2606.26381
AB - The PDS 70 cavity hosts two confirmed directly imaged protoplanets and a third inner planet candidate at 13au, labeled PDS 70 d. Despite its Keplerian motion, its unusually blue spectrum challenges a planetary interpretation. We further investigate the presence and nature of a third inner planet using new SPHERE and GRAVITY+ observations. Using the star-hopping strategy, we obtained coronagraphic IRDIS polarimetric observations in the H-band, and non-coronagraphic observations with IRDIFS in the YJHK-bands. We also searched for a planetary signal with GRAVITY in the 4UT configuration. We consistently detect two elongated inner emissions with SPHERE: the previously proposed planet candidate and another feature that appears to share the same orbit while leading it by ~120^∘. Both features show dust-scattered-light spectra but different colors, possibly indicating different grain sizes. Such configuration is consistent with co-orbital dust accumulated at the stable Lagrangian regions of a distinct and yet undetected planet. GRAVITY yields a marginal (3σ) detection at the predicted location along the same orbit (ρ=76.2±0.29mas, PA=226.50±0.21^∘), and consistent with a ~3M_Jup planet. This planet-like signal is aligned with a narrow shadow that we detect in the outer disk. We also detect polarized emission very close to the star likely arising from the inner disk. The apparent embedding of the two dust clumps within it motivates an inner-disk origin as an alternative scenario. We conclude that the previously reported third planet candidate traces a dust clump either trailing an unseen planet on the same orbit or a rotating substructure within the inner disk. Further observations are needed to test these scenarios. Confirming the new GRAVITY planet-like signal would support co-orbital substructures as indirect tracers of protoplanets.
ER -