Graduate student Agustin Heron along with faculty member Cristobal Petrovich and collaborators recently published their work on substructures in planet forming disks based on high-resolution images from the Atacama Large Millimeter/submillimeter Array (ALMA). These images reveal that planet-forming disks are rich in substructures — rings, gaps, spirals, clumps, and bright crescent-shaped asymmetries. Many of these features are thought to signal young planets embedded in the disk.
Classical celestial mechanics predicts that material near a planet’s orbit can collect at two stable locations, the Lagrange points L₄ and L₅, which should be symmetric. Yet observations and simulations increasingly show that these co-orbital structures are often asymmetric, with one side brighter than the other. What sets this imbalance?
The team used hydrodynamic simulations to investigate the origin of these asymmetries. They show that the disk’s radial temperature gradient determines which Lagrange point accumulates more gas: positive gradients enhance L₄, while negative gradients favor L₅. In a globally isothermal disk, the symmetry is restored.
The team also develops a semi-analytic model demonstrating how planet-induced gas flows modify the classical three-body configuration. They find that the gas concentrations can shift away from the nominal L₄ and L₅ positions depending on the disk’s pressure scale height and the star–planet mass ratio.
These results provide a new framework for interpreting asymmetric disk structures and suggest that co-orbital gas concentrations can probe local disk thermodynamics.
The study is published in the The Astrophysical Journal. The full article is available at: https://doi.org/10.3847/1538-4357/ae3a89
ALMA 1.3 mm continuum image of the protoplanetary disk LkCa 15 (Long et al. 2025), revealing asymmetric dust clumps that may trace material accumulating near the L₄ and L₅ Lagrange points of a candidate embedded planet
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