A second planetesimal collision in the Fomalhaut system

2025/12/17 by Paul Kalas, Jason J. Wang, Kalas, Paul +22 · 3 voices · 3 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Collision #Debris #Exoplanet #Planet #Planetary system #Planetesimal #Spitzer Space Telescope #Stellar, planetary, and galactic studies

paper · pdf · doi:10.1126/science.adu6266

published in Science 391(6783), 371-373 (American Association for the Advancement of Science)

openalex created_date 2025/12/18 · openalex publication_date 2025/12/18 · openalex updated_date 2026/08/05

Abstract

The nearby star Fomalhaut is orbited by a compact source, Fomalhaut b, which has previously been interpreted as either a dust-enshrouded exoplanet or a dust cloud generated by the collision of two planetesimals. Such collisions are rarely observed, but their debris can appear in direct imaging. We report Hubble Space Telescope observations that show the appearance in 2023 of a second point source around Fomalhaut, resembling the appearance of Fomalhaut b 20 years earlier. We interpret this additional source as a dust cloud produced by a recent impact between two planetesimals. The positions and motion of two impact-generated dust clouds over 20 years provide constraints on the collisional dynamics in the debris belt.

Citations

• A New Algorithm for Point‐Spread Function Subtraction in High‐Contrast Imaging: A Demonstration with Angular Differential Imaging
• The Space Telescope Imaging Spectrograph Design
• Angular Differential Imaging: A Powerful High‐Contrast Imaging Technique
• emcee: The MCMC Hammer

Discussions

• And sometimes what looks like a planet being born is actually a smash-up in which a planet is being destroyed. We saw it happening twice (!) around the star Fomalhaut: clouds of debris that appeared a [bsky, 27 points, 2 comments]
• Today on the #arXiv and in Science: Kalas et al. 2025, "A second planetesimal collision in the Fomalhaut system" - arxiv.org/pdf/2512.15861 Reporting another orbiting dust cloud from collisions around [bsky, 3 points, 0 comments]
• Today on the # arXiv and in Science: Kalas et al. 2025, "A second planetesimal collision in the Fomalhaut system" - https:// arxiv.org/pdf/2512.15861 Reporting another orbiting dust cloud from collisi [mastodon, 0 points, 0 comments]

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