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Nature
Sep, 2024;633 (8028): 58-62.

Gravitational instability in a planet-forming disk.

Jessica Speedie, Ruobing Dong, Cassandra Hall, Cristiano Longarini, Benedetta Veronesi, Teresa Paneque-Carreño, Giuseppe Lodato, Ya-Wen Tang, Richard Teague, Jun Hashimoto
Author Information
  1. Jessica Speedie: Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, Canada. jspeedie@uvic.ca. ORCID
  2. Ruobing Dong: Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, Canada. rbdong@uvic.ca. ORCID
  3. Cassandra Hall: Department of Physics and Astronomy, The University of Georgia, Athens, GA, USA. ORCID
  4. Cristiano Longarini: Università degli Studi di Milano, Milan, Italy. ORCID
  5. Benedetta Veronesi: Univ Lyon, Univ Lyon1, Ens de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, Saint-Genis-Laval, France.
  6. Teresa Paneque-Carreño: Leiden Observatory, Leiden University, Leiden, The Netherlands. ORCID
  7. Giuseppe Lodato: Università degli Studi di Milano, Milan, Italy.
  8. Ya-Wen Tang: Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan.
  9. Richard Teague: Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA.
  10. Jun Hashimoto: Astrobiology Center, National Institutes of Natural Sciences, Mitaka, Japan. ORCID
PMID: 39232150 DOI: 10.1038/s41586-024-07877-0

Abstract

The canonical theory for planet formation in circumstellar disks proposes that planets are grown from initially much smaller seeds. The long-considered alternative theory proposes that giant protoplanets can be formed directly from collapsing fragments of vast spiral arms induced by gravitational instability-if the disk is gravitationally unstable. For this to be possible, the disk must be massive compared with the central star: a disk-to-star mass ratio of 1:10 is widely held as the rough threshold for triggering gravitational instability, inciting substantial non-Keplerian dynamics and generating prominent spiral arms. Although estimating disk masses has historically been challenging, the motion of the gas can reveal the presence of gravitational instability through its effect on the disk-velocity structure. Here we present kinematic evidence of gravitational instability in the disk around AB Aurigae, using deep observations of CO and CO line emission with the Atacama Large Millimeter/submillimeter Array (ALMA). The observed kinematic signals strongly resemble predictions from simulations and analytic modelling. From quantitative comparisons, we infer a disk mass of up to a third of the stellar mass enclosed within 1″ to 5″ on the sky.

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