A 3D View of Orion: I. Barnard's Loop

Michael M. Foley, Alyssa Goodman, Catherine Zucker, John C. Forbes, Ralf Konietzka, Cameren Swiggum, João Alves, John Bally, Juan D. Soler, Josefa E. Großschedl, Shmuel Bialy, Michael Y. Grudić, Reimar Leike, Torsten Ensslin

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Barnard’s Loop is a famous arc of Hα emission located in the Orion star-forming region. Here, we provide evidence of a possible formation mechanism for Barnard’s Loop and compare our results with recent work suggesting a major feedback event occurred in the region around 6 Myr ago. We present a 3D model of the large-scale Orion region, indicating coherent, radial, 3D expansion of the OBP-Near/Briceño-1 (OBP-B1) cluster in the middle of a large dust cavity. The large-scale gas in the region also appears to be expanding from a central point, originally proposed to be Orion X. OBP-B1 appears to serve as another possible center, and we evaluate whether Orion X or OBP-B1 is more likely to have caused the expansion. We find that neither cluster served as the single expansion center, but rather a combination of feedback from both likely propelled the expansion. Recent 3D dust maps are used to characterize the 3D topology of the entire region, which shows Barnard’s Loop’s correspondence with a large dust cavity around the OPB-B1 cluster. The molecular clouds Orion A, Orion B, and Orion λ reside on the shell of this cavity. Simple estimates of gravitational effects from both stars and gas indicate that the expansion of this asymmetric cavity likely induced anisotropy in the kinematics of OBP-B1. We conclude that feedback from OBP-B1 has affected the structure of the Orion A, Orion B, and Orion λ molecular clouds and may have played a major role in the formation of Barnard’s Loop.

Original languageEnglish
Article number66
Number of pages19
JournalThe Astrophysical Journal
Issue number2
Publication statusPublished - Apr 2023

Austrian Fields of Science 2012

  • 103003 Astronomy
  • 103004 Astrophysics


  • Astrophysics - Astrophysics of Galaxies

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