University of Hertfordshire

From the same journal

From the same journal

By the same authors

3D shape of Orion A from Gaia DR2

Research output: Contribution to journalArticlepeer-review


  • 1808.05952v1

    Accepted author manuscript, 7.08 MB, PDF document

  • Josefa E. Grossschedl
  • Joao Alves
  • Stefan Meingast
  • Christine Ackerl
  • Joana Ascenso
  • Herve Bouy
  • Andreas Burkert
  • Jan Forbrich
  • Verena Fuernkranz
  • Alyssa Goodman
  • Alvaro Hacar
  • Gabor Herbst-Kiss
  • Charles J. Lada
  • Irati Larreina
  • Kieran Leschinski
  • Marco Lombardi
  • Andre Moitinho
  • Daniel Mortimer
  • Eleonora Zari
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Original languageEnglish
Article numberA106
Number of pages9
JournalAstronomy & Astrophysics
Early online date14 Nov 2018
Publication statusE-pub ahead of print - 14 Nov 2018


We use the Gaia DR2 distances of about 700 mid-infrared selected young stellar objects in the benchmark giant molecular cloud Orion A to infer its 3D shape and orientation. We find that Orion A is not the fairly straight filamentary cloud that we see in (2D) projection, but instead a cometary-like cloud oriented toward the Galactic plane, with two distinct components: a denser and enhanced star-forming (bent) Head, and a lower density and star-formation quieter ~75 pc long Tail. The true extent of Orion A is not the projected ~40 pc but ~90 pc, making it by far the largest molecular cloud in the local neighborhood. Its aspect ratio (~30:1) and high column-density fraction (~45%) make it similar to large-scale Milky Way filaments ("bones"), despite its distance to the galactic mid-plane being an order of magnitude larger than typically found for these structures.


Reproduced with permission from Astronomy & Astrophysics. © 2018 ESO.

ID: 15201226