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Lego Figure holding a lego telescope. Photo

Eero Vaher

Doctoral student

Lego Figure holding a lego telescope. Photo

Runaway and walkaway stars from the ONC with Gaia DR2


  • Christina Schoettler
  • Jos De Bruijne
  • Eero Vaher
  • Richard J. Parker

Summary, in English

Theory predicts that we should find fast, ejected (runaway) stars of all masses around dense, young star-forming regions. N-body simulations show that the number and distribution of these ejected stars could be used to constrain the initial spatial and kinematic substructure of the regions. We search for runaway and slower walkaway stars within 100 pc of the Orion Nebula Cluster (ONC) using Gaia DR2 astrometry and photometry. We compare our findings to predictions for the number and velocity distributions of runaway stars from simulations that we run for 4 Myr with initial conditions tailored to the ONC. In Gaia DR2, we find 31 runaway and 54 walkaway candidates based on proper motion, but not all of these are viable candidates in three dimensions. About 40 per cent are missing radial velocities, but we can trace back nine 3D runaways and 24 3D walkaways to the ONC, all of which are low/intermediate mass (<8 M⊠). Our simulations show that the number of runaways within 100 pc decreases the older a region is (as they quickly travel beyond this boundary), whereas the number of walkaways increases up to 3 Myr. We find fewer walkaways in Gaia DR2 than the maximum suggested from our simulations, which may be due to observational incompleteness. However, the number of Gaia DR2 runaways agrees with the number from our simulations during an age of ∼1.3-2.4 Myr, allowing us to confirm existing age estimates for the ONC (and potentially other star-forming regions) using runaway stars.


  • Lund Observatory - Undergoing reorganization

Publishing year







Monthly Notices of the Royal Astronomical Society





Document type

Journal article


Oxford University Press


  • Astronomy, Astrophysics and Cosmology


  • astrometry
  • open clusters and associations: individual: Orion Nebula Cluster
  • stars: kinematics and dynamics




  • ISSN: 0035-8711