The origin of very wide binary systems

M. B.N. Kouwenhoven, S. P. Goodwin, Richard J. Parker, M. B. Davies, D. Malmberg, P. Kroupa

Research output: Chapter in Book or Report/Conference proceedingChapterpeer-review


The majority of stars in the Galactic field and halo are part of binary or multiple systems. A significant fraction of these systems have orbital separations in excess of thousands of astronomical units, and systems wider than a parsec have been identified in the Galactic halo. These binary systems cannot have formed through the 'normal' star-formation process, nor by capture processes in the Galactic field. We propose that these wide systems were formed during the dissolution phase of young star clusters. We test this hypothesis using N-body simulations of evolving star clusters and find wide binary fractions of 1-30%, depending on initial conditions. Moreover, given that most stars form as part of a binary system, our theory predicts that a large fraction of the known wide 'binaries' are, in fact, multiple systems.

Original languageEnglish
Title of host publicationStar clusters
Subtitle of host publicationbasic galactic building blocks throughout time and space
EditorsRichard de Grijs, Richard de Grijs, Jacques Lepine
Number of pages4
Publication statusPublished - 2009
Externally publishedYes

Publication series

NameProceedings of the International Astronomical Union
ISSN (Print)1743-9213
ISSN (Electronic)1743-9221


  • Binaries: general
  • Methods: N-body simulations
  • Stars: formation
  • Stellar dynamics

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