On blue straggler formation by direct collisions of main-sequence stars

James C. Lombardi*, Frederic A. Rasio, Stuart L. Shapiro

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

72 Scopus citations


We report the results of new smoothed particle hydrodynamics calculations of parabolic collisions between main-sequence (MS) stars. The stars are assumed to be close to the MS turnoff point in a globular cluster and are therefore modeled as n = 3, Γ = 5/3 polytropes. We find that the high degree of central mass concentration in these stars has a profound effect on the hydrodynamics. In particular, very little hydrodynamic mixing occurs between the dense, helium-rich inner cores and the outer envelopes. As a result, and in contrast to what has been assumed in previous studies, blue stragglers formed by direct stellar collisions are not necessarily expected to have anomalously high helium abundances in their envelopes or to have their cores replenished with fresh hydrogen fuel.

Original languageEnglish (US)
Pages (from-to)L117-L120
JournalAstrophysical Journal
Issue number2 PART 2
StatePublished - Jun 1 1995


  • Blue stragglers
  • Celestial mechanics, stellar dynamics
  • Globular clusters: general
  • Hydrodynamics
  • Stars: interiors

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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