Star Formation

Many stars don't form in clusters

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Science  02 Feb 2018:
Vol. 359, Issue 6375, pp. 531-532
DOI: 10.1126/science.359.6375.531-e

Most stars are thought to form in dense, gravitationally bound molecular clouds, which should produce a bound cluster of stars. As unused gas is expelled from the system by stellar feedback, the cluster becomes gravitationally unbound to form an association, which gradually drifts apart. Associations of young stars (no more than a few million years old) should therefore be slowly expanding. Ward and Kruijssen use astrometric data to test this idea by looking for evidence of expansion in several nearby young associations. They do not find any; the associations show no sign of ever having been gravitationally bound. The authors suggest that this indicates that star formation is dominated by turbulent fragmentation, not monolithic collapse.

Mon. Not. R. Astron. Soc. 10.1093/mnras/sty117 (2018).

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