R associations are one of three recognized types of stellar association. The R classification was first suggested by the the Canadian astronomer Sidney van den Bergh (1929–).
Being relatively common, R associations are useful markers of the structure of our galaxy's spiral arms. An example is Vela R2, a very young group at a distance of about 2,800 light-years (850 parsecs).
Related entry T association
Related category• NEBULAE AND STAR CLUSTERS
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