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The Coathanger

Brocchi’s Cluster, Al Sufi’s Cluster, Collinder 399

A collection of faint stars - none brighter than fifth magnitude - that fall across the Milky Way in the southern parts of Vulpecula along its border with neighbouring Sagitta. Six of these stars form a line running west to east, while four further stars loop southward of the line to create an approximate 'hook' shape, giving this group the common name of the Coathanger. Though commonly referred to as a cluster (especially in its alternative names of Brocchi's or Al Sufi's Cluster), this formation does not represents a true open cluster: its member stars are separated by hundreds of light years, and only appear related due to their line of sight from Earth. The Coathanger is therefore categorised as an asterism; that is, simply a collection of stars in the sky, rather than a true star cluster.

The brightest of the stars making up the Coathanger are within the 'hook', especially 4 and 5 Vulpeculae, which also happen to be much closer to the Solar System than any of the other members of the group. The closest of these is 5 Vulpeculae, a white star some 218 light years from Earth, while the most distant of the asterism's major stars is the blue dwarf HR 7364. This is a faint star towards the western end of the line structure, at a distance of more than 1,100 light years.


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