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The Coathanger

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

Proper NamesThe Coathanger, Al Sufi’s Cluster, Brocchi’s Cluster
Other DesignationsCollinder 399
ConstellationVulpecula
GenitiveVulpeculae
AbbreviationVul
Right Ascension19h24 to 19h30
Declination+19° 51' to +20° 27'
Area (sq deg)!0.36
Brightest Star4 Vulpeculae
Optimum VisibilityJuly / August

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 that line to create an approximate 'hook' shape, giving this group the common name of the Coathanger.

Though often referred to as a cluster (especially in its alternative names of Al Sufi's or Brocchi's Cluster), this formation does not represent a true open cluster. Its member stars are separated by hundreds of light years, and only appear as a group because they lie on the same line of sight from Earth. The Coathanger is therefore categorised as an asterism; that is, simply a collection of unrelated stars in the sky, rather than a true star cluster.

Imagery provided by Aladin sky atlas

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. Of these, the closest of all 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 an estimated distance of more than 1,100 light years.

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