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Alkaphrah

Talitha Australis, Kappa Ursae Majoris, 12 Ursae Majoris

A system consisting of a binary pair of stars lying in the southwest of Ursa Major, near its border with neighbouring Lynx, and representing one of the forepaws of the Great Bear. The system lies some 358 light years from the Sun, and consists of two similar stars, each of which is an A-type white star of similar magnitude and age. Of these two, the primary star, Kappa Ursae Majoris A, formally holds the common name of Alkaphrah, while the entire system is often referred to by the traditional name of Talitha Australis.

The two stars that comprise the system are separated from one another by approximately twenty-four Astronomical Units, but the orbital arrangement of the system is highly eccentric, so that the component stars can approach as closely as 11 AU at times over their thirty-six-year orbital cycle. Each star is much more luminous than the Sun, and each is approaching the end of its hydrogen-burning existence, and will eventually develop into a subgiant. Beyond the orbit of the B star, the system also possesses a debris disc, circling the inner stars at a distance of some 55 AU.

Imagery provided by Aladin sky atlas

The name Alkaphrah derives ultimately from Arabic, meaning 'the leap'. This comes from Arabic tradition, which saw three pairs of stars running northwestward through Ursa Major as marking the footprints of a springing gazelle. Alkaphrah (together with nearby Talitha) marks the third of these pairs of stars (hence the name Talitha - and the occasional name Talitha Australis for Alkaphrah itself - which means 'third').

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