Deneb el Okab: The Tail of the Eagle

Deneb el Okab joins two Arabic words, dhanab, tail, and uqab, eagle: the tail of the eagle. The name is used in modern star atlases for the pair Delta and Zeta Aquilae, distinguished as Deneb el Okab Australis and Borealis, the southern and northern; the older astrological lists do not always make that distinction and sometimes carry the name as a single entry. This star and the entry immediately following it in the atlas stand at the same recorded ecliptic longitude, which strongly suggests they are two spellings of the same object rather than two distinct stars, a common condition in catalogues assembled by copying from several sources.

Delta and Zeta Aquilae, the two stars usually intended by this name, are themselves unrelated to each other, a hot subgiant and a cooler evolved star at different distances that happen to sit near each other in the sky along the eagle's tail; their pairing under one descriptive phrase is a matter of appearance from Earth rather than any physical association. Both stars are considerably hotter and more distant than the Sun, and neither has any recorded planetary system; their interest to the tradition rests entirely on position within the eagle's outline rather than on any distinguishing physical property.