1911 Encyclopædia Britannica/Aquila (constellation)
AQUILA, in astronomy, the “Eagle,” sometimes named the “Vulture,” a constellation of the northern hemisphere, mentioned by Eudoxus (4th cent. B.C.) and Aratus (3rd cent. B.C.). Ptolemy catalogued nineteen stars jointly in this constellation and in the constellation Antinous, which was named in the reign of the emperor Hadrian (A.D. 117-138), but sometimes, and wrongly, attributed to Tycho Brahe, who catalogued twelve stars in Aquila and seven in Antinous; Hevelius determined twenty-three stars in the first, and nineteen in the second. The most brilliant star of this constellation, α-Aquilae or Altair, has a parallax of 0.23″, and consequently is about eight times as bright as the sun; η-Aquilae is a short-period variable, while Nova Aquilae is a “temporary” or “new” star, discovered by Mrs Fleming of Harvard in 1899.