Page:Star Lore Of All Ages, 1911.pdf/94

50 Venus in brilliancy. It vanished three after weeks' visibility.

Altair with its two companions Beta and Gamma Aquilæ constitute the so-called "Family of Aquila." The line joining these stars is five degrees in length. In China these stars were known as "Ho Koo," meaning "a river drum," and the Persians-called them the "Star Striking Falcon." They formed the 23d Hindu lunar station known as "the Ear." The regent of the asterism is Vishnu, and these three stars represent the three steps with which Vishnu is said in the early Hindu mythology to have strode through heaven. A trident is often given as the figure of this group.

Eta Aquilæ is a remarkable variable star. Its greatest brightness continues but forty hours. It then gradually diminishes for sixty-six hours, when its lustre remains stationary for thirty hours. It then waxes brighter and brighter until it appears again as a star of the third magnitude. From these phenomena, says Burritt, it is inferred that it not only has spots on its surface like our sun, but that it also turns on its axis. The spectrum of this star is similar to that of our sun. Lockyer thinks it is a spectroscopic binary, that is a star with a companion too close to be revealed by the most powerful telescope.