Fig. 409.
Epsilon Lyræ is a good example of a pair of stars that can barely be separated with a good eye. Figs. 407 and 408 show this pair as it appears in telescopes magnifying respectively four and fifteen times; and Fig. 409 shows it as seen in a more powerful telescope, in which each of the two components of the pair is seen to be a truly double star.
Fig. 410.
Fig. 411.
348. Multiple Stars.—When a star is resolved into more than two components by a telescope, it is called a multiple star. Fig. 410 shows a triple star in Pegasus. Fig. 411 shows a quadruple star in Taurus. Fig. 412 shows a sextuple star, and Fig. 413 a septuple star. Fig. 414 shows the celebrated septuple star in Orion, called Theta Orionis, or the trapezium of Orion.
349. Optically Double and Multiple Stars.—Two or more stars which are really very distant from each other, and which have no physical connection whatever, may appear to be near together, because they happen to lie in the same direction, one behind the other. Such accidental combinations are called optically double or multiple stars.
Fig. 412.