-------------------------------------------------------------------- | | | |Dist. of|Magni-| | |No.| Name. | Fig. | Parts. |tudes.| Remarks. | |---|------------|-------------|--------|------|---------------------| | 1.| e Lyræ | 72 | 1' 56" | |Quadruple. | | 2.| z Lyræ | 72 | 44 |5 & 6 |Topaz and green. | | 3.| b Cygni | 73 | 34-1/2|3 & 6 |Yellow and blue. | | 4.| 61 Cygni | 73 | 20 |5 & 6 |Nearest star but one.| | 5.| Mizar | 67 | 14 |3 & 4 |Both white. | | 6.| Polaris | 67 | 18-1/2|2 & 9 |Test object of eye | | | | | | | and glass. | | 7.| r Orionis |Frontispiece.| 7 |5 & 8 |Yellow and blue. | | 8.| b Orionis | " | 9 |1 & 8 | Rigel. | | 9.| d " | " | 10 |2 & 8 | Red and white. | |10.| th " | " | | |Septuple. | |11.| l " | " | 5 | |White and violet. | |12.| s " | " A, B.| 11 |4 & 10|Octuple. | |13.| Castor | 69 | 5-1/2|2 & 3 |White. | |14.| Pollux | 69 | |Triple|Orange, gray, lilac. | |15.| g Virginis | 70 | 5 |3 & 3 |Both yellow. | -------------------------------------------------------------------- ] When g Virginis was observed in 1718 by Bradley, the component parts were 7" asunder. He incidentally remarked in his note-book that the line of their connection was parallel to the line of the two stars Spica, or a and d Virginis. By 1840 they were not more than 1" apart, and the line of their connection greatly changed. The appearance of the star is given in Fig. 75 (15), commencing at the left, for the years 1837 '38 '39 '40 '45 '50 '60 and '79. also a conjectural [Page 213] orbit, placed obliquely, and the position of the stars at the times mentioned, commencing at the top. The time of its complete revolution is one hundred and fifty years. [Illustration: Fig. 75.--Aspects and Revolution of Double Stars.] The meaning of these double stars is that two or more suns revolve about their centre of gravity, as the moon and earth about their centre. If they have planets, as doubtless they have, the movement is no more complicated than the planets we call satellites of Saturn revolving about their central body, and also about the sun. Kindle Saturn and Jupiter to a blaze, or let out their possible light, and our system would appear a triple star in the distance. Doubtless, in the far past, before these giant planets were cooled, it so appeared.