NEW, VARIABLE, AND COMPOUND STARS. 



173 



northern hemisphere, and within 15 south of the equator. From the southern heavens 

 an equally plenteous harvest may be gathered, of which Mr. Dunlop's catalogue of 250, 

 observed at Paramatta, may be regarded as the first-fruits. Upon the whole, the number 

 of stars whose multiple character and respective positions have been determined, cannot 

 be rated at less than 6000. Of these the most numerous are twin-stars, or binary systems. 

 Some of the more remarkable specimens are Castor, 77 Coronas, Rigel, Polaris, Mirac or 

 Bootis, y Leonis, y Virginis, Ursae Majoris, a Herculis, 36 Andromedte, \ Ophiuchi, 

 and TT Aquike. 



Of all the binary stars in the heavens, Castor is the largest and the finest ; the one also 

 which has been the longest observed. Its structure and position were 

 recorded by Pound in 1718, by Bradley and Maskelyne in 1759, 

 and by Herschel in 1799 ; and, in the present day, it has been closely 

 and perseveringly examined by Sir John Herschel, Struve, and Sir 

 James South. Castor is a Geminorum, one of the bright stars in 

 castor. the head of the Twins, the most northerly of the two, and is easily 



separated by a moderately good telescope. Its constituents are of the third and fourth 

 magnitude, at present about 3" apart. The diagram shows the pair which now make 

 an angle with Pollux, the other principal star in Gemini. But in Bradley's time the 

 position was diiferent, as appears from a memorandum of one of his observations : 

 " Double star Castor. No change of position of the two stars : the line joining them at 

 all times of the year parallel to the line joining Castor and Pollux in the heavens seen 

 by the naked eye." Sir John Herschel speaks of this object as that whose unequivocal 

 angular motion first impressed on his father's mind a full conviction of the reality of his 

 long-cherished views on the subject of the binary stars, rj Coronae, 

 halfway between the Northern Crown and the club of Bootes, is a 

 delicate double star, not to be seen but under favourable circum 

 stances, requiring the most powerful and perfect instruments. Its 

 compound character was discovered by Herschel 

 in 1781, since which time its constituents have 

 gone through more than a complete revolution, 

 which renders it the most remarkable binary 

 star known. Rigel, the well-known star in the 

 foot of Orion, consists of one large and brilliant 

 with a minute companion. The attendant 

 point was seen by Herschel with a power of 

 227, but has been reached by one of Dollond's 

 two-foot telescopes with a power of 70. Po 

 laris, the pole star, is resolved into two of very 

 unequal size, the smaller appearing a mere point 

 in comparison with its companion. Mirac, or e 

 Bootis, about 10 north-east of Arcturus, is 

 one of the loveliest objects in the heavens, 

 on account of the contrasted colours of the 

 two stars composing it. It requires a 

 power of 200 distinctly to define the pair, 

 y Leonis, about 7-| north-east of Regulus, is 

 another striking example of a double star. 



Besides stellar pairs, there are many instances of triple combination, of points 

 apparently individual resolving into three distinct bodies when examined by an instrument 

 of high power. An object of this kind is in the constellation Monocerotis, or the 



Rigel. 



i Bootis. 



y Leonis. 



