THE STELLAR UNIVERSE. 361 



have shone with extraordinary lustre for a limited time, and have disappeared 

 finally, never having been again observed. Such are called TEMPORARY STARS. 



The first star of this class which has been recorded, is one observed by 

 Hipparchus, 125 B. C., the disappearance of which is said to have led that 

 astronomer to make his celebrated catalogue of the fixed stars, a work which 

 has proved in modern times of great value and interest. In the 389th year 

 of our era, a star blazed forth near *Aquil<B, which shone for three weeks, ap- 

 pearing as splendid as the planet Venus, after which it disappeared and has 

 never since been seen. In the years 945, 1264, and 1572, brilliant stars ap- 

 peared in the region of the heavens between the constellations of Cepheus and 

 Cassiopeia. The accounts of the position of these objects are obscure and un- 

 certain, but the intervals between the epochs of their appearances being nearly 

 equal, it has been conjectured that they were successive returns of the same 

 periodic star, the period of which is about 300 years, or possibly half that 

 interval. 



The appearance of the star of 1572 was very remarkable, and having been 

 witnessed by the most eminent astronomers of that day, the account of it may 

 be considered to be well entitled to confidence. Tycho Brake, happening to be 

 on his return on the evening of the 1 1th November from his laboratory to his 

 dwelling-house, was astonished to find a crowd of peasants gazing at a star 

 which he was sure did not exist half an hour before. This was the temporary 

 star of 1572. It was then as bright as the Dog-star, and it continued to in- 

 crease in splendor until it surpassed Jupiter when that planet is most brilliant, 

 and finally it attained such a lustre, that it was visible at mid-day. It began 

 to diminish in December, and altogether disappeared in March, 1574. 



On the 10th October, 1604, a splendid star suddenly burst out in the con- 

 stellation of Scrpentarius, which was as bright as that of 1572. It continued 

 visible till October, 1605, when it vanished. 



To this class may be referred the cases of numerous stars which have dis- 

 appeared from the firmament. On a careful examination of the heavens, and 

 a comparison of the objects observed with former catalogues, and of catalogues 

 ancient and modern with each other, many stars formerly known are now as- 

 certained to be missing ; and although, as Sir John Herschel observes, there 

 is no doubt that in many instances these apparent losses have proceeded from 

 mistaken entries, yet it is equally certain that in numerous cases there can 

 have been no mistake in the observation or the entry, and that the star has 

 really existed at a former epoch, and as certainly has since disappeared. 



When we consider the vast length of many of the periods of astronomical 

 phenomena, it is far from being improbable that these phenomena which seem 

 to be occasional, accidental, and springing from the operation of no regular 

 physical causes, such as those indicated by the class of variable stars first con- 

 sidered, may after all be periodic stars of the same kind, whose appearances 

 and disappearances are brought about by similar causes. All that can be cer- 

 tainly known respecting them is, that they have appeared or disappeared once 

 in that brief period of time within which astronomical observations have been 

 made and recorded. If they be periodic stars, the length of whose period ex- 

 ceeds that interval, their changes could only have been once exhibited to us, 

 and after ages have rolled away, and time has converted the future into the 

 past, future astronomers may witness the next occurrence of their phases, and 

 discover that to be regular, harmonious, and periodic, which appears to us ac- 

 cidental, occasional, and anomalous. 



