﻿NATURE OF THE TEMPORARY STAR OF 1572. 311 



Certain astronomers refused to adopt the views of Tycho Brahe from scholastic and 

 religious scruples. These maintained that the star was as ancient as the world itself, 

 but had not been seen because of its distance. Having approached the earth, it had 

 become visible ; and again receding, it had been lost to our sight. Its path in both 

 instances was a straight line, as its position among the other stars did not vary. 



Tycho opposed this hypothesis with an objection which he considered conclusive, 

 viz. : that motion in a right line was not natural to the heavenly bodies. 



The star of the year 1572 differed from all the other stars called temporary, in 

 that, on two former occasions, stars had appeared for a time near the same point in 

 the heavens. The first of these was in the year 945; and the second in 1264 ; and 

 both were seen between the constellations of Cepheus and Cassiopeia. 



Even while the star of 1572 was shining, it was considered to be identical with 

 those of 945 and 1264. This view has been adopted by Keill, Pigott and Goodricke, 

 and reduces it to the class of the variable or periodical stars. 



The views held by Sir Isaac Newton upon the subject of this star were bold, but 

 purely conjectural. He says : " Fixed stars that have been gradually wasted by the 

 light and vapors emitted from them for a long time, may be recruited by comets that 

 fall upon them, and from this fresh supply of new fuel, these old stars, acquiring new 

 splendor, may pass for new stars. Of this kind are such fixed stars as appear on a 

 sudden, and shine with a wonderful brightness at first, and afterwards vanish by little 

 and little. Such was that star which appeared in Cassiopeia's chair in 1572."* 



De Maupertuis, whose opinion in his day had some weight, entertained the follow- 

 ing views upon the subject of the variations of the stars. He conceived that, owing to a 

 great centrifugal force, some stars had taken the form of circular disks, which, when 

 their faces were turned towards the earth, were seen in all their brightness ; but 

 which were but little seen, if at all, when the edge of the disk was turned toward the 

 earth. The changing of the plane of the disk, he imagined might be owing to the 

 perihelion passage of a huge planet, or a comet, with an orbit which was very 

 elliptical and highly inclined to the plane of the star's equator.! 



In undertaking to explain the cause of a phenomenon of unusual occurrence, it 

 should be the aim of the theorist to do so in conformity to laws whose existence is 

 ascertained. And if it be necessary to assume conditions not known to exist, it is 

 indispensable to exclude such as violate established principles. 



The objection to the views of Tycho Brahe are, that they have no independent 

 basis, they are supported neither by analogy nor by observation, and are in fact mere 

 surmise. They have, however, this claim to our consideration, that they present 

 many points of resemblance to those adopted by the elder Herschel. 



*Principia, lib. 3. 



fDe Maupertuis, " De figuris Astrorum," Paris, 1734, or Tegg's edition of the " Principia," with com- 

 mentaries by Le Seur and Jaquier, London, 1833, vol. ii. p. 197, Note 174. 



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