Popular Science Monthly 



505 



crably, we are apt to feel perhaps that 

 something has gone off from us whose 

 place was with us. It is a case of a 

 lost lonicl. 



Thrown Off the Track by Jupiter 



In the summer of 1770 a monstrously 

 large comet appeared. Its apparent 

 area was tweniy-fi\c limes that of the 

 moon. Astronomers made observations 

 from time to time during its sojourn of 

 several months. Difficulty was experi- 

 enced in determining whether the comet 

 was traveling in an open or a closed 

 curve. If the orbit 



very probably identical with the comet 

 seen in the earlier years. This body 

 became celebrated from the fact that 

 calculations showed that ujwjn its next 

 return in 1832 it would pass the orbit of 

 the earth at a distance of only twent\- 

 thousand miles. A slight derangement 

 of its orbit and it might approach more 

 doseh' still. If the earth should be in 

 the immediate vicinity at the time, then 

 our planet's own attractive power would 

 probably result in the comet coming 

 into collision with us. The figures 

 showed, h(jwe\er, that the comet would 

 reach the region of 



was an open cur\e, 

 then there woukl 

 be no reappearance 

 as long as this char- 

 acter of orbit was 

 followed. Finally, 

 however, the as- 

 tronomer Lexell 

 succeeded in estali- 

 lishing that the 

 comet was moving 

 in an ellipse and 

 that it should re- 

 turn in five and 

 one half years. It is not known that 

 this comet ever did really return. 



There was so much ascertained about 

 its moxements during its short stay" that 

 astronomers were reluctant to give up 

 this comet t)f Lexell's. Inxestigation 

 showed that, before its appearance in 

 1770, the comet had proljably been 

 forced into a somewhat different path 

 from that which it had been following. 

 In 1767, it had come within range of 

 Jupiter's influence which may very well 

 lia\e modified its orbit into the curve 

 noted by observation during the \isit 

 three years later. It was thought In- 

 Burikiiardt, a I-Vench astronomer, that 

 probably another passage near Jupiter 

 liad resulted not in creating a smaller 

 rrbit but in enlarging the ellipse. The 

 new path that was calculated required 

 the comet to reappear once in a period 

 ( f sixteen years. However, the comet 

 has never again been recognized. Lexell's 

 Comet is for the present a lost comet. 



In each of the years 1772 and 1805 a 

 comet was observed. Again, in 1826 

 Biela, an Austrian officer, discovered a 



HYPERBOLA ^ COMET DOES 



PftRAeOLA 



. (NOT RETURN 



ellipse: comet 

 RETURNS PERIODICALLY 



Sir Isaac Newton proved that a heav- 

 enly body controlled by our sun moves 

 in an ellipse, a parabola or an hyperbola 



Forty years later, 

 according to the 



close approach a 

 month earlier than 

 the earth. It seems, 

 though, that it was 

 a close shave. 

 People at the time 

 appear to ha\e 

 been stirred up over 

 the possibilities. 

 The comet came 

 into view again at 

 theperiod expected, 

 but no untoward 

 results occurred, 

 in 1872, the comet, 

 astronomer, Klin- 

 kerfucs, actually came into contact with 

 the earth. He telegraphed to another 

 astronomer his statement as to contact 

 and suggested a search in a certain 

 definitely named locality of the heavens. 

 Here, the second astronomer actually 

 saw some comet, but was unable because 

 of unfavorable conditions to carry hi:, 

 observations very far. It is uncertain 

 whether he saw Biela's Comet. If he 

 did, then he was the last obserx-ef cf 

 that remarkable hea\enly body. 



Enough happened, howe\'er, in the 

 forty years, 1832- 1872, to lead us to 

 think that very probably Biela's Comet 

 has disappeared forever as a comet and 

 that it is now a stream of comparati\ely 

 tiny bodies. This statement requires 

 explanation. In the first place, Biela's 

 Comet broke into two separate parts, 

 each becoming a complete comet. The 

 two bodies traveled more or less closely 

 together for a number of years. That 

 there were two comets instead of one 

 was first observed in 1846. While under 



comet which was soon ascertained to be observation by astronomers at this time, 



