Page:Popular Science Monthly Volume 89.djvu/519

 Popular Science Monthly

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��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,

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