Sept. 11, 1885.] 



♦ KNO\A/LEDGE ♦ 



215 



-^L V^ AN ILLUSTRATED ^^^J^ 



^>^ MAGAZINE OF SCIENCE ^ 



ePUINiyWORDED-EXACTLYDESCRIBED 



LONDON: FRIDAY, hlJI'IJJMJ.HJ; 11, lb; 



Contents of No. 202. 



A NEW STAR IN A STAR CLOUD. 



By Richard A. Proctor. 



THE discovery of a new star in the midst of the Great 

 Nebula in Andromeda must be regarded as one of 

 the most remarkable astronomical events of the age. It 

 is true that great changes have ere now been recognised 

 in stars lying within nebulous clouds. The star Eta 

 Argus for example, which lies in the midst of that 

 wonderful mass of luminoas gas called the Keyhole 

 Nebula in Argo, has changed so marvellously in lustre 

 since it was first catalogued as a fourth magnitude star 

 as to present a case corresponding so far as the star is 

 concerned with the sudden appearance of the new star in 

 the Andromeda Nebula. For Eta Argils sank from the 

 fourth magnitude to the sixth, then rose rapidly to the 

 second, and after remaining for some time at that magni- 

 tude increased almost suddenly in splendour until it 

 rivalled Canopus and was surpassed only by Sirius. 

 Undoubtedly to an observer set at such a distance that 

 Eta Argus when thus resplendent would have appeared 

 only as an eighth magnitude star, like the new star ia 

 Andromeda, Eta with its present light of a sixth magni- 

 tude star would be altogether invisible. So that viewed 

 from that imagined distance Eta Argus when it rose to 

 its greatest splendour would have appeared as a new 

 star, and as it faded out of view would come to be re- 

 garded as having been but a temporary star. 



Again the star which appeared in Cygnus in 1876 

 must be regarded as a star which had suddenly shone 

 out in a nebula, although no nebula had been known where 

 the star appeared. For when that star had disappeared 

 there still remained a blue planetary nebula in the place 

 which the star had occupied. And this nebula was and 

 is so faint that one can readily uudei-stand it having 

 escaped notice before. No one, I imagine, can doubt 

 that the nebula which is seen there now existed there 

 before the star appeared. 



The stars in the great Fish-mouth Nebula in Orion 

 exhibit iilso a certain degree of variability, which, 

 though not so striking as the appearance of "new stars," 

 is in reality a phenomenon of the same sort. For every 



so-called " ne^v star ' may be regarded as a variable of 

 an unusually irregular kind. 



But m all those cases the star which shone with 

 viriible lustre, or -which for a time appeared as a new 

 star, has been ux the midst of a gaseous nebula. The 

 great nebula in Andromeda has always be( n regarded as 

 a stellar nebula, although it has never been resolved into 

 stars Under spectroscopic examination it presents the 

 rainbow-tinted streak crossed by absorption lines which 

 indicates the existence of glowing solid or liquid or 

 highly - compressed vaporous matter shining through 

 absorptive vapours. I remember Dr. Huggins describing 

 the spectrum of this object to me, during a visit which 

 I paid to his observatory in 1866 ; and he then said that 

 the spectrum difPered only from that of a star, in being 

 rather sharply cut off at the red end, as if through the 

 action of vaporous envelopes more powerfully absorptive 

 of red light than the vapours around our sun and most 

 other stars. 



In a rather carelessly-written paragraph in the Times- 

 of Saturday last, manifestly by a person not well ac- 

 quainted with astronomical facts, the new star is spoken 

 of as if it gave support to Laplace's nebular theory. In 

 reality the appearance of the star is most strongly 

 opposed to that theory, for the simple reason that all the 

 processes involved in Laplace's nebular theory are slowly- 

 acting ones, while the appearance of a new star where a 

 star had not before been visible, signifies events of a 

 catastroi^hic nature. Moreover the theory of Laplace, in 

 the form in which it was present ed, cannot be maintained 

 by any one acquainted with the laws of physics. A vast 

 disc of gaseous matter, extending beyond the orbit of 

 Neptune, but containing no more matter than there is in 

 the whole solar system would not have the .slightest co- 

 hesion among its various parts. To conceive of it as 

 rotating like a single mass is to imagine the impossible. 

 One may say indeed of Laplace's nebular hyiiothe>is — 

 which was very properly regarded by liiiii.st-lf us but a 

 guess — that astronomers suppose it jiliy-irii;, [— -ilile 

 and physicists suppose it astronomically | < - i : ! ■• lu) 

 one who combines a knowledge of bi'tii ■ ■ .nd 



physics can accept it in the wide generality if n- . i i_iiia} 

 form. 



WTiat the new star really does throw light upon, and 

 light of a very clear and unmistakable sort, is not the 

 theory of the solar system, but the theory of the stellar 

 system — that grand gathering of stars, star-clusters, star- 

 clouds, and star-streams, which we call the galaxy. 



If there was one member of the family of nebula^ 

 which was still supposed to remain possibly an external 

 galaxy, after all the evidence which had been collected 

 to show that nebulas belong to our own galas 



great nebula in Androu 

 beautiful queen of tlir iirlni'ir as ilir i M :,-: 

 enthusiastically callril ii. Mr. II. li- ;■ >i ■ ■ . 

 as far back as 18;Vj , r Is,;,., j,, hi '^^ . ; 

 Nebular Hypothesis in thu irc6.'.,./,...v , /; 

 theory according to which numbers of tlic i 

 nebulffi are external star systems is absolutely u 

 He pointed to this fatal objection, that Sir 

 H.Tsrlirrs „w.st in.NNrrful l,.l,^,-o]v. fii'. ,1 tn v.. 



ndently 



that appaiMit si 

 I its own diamoti 



