494 



On Nova Aurigce. 



[May 19, 



concede to them a mass very great as compared with that of the Sum 

 Such a near approach of two bodies of great size is very greatly less 

 improbable than would be their actual collision. The phenomena 

 of the new star, indeed, scarcely permit us to suppose even a 

 partial collision ; though if the bodies were very diffuse, or the 

 approach close enough, there may have been possibly some mutual 

 interpenetrati on and mingling of the rarer gases near their boundaries. 



A more reasonable explanation of the phenomena, however, may be 

 found in a view put forward many years ago by Klinkerfues, and 

 recently developed by Wilsing, that under such circumstances of near 

 approach enormous disturbances of a tidal nature would be set up, 

 amounting it may well be to partial deformation in the case of gaseous 

 bodies, and producing sufficiently great changes of pressure in the 

 interior of the bodies to give rise to enormous eruptions of the hotter 

 matter from within, immensely greater, but similar in kind, to solar 

 eruptions ; and accompanied probably by large electrical disturb- 

 ances. 



In such a state of things we should have conditions so favourable 

 for the production of reversals undergoing continual change, similar 

 to those exhibited by the bright and dark lines of the Nova, that we 

 could not suppose them to be absent; while the integration of the 

 light from all parts of the disturbed surfaces of the bodies would give 

 breadth to the lines, and might account for the varying inequalities 

 of brightness at the two sides of the lines.. 



The source of the light of the continuous spectrum, upon which 

 were seen the dark lines of absorption shifted towards the blue, must 

 have remained behind the cooler absorbing gas ; indeed, must have 

 formed with it the body which was approaching us, unless we assume 

 that both bodies were moving exactly in the line of sight, or that the 

 absorbing gases were of enormous extent. 



The circumstance that the receding body emitted bright lines, 

 while the one approaching us gave a continuous spectrum with 

 broad absorption lines similar to a white star, may, perhaps, be 

 accounted for by the two bodies being in different evolutionary stages, 

 and consequently differing in diffuseness and in temperature. Indeed 

 in the variable star /3 Lyrse, we have probably a binary system, 

 of which one component gives bright lines, and the other dark lines 

 of absorption. We must, however, assume a similar chemical nature 

 for both bodies, and that they existed under conditions sufficiently 

 similar for equivalent dark and bright lines to appear in their re- 

 spective spectra. 



We have no knowledge of the distance of the Nova, but the 

 assumption is not an improbable one that its distance was of the 

 same order of greatness as that of the Nova of 1876, for which Sir 

 Robert Ball failed to detect any parallax. In this case, the light- 



