1892.] 



On Nova Aurigat. 



493 



becoming much the brightest when the star was faint." The calcium 

 lines K and H showed signs of variation during the whole time of the 

 star's visibility, and I may remark that the order of the other lines 

 agrees with the relative sensitiveness of the gelatine plate for these 

 parts of the spectrum. Professor Pickering's photographic results 

 appear to us to be in accordance with those we arrived at by. eye, in 

 not showing any material alteration in the nature 'pf the star's light, 

 notwithstanding its very large fall of intensity. 



General Conclusions. 



Among the principal conditions which must be met by any theory 

 put forward to account for the remarkable phenomena of the new 

 star stands the persistence without any great alteration — though 

 probably with small changes — of the large relative velocity of about 

 .550 miles a second in the line of sight between the hydrogen which 

 emitted the bright lines and the cooler hydrogen producing the dark 

 lines of absorption. 



If we assume .two gaseous bodies, or bodies with gaseous atmo- 

 spheres, moving away from each other after a near approach, in 

 parabolic or hyperbolic orbits, with our Sun nearly in the axis of tho 

 orbits, the components of the motions of the two bodies in the line of 

 sight, after they had swung round, might well be as rapid as those 

 observed in the new star, and might continue for as long a time 

 without any great change of relative velocity. Unfortunately infor- 

 mation as to the motions of the bodies at the critical time is wanting, 

 for the event through which the star became suddenly bright had 

 been over for some forty days before any observations were made with 

 the spectroscope. 



Analogy from the variable stars of long period would suggest the 

 view that the near approach of the two bodies may have been of the 

 nature of a periodical disturbance, arising at long intervals in a 

 complex system of bodies. Chandler has recently shown in the case 

 of Algol that the minor irregularities in the variation of its light are 

 probably caused by the presence of one or more bodies in the system, 

 besides the bright star and the dusky one which partially eclipses it. 

 To a similar cause are probably due the minor irregularities which 

 form so prominent a feature in the waxing and waning of the variable 

 stars as a class. We know, too, that the stellar orbits are usually very 

 eccentric. In the case of 7 Virginis the eccentricity is as great as 

 0*9, and Auwers has recently found the very considerable eccentricity 

 of 0*63 for Sirius. 



The great relative velocity of the component stars of the Nova, 

 however, seems to point rather to the casual near approach of bodies 

 possessing previously considerable motion ; unless we are willing to 



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