F. W. Very — Nebulosity around Nova Persei. 55 



by phosphorescence of dark matter, previously existing in the 

 surrounding spape, and made himinous by colliding ions, (hj 

 The moving ions are themselves luminous. 



On either hypothesis, the luminous shape is a species of 

 magnetic phantom, wliere only those portions of the general 

 magnetic figure are visible which happen to be infilled with 

 matter capable of becoming luminous under the given condi- 

 tions. 



Two distinct processes can be inferred from the succession 

 of phenomena exhibited by Nova Persei. First, there were 

 violent eruptions of hydrogen, helium, etc., with velocities up 

 to 2000 km. per sec, and the formation of concentric shells of 

 glowing gas, reaching distances comparable with those of the 

 planetary orbits ; and, second, there was a profound electrical 

 disturbance accompanying this turmoil of the elements, pro- 

 ducing a complex and excessively attenuated appendage, thrown 

 off with velocities possibly 150 times as great as those of the 

 gaseous eruptions, and reaching far out into stellar space. It 

 is this second appendage with which we are now concerned. 

 "We see this object on the photographic plate in projection, 

 and must infer its shape from such details as are visible. A 

 strong condensation on the S.S.TT. side reminds one of the 

 jets from a cometary nucleus on the side towards the sun, and 

 to this extent favors some such theorj^ as that of Professor T. 

 C. Chamberlin, who has suggested" the tidal disruption of a 

 star upon the near approach of a massive dark body. The con- 

 densation in question, called m by Ritchey and D by Perrine, 

 bears an even stronger resemblance to the polar coronal fila- 

 ments of the eclipsed sun, which curve away on either side of 

 the coronal axis, but with the difference that it appears at 

 only one pole. 



Let us assume that there has been an ionic discharge follow- 

 ing the lines of magnetic force around a highly magnetized 

 sphere. The general form of an envelope, consisting of a series 

 of such discharges, will be that of an oblate spheroid with polar 

 depressions (i. e., a species of lemniscoid) ; and if the nebula 

 about Nova Persei is to be thus interpreted, its southern pole 

 is directed towards us, the axis forming an angle of 40° with 

 the line of sight. 



Consider a magnetic line of force lying in a plane including 

 the line of sight from the star to the earth (whose direction is 

 indicated by the arrow from the nova o in fig. 1). Particles 

 emitted from o and passing to m will be moving almost end-on, 

 and the line of sight will encounter man}^ such particles. The 

 prominence rii is therefore brilliant and changes its position 

 slowly. Particles moving along the curve to^ reach a part of 



*AstropliYsieal Journal, xiv, 17, 1901. 



