Airr. I.— The Theory of Temporary Stars/\"\:'i^'-'^'y-.^(. s 



By E. R J. LOVE, M.A., F.R.A.S. 1^1^ 



'iLulLlBHAHY 



[Eead 13th March, 1902.] 



1. — Introductory. 



The two rival theories concerning the origin of temporary 

 stars — or Novae — respectively ascribe their phenomena to col- 

 lision and to eruption. Till within the last three years the 

 collision theory was preferred by astrophysicists, a lai'ge majority 

 of them deeming the spectroscopic evidence conclusive in its 

 favour ; but the publication by Wilsing^ of his famous memoirs 

 "On the interpretation of the typical spectrum of new stars," and 

 " On the effect of pressure upon the wavelength of the lines in 

 the hydrogen spectrum," put a new face on the matter by 

 showing that the emission from the star of gases under pressure 

 was competent to account for the spectroscopic phenomena. Of 

 special importance was his experimental proof of the fact that 

 the dark lines must, on this hypothesis, always be more refran- 

 giVile than the corresponding bright ones, since this fact was one 

 of the principal difficulties in the way of the collision theory, or 

 for that matter of any reasonable mechanical explanation of the 

 typical spectrum, a difficulty emphasized of recent years by Mrs. 

 Fleming's discovery of a considerable number of novae on the 

 Draper memorial photographs." 



Such was the state of the question when Nova Persei made its 

 appearance on 21st February, 1901. Owing partly to its great 

 brilliancy — even in the latest stages discussed here it was still 

 very little below the 6th magnitude — partly to the improvement 

 in photographic processes, the transformations of this star have 

 been studied with a degree of closeness, accuracy and continuity 

 never approached in the case of other novae. Naturally each 

 investigator attempts to explain his results in terms of the 



1 Ap. J., X., pp. 113, 269. 



2 See Pickering (Ap. J., xiii., p. 173) for a list of these. 



