58 



KNUT LUNDMARK, GLOBULAR CLUSTERS AND SPIRAL NEBULJE. 



P Cygni occupies a peculiar position among the novse, as its light-variation is 

 much slower than is the case with the typical novse. Nevertheless, as shown by 

 Merrill (P. A. S. P. 24: isi), it is really a nova. This is the reason why we have 

 used its parallax for determining 7c nov but omitted it at the determination of the 

 difference between the maximum and minimum intensity of the novse, although by 

 employing it we would not have considerably altered the result. 



We consider the following galactic novse for which measurements exist of their 

 greatest and smallest apparent magnitude: 



7) 



'max. 



Wmin. 



^min. '"max 



T Coronse 



m 



2 ; o 



m 



y : 5 



m 



7,5 



Q Cygni 



3 



15 



12 



T Aurigse 



4,3 



14 



9,7 



Nova Sag. 1 



4.7 



15 



10 3 



Nova Persei 



O.o 



13 



13 



Nova Gem. 1 



5,i 



16.3 



11/2 



Nova Lacertse 



5 : o 



12 ; 5 



7.5 



Nova Gem. 2 



3,7 



12 



8 ; 3 



Nova Aqv. 3 - 



-1.4 



11,5 



12.o 





2™ 9 



13 m 2 



10 m .3 



Consequently we obtain the result that w max . on an average is 2 m ,9, while w m j n . 

 on an average is 13 m .2. If we make the plausible supposition, that the mean mag- 

 nitude before their appearance is = m m ] n ., and if ilf m i n . is supposed as equivalent to 

 the absolute magnitude of the Wolf-Rayet stars, taken as a mean from the following 

 determinations : 



J^Woif-Rayet = + 1,2 van Maanen, from three directly measured parallaxes 



— l,i Kapteyn, from stream motion 



— 2,8 Hertzsprung, from parallactic motion 

 ~^Ö7 



we obtain: 



5tnov. = 0", 00015 



from which is obtained the following new determination of the mean parallax of 

 spiral nebulse: 



^sp. = 0",0000005. 



On the presumption, that the novse employed in this determination have a 

 mean parallax as great as the mean parallax for the Ostars examined by Gyllen- 

 berg 70 , i. e. 7r nov . = 0",oo27 ± 0,00018, we obtain: 



