TABLE 865.— NUMBERS AND EQUIVALENT LIGHT OF THE STARS* 



757 



This table derived from vanRhijn's counts (Table 7 of reference 281) shows that to photo- 

 graphic magnitude 18.0 the total of starlight received is equivalent to 652 stars of photographic 

 magnitude 1.0. If all the remaining stars are included, the equivalent addition is only 48 lst-mag- 

 nitude stars, giving a total of 700, equal to about a hundredth part of full moonlight. The corre- 

 sponding total of stars of visual magnitude 1.0 would be about 1,320, which agrees reasonably 

 well with the equivalent total of 1,440 stars (zenith) found by van Rhijn from direct measure- 

 ment of the visual brightness of the sky; or 1,674 stars outside the earth's atmosphere. Density 

 of stellar radiation = 0.8 X 10" 13 erg/cm 3 . Cosmic radiation density = 1.3 X 10" 13 erg/cm 3 (near 

 the earth). 



The number of stars in each magnitude interval is still increasing rapidly at m = 18, but the 

 run in the numbers in the second column of the table indicates that somewhere about m = 30 

 the numbers begin to decrease and eventually to approach zero as the limit of the stellar system 

 is reached. The extrapolated total number of stars in the system given by different investiga- 

 tions ranges from 30 to 100 billion. The great inherent uncertainty of this total is further in- 

 creased by the unknown influence of interstellar absorption. 



Practically all the stars visible to the naked eye lie within 1,000 parsecs of the sun, and most 

 of them are more than 100 parsecs distant. In the vicinity of the sun, the majority of the stars 

 lie within 200 or 300 parsecs of the galactic plane ; but along this plane the star-filled region 

 extends far beyond 1,000 parsecs in all directions, and may reach 30,000 parsecs in the great 

 southern star clouds CShapley). 



* Prepared by F. H. Seares, Mount Wilson Observatory. 



TABLE 866.— BRIGHT OR WELL-OBSERVED NOVAE* 



* Prepared by D. P». McLaughlin. University of Michigan. a. Absorption velocities increased with time: 



N Aql, to —1700 km/sec; OP I.ac, to —2500 km/sec. b. Absolute magnitude assumed; distance based on 



assumed absolute magnitude. c, Recurrent novae: T Crli; RS Oph, 1898; T Pyx, 1890, 1902, 1920. 



T OH : distance based on spectroscopic parallax of class M companion. d, Nova Gem and CP Pup; 



distances based on strength of interstellar calcium lines. e, RT Serpentis reached maximum in 1919. 



f, Nova Tauri 1054; a super nova; now the Crab Nebula Note on velocity of RS Ophiuchi: there was no 

 system of absorption lines at the short-wavelength edge of the emissions as in other novae. 



SMITHSONIAN PHYSICAL TABLES 



