TABLES 641-542. 

 ASTRONOMICAL DATA. 



415 



TABLE 541. The First-magnitude Stars. 



* Visual binary. t Spectroscopic binary. { Pair with common proper motion. 



Wide pair probably optical. 



Mass relative to sun of (7) is 3.1; of (8), 1.5; of (16), 2.0. For description of types, see Table 534 or Annals of 

 Harvard College Observatory, 28, p. 146, or more concisely 56, p. 66, and 91, p. 5. The light ratio between successive 

 stellar magnitudes is "V^ioo or the number whose logarithm is 0.4000, viz., 2.512. The absolute magnitude of a star 

 is its magnitude reduced to a distance corresponding to o.i" parallax. 



TABLE 542. Wolf's Observed Sun-spot Numbers. Annual Means. 



Sun-spot number = k(io X number of groups and single spots observed + total number of spots in groups and 

 single spots), k depends on condition of observation and telescope, equaling unity for Wolf with 3-in. telescope and 

 power of 64. Wolf's numbers are closely proportional to spotted area on sun. 100 corresponds to about 1/500 of 

 visible disk covered (umbras and penumbras). Periodicity: mean, 11.13, extremes, 7.3 and 17.1 years. Monthly 

 Weather Review, 30, p. 171, 1002; monthly means, revised, 1749-1901; see A. Wolfer in Astronomische Mitteilungen 

 and Zeitschrift fur Meteorologie, daily and monthly values. 



NOTE: The sun's apparent magnitude is 26.5, sending the earth 00,000,000,000 times as much light as the star 

 Aldebaran. Its absolute magnitude is +4-8. 



Ratio of total radiation of sun to that of moon about 100,000 to i 1 T , np i cv 

 " " light " " " ' 400,000 to i / 



SMITHSONIAN TABLES. 



