Tables 646-648. 

 ASTRONOMICAL DATA. 



417 



TABLE 546. — Numbers and Equivalent Light of the Stars. 



The total of starlight is a sensible but very small amount. Thi.s table, taken from a paper by Chapman, shows 

 that up to the zot.h magnitude the total light emitted is equivalent to 687 ist-magnitude stars, equal to about the 

 hundredth pirt of full moonlight. If all the remaining stars are included, following the formula, the equivalent addi- 

 tion would be only three more ist-magnitude stars. The summation leaves off at a point where each additional magni- 

 tude is adding more stars than the last. But, according to the formula, between the 23d and 24th magnitudes there 

 is a turning point, after which each new magnitude adds less than before. The actual counts have been carried so 

 near this turning point that there is no reasonable doubt of its existence. Given its existence, the number of stars is 

 probably finite, a conclusion open to very little doubt. All the indications of the earlier terms must be misleading if 

 the margin between i and 2 thousand millions is not enough to cover the whole. (Census of the Sky, Sampson, Observ- 

 atory, 1915.) 



Magnitude, 



-1.6. ... 



-0.9 



0.0. . . . 

 o.o-i.o. . . . 

 1.0-2.0. . . . 



2.0-3.0 



3.0-4.0.... 

 4.0-s.o.... 



S. 0-6.0 



6.0-7.0 . . . . 



7 . 0-8 .0 



8.0-9.0. . . . 



Number. 



Sirius 



a Carinse 



a Centauri 



8 



27 



73 



189 



650 



2,200 



6,600 



22,550 



65,000 



Equivalent 

 number 

 of ist- 

 magnitude 

 stars. 



14 

 17 

 18 

 19 

 26 

 35 

 42 

 S6 

 65 



Totals to 

 magnitude 



33 



50 

 68 

 87 

 113 

 148 

 190 

 246 

 311 



Magnitude, 



9.0-10.0 



lO.O-II.O 



II. 0-12.0 



12. 0-13.0 



13. 0-14.0 



14.0-15.0 



15.0-16.0 



16. 0-17.0 



17. 0-18.0 



18. 0-19.0 



19.0-20.0 



All stars fainter than 20.0 



Number. 



174,000 



426,000 



961 ,000 



2,020,000 



3,960,000 



7,820,000 



14,040,000 



25,400,000 



38,400,000 



54,600,000 



76,000,000 



Equivalent 

 number 

 of ist- 

 magnitude 

 stars. 



69 



68 



60 



SI 



40 



31 



22 



16 



10 



6 



3 



3 



Totals to 

 magnitude, 



380 

 448 

 508 

 559 

 599 

 630 

 652 

 668 

 678 

 684 

 687 

 6go 



TABLE 547. — Albedos. 



The albedo, according to Bond, is defined as follows: "Let a sphere 5 be exposed to parallel light. Then its Albedo 

 is the ratio of the whole amount reflected from 5 to the whole amount of light incident on it." In the following table, 

 m = the stellar magnitude at mean opposition; g = magnitude it would have at full phase and unit distance from 

 earth and sun; <r = assumed mean semi-diameter at unit distance; p = ratio of observed brightness at full phase to 

 that of a flat disk of same size and same position, illuminated and viewed normally and reflecting all the incident light 

 according to Lambert's law; g depends on law of variation of light with phase; albedo = pq. Russell, Astrophysical 

 Journal, 43, p. 173, 1916. 



Albedo of the earth: A reduction of Very's observations by Russell gives 0.45 in close agreement with the recent 

 value of Aldrich of 0.43 fsee Aldrich, Smithsonian Misc. Collections, 69, 1919). 



Smithsonian Tables. 



For more extensive table, see Smithsonian Meteorological Tables. 



