SOLUTION OF THE EQUATIONS 
141 
whole spectrum the radiation may become differently distributed in wave 
length. Strong absorption in the yellow would divert the radiation into 
regions of less luminous efficiency. We can only hope that since the whole 
correction Am is not unduly large the faults of Tables 15 and 16 will not 
be serious. 
The temperature scale to correspond with spectral type is not as yet 
very certain. It is inferred partly from the measurements of T e ' above 
mentioned; but these somet i mes differ rather widely from one another. 
It is also based partly on Saha’s theory of stellar spectra (§ 240), which 
determines the temperature of a layer rather vaguely defined. We have 
also the fixed datum that T 6 for the sun is 5740°. The following table 
given by Miss Payne* embodies the most recent evidence. 
Table 16 a. 
Temperature Scale. 
Type 
T e 
Type 
T e 
Ma 
3000° 
A 5 
8,400° 
K 5 
3000 
A 3 
9,000 
K 2 
3500 
A 0 
10,000 
K 0 
4000 
B 8 
13,500 
G 5 
5000 
B 5 
15,000 
GO 
5600 
B 3 
17,000 
F 5 
7000 
B 0 
20,000 
F 0 
7500 
O 
25,000-35,000 
This presumably refers to the stars of the “main series,” the giants of 
types G-M being 400-800° lower for the same spectral type. On the 
whole, the temperature scale used in the calculations in this book accords 
very well with the above tablef. 
Energy of a Star. 
103. The negative gravitational energy of a star, found by setting 
n = 3 in (60-4), is 
.2 GM 2 
.(103-1). 
3 GM ‘ 2 
~ 2 R 
The quantity of radiant energy enclosed in the star is 
H = J 3p R 47rr 2 dr, 
* Stellar Atmospheres (Harvard Observatory Monographs, 1925), p. 33. 
f The calculations were made at various times; and, as no systematic temperature 
scale was adopted at the beginning, occasional deviations from uniformity may be 
noticed.