THE OUTSIDE OF A STAR 
331 
/ 
wave-length. This seems a very reasonable explanation. We might expect 
some such modification of Kramers’ formula for emission when account 
is taken of the finite size of the ions responsible for the radiation of optical 
frequencies. It may be remarked that between wave-lengths 3000 and 
12,000 the emission is due mainly to capture of electrons in excited orbits; 
electron switches without capture would give longer waves, and capture 
in normal orbits would give shorter waves. The reduction of the emission 
cannot be attributed to the guillotine effect of occupied orbits; it is, 
perhaps, due to the fact that for these close approaches the atom with 
one or two electrons missing cannot be treated as equivalent to a point 
charge. 
Table 44. 
Analysis of the Observed Solar Energy Curve. 
A 
k v (obs.) 
k v (calc.) 
1 /> 
3230 
1-97 
4-89 
2-48 
3860 
1-09 
2-35 
2-16 
4330 
•81 
1-65 
2-03 
4560 
•69 
1-44 
2-08 
4810 
•68 
1-27 
1-87 
5010 
•70 
1-16 
1-66 
5340 
•70 
1-03 
1-48 
6040 
•71 
•87 
1-22 
6700 
•76 
•78 
1-03 
6990 
•77 
•76 
•98 
8660 
116 
•70 
•61 
10310 
1-36 
•72 
•53 
12250 
1-02 
•79 
•77 
Against this interpretation of the observed energy curve there is the 
objection raised by Milne that his values of k v in Table 44 are not supported 
by the centre-limb contrast which agrees much better with a nearly con 
stant k v . Milne concludes “with considerable assurance that the departure 
of the sun’s energy spectrum from that of a black body is not due to a 
varying general absorption in the layers contributing to the radiation.” 
It depends on how closely we can trust the observed values of the centre- 
limb contrast. If Milne is right, we must turn to cause (c). 
(c) Deviation from equilibrium conditions. 
There is the possibility that owing to its exposure to non-equilibrium 
radiation the material may not have the normal absorbing and emitting 
power for its temperature and density so that jJTc v is not given by (228-5). 
The radiation is richer in the high-frequency constituents which are capable 
of ionising normal atoms; the ionisation may therefore be greater than the 
equilibrium value. For the most part emission by capture can only be