8 
The N.Z. Journal of Science and Technology. 
[Mar. 
At this rate each gramme would lose a calorie in 2T53 X 10 7 second— 
that is, in 249 days. This loss amounts to 1-46 calories per year. 
If the third body at the stage when its volume is equal to that of the Sun 
has a temperature of 6,000,000° absolute, its total radiation should be a 
billion (10 12 ) times as great as the solar. At this rate, supposing its mass 
equal to that of the Sun, an average of some 46,000 calories would be radiated 
from each gramme per second. It is clear that even the vast store of energy 
a nova possesses could not stand such prodigal expenditure for more than 
a very brief time. In fact, if this output could continue the energy would 
be dissipated in less than half an hour. The mass being probably less than 
that of the Sun accentuates the case. For instance, if its mass were only 
9 
8 
7 
6 
S' 
4 
3 
Z 
/ 
o 
Fig. 2. 
one-tenth of that of the Sun the radiation per gramme, for the same tempera¬ 
ture, would be ten times as great. This does not imply that radiation of 
this explosive type actually persists for any appreciable time. If Stefan’s 
law holds at such extremely high temperatures, it appears as if radiation 
must prevent the maintenance, and possibly even the establishment, in the 
outer layers of a nova, of temperature of many millions of degrees, such 
as must be found within it. Further, it is only during the first brief stage, 
before atmospheric envelopes have developed, that the nova approximates 
to a full radiator. 
3. We have seen that the radiation emitted by a nova during the first 
stage is mostly invisible ; we must now consider what may be expected 
in the visible part of the spectrum at the same time. To do so we must 
