144, 145] 
Stable and Unstable Configurations 
159 
Comparison with Observation. 
145. The graph of E shewn in fig. 11 is drawn for a star of given 
constant mass. On drawing a number of such graphs in a diagram in 
which log E and log R are taken as coordinates, we obtain a complete map 
of the configurations possible for stars of all masses. We have already 
noticed that, since E— 4nrR*<rT e *, 
log E= 2 log R + 4 log T e + a cons (145T). 
Fig. 12. Division of the Temperature-Luminosity diagram into Stable (thick) 
and Unstable (thin) configurations. 
Instead of taking log# and log# as coordinates, it is more convenient 
to take log E and log T e , the transformation between the two sets of co 
ordinates being made by equation (1451). In this way we obtain a diagram 
of the kind already introduced in § 56 (fig. 5). On changing coordinates in 
this way and drawing graphs of log E for a number of stars of different 
masses we obtain a diagram of the general character shewn in fig. 12.