EVOLUTION OF THE STELLAR SYSTEMS. 227 
which in special units is p?. Now the total moment of momentum of the system is con- 
stant, and is given by 
JEL == Joys JPe se flu (UE TEL) seepenpepaecoee coon (1) 
The kinetic energy of orbital motion is 
7 (, GP LP | oO aa crops ne 
The kinetic energ ey of rotation is 
i 9 
The potential energy of the system is 
‘ MM’ 
p 
By adding all these energies together we get the total energy of the system : 
E rime oe inl ae 
where £ is twice the whole energy. 
, 
In the system of special units, J, wJZM/, are equal to unity. If we put = = we 
shall get 
H=y+k? 
Let ¢ = ©, and then O* = 63, x = 9}, and we have finally 
If we suppose the two stars to turn on their axes in the same time in which they 
revolve in their orbits, so that they show always one face to each other, the motion of the 
system will be as if the masses were rigidly connected. ‘This condition is given by 
OF =) 
l| 
& 
o 
Lard 
Oke th == 2 = ee OL 
ys Moa a aeialitns is. Beste sb hed mea ehk ees, (3) 
