Mu Herculis
Primary of Olympias.
The main star, Mu Herculis A is fairly similar to the Sun although more highly evolved with a stellar classification of G5 IV. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.[4] Its mass is about 1.1 times that of the Sun, and it is beginning to expand to become a giant.
The secondary component consists of a pair of stars that orbit about each other with a period of 43.2 years. Mu Herculis A and the binary pair B-C are separated by 286 AUs. The stars B-C are separated from each other by 11.4 AUs. Their orbit is quite elliptic (e=0.18) and both stars swing each other between 9.4 and 13.5 AUs.
Star A is itself suspected to be a close binary with a low mass stellar or a large substellar companion, probably at 17.2 AUs in an elliptic orbit. Nevertheless the existence of such an object has still not been confirmed.