SYSTEM DYNAMICS

The average distance between the A and B components from the system is only 0.062 AU (10.4 million km). They orbit around each other in an almost perfect circular orbit for a period of only 2.867315 earth days, which is slowly lengthening. The third star circles in an elliptic orbit (e=0.225) at a distance about 2.69 AU from the A and B stars for a period of 1.86 years (681 days).

The A and B stars are probably the same age. However, because more massive stars use up their hydrogen faster, Beta Persei B must have been more massive than Beta Persei A when the system originated. Now Beta Persei B has filled Roche Lobe, the region where gases are held by the gravitation of the star and is far less dense than its A companion. Due to the strong gravitational interaction between the two stars, an accretion stream flows from the Beta Persei B to Beta Persei A with a rate of exchange of matter ranging from 0.4 to 2.0 x 10-11 solar masses/year. The fact that the originally more massive star is now less massive is called the “Algol Paradox”.

In the future, it is possible that all the gaseous matter from the B component be transferred to the A component. If this happens, Beta Persei B will expose its cooling core and Beta Persei A will overfill its Roche Lobe. This will result in the reverse process: matter from the A star will start to float to the B star.