Ratio of Total Angular Momentum to Star Angular Momentum in Binary Star System
A binary star consists of two stars A (mass ) and B (mass ), where is the mass of the sun. They are separated by distance and are rotating about their centre of mass, which is stationary. The ratio of the total angular momentum of the binary star to the angular momentum of star B about the centre of mass is
Step-by-Step Solution
Let the masses of star A and star B be denoted by and , respectively:
The two stars orbit their stationary centre of mass (CM) with a common angular velocity .
Let the distance of star A and star B from the centre of mass be and , respectively. By the definition of the centre of mass:
The angular momentum of star A about the centre of mass is:
The angular momentum of star B about the centre of mass is:
The total angular momentum of the binary star system is:
The ratio of the total angular momentum of the system to the angular momentum of star B is:
Substituting the expressions for and :
Substituting the given values of the masses:
Therefore, the required ratio is: