Here's why:
* Kepler's Laws of Planetary Motion: These laws apply to binary star systems as well. One of the key laws states that the period of the orbit is proportional to the cube of the semi-major axis (the average distance between the stars).
* Center of Mass: Both stars orbit around their common center of mass. The more massive star is closer to the center of mass, and therefore has a smaller orbital radius.
* Velocity and Radius: For a fixed orbital period, a smaller orbital radius means a higher orbital velocity.
In summary: The less massive star in a binary system has a larger orbital radius and therefore a higher velocity to maintain the same orbital period as the more massive star.
