A planet \( P_{1} \) is moving around the star of mass \( 2M \) in the orbit of radius \( R \). Another planet \( P_{2} \) is moving around another star of mass \( 4M \) in a orbit of radius \( 2R \). Ratio of time periods of revolution of \( P_{2} \) and \( P_{1} \) is ______.
