An orbiting satellite has an orbital speed v = √(G M / r). If the orbital radius r is quadrupled, the new speed is

1. Orbital speed v = √(G M / r), so v ∝ 1/√r. 2. New r = 4r; new v = √(G M / 4r) = √(G M / r) / 2 = v/2. 3. Higher orbits have lower speeds but longer periods (Kepler's third law). 4. This is consistent with slower motion for outer planets like Neptune. _Source: syllabus Physics, Ch 7 "Gravitation", §7.6_