This might explain why planets like Jupiter seemed over-sized. It is very much less dense than Earth, given its observed size and its orbit (and period) around the Sun. We are looking not at the planet's surface but at a gravitational phenomenon that traps debris around the planet. These spheres are much bigger that the planet and shade the whole planet.
A planet in rotation will budge at the equatorial plane. It is expected that the heat radiating from the planet is maximum at the equatorial plane. As the interaction between gravity, \(g\) and thermal gravity \(g_T\) is strongest on this plane, the formation of rings will reach furthest into space in the equatorial plane; and then spheres around the planet will form at distances closer to the planet's center.
Other factors may also be at play. The planet magnetic field for example.
It would be interesting to find a planet that change size as it orbits around its sun. Gravity around the planet might just be strong enough to effect the formation of such spheres. If this happens, the planet will change size periodically as it revolve around its sun.
