Definition of planet object can be irregular in shape, but beyond that point gravity begins to pull an object towards its own centre of mass until the object collapses into an ellipsoid. (None of the large objects of the Solar System are truly spherical. Many are spheroids, and several, such as the larger moons of Jupiter and Saturn and the dwarf planet , have been further distorted into ellipsoids by rapid rotation or tidal forces, but still in hydrostatic equilibrium.) However, there is no precise point at which an object can be said to have reached hydrostatic equilibrium. As Soter noted in his
Wonders of the Solar System Wonders of the Solar System Wonders of the Solar System is a 2010 television series co-produced by the BBC and Science Channel, and hosted by physicist Brian Cox. "Wonders of the Solar System" was first broadcast in the United Kingdom on BBC Two on 7 March 2010. The series comprises five episodes, each of which focuses on an aspect of the Solar System and features a 'wonder' relevant to the theme. The series was described as one of the most successful to appear on BBC Two in recent years. An accompanying book with the same name was also published. On