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
The Magic School Bus Lost in the Solar System The Magic School Bus Lost in the Solar System The Magic School Bus Lost in the Solar System is the fourth book in Joanna Cole and Bruce Degen's "The Magic School Bus" series. The book depicts arguably the most well-known adventure of the series and introduces the character of Janet. Ms. Frizzle's class is learning about the solar system and Arnold's unpleasant cousin Janet, who constantly raves about herself, has joined them. The Friz decides to take the kids on a field trip to the planetarium, but, once they get there, they find the planetarium is closed. However, on the