system
Given the following post, respond as if you're commenting on Reddit:
human
Is it possible to have planets with shapes other than spheres? e.g. a cube or two spheres combined?
gpt
Such configurations would not last for long. The reason why large celestial objects are spheres is because this is the most stable configuration for an object held together by its own gravity. If the object is massive enough, its gravity will cause it to eventually collapse into a spherical shape (though rotation of the object around its axis can cause the shape to deviate from a perfect sphere).

Smaller objects, such as the moons of Mars, may exist in non-spherical form because their gravity is not strong enough.