What non-spherical shape do simulations suggest for planets formed via disk instability?

Answer

Oblate spheroids.

The standard core accretion model often implicitly assumes that growing protoplanets maintain a near-spherical shape throughout their formation, consistent with the final state of terrestrial planets formed through standard accretion. However, when simulations investigate competing formation pathways, specifically the disk instability mechanism where massive clumps form directly, the resulting structure is significantly different. These high-fidelity simulations indicate that young, massive protoplanets are not perfect spheres but rather possess a flattened, non-spherical geometry, specifically described as oblate spheroids—similar in shape to candies like 'Smarties.' This indicates that the 3D structure of the forming body is influenced by the disk environment and dictates how material is accreted, a nuance potentially missed by simpler spherical assumptions.

What non-spherical shape do simulations suggest for planets formed via disk instability?

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