Why might some young super-Earths be covered by magma oceans?

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Extrasolar planet Artist's conception of the extrasolar planet HD 209458b, some 150 light-years from Earth.

Some young super-Earths are covered by magma oceans primarily because of their proximity to their host stars. These planets, often referred to as lava worlds, experience intense heat due to their close orbital distance, which keeps their surfaces in a molten state.1

Additionally, being very young contributes to this state, as these planets may still retain significant primordial heat from their formation. While some super-Earths are rocky or may host liquid water under specific conditions, those that are either very young or orbit very close to their stars are characterized by these global magma oceans.1