The familiar concept of a planetary core, a small, dense metallic heart we take for granted, may be the exception rather than the rule for exoplanets.

The most common type of planet in the galaxy may not look anything like Earth on the inside

Source: space
Source Link: https://www.space.com/astronomy/exoplanets/the-most-common-type-of-planet-in-the-galaxy-may-not-look-anything-like-earth-on-the-inside