HD149026 b in the context of Core (geology)

A planetary core consists of the innermost layers of a planet. Cores may be entirely liquid, or a mixture of solid and liquid layers as is the case in the Earth. In the Solar System, core sizes range from about 20% (the Moon) to 85% of a planet's radius (Mercury).

Gas giants also have cores, though the composition of these are still a matter of debate and range in possible composition from traditional stony/iron, to ice or to fluid metallic hydrogen. Gas giant cores are proportionally much smaller than those of terrestrial planets, though they can be considerably larger than the Earth's nevertheless; Jupiter's is 10–30 times heavier than Earth, and exoplanet HD149026 b may have a core 100 times the mass of the Earth.