Core

The central part of a planet, such as Earth is called the core. The Earth's inner core is a solid 2432 km across, probably formed mostly from heavy atoms such as iron and uranium. Around this is a liquid outer core 2270 km thick made of iron and lighter atoms such as oxygen and sulfur.

Around the core is the mantle.

The Earth's magnetic field is thought to originate in the core. The core is believed to be kept warm by radioactive decay.