20x Earth

Earth is the third planet in Sol System. It is the only planet known to contain life on the surface.

Structure
Earth has:
 * Crust, 0-40 km downwards from the surface, mainly solid, temperature 180-1200 K
 * Mantle, 40-7000 km downwards from the surface, molten, temperature 1200-3000 K
 * Core, 7000-127456 km downwards from the surface, gas/plasma, temperature 3000-100000 K

In terms of mass, Earth is a hollow sphere. The mantle has the greatest density, ~5 kg/dm³, and the core has only ~5 kg/m³. This is possible, because the enormous temperature of the core forces everything to become plasma or gas and lose density.