What is Neptune the planet's core made of?

Answer 1

The mantle of Neptune is rich in water, ammonia, and methane. As is customary in planetary science, this mixture is referred to as icy even though it is a hot, highly dense fluid. This fluid, which has a high electrical conductivity, is sometimes called a water-ammonia ocean. At a depth of 7,000 kilometres (4,300 mi), the conditions may be such that methane decomposes into diamond crystals that then precipitate toward the core. The Core of Neptune is composed of iron, nickel and silicates, with an interior model giving a mass about 1.2 times that of the Earth. The pressure at the centre is 7 Mbar (700 GPa), millions of times more than that on the surface of the Earth, and the temperature may be 5,400 K.

So basically, the pressure is so great at its mantle, it crushes methane into solid diamond, and the diamond sinks to the core. It's estimated that it has a solid diamond core larger than Earth.

Answer 2

Neptune's atmosphere is made out of hydrogen, helium, and methane outside is made out of water and clouds.

Answer 3

it is made of rocky gases