So far as we can tell, the cores of the planets formed as dense materials sank and light materials floated through the material of the planet, under the influence of the planet's own gravity.
In the case of the terrestrial planets (Mercury, Venus, Earth, Mars) the dense material forming the cores would seem to be mostly iron, iron sulphide, nickel, and various other elements that mix well with iron and are called "siderophiles", with elements that combine readily with sulphur ("chalcophiles") above them, elements that combine well with silicates (lithophiles) forming the crust, and elements that tend to form compounds that are liquids, gases, and vapours (atmophiles) either on top of that or drifting away to space.
In the case of the giant planets the light fraction is a mixture of hydrogen and helium along with a few other gases and vapours, and teh core, if any, it rather mysterious. There might be a ball of iron wrapped in sulphides and silicates in the middle, but we can't tell at present. It seems clear though, that in the case of Uranus and Neptune there is a significant ball or layer of water ice.
The larger, spherical moons of the giant planets are interesting. They seem to be differentiated into layers like the terrestrial planets except that the layer of water is frozen, or at least the top of it is.
As for the dwarf planets, I don't think we can tell yet. They certainly have enough gravity to achieve a spheroid shape, but whether they all have enough to differentiate themselves into layers we don't know.
Inner planets are made mostly of rock, although the Earth also has quite a substantial metallic core, of nickel and iron.
core
There are four planets that are made out of gas: Jupiter, Saturn, Urans and Neptune. These planets are called the "gas giants" . The other four planets (Earth, Mercury, Venus and Mars) are mostly made out of rock.
Yes Pluto has a core. It is believed that it's rocky material would have settled into a dense core surrounded by a mantle of ice. The diameter of the core should be around 1,700 km, 70% of Pluto's diameter.
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there are 9 planets
rocky iron ore
Inner planets are made mostly of rock, although the Earth also has quite a substantial metallic core, of nickel and iron.
All planets have a core.
Yes, Jupiter is believed to have a dense core of rock and metal about the size of Earth. This core is thought to be surrounded by a thick layer of metallic hydrogen, followed by a gaseous outer layer.
Yes. Like most terrestrial planets it has a core made mostly of iron.
Within our solar system, four planets are mostly made of gas - Jupiter, Saturn, Uranus and Neptune, but all are thought to possibly have a solid core of some type.
the Core
core
There are four planets that are made out of gas: Jupiter, Saturn, Urans and Neptune. These planets are called the "gas giants" . The other four planets (Earth, Mercury, Venus and Mars) are mostly made out of rock.
The whole planets made up of gas, and underneath that is a layer of liquid and then a hard rocky core.
No, the core is the innermost section of the planet, at the centre.