Answer:
Neptune is the farthest of all the planets in the solar system. It is a gaseous planet. Due to this larger distance from the sun, the planet receives less amount of heat energy emitted from the sun, and this helps in the formation of methane (CH₄) as well as diamond. As the pressure exerted on this planet is extremely high, so the diamond present in it sinks into the deeper zone of the planet where the temperature of its core is very high which is roughly about 7000°C. This results in the releasing of heat energy which is about 2.5 times amount of energy that it receives from the sun.