Like Jupiter and Saturn, Neptune emits about 2.5 times as much heat energy as it receives from the Sun, although calculations show it should have already lost all of its original heat. What is the most likely explanation

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.

the branch of biology that deals with the normal functions of living organisms and their parts.

the way in which a living organism or bodily part functions.