The jovian planets get their heat from the Sun and from their interiors. Jupiter creates a lot of internal heat and releases this heat by emitting thermal radiation. In fact, Jupiter creates so much internal heat that it emits almost twice as much energy as it receives from the Sun.

How much heat does Jupiter generate?

The internal heat generation of Jupiter is about 6 Watts per square meter. The amount of sun energy that falls onto Jupiter is about 10 watts per square meter. So unlike the case on Earth Jupiter's output due to internal processes (contraction) is about half as large as the input due to sunlight falling on its clouds.

Why does Jupiter radiate heat?

Jupiter Formation

Unlike most of the planets, Jupiter, whose volume is mostly gas, is still contracting. As its material falls toward the planet's center, it releases stored gravitational energy, eventually becoming heat.