Neptune, the unexpected hottie
Neptune is the farthest planet from the Sun in our solar system, so it’s pretty cold. It is not called an “ice giant” for nothing since temperatures are about -328 °F at their warmest. Nevertheless, some experts believe that they should be even lower.

There is evidence that Neptune radiates 2.4 times more energy than it gets from the Sun. This means that the planet could have an internal heat source! Some believe that it is caused by its diamond showers since the friction created as they fall produces heat.