Neptune

Neptune is the planet farthest from our Sun. It is a cold ice planet on which extremely strong winds blow. These reach top speeds of 2100 km/h. This is astonishing, because its great distance from the Sun means that very little of its radiated energy, which could cause the winds, reaches Neptune. However, Neptune apparently has an internal heat source that causes the winds. This is because it actually emits 2.61 times more energy than it receives from the Sun.

Neptune appears blue and is surrounded by fine rings. As with Uranus, the blue colour is due to the presence of methane in its atmosphere, as this absorbs red light. There are 14 moons orbiting Neptune. The largest is called Triton. It is even larger than the dwarf planet Pluto. At -235°C, it is the coldest known object in our Solar System.

The astronomer Johann Gottfried Galle discovered Neptune in 1846 with the aid of mathematical predictions from Urbain Le Verrier. Le Verrier calculated from orbital perturbations of Uranus where an object could be located that is responsible for the aforementioned perturbations. This object turned out to be the planet Neptune. Voyager 2 is the only space probe to have visited Neptune, arriving in 1989.