Neptune is the eighth and farthest known planet from the Sun in our Solar System.
It marks the start of the Kuiper Belt which is a region of leftovers from the solar system's early history and includes the dwarf planet Pluto.
NASA's New Horizons project made history by being the first space project to explore Pluto.
It was in the news again very recently by flying past Ultima Thule in the early hours of New Year's Day, the most distant object in our Solar System ever visited by a spacecraft built by humans.
Instrumentation on the craft will now directly explore the Kuiper Belt which holds some of the secrets from the birth of our solar system and then beam the information back to us back on Earth.