Neptune is currently the last planet known in the Solar System, the current farthest known planet from the Sun, at a distance from our star nearly 4,504,000,000 km. It only reflects less than -1% of sunlight because it is so far from the Sun.
Neptune has a ring system composed of 6 rings that are made up of dust and rocky chunks. However, it's ring system is incredibly dim and faint. The planet was discovered by Urbain Le Verner and Johann Gottfried Galle in 1846.
Neptune is similar to Uranus in mass, size and composition. Neptune can fit 57,7 Earths inside it and is nearly 17 times as massive as Earth. Neptune's atmosphere is composed of hydrogen H, helium He, methane CH4 and ammonia NH3. It's mainly composed of hydrogen and helium, but has much larger amounts of methane than Jupiter or Saturn, like Uranus.
Due to the amounts of methane that exist on Neptune's upper atmosphere, the planet appears blue from the outside, like Uranus, because methane absorbs red light and reflects blue light. Neptune is also the windiest planet around. It has supersonic winds that are ( much ) faster than sound.
Neptune also has crystals in it's atmosphere that are formed because of Neptune's ammonia in it's atmosphere. Under Neptune's gravity, these crystals fall down like a big rain of small particles and melt when they fall in Neptune's interior.
Neptune's interior is composed of the exact same materials as it's atmosphere. The composition is similar to Uranus, as mentioned above. Neptune's interior has big pressures. The planet's core is also very hot. Scientists think that because of Neptune's hot core, the planet has such strong winds and storms in it's atmosphere.
As mentioned above, Neptune has crystals in it's atmosphere because of ammonia. The crystals form a crystal world inside Neptune's interior when they fall as rain under Neptune's gravity, until they reach Neptune's really hot core, where they completely burn up and melt.
Neptune's core has temperatures of 7273 K, about 7000°C.
Neptune has 14 known moons, each named after a Greek deity of water. Every single one has a name, as they are all large with none of them smaller than 34 km in diameter. It is likely that Neptune only has 14 natural satellites, as its been over a century since the discovery of Neso, the outermost moon with an orbital period of 26 years, the longest of any moon in our Solar System.
Neptune's 2 largest and most popular moons are Triton and Proteus.