Neptuun

Neptuun is the eighth and farthest known planet from the Sun in the Solar System. It is an ice giant and the fourth-largest planet by diameter. Neptuun is also the third-most massive planet, smaller only than the three gas giants, Jupiter, Saturn, and Uranus. Its diameter is about 49,500 kilometers, and its mass is approximately 17 times that of Earth.

Neptuun has a blue hue due to the presence of methane in its atmosphere, which absorbs red light and reflects blue light. The planet has a dynamic atmosphere with visible cloud bands and storm systems, including the Great Dark Spot, a large anticyclonic storm similar to Jupiter's Great Red Spot, though it is not permanent. Neptuun's winds are the strongest recorded in the Solar System, reaching speeds of up to 2,100 kilometers per hour.

The planet has a system of rings, though they are much fainter and less substantial than Saturn's. Neptuun has 14 known moons, the largest of which is Triton. Triton is unique in that it orbits Neptuun in a retrograde direction, suggesting it was captured from the Kuiper Belt.

Neptuun was the first planet discovered through mathematical prediction rather than observation. Its existence was inferred from irregularities in the orbit of Uranus. German astronomer Johann Galle discovered Neptuun in 1846, based on calculations by Urbain Le Verrier and John Couch Adams. The Voyager 2 spacecraft is the only probe to have visited Neptuun, conducting a flyby in 1989.