It’s the first anniversary of the discovery of Neptune. The first Neptune-year anniversary; one Neptune year is about 164.79 Earth years.
This planet was discovered as a result of some astronomers discovering that planet Uranus’s observed positions did not quite match its calculated ones. Urbain Leverrier and John Couch Adams decided that there was an additional planet pulling on Uranus, and they tried to predict its position. In 1846, some British astronomers were already searching, but without success. Leverrier tried to interest some French astronomers, also without success, but he was more successful with Johann Gottfried Galle at Berlin. On September 24th that year, Galle succeeded, finding the planet 1 degree from Leverrier’s calculated position.
After its discovery, various astronomers extrapolated Neptune’s position backwards, and discovered that some other astronomers had seen it without recognizing it, including Galileo.
When William Lassell learned of this discovery, he looked for moons of that planet, discovering Triton 17 days after Neptune itself. Neptune’s other moons are much smaller; the next moon discoveries were in 1949 and 1981.
The only spacecraft to visit Neptune has been Voyager 2 in August 1989. That spacecraft returned pictures of Neptune itself, several Neptune moons, and some Neptune rings. Neptune is bluish with white cloud streaks; it has big storms like the Great Dark Spot. Triton’s surface is icy, with nitrogen geysers.
BBC News – Neptune’s birthday and a beautiful piece of maths
Discovery of Neptune
Happy Anniversary, Neptune!
Neptune Completes First Orbit Of The Sun Since Its Discovery By Humans | SpaceRef – Your Space Reference