The planet Uranus has probably been seen long time ago but was most likely thought of as a star.
When Herschel officially discovered it in 1781 he first thought it was a comet.
So is the question about who found out that it was a planet or who first officially observed it?
"In music,a demisemiquaver is half of half of half a crotchet, there are 4 crotchets in a semibreve.How many demisemiquavers are there in a semibreve?"