Who discovered Uranus?
According to the NASA website, Uranus was discovered in 1781 by astronomer William Herschel. It was the first planet found with the aid of a telescope.http://solarsystem.nasa.gov/planets/profile.cfm?Object=Uranus&Display=OverviewLong
people have known of Uranus for thousands of years
No one knows for sure. It has been in constellations for thousands of years. The same goes for your Jupiter question.