Um, well, people have noticed that certain objects in the sky that appear to be stars but which move through the sky since as long as people have looked up at the sky at night.

I believe it was Thomas Aquainus who created his "crystal spheres" cosmology, in which the moving "stars" were on different "spheres" from the night sky background, and moved in orbit-like motions, but he had them orbiting the Earth, not the sun.

Copernicus proposed that the spheres orbited the sun and NOT the Earth.

Galileo actually made observations to demonstrate it, though, as well as discovered that Jupiter has a system of moons that orbit it just as Jupiter itself and the other planets orbit the sun.

Scientifically, I'd credit Galileo with the discovery of planets as we now think of them.

Hello there! Most of the planets have been known about since ancient times, so we don't really know who they were. Only three planets in our solar system has officially been "discovered" since these were not able to be seen by our human eyes. Uranus was discovered by Sir William Herschel in 1781. Neptune was discovered by John Couch Adams in 1846. And Pluto was discovered by Clyde Tombaugh in 1930.