The inner rocky planets, Mercury, Venus and Mars and the 2 gas giants Jupiter and Saturn, have always been visible to humans. This is either due to their closeness with the rocky planets or their sheer size with the gas giants. The first planet to be discovered with a telescope was Uranus in March 1781 by astronomer William Herschel. If you know where to look, it is visible to the naked eye but wasn’t recognised as a planet before then due to it being so dim and far away. Galileo actual saw it in 1612 but didn’t realise it was a planet. William’s sister Caroline was also an eminent astronomer.
Nice planetary enquiry, Steve
Nice planetary enquiry, Steve