Neptune

© NASA/JP

A distant ice giant

Official confirmation of Neptune's presence came on 23 September 1846. But the discovery inspired a dust-up in the international astronomy community, as scientists from both Britain and France claimed they had been the first to see the eighth and most-distant planet in the Solar System. Eventually peace was brokered, and credit is now shared between the two factions. But those 19th-century astronomers were using coordinates first recorded by Galileo in 1612. The Italian polymath had correctly mapped Neptune's position more than 200 years earlier using a less-powerful telescope. Galileo mistook Neptune for a star – but his coordinates helped point the stargazers who followed him in the right direction to spot and identify Neptune.