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The planet Neptune's existence was confirmed in 1846. Scientists from Britain and France argued over who deserved credit for the discovery, after both claimed they had been the first to see the eighth and most-distant planet in our solar system. Eventually peace was restored, and credit is now shared between the pair. But those 19th-century astronomers were using solar system coordinates first recorded by Galileo in 1612. The Italian polymath correctly mapped Neptune's position more than 200 years earlier using a less powerful telescope. Galileo mistook Neptune for a star – but his coordinates prompted many stargazers who came along after him to look in the correct direction and identify Neptune.
© NASA/JPL