Johann Gottfried Galle ( 9 June 1812 -- 10 July 1910 ) was a German astronomer from Radis , Germany , at the Berlin Observatory who , on 23 September 1846 , with the assistance of student Heinrich Louis d'Arrest , was the first person to view the planet Neptune and know what he was looking at .
Johann Gottfried Galle ( 9 June 1812 in Radis , Saxony-Anhalt -- 10 July 1910 in Potsdam , Brandenburg ) was a German astronomer at the Berlin Observatory who , with the help of student Heinrich Louis d'Arrest , was the first person to view the planet Neptune , and know what he was looking at .