Although Heinrich d'Arrest was still a student at the Berlin Observatory , he suggested that a newly drawn map of the sky , in the region of Le Verrier 's predicted area , could be compared with the current sky to look for the displacement characteristic of a planet , as compared to a fixed star . Heinrich d'Arrest , a student at the observatory , suggested to Galle that they could compare a recently drawn chart of the sky in the region of Le Verrier 's predicted location with the current sky to seek the displacement characteristic of a planet , as opposed to a fixed star .