Meanwhile, Le Verrier by letter urged Berlin Observatory astronomer Johann Gottfried Galle to search with the observatory's refractor. 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. On the evening of 23 September 1846, the day Galle received the letter, he discovered Neptune within 1° of where Le Verrier had predicted it to be, about 12° from Adams' prediction. Challis later realised that he had observed the planet twice, on 4 and 12 August, but did not recognise it as a planet because he lacked an up-to-date star map and was distracted by his concurrent work on comet observations. COUNT 5
QSN1 Who was Henrich d'Arrest?  ANS1 student at the observatory QSN2 When did Galle discover Neptune?  ANS2 23 September 1846 QSN3 How many degrees off was Adams' prediction? ANS3 12° QSN4 What did Henrich d'Arrest seek to find?  ANS4 the displacement characteristic of a planet QSN5 What was Challis looking for when he saw Neptune the first two times?  ANS5 comet observations