I want to know the answer to the following question:
Who was Henrich d'Arrest?
All the background I'm provided with is that "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.". Is that enough to answer the question?
Answer: no