"That Star Is Not on the Map": The German Side of the discovery

Abstract

Neptune was telescopically discovered by Johan Gottfried Galle and Heinrich Louis d'Arrest in Berlin on 23 September 1846 based on the prediction by Urbain Jean Joseph Le Verrier. The role German astronomers played in the discovery has often been overshadowed by the controversies that erupted in England and France after the discovery. However, their role was crucial, not only in bringing about the discovery in the first place, but also in resolving some of the post-discovery controversies that erupted around priority for the prediction and naming of the planet. German astronomers in Central and Eastern Europe possessed some of the best telescopes of the day and had established themselves over several decades as being at the forefront of observational astronomy. They had produced the star charts that in the end proved indispensable for allowing identification of the planet, while a German publication, Astronomische Nachrichten, published by H. C. Schumacher in Altona, in the vicinity of Hamburg, then part of the Kingdom of Denmark, served as the journal of record. The general neglect of the German part of the story is most strongly attested by the inaccuracies concerning what actually happened on discovery night, which were long propagated in the English-speaking literature. Notably, for 30 years after the discovery, it was not appreciated that there were two observers, while the role of the sky map used was often exaggerated. This chapter sets forth a more complete picture, and in particular emphasises more than previous accounts the critical role of d'Arrest, arguing that he should be celebrated as a co-discoverer. In addition, evidence presented here, much of it not previously available in the English-speaking literature, shows that the name "Neptune" was eventually accepted throughout the scientific community based on German precedents.