The Observatory is the oldest university building in Oslo. Built in 1833, to a design by Christian H. Grosch, until 1999 it housed the reading room and archive of the Norwegian Music Collection (Norsk Musikksamling), a branch of the University Library. During his studies (1948–1952), Nordheim would come here often when he wanted to borrow scores by Gustav Mahler or other music he was working on. In 1999, the Observatory regained all its original astronomic equipment, and the building now serves as an educational centre for the natural sciences, where pupils of the capital’s schools, from year seven up, can learn more about the universe.
In 2001, Arne Nordheim, celebrating his seventieth birthday, was awarded a truly celestial distinction. The International Astronomical Union announced that his name had been given to a planetoid from the main belt of planetoids, with number 3457, earlier identified as 1985 RA3, with the following explanation: “The Norwegian composer Arne Nordheim is one of the most influential musical voices of his country, and he has achieved wide international acclaim. He has on several occasions found inspiration in the heavens, as in his Celestial Mechanics, written for the opening ceremony of the 1994 Olympic Winter Games in Lillehammer”. The Arnenordheim planetoid was discovered on 5 September 1985 by Henri Degehogne of the European Southern Observatory.