Olof Hiorter Olof Hiorter Olof Petrus (or Peter) Hiorter (or Hjorter) (1696–1750) was a Swedish astronomer. After studying in the Netherlands, he was appointed lecturer at the University of Uppsala in 1732 to fill the vacant position of Anders Celsius then on his grand tour of European observatories. From 1737 onwards, he studied together with Celsius the aurora phenomenon and a number of astronomy subjects (solar eclipse, comet like the one of 1744, latitude measurements). Pehr Wilhelm Wargentin was his pupil. Hiorter was elected a member of the Royal Swedish Academy of Sciences in 1745 and appointed "Observator Regius" - "Royal Astronomer"
Anders Celsius conducted with his assistant Olof Hiorter, and he was the first to suggest a connection between the aurora borealis and changes in the magnetic field of the Earth. He observed the variations of a compass needle and found that larger deflections correlated with stronger auroral activity. At Nuremberg in 1733, he published a collection of 316 observations of the aurora borealis made by himself and others over the period 1716–1732. Celsius traveled frequently in the early 1730s, including to Germany, Italy and France, when he visited most of the major European observatories. In Paris he advocated the measurement of an