The Astronomer Jules Janssen ─ A Globetrotter of Celestial Physics

A physicist and an inventor, Jules Janssen (1824-1907) devoted his life to astronomical research. He spent many years traveling around the world to observe total Solar eclipses, demonstrating that a new era of science had just come thanks to the use of both spectroscopy and photography, and persuading the French Government of the necessity of founding a new observatory near Paris. He became its director in 1875. There, at Meudon, he began routine photographic recordings of the Sun surface and had a big refractor and a big reflector built. Meanwhile, he also succeeded in building an Observatory at the summit of Mont-Blanc.The story of this untiring and stubborn globe-trotter is enriched by extracts of the unpublished correspondence with his wife. One can thus understand why Henriette often complained of the solitude in which she was left by her peripatetic husband: “There are men who leave their wives for mistresses; you do it for journeys!” ...Basking in the glow of his success, Janssen was able to undertake the construction of the great astrophysical observatory of which he had dreamed. It was at Meudon that he had it built.

Francoise Launay spent her whole career as a research engineer at the Meudon Observatory, where she was the technical head for a large spectrograph, installed in part of the Chateau’s outbuildings, in the very location where Janssen carried out his laboratory experiments. She has now joined the history team at the Paris Observatory as an associate researcher, and she devotes herself to discovering unpublished material that documents the lives and work of individuals involved in astronomy, no matter whether they used, conceived, or constructed observational instruments.