The Observatory is the witness of a long and amazing history where finally the 3 sites: Paris, Meudon and Nançay were joined
into a single administrative structure.
In 1667, outside of the Paris area at that time, the l'Observatoire royal come into the world, with the impulse of the
Scientific Royal Academy. The building is conceived by Claude Perrault. Two wings were added to the first building, then two
other buildings were built after 1970. It is directed by famous astronomers ( Cassini, Lalande, Arago, Le Verrie, l'amiral
Up to the beginning of the 20th century, the Observatory is specialised in celestial mechanics and positional astronomy.
These topics spread when an ordinance in 1925 joins the Meudon site to the Observatory.
In 1876, at Meudon, an old royal estate is placed at Jules Janssen disposal, in order to allow him to develop his researchs
far from urban pollution. Several instruments are installed: grande lunette under the dome over the castle, 1m telescope,
spectroheliographs, siderostats...; then an equatorial table, a 60cm telescope, and later a solar tower. The spatial techniques
spread out. New buildings are erected, one of them being devoted to theoretical astrophysics. Meanwhile, under the leadership
of Danjon, the Nançay station is added to the Paris Observatory.
As a matter of fact, researchers from the Ecole normale supérieure de Paris create the station de radioastronomie de Nançay
(Cher) which is associated to the Paris Observatory. It has 3 main instruments. The decametric radiotelescope is dedicated
to the study of comets, physics of galaxies, great structures of the Universe, pulsar chronometry. The radioheliograph gives
regularly images of the solar corona. The network of decametric antennas is mainly dedicated to the study of Jupiter and the
All along its evolution, the Observatory has been the foundation of great works which marked the history of sciences -
discovery the finite speed of light (1676), measure of a degree of a meridian (up to 1784), and nowadays the participation
to peak international experiences, on the ground or in the space.