Presentation

Geographical position 

61 Avenue de l’Observatoire, 75014 Paris, France.

Location 

Latitude 48° 48′ 18″ N, longitude 2° 13′ 52″ E. Elevation 160m above mean sea level.

General description 

Meudon is one of a number of new observatories built in Europe in the 1870s that integrated telescope and laboratory facilities in order to carry out astronomical spectroscopy and address the big questions of the new discipline of astrophysics—the nature of the physical structure and the chemical composition of the stars.

Brief inventory 

The buildings on the site include:

• The Grande Coupole, 18.5m in diameter, completed in 1895. It houses the Grande Lunette, a double refractor with an 83cm lens for visual observation and a 62cm one for photography. This instrument remains today the third largest refractor in the world after those at Lick (put into service in 1888, with a diameter of 91cm) and Yerkes (1897 and 1.02m) observatories in the USA.
• Two 7.5m cupolas, one containing a 1m reflector with 3m focal distance, suitable for the study of the planets, the Moon, or comets, whose constructions was also completed in 1895.
• A laboratory situated in the outbuildings, containing two spectroheliographs installed in 1897 and 1906 by Henri Deslandres (Janssen’s successor as observatory director). These are constantly improved and still used.

Other important equipment at the observatory includes a large siderostat built in 1908 (put into service in 1910); a coelostat built by Georges Prin in 1909; an equatorial table put into service in 1931 and now used with a 60cm reflector for educational purposes; a Lyot monochromatic heliograph (1953); a solar tower built in 1969; and a high-resolution 10m vacuum ultra-violet (VUV) spectrograph put into service in 1972.

History 

’L’observatoire d’astronomie physique de Paris‘ was officially created on 6 September 1875, thanks to a decree signed by the president of the French republic. The same decree appointed the physicist and astronomer Jules Janssen to be its director. Janssen had worked since 1860 applying spectral analysis to the study of the stars, and helped to create a new discipline: physical astronomy, today called astrophysics. This new field of knowledge represented a break from the traditional practice of astronomy: while celestial mechanics and positional astronomy continued to prevail in the Paris Observatory, at Meudon Janssen promoted the introduction of methods from physics and chemistry—spectroscopy, photography, and photometry—as an integral part of the work of the observatory.

For Janssen, the choice of site was dictated by reasons both scientific and political: it had to be close to Paris, but also sufficiently isolated ’to escape the vibrations of the earth and the illumination of the atmosphere in the capital‘ (Janssen Jules, Rapport au Ministre, 05/1874, AN F17 3745). It also had to be set in a reasonably clear spot (especially to the south and to the east), such as a slight eminence surrounded by meadows. The chosen property was a dilapidated castle, Château Neuf, at Meudon. Janssen received a large budget to renovate and fit out the place for its new function. A law passed in 1879 formally allocated the Meudon property to the new observatory and over the next three years the process began of transforming the castle and buying instruments.

Since 1926 the Meudon observatory has been attached to the Paris Observatory.

Cultural and symbolic dimension 

Meudon was the first observatory in France of a new type: a place where physics met astronomy, and where the laboratory entered into the observatory. The spectroscopic analyses undertaken in the outlying buildings and the photographs obtained with Janssen’s instruments permitted the astronomers at Meudon to draw important conclusions about the physical structure and chemical nature of the Sun, which was the main focus of research at this site. However, important work on the planets has also been carried out in Meudon: for example, it is thanks to the Grande Lunette that the controversy about Martian canals was finally brought to an end in 1909.

Management and use

Present use 

Meudon is currently one of the three sites of the Paris Observatory, the others being the historical (17th-century) Observatory of Paris itself and the radio-astronomy station at Nançay (Cher) founded in 1953.

State of conservation 

A general renovation of the Meudon buildings was undertaken in 2001, respecting the scientific designation of the site and the original architecture and its decoration, and following the law for the protection of historical monuments in France.

Protection 

The Château Neuf is scheduled as historical monument by a law passed on 12 April 1972.

Context and environment 

The Château Neuf is itself a French heritage monument. The Duchess of Etampes, a favourite of François I, received the original Meudon Castle in 1527. New buildings were constructed during the 16th century, and at the end of the 17th century it acquired gardens designed by the architect Le Nôtre. In 1695, the castle was purchased by Louis XIV for the use of his son, the Grand Dauphin, and it was at this time that new outbuildings (those in which the astronomers work today) and the Château Neuf, the present building of the Grande Coupole, were constructed. After a period of decline under Louis XV and Louis XVI, Napoleon called for the restoration of the Château Neuf, but it was burned down during the war of 1870 and was in danger of disappearing completely. Astronomy is to be thanked for this not having happened.

Management, interpretation and outreach 

As part of the Paris Observatory, Meudon is under the guardianship of the Ministry of Youth, Public Education and Research. The administration of scientific matters is the responsibility of the president, board of directors and scientific council of the Paris Observatory. The administration of the buildings is carried out by the president of the Paris Observatory and the Division Immobilière et Logistique (DIL).