A visionary project for French radio astronomy
In the 1950s, under the impetus of physicist Yves Rocard, France decided to build a large radio telescope to explore the Universe in radio waves. The Nançay site in Sologne was chosen for its optimal observing conditions.
On May 14, 1965, the Grand Radiotélescope was inaugurated. With its impressive dimensions - a fixed spherical mirror 300 meters long and 35 meters high, and a plane orientable mirror 200 meters by 40 meters - it offers a collecting surface of 8,000 m², equivalent to a parabola 94 meters in diameter.
A major contribution to the exploration of the Universe
For six decades, the Nançay radio telescope has contributed to fundamental advances in astrophysics. It is renowned for its observations of pulsars, fast-rotating neutron stars that provide invaluable data for understanding general relativity.
Nançay has also played a pioneering role in the study of comets, detecting the OH radical in the Kohoutek comet as early as 1973, making it possible to quantify the water released by these celestial bodies.
The instrument also enables us to observe transient phenomena such as gamma-ray bursts, solar flares and radio emissions close to black holes. It helps to measure the velocities of thousands of galaxies, contributing to work on the expansion of the Universe and Hubble’s constant.
An instrument in constant evolution
The Grand Radiotélescope de Nançay has been continuously upgraded since its commissioning. It is equipped with sensitive receivers covering a wide range of frequencies, from 1.060 GHz to 3.500 GHz, including the hydrogen line at 21 cm wavelength.
The focal carriage, which houses the receivers, moves along an 80-metre track to follow the celestial sources as they cross the meridian. The extremely weak radio signals are amplified by devices cooled to very low temperatures to limit thermal noise.
Always looking to the future
The Observatoire Radioastronomique de Nançay continues to develop with the installation of new instruments such as NenuFAR, a new-generation low-frequency radio telescope, and the French station of the European LOFAR network. These projects strengthen Nançay’s position in world radio astronomy, and foreshadow the technologies of the future Square Kilometre Array (SKA).