NOEMA, the successor to the Plateau du Bure observatory, is the most powerful millimeter radiotelescope of the Northern Hemisphere and one of the most advanced facilities existing today for radio astronomy:
Located in the French Alpes on the wide and isolated Plateau de Bure at an elevation of 2550 meters, the telescope currently consists of eight antennas, each 15 meters in diameter. Each antenna is equipped with state-of-the-art high-sensitivity receivers. Two tracks, extending on a north-south and east-west axis, enable the antennas to be moved up to a maximum separation of 760 meters.
NOEMA will double the number of antennas of its predecessor from six to twelve. The first of the six new NOEMA antennas was inaugurated end of September 2014. During the next years, construction of the array will continue and five other antennas will follow, approximately one per year until 2019.
Once finished, NOEMA will be the most advanced facility for millimeter radio astronomy in the Northern Hemisphere. Its spatial resolution will be four times higher and its sensitivity ten times better than those of its predecessor. NOEMA will be a revolutionary instrument and a high-precision tool allowing astronomers to explore some of the most fundamental questions of modern astronomy.
While construction of the new antennas continues, the NOEMA observatory is functioning fully with its current eight antennas. During observations, the antennas work as a single telescope, a technique called interferometry. With the antennas pointing towards the same cosmic source, the signals received by each of them are subsequently combined. The angular resolution achieved during observation is that of a single telescope, whose diameter corresponds to the maximum distance between the individual antennas. In the case of the NOEMA interferometer, this is equivalent (for the longest baselines) to a telescope with a diameter of 760 meters, which can distinguish two one-cent coins placed next to each other at a distance of 5000 meters. Due to the complexity of such an advanced antenna array system, only IRAM operators perform the observations.
To obtain a complete image of a cosmic object, interferometry uses the earth’s rotation, which slowly turns the antennas with respect to the source, thus enabling step by step scanning of the source’s structure. Astronomers are able, after several hours of observation, to reconstruct a high angular resolution image of a cosmic object and study its detailed morphology.
The two IRAM facilities can also be combined with other radio telescopes into one giant interferometer with intercontinental baselines (Very Large Baseline Interferometry or VLBI). This global technique is particularly well adapted to the exploration of ultra luminous cosmic phenomena, such as brightly shining matter around black holes (quasars) or shells ejected by dying stars. The angular resolution that is achieved with this technique is such that it would be possible to detect a golf ball on the moon! VLBI is also used to measure the movements of the tectonic plates and to pinpoint the position of a spacecraft.