ALMA is one of the largest, ground-based astronomical facilities ever built. The array of 66 antennas is located on the Chajnantor plateau in northern Chile, at an altitude of 5000 metres.
Observations made with individual antennas—separated by as much as 16 kilometres—are combined using a technique called interferometry, resulting in much higher-resolution observations than would be possible with a single antenna; the resulting resolution equals that of a radio dish with a diameter equal to the distance between interferometric antennas.
Using ALMA, astronomers observe clouds of cold gas and dust in the millimetre/sub-millimetre range, studying star formation, planetary-system formatione, and chemistry in space. The project, which completed construction in March 2013, is an international collaboration between Europe, East Asia and North America in cooperation with Chile.
