Where Is the ALMA Observatory?

ALMA is an array of 66 high-precision radio antennas (54 with 12-metre dishes and 12 with 7-metre dishes) that work together as a single telescope using interferometry. Located on the Chajnantor Plateau at 5,058 metres above sea level, it sits above much of Earth water vapour (the main obstacle for millimetre-wave astronomy) in one of the driest places on Earth. ALMA observes the universe in millimetre and submillimetre wavelengths — between infrared and radio waves — revealing cold gas and dust that is invisible to optical telescopes. Key discoveries include the first image of a protoplanetary disk (around HL Tauri) showing rings where planets are forming, detection of complex organic molecules in distant galaxies, and observations of the gas dynamics around supermassive black holes. The antennas can be spread across baselines up to 16 km, providing angular resolution surpassing the Hubble Space Telescope at these wavelengths. ALMA is a partnership among Europe (ESO), North America (NRAO), and East Asia (NAOJ), costing about $1.4 billion.