APEX

While ALMA is currently under construction, astronomers are already doing millimetre and submillimetre astronomy at Chajnantor, with the Atacama Pathfinder Experiment (APEX). This is a new-technology 12-m telescope, based on an ALMA prototype antenna, and operating at the ALMA site. It has modified optics and an improved antenna surface accuracy, and is designed to take advantage of the excellent sky transparency working with wavelengths in the 0.2 to 1.4 mm range.

The 5100 m high site opens new atmospheric windows allowing astronomers to observe molecular and atomic lines at wavelengths where previous ground-based telescopes were almost blind. Astronomers are using APEX to study the conditions inside molecular clouds, such as those around the Orion Nebula, or the ‘Pillars of Creation’ in the Eagle Nebula. They have found carbon monoxide gas and complex organic molecules, as well as charged molecules containing fluorine which had never been detected before. These discoveries advance our understanding of the cradles of gas where new stars are born. New generation wide-field bolometer arrays allow astronomers to map the dust emission from nearby star-forming objects to the most distant galaxies in the Universe.

APEX is a collaboration between the Max-Planck-Institut für Radioastronomie (in collaboration with Astronomisches Institut Ruhr Universität Bochum), Onsala Space Observatory and ESO. It follows in the footsteps of the Swedish-ESO Submillimetre Telescope (SEST) which operated at La Silla from 1987 until 2003 in a collaboration between ESO and the Onsala Space Observatory. SEST worked in the wavelength range from 0.8 to 3 mm.

For more information please visit the APEX Web site