A wild encounter in the desert

Stay very still — in this Picture of the Week, we have encountered a wild pack of ALMA antennas huddled for warmth in their natural habitat: the Chajnantor Plateau in Chile. This unique species of telescope lives at an incredible altitude above 5000 metres, making it one of the highest sites for astronomical observations on Earth.

The 66 antennas of the Atacama Large Millimetre/submillimetre Array (ALMA) watch the sky day and night for incoming light at wavelengths around a millimetre. This selective eyesight observes some of the coldest objects of the cosmos, from the bleak clouds of gas and dust between stars to the far-off galaxies of the early Universe.

Light at millimetre wavelengths is easily absorbed by water vapour in the Earth’s atmosphere, but the immensely dry climate of the Chajnantor Plateau is ideally suited to get the best possible observations. ALMA — in which ESO is a partner — has adapted well to this harsh desert environment, being operated remotely. 

Fun fact: sometimes the ‘herds’ of antennas need to be rearranged on site with huge robotic shepherds!