A nightscape picture taken at the ALMA Operations Support Facility constructed at an altitude of 2900 meters. Venus shines dazzlingly between a Japanese 12 meter antenna (right) and a European 12 meter antenna (left) conducting performance confirmation observations at the Operations Support Facility. And the faint Milky Way stretches out just above the building. Thanks to the clear skies at Atacama, the Milky Way can be seen even near the horizon and Venus is glaringly bright.

Clear Skies and Little Oxygen

Thanks to Atacama’s clear skies, you can enjoy a starry sky which can’t be seen from Japan. In cities, urban lights and haze drown out the starlight when the elevation of the stars drops low. But at Atacama, stars sparkle until they disappear below the horizon. Because of light scattering by particles in the air, the crescent moon looks yellow. But from Atacama you can see a dazzling, pure white crescent moon. But even with this wonderful sky, the stars don’t look any better when viewed from a location at 5000 meters elevation. This is because there is half as much oxygen as compared to sea-level, so human eyes and brains can’t cope. The instant you take a breath from an oxygen cylinder, your field of view expands and you can see the stars clearly. For humans, it’s better to view the stars from a little milder environment.

Author: Masaaki Hiramatsu (NAOJ Chile Observatory)