Massive antenna, silent mirror in Chile | European Southern Observatory
In this picture, the decommissioned Swedish-European Southern Observatory Submillimeter Telescope (SEST), at the European Southern Observatory's La Silla Observatory in Chile’s Atacama Desert, shows its 15-meter diameter surface, reflecting the starry night sky of one of the most pristine sites for astronomical observations on Earth.
SEST was, at the time of its first light in 1987, the only large telescope in the southern hemisphere designed for submillimeter astronomy. It studied radiation with longer wavelengths than visible light, coming from cold clouds of gas and dust where stars form. To catch these weak signals and produce sharp images, large collecting areas are needed, resulting in telescopes as massive as SEST. “Despite knowing about its 15-meter diameter beforehand, I was amazed by its size,” says José Rodrigues, visiting astronomer at La Silla and photographer who captured this image.
While no longer in operation, SEST remains a silent mirror of La Silla’s dark night sky, colored here by the faint natural airglow coming from atoms in our atmosphere.
The gorgeous orange tint of the night sky seen here is due to a phenomenon called airglow. Airglow is primarily caused when sunlight excites atoms and molecules in Earth’s upper atmosphere by transferring energy to them. This excess energy is released as a particle of light called a photon. The frequency of each photon determines which captivating color will appear. It is possible to see this light with the naked eye under very dark skies, but a camera can capture it more easily.
Image Description: The image shows a reflective telescope dish, occupying a large portion of the frame. A person is standing close to the telescope, with their back to the camera, and wearing darker clothes. The sky in the background is filled with stars and orange to green undertones, and a white telescope, as well as a white container building, can be seen.
Date: Oct. 12, 2026
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