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The universe in the eye of a telescope | Space photo of the day for Oct. 29, 2026
The Swedish-ESO Submillimetre Telescope (SEST) keeps its eye on the cosmos decades after being decommissioned.
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Stars shine in the vast aluminum dish of the Swedish-ESO Submillimetre Telescope (SEST) in this photograph captured by astronomer and astrophotographer José Rodrigues during a recent visit to the European Southern Observatory's La Silla Observatory in Chile.
Rodrigues' image captures "airglow" infusing the night sky over La Silla with a soft orange glow, which is created as sunlight interacts with molecules in the upper atmosphere, according to the University of Lancaster.
The subtle phenomenon can be seen reflected in the 15-meter (49-foot) primary dish of the SEST telescope along with the myriad stars of the Southern Hemisphere, as the dome of the ESO's 3.6-meter telescope looms in the background.
"Despite knowing about its 15-meter diameter beforehand, I was amazed by its size," Rodrigues noted in the ESO image release. The SEST first opened its great eye to the universe in 1987, at which time it was the only large telescope in the Southern Hemisphere tasked with collecting submillimeter wavelengths of light that exist beyond the visible light spectrum.
These specific wavelengths of light are emitted by wandering comets and colossal clouds of cold molecular dust and gas threaded throughout the Milky Way and beyond. SEST's observations improved our knowledge of ancient galaxies, star formation and so much more, with its perch 2,375 meters (7,792 feet) above sea level granting it a near unrivalled view of the heavens above.
The SEST telescope was decommissioned in 2003, though its work was continued by the more capable Atacama Pathfinder Experiment (APEX) and the Atacama Large Millimeter/Submillimeter Array (ALMA).
With its working days over, the SEST telescope now stands as a quiet mirror reflecting the stars of the Southern Hemisphere night sky, seemingly pondering mysteries of the universe that it once tried to solve
Anthony Wood joined Space.com in April 2025 after contributing articles to outlets including IGN, New Atlas and Gizmodo. He has a passion for the night sky, science, Hideo Kojima, and human space exploration, and can’t wait for the day when astronauts once again set foot on the moon.