AI Insight
A photograph by astrophotographer José Rodrigues captures the decommissioned Swedish-ESO Submillimetre Telescope at Chile's La Silla Observatory, showing stars and airglow reflected in its 15-meter aluminum dish. The SEST telescope operated from 1987 to 2003 as the Southern Hemisphere's only large submillimeter telescope, observing wavelengths beyond visible light emitted by comets and molecular clouds. Its scientific work advanced understanding of ancient galaxies and star formation before being succeeded by APEX and ALMA telescopes.
Why it matters
This highlights the legacy of submillimeter astronomy infrastructure that enabled breakthrough observations of cold interstellar material and early universe phenomena. The telescope's location at 2,375 meters elevation provided exceptional atmospheric conditions for detecting these difficult-to-observe wavelengths that reveal star formation processes and distant galaxy evolution.
Understand the Science
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.
What is it?
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.
Why is it incredible?
“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
Source: The universe in the eye of a telescope | Space photo of the day for Oct. 29, 2026