A striking new image captured at Chile’s La Silla Observatory offers a haunting look at the Swedish-ESO Submillimetre Telescope (SEST), an instrument that has remained silent for over two decades. Despite its retirement in 2003, the telescope’s massive 15-meter aluminum dish continues to stand watch under the Southern Hemisphere’s pristine night sky, serving as a monument to a pivotal era in space exploration.
The photograph, credited to J. Rodrigues/ESO, highlights the scale of the aging antenna against a backdrop of distant stars. Beyond the telescope itself, the image features a subtle orange band stretching across the horizon. This luminescence is identified as airglow, a natural atmospheric phenomenon caused by chemical reactions in the upper reaches of Earth’s atmosphere, which can sometimes be captured by high-sensitivity cameras even in the absence of light pollution.
#PPOD: Massive Antenna, Silent Mirror
The star-filled sky above ESO’s La Silla Observatory in Chile reflects off the enormous dish of the Swedish–ESO Submillimetre Telescope (SEST). Photographed by José Rodrigues, the now-retired telescope stands beneath the southern night sky, its 15-meter antenna still reflecting the cosmos it once helped astronomers explore.
When SEST began operating in 1987, it was the only large submillimeter telescope in the Southern Hemisphere. Unlike optical telescopes that observe visible starlight, SEST detected longer-wavelength radiation, allowing astronomers to study cold clouds of gas and dust where new stars and planetary systems form. Although the telescope ceased operations in 2003, its scientific legacy lives on in modern facilities such as the Atacama Large Millimeter/submillimeter Array (ALMA), which continues investigating the cold universe in extraordinary detail.
Credit: J. Rodrigues / @ESO
#science
When it first went online in 1987, SEST was a singular achievement for Southern Hemisphere astronomy. Perched at an altitude of approximately 2,375 meters, the telescope was designed to pierce through the “invisible” universe by detecting submillimeter wavelengths. Unlike optical telescopes that rely on visible light, SEST focused on the cold molecular clouds and interstellar dust that serve as the nurseries for young stars and planetary systems.
“Despite knowing about its 15-meter diameter beforehand, I was amazed by its size,” remarked photographer José Rodrigues regarding the sheer presence of the dormant structure. During its 16-year active lifespan, the telescope provided researchers with vital data on how galaxies evolve and how matter coalesces in the darkest, coldest regions of space.
From Legacy to Modern Discovery
While SEST was decommissioned in 2003, the research it pioneered has only accelerated. The telescope paved the way for current-generation observatories like the Atacama Pathfinder Experiment (APEX) and the Atacama Large Millimeter/submillimeter Array (ALMA). These modern facilities utilize interconnected antenna arrays to achieve levels of precision that were impossible during the late 20th century, allowing scientists to map the structure of distant galaxies with unprecedented clarity.
The image of the retired dish serves as a bridge between two eras of discovery. Though it no longer transmits data back to Earth, the telescope remains a prominent feature of the La Silla landscape. It stands as a reminder of the foundational work that allows today’s astronomers to peer deeper into the cosmos, using the very techniques and sites that SEST helped refine.
Fact Checked
This article has been fact checked for accuracy, with information verified against reputable sources. Learn more about us and our editorial process.
