The European Southern Observatory’s (ESO) Extremely Large Telescope (ELT) in Chile has achieved a significant engineering milestone, successfully completing the first full rotation of its massive 7.7 million-pound (3,500 metric tons) telescope structure. This pivotal test ensures the telescope can smoothly point across the night sky, marking a crucial step in the construction of the world's largest optical/infrared telescope. The development was highlighted by Rakesh Agrawal, who noted on social media, "In Chile, the European Southern Observatory’s (ESO) Extremely Large Telescope achieved a massive engineering milestone."
The complex maneuver involved the dedicated crew initially rotating the structure by hand, centimeter by centimeter, before auxiliary motors took over to complete the full rotation. This operational check is vital for the ELT, which is being constructed on Cerro Armazones in the Atacama Desert and is designed to house a 39-meter primary mirror. Roberto Tamai, the ELT's Program Manager at ESO, emphasized the collaborative effort, stating, "For me, this is a beautiful reminder of what can be achieved when people push in the same direction, literally and figuratively."
This recent achievement follows another major milestone in April 2025, when the ELT's dome structure reached its highest point during a "Topping Out" ceremony. The project, which passed the 60% completion mark at that time, continues to advance towards its operational phase. Once complete, the ELT is expected to gather 13 times more light than current large optical telescopes and produce images 16 times sharper than those from the Hubble Space Telescope.
The ELT is poised to revolutionize ground-based astronomy, offering unprecedented capabilities to observe exoplanet atmospheres, study the earliest galaxies, and search for life beyond Earth. ESO, an intergovernmental astronomy organization, already operates other world-class observatories in Chile, including the Very Large Telescope (VLT). As Agrawal humorously remarked, "There are also Very Large Telescope and Large Telescope. (Astronomers seem to be focusing on astronomy, not branding.)" highlighting the impressive scale of ESO's instruments and their focus on scientific advancement.
