Free Astronomy Magazine September-October 2023

7 SEPTEMBER-OCTOBER 2023 ASTRO PUBLISHING majority of components to be man- ufactured for the ELT. In addition, some of the elements, such as mir- ror segments and its supporting components and sensors, required detailed prototyping and significant testing before being produced en masse. Furthermore, construction was affected by the COVID-19 pan- demic, with the site closing for sev- eral months and production of many of the telescope components suffering delays. With production processes now fully resumed and streamlined, finalising the remain- ing half of the ELT is anticipated to take only five years. Nonetheless building such a large and complex telescope like the ELT is not free of risks until it’s finished and working. ESO Director General Xavier Bar- cons says: “ The ELT is the largest of the next generation of ground- based optical and near-infrared tel- escopes and the one that is most advanced in its construction. Reach- ing 50% completion is no small feat, given the challenges inherent to large, complex projects, and it was only possible thanks to the commitment of everyone at ESO, the continued support of the ESO Member States and the engage- ment of our partners in industry and instrument consortia. I am ex- tremely proud that the ELT has reached this milestone.” Planned to start scientific observa- tions in 2028, ESO’s ELT will tackle astronomical questions such as: Are we alone in the Universe? Are the laws of physics Universal? How did the first stars and galaxies form? It will dramatically change what we know about our Universe and will make us rethink our place in the cosmos. T his video gives an overview of the progress of the Extremely Large Telescope. [ESO] !