Free Astronomy Magazine November-December 2019

14 NOVEMBER-DECEMBER 2019 SPACE CHRONICLES Construction of the ELT by ESO Mariya Lyubenova C onstruction is now underway of the foundation of ESO’s Extremely Large Telescope (ELT) in the remote Chilean Atacama Desert. Once complete, the tele- scope will be the largest ground- based telescope in operation, weighing in at 3400 tonnes. The ELT is a reflecting, fully-steer- able telescope. The design includes a segmented primary mirror measur- ing 39.3 metres in diameter, a sec- ondary mirror (4.2 metres in diam- eter) and a tertiary mirror (3.75 me- tres in diameter). The telescope will also feature groundbreaking adap- tive optics technology that will help correct the distortions in Earth’s at-