The Extremely Large Telescope

Abstract

AbstractExtremely large telescopes (ELTs) are considered worldwide to be one of the highest priorities in ground-based astronomy. The European Southern Observatory (ESO) is developing an ELT that will have a 39 m main mirror and will be the largest visible and infrared light telescope in the world. The ELT will be equipped with a lineup of cutting-edge instruments, designed to cover a wide range of scientific possibilities. The leap forwards with the ELT can lead to a paradigm shift in our perception of the Universe, much as Galileo's telescope did 400 years ago. We illustrate here the various components of the ELT, including the dome and main structure, the five mirrors, and the telescope systems. We then describe the ELT instrumentation and some of the astronomical topics it will address. We then conclude by examining the synergies with other astronomical facilities.Keywords: ELTextremely large telescopesscienceastronomytechnologytelescopessolar systemexoplanetsstarsblack holesgalaxiescosmologydark matterfundamental physics AcknowledgmentsMaking the ELT a reality is only being possible thanks to a collaboration between a large number of different people in an enormous variety of roles, ranging from scientists and engineers to project managers and technicians, at ESO and across the ESO member states. The key responsibilities of some of the team members are shown at https://elt.eso.org/about/team/. This paper would not have been possible without them. There are many contractors and institutions working for the ELT dealing with, e.g. the dome and the main structure, the five mirrors, the instruments, the roads, software writing, consultancy, etc. A complete list can be found here: https://elt.eso.org/about/industrial/. We thank Richard Ellis and Olivier Hainaut for many useful comments, Michael Meyer for producing Figure 8, and Alessandro Marconi and Valentina D'Odorico for providing us with Figure 11.Disclosure statementNo potential conflict of interest was reported by the author(s).Notes1 https://elt.eso.org/2 https://giantmagellan.org/3 https://www.tmt.org4 This special material is not sensitive to thermal fluctuations thanks to its very low thermal expansion coefficient. This means that the form and the shape of the mirrors will not change significantly with temperature during observations. It is also extremely resistant, can be polished to the required finishing level, and has been used in telescope mirrors for decades.5 https://www.eso.org/public/announcements/ann19049/6 https://www.eso.org/public/news/eso2017/7 https://www.skatelescope.org/the-ska-project/8 https://webb.nasa.gov/9 https://www.cosmos.esa.int/web/euclid10 https://www.lsst.org/11 https://www.cosmos.esa.int/web/plato12 https://www.cta-observatory.org/Additional informationNotes on contributorsPaolo PadovaniPaolo Padovani Paolo Padovani is Full Astronomer in the ELT Science office at ESO. After getting his PhD at the University of Padova, Italy, in 1989, he worked at the Space Telescope Science Institute (STScI), Baltimore, USA, at ESO, at the II University of Rome, Italy, and again at STScI for the European Space Agency. He finally (re-)joined ESO in 2003. He has authored a number of ELT requirement documents and is currently the overall coordinator of the ELT Working Groups, which bring together expertise from within ESO, the Instrument Consortia, and the wider Community. He works on Active Galactic Nuclei over the whole electromagnetic spectrum and has been recently expanding his research interests to Neutrino Astronomy.Michele CirasuoloMichele Cirasuolo Michele Cirasuolo is the ELT Programme Scientist at ESO and is responsible for the scientific leadership of the telescope and its instrumentation. He has got a long experience with astronomical instrumentation and has been instrument scientist for the KMOS instrument and is principal investigator of the multi-object spectrograph MOONS for the VLT in Chile. With a PhD in astrophysics and two decades of active research, he has published extensively in the field of galaxy formation and evolution across cosmic time.