Extremely Large Telescope
General Info


Garching-bei-München Germany

legal status



remote, physical

Extremely large telescopes are considered worldwide to be one of the highest priorities in ground-based astronomy. They will lead to a greater advancement of astrophysical knowledge, allow a deeper exploration of our Universe, and give sharper views of cosmic objects than ever before.  Since 2005 ESO has been working with its community and industry to develop an extremely large optical/infrared telescope. ESO’s Extremely Large Telescope, or ELT for short, is a revolutionary ground-based telescope that will have a 39-metre main mirror and will be the largest visible and infrared light telescope in the world: the world’s biggest eye on the sky. In addition to this unparalleled size, 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. The past decade has brought astronomical revelations that have excited people from all walks of life, from finding planets around Proxima Centauri, the nearest star to the Sun, to the first image of a black hole. In the next epoch of astronomy, with the ELT, we will go on to tackle some of the biggest scientific challenges of our time. The ELT will track down Earth-like planets around other stars, and could become the first telescope to find evidence of life outside of our Solar System. It will also probe the furthest reaches of the cosmos, revealing the properties of the very earliest galaxies and the nature of the dark Universe. On top of this, astronomers are also planning for the unexpected — new and unforeseeable questions that will surely arise, given the new capabilities of the ELT. The ELT programme was approved in 2012 and the green light for construction at Cerro Armazones in Chile’s Atacama Desert was given at the end of 2014. From construction of the immense telescope dome structure to casting of the mirrors, the work on this wonder of modern engineering has been made possible thanks to the spirit of collaboration. ESO has been working alongside a worldwide community and dozens of Europe’s most cutting-edge companies to bring the ELT to “technical first light” later this decade. Once operational, ESO faces the challenge of scheduling numerous planned and spontaneous observations across various scientific domains while maintaining data quality. Drawing from scheduling expertise fine-tuned for operations of the Very Large Telescope (VLT), operations will be coordinated from an observatory hub 23km away on Cerro Paranal. This control centre will oversee ELT and VLT operations, supported by extensive computing power and ESO engineers for maintenance. Tasks include monitoring, optimizing instruments, celestial object tracking, and scientific data evaluation.
Total Investment 1463 M€ Design Preparation Implementation Operation Project Landmark 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024 2026 2028 2030 2032 2034 2036 2038 RM06 RM08 RM10 RM16 RM18 RM21 LA24
Roadmap Entry
as project: 2006
as landmark: 2016
Total investment
1463 M€
Design Phase
Preparation Phase
Implementation Phase
Operation start
ESO’s mission is to enable major scientific discoveries by constructing and operating world-leading observatories. Complex and technically challenging projects, such as the ELT, represent a major impact of ESO, transforming science and engineering in European astronomy and increasing our knowledge of the Universe and our ability to explore it. ESO’s and its Member States’ investments into the ELT contribute to the development of state-of-the-art instrumentation and new technologies, leading to growing expertise in industry and R&D institutions that generate new markets and opportunities, as well as the creation of jobs and industrial collaborations. ESO plays a pivotal role in attracting and developing the talent base required to maintain European astronomy research and technology at world-leading levels. The training in astronomy and engineering at ESO provides skills and critical thinking that are beneficial for pursuing a range of careers. Astronomy has a strong popular appeal, and its major scientific discoveries generate genuine excitement and interest. ESO’s communication, education and outreach activities, which have served as a benchmark for other astronomy organisations, harness this excitement to help promote and increase scientific literacy in society, as well as to inspire more children and young people to engage in science, technology, engineering and mathematics (STEM) fields. By developing large infrastructures like the ELT, ESO serves as a platform for science diplomacy, actively encouraging international, political and cultural understanding. It encourages countries to work together to create a scientific and political capacity for development that is beyond the reach of its individual Member States. ESO is firmly embedded in, and has an impact on, science policy, is a cornerstone of the European Research Area in astronomy and is one of the vectors of scientific cooperation between Europe and Latin America.
The ESO Extremely Large Telescope (ELT) will provide astronomers with the opportunity to conduct groundbreaking observations. As is the case for current ESO facilities, observing time will be assigned through competitive access. Researchers will be able to submit proposals to use a suite of high-powered instruments, enabling observations across a range of optical and infrared wavelengths. This will allow astronomers to study a multitude of astronomical phenomena, including the formation of exoplanets, the earliest galaxies, and the mysteries of dark matter. A mix of different observing modes and programme types will be offered to optimise efficiency and science return. The raw data and data products resulting from the ELT observations will be stored in the ESO science archive and eventually become public. Science with the ELT covers many areas of astronomy – from the Solar System to extra-solar planets, from nearby galaxies to the furthest observable objects at the edge of the visible Universe, from fundamental physics to cosmology. They include discovering and characterising planets and proto-planetary systems around other stars, resolving stellar populations in a representative sample of the Universe, the study of the physical processes that form and transform galaxies across cosmic time, the discovery and identification of distant type Ia supernovae and constraining dark energy by directly observing the global dynamics of the Universe, as well as searching for possible variations over cosmic time of fundamental physical constants.
S S H D I G I T E N E E N V H & F
The ELT is developed and will be operated by ESO, as part of the Paranal Observatory. Cerro Paranal is the home of the Very Large Telescope, the VLT, the VLT Interferometer (VLTI), the VISTA survey telescope, and several hosted Telescope projects. Paranal Observatory will further be responsible for the operation of the ELT at Cerro Armazones and the southern array of the Cherenkov Telescope Array Observatory (CTAO). ESO is developing an integrated operations model for Paranal Observatory aiming at a financially, environmentally and socially sustainable operations paradigm. ESO signed in 2023 a collaboration agreement with SKAO with the aim to promote the strategic coordination of ESO’s and SKAO’s long-term plans. The agreement establishes a framework for mutual cooperation covering areas such as strategy and governance, communications, international relations, scientific coordination and sustainability, diversity and inclusion. In addition, the Director-General of each organisation will meet annually.