ELT

Infrastructure and User Services  

The ELT is a ground-based optical telescope currently under construction in Chile, being built by the European Southern Observatory (ESO), an intergovernmental organization of which the Netherlands is a founding member. With its large segmented mirror measuring over 39 meters in diameter, the ELT constitutes a quantum leap for ground-based astronomical telescopes. Thanks to this enormous aperture, the light-gathering power will increase by a factor of 15 with respect to current facilities, and the spatial resolution (i.e. image sharpness) by a factor of 4 to 5. At visible wavelengths, the ELT will provide an angular resolution of 5 milli-arcseconds, thanks to its extensive use of advanced active and adaptive mirrors. These systems continuously monitor and optimize the shape of the 1st, 4th and 5th telescope mirrors to correct the image for deformations caused by atmospheric turbulence, wind-induced vibrations and thermal deformations of the telescope structure, imperfections in other optical components, and other sources. The use of highly reflective broad-band mirror coatings means that the telescope can observe throughout the optical-infrared windows of the atmosphere, between wavelengths of 0,4 and 14 microns. 

The telescope provides two observing platforms, each capable of hosting 3 to 4 scientific instruments. While the telescope is being built by ESO, the instruments will be provided by different international consortia of astronomical institutes. Each instrument will be optimized for a different set of science cases. Together, the instruments will provide a wide range of imaging and spectroscopic observing modes across the accessible spectrum. 

Examples/description of the type of research  

The ELT will have a transformative impact on almost every field of astronomical research, from cosmology to astrobiology. Here are some examples: 

• Our current understanding of physics is unable to explain the observed accelerating expansion of the Universe. ‘Dark energy’ has been proposed as an ingredient that counteracts gravity and causes space to expand. The ELT will be able to trace the expansion history back to the early Universe, hopefully revealing the new physics required to understand this mysterious force. 
• The ELT will study the formation and evolution of galaxies throughout cosmic time. In the very early Universe, it will observe the formation of the very first galaxies from the first generations of stars. In the galaxies of our local group, the ELT will be able to resolve and study individual stars and learn if their composition and evolution history differs from those in our own. The ELT will also look for signs of halos of ‘dark matter’ around galaxies that have been proposed as explanations for the deviations of their rotation curves from current physical models. 
• With the ELT, we will be able for the first time to directly observe and characterize exoplanets in the ‘habitable zones’ around other stars, zones where planets with temperate atmospheres can exist. Using spectroscopy, the ELT will be able to study the chemical composition of these atmospheres and look for indicators of life. It will also be transformational in the study of how planets form. 

How to access the infrastructure ? 

1. Scientific consortia can propose experiments (instruments) to be installed in the telescope to conduct observations serving a subset of science cases. Being part of such a consortium provides NL astronomers with access to observing time and the data produced. 
2. Researchers can also submit observing proposals outside of time allocated to consortia in which they participate. Since the ELT is an ESO facility, proposals should be submitted via the regular ESO calls for proposals.Proposals are selected based on peer review. 
3. Open access: Observation data becomes available via the ESO Science Archive Facilityto all interested researchers after the end of the proprietary period, typically one year.