When it’s complete in 2024, the Extremely Large Telescope (ELT) will be the largest visible to infrared telescope in the world, capable of collecting more light than all of the other telescopes in this class combined.
This collecting power will open a new window onto the universe, allowing us to observe planets in our solar system and those orbiting distant stars in unprecedented depth. Its power will also allow researchers to explore fundamental questions about how our universe was formed and the forces that shape it.
We spoke to Professor Simon Morris—Head of the Physics Department at Durham University, member of the European Southern Observatory (ESO) Council, and one of the UK’s ELT project leaders—about the world’s largest eye on the sky, which he hopes to see through from conception to completion.
“My team started working on the instrument proposals for the ELT for ESO in 2007” says Professor Morris “And we have come really far in the last decade. You need to have patience and vision to see a project like this through, because it will be at least another 7 years before the telescope is fully operational.”
It is an exciting time for the ELT, with 80% of the funding needed for the project already in place. For Professor Morris, this means activity around the telescope is starting to increase: “At ESO, we’ve been able to award real contracts to real companies to start building the telescope itself, meaning it’s really going to happen.”
For the world’s largest optical/infrared telescope to actually work, the telescope is just one of the elements that need to be in place. As well as the telescope itself, astronomers need access to instrumentation that interprets the light the telescope captures and allows them to answer scientific questions.
The ELT is planned to have eight instruments, although what these will be is still being discussed. At ‘first light’, when the telescope is turned on and used to collect light for the first time, it will have two of its eight instruments in place, with another following soon after.
The most critical of these is the HARMONI instrument. HARMONI is being built by a team in the UK, and will underpin the ELT’s core capability by separating and measuring light in the visible and infrared parts of the spectrum.
“Other instruments will be added to the telescope in later phases, after first light has been achieved” explains Professor Morris. “For me, the most exciting of these is MOSAIC, a large part of which is also being designed and delivered by scientists and engineers from the UK.”
“MOSAIC will be the ELT’s multi-object spectrograph. Ordinary telescopes generally look at one area or object in the sky, but MOSAIC will allow us to look at lots of different things at the same time. Time on the telescope will be limited, but MOSAIC will allow astronomers to use their time more efficiently, increasing the amount of science they can do and increasing our return on investment.”
The incredible scale of the ELT and the range of its instrumentation means it can help to address a huge list of scientific questions.
“The science we are hoping to get back from the ELT is incredibly wide-ranging. We wanted the project to support research into as many different areas as possible. It will be used for everything from looking at planets in our solar system to other stars and supermassive black holes, to answering questions about fundamental physics and the constants of nature.”
But what is Professor Morris hoping to discover? “One of the things I am most looking forward to finding out is how gas came together in the early universe to form galaxies. Because the speed of light is finite, with a powerful telescope like the ELT we can look far enough away to look back through history and actually see the time when these galaxies were forming.”
With the funding in place for the telescope and agreements to proceed with its first light instruments, the future of the ELT is certain. However, to maintain the project’s momentum and retain the skilled experts working on the telescope, Professor Morris says there is always need for further investment:
“One of the ways that we can do this is to look for new countries to join” explains Professor Morris “Although ESO is the European Southern Observatory it is not limited to Europe. We do global science, and have partners all around the world.”
“The UK government has already committed a huge amount to the ELT so far, which is fantastic. This does not capture the person power and expertise that will be involved in building the kit and delivering the instruments.”
“National governments provide the funding for the telescope, but we also need investment to put the instrumentation in place and keep the telescope running for the next 30 years. Very few companies have to work on such long-term projects in such a collaborative way.”
It is clear when you look at the research that is being done and the papers that being published, astronomy is international by nature. There might be the odd paper from a team in a single country, but they are the exception rather than the rule—most include collaborators from a number of different countries and institutions.
As Professor Morris put it, “Astronomy is an international business.”