UK to invest in world’s biggest telescope

Britain will play a leading role in building and operating the world’s biggest eye on the sky, the European Extremely Large Telescope in Chile, following a government decision to invest £88m in the €1.1bn project.

With its 39m mirror, the monster E-ELT may provide the first direct images of planets orbiting distant stars and indicate whether any of them host life, through the presence in their atmosphere of oxygen and organic chemicals associated with biological processes. Until now, all planets beyond our solar system have been detected using indirect methods.

But planet hunting will only be a small part of E-ELT’s repertoire. Its light gathering capacity – greater than all existing telescopes put together – will enable astronomers to examine the earliest and most distant features of the universe and track their evolution into stars, galaxies, black holes and more exotic objects, such as quasars and pulsars.

The telescope will be built by the European Southern Observatory, an international scientific organisation similar to Cern, the European centre for particle physics, and the European Space Agency. The ESO operates telescopes in Chile’s Atacama Desert, where extremely dry and clean air gives the best viewing conditions on Earth.

“In addition, the southern hemisphere is scientifically more attractive for astronomy than the northern hemisphere,” said John Womersley, chief executive of the Science and Technology Facilities Council, which manages UK participation in ESO. “The centre of our Milky Way galaxy is to the south, so there is more to see.”

The site selected for the E-ELT on the Cerro Armazones mountain is 3,000m above sea level and close to Cerro Paranal, where ESO’s current flagship instrument, the Very Large Telescope, has been running successfully since 1999.

In the late 20th century, many astronomers thought ground-based optical telescopes were reaching their limits, because the atmosphere inevitably distorts incoming light even on the best mountain-top sites. So big investments were made in orbiting observatories, notably the Hubble Space Telescope.

But the balance of benefits has tilted back to Earth, says Prof Womersley: “By using new technologies, such as adaptive optics, which take out the effects of the atmosphere, we can do a lot more from the ground than people thought was possible when Hubble was designed.”

The UK’s decision to fund the E-ELT means that construction can start as soon as Brazil, which is about to become the first non-European member of ESO, ratifies its membership. If this happens this year as expected, the schedule calls for the telescope to start observing in 2023.

The telescope has an innovative five mirror design. The primary mirror will have 798 hexagonal segments, each 1.4m wide and 5cm thick.

“UK teams of scientists and engineers have built strong positions over the past few years to enable them to make major contributions to the instruments, telescope engineering and optical systems,” says Colin Cunningham, leader of the UK E-ELT project office.

“We look forward to UK industry making competitive bids for contracts to supply optical devices, detectors, software and engineering services for this challenging project.”