Installed on a 2,400m-high (7,900ft) peak on the Canary Island of La Palma, the huge telescope consists of a mirror measuring 10.4m (34.1ft) in diameter.

The Spanish-led Great Canary Telescope (GTC) is extremely powerful and will be able to spot some of the faintest, most distant objects in the Universe.

The "first light" ceremony will take place on Friday.
If the initial test run is successful, GTC's team expect it to be up and running for the scientific community to use within the next 12 months.

The enormous instrument has taken seven years to construct; its installation has been hampered by poor weather and the logistical difficulties of transporting equipment to such an inaccessible location.

The project is estimated to cost 130m euros (£88m).

Another Earth?

Based at the Roque de los Muchachos Observatory, the optical telescope is made up from 36 separate hexagonal mirror segments which together form the 10.4m primary mirror.

Its vast size will enable it to capture some of the most distant light in the Universe, helping researchers look for information that might help to explain the origins of life.

It will also be able to probe far-off galaxies and look into the secrets of star formation, and hunt for Earth-like planets.

"It would be wonderful if this telescope allowed us to detect a planet like ours," project director Pedro Alvarez told the Spanish El Mundo newspaper.

Campbell Warden, the executive secretary of the Canary Islands Astrophysics Institute, told BBC News: "The big advantage of the GCT over existing telescopes... is that because of the combination of the very advanced technology and the largest optical infrared mirror we'll be able to characterise the atmospheres of planets, instead of just having, as we have at the moment, mathematical speculations of what planets could be like, we'll actually be able to take a much better look at them."

He added: "We'll be able to throw back the curtains that shroud the early Universe, revealing many of its mysteries."