A view of the Gran Telescopio Canarias Enlarge photo

Scientists behind the Great Canary Telescope (GTC) say it is as powerful as four million human eyes combined and will allow researchers to peer into the darkest and most distant corners of space.

The observatory, perched on a mountain on the island of La Palma, will help astronomers with a wide range of research, from discovering new planets, to exploring galaxies and analysing black holes.

Spain's King Juan Carlos will on Friday officially inaugurate the telescope, which cost more than 100 million euros (143 million dollars) to build.

Its 36 separate pieces form a huge circular mirror which collects light on a surface almost 82 square metres in size, according to the scope's developer, the Institute of Astrophysics of the Canaries (IAC).

The IAC says is it is the largest device of its kind in the world and is bigger than the American Keck observatory in Hawaii and the four European VLT telescopes in Chile.

Researchers involved in the project believe the device will help "to discover things that are yet to be discovered" and "produce comparable images to those made by space telescopes, but of better quality as the GTC is bigger".

Project director Pedro Alvarez said the GTC will be one of the world's leading telescopes in the coming decade.

The observatory has been working partially since March with one of its optical devices, Osiris, which picks up objects visible to the naked eye, such as stellar explosions called supernovas.

Towards the end of the year an infrared camera called CanariCam, which picks up objects invisible to the naked eye, will start working.

Built in Florida, the camera will allow astronomers to observe the formation of stars and the most distant and faintest galaxies.

Scientists began mulling the idea of the huge telescope back in the late 1980s.

The telescope cost 104 million euros, 90 percent of which came from the Spanish government.

The rest was paid for by Mexico and the University of Florida in the United States.

Half-brain girl sees all in one eye

The 10-year-old, who is from Germany, is able to see with the power of both the left and right eye in a single eye despite the failure of the right hemisphere of her brain to develop in the womb.

Scientists at Glasgow University now believe that the girl's brain rewired itself during its development in the only known case of its kind in the world.

In other cases where patients have half of the brain removed - for example to treat severe epilepsy - one field of vision is lost in both eyes.

This would leave them only able to see objects on the left or right side of their vision. In the case of the German girl, her left and right field vision is almost perfect in one eye.

Scans on the girl showed that retinal nerve fibres which should have gone to the right hemisphere of the brain diverted to the left.

Dr Lars Muckli, of the university's Centre for Cognitive Neuroimaging, said: "The brain has amazing plasticity but we were quite astonished to see just how well the single hemisphere of the brain in this girl has adapted to compensate for the missing half.

"Despite lacking one hemisphere, the girl has normal psychological function and is perfectly capable of living a normal and fulfilling life. She is witty, charming and intelligent."

The girl's underdeveloped brain was discovered when, aged three, she underwent an MRI scan after suffering seizures of brief involuntary twitching on her left side. Apart from the seizures, which were successfully treated, and slight weakness on her left side, the girl has had a normal medical history, attending school and taking part in regular activities.

The study, which also involved researchers in Germany, is published in the Proceedings of the National Academy of Science USA.