Nasa engineers complete the unfolding of the James Webb space telescope

The telescope, which has already travelled more than 600,000 miles across space, is the largest, most powerful space telescope ever built and had to be folded up tightly, so it would fit inside its Ariane 5 launch rocket.

The James Webb, named after a former Nasa administrator, still has to travel 400,000 miles to its destination and will then need five more months for its instruments to be carefully calibrated.

For astonomers, the James Webb offers the prospect of capturing images of the first galaxies to form after the big bang, understanding how stars are born and evolve, and investigating the potential for life to appear in planetary systems. All this will have to be done in a decade, its maximum likely lifetime. After 10 years, it is expected the telescope will run out of fuel and slowly drift off course.