HST image of the cluster of galaxies and the gravitationally lensed Lynx arc. The arc itself is visible as a red curve to the right of centre.Image: European Space Agency, NASA and Robert A.E. Fosbury (European Space Agency/Space Telescope-European Coordinating Facility, Germany) North American and European astronomers have discovered a huge star-forming region in the early universe.

The scientists used telescopes including the Hubble Space Telescope (HST), the X-ray satellite ROSAT and the Keck telescopes on Hawaii to look at the most distant objects in visible light, X-rays and the infrared.

Astronomers then found a mysterious red arc behind a cluster of galaxies some 5400 million light years away in the direction of the northern constellation Lynx. Galaxy clusters of this kind have strong gravitational fields that bend the light of more distant objects through 'gravitational lensing’ and makes them act like giant telescopes. The arc is the lensed image of an object at a distance of 12000 million light years, which means that we see it as it was when the universe was just 2000 million years old.

Looking at the spectrum of its light, the arc seems closely related to the nearby Orion nebula, an object visible in the winter sky from the UK. The Orion nebula is a star-forming region in our galaxy lit up by four bright stars but the red arc is the same kind of object on an enormous scale – it may contain as many as one million such stars.

Unlike in the present-day universe, the Lynx arc’s stars have surface temperatures of 80,000° C – more than twice as hot as the stars in the Orion nebula. In the early Universe the first super-massive stars to form – perhaps just 200 million years after after the Big Bang – may have had surface temperatures of up to 120,000° C. But the Lynx arc is an important stepping-stone in the search for the earliest stars – astronomers hope to see them with the James Webb Space Telescope when it comes into operation after 2010.