They are dim smudges of light that have been traversing the cosmos since almost the begining of time.

They must be old now but we see them as they were billions of years ago, youthful galaxies arranged in clusters.

That these clusters formed so swiftly tells astronomers a lot about the early universe.

Formed when the universe was young

These new observations of clusters of young galaxies may hold clues about how how galaxies quickly formed into massive large-scale structures relatively soon after the Big Bang.

They may also tell us something about the fate of the universe.

If the clusters turn out to be massive and very distant, they could imply that the cosmos does not contain enough matter for gravity to stop the expansion of the universe.

Cosmologists believe that a universe that will expand forever would have built most of its galaxy clusters long ago.

Between 10 and 20 of the farthest clusters in the Hubble survey may be over seven billion light years away.

This means that the clusters, which are made of up to hundreds of galaxies each, were formed very early in the history of the universe.

The Hubble survey contains 92 new clusters uncovered during a six-year sky survey known as the Medium Deep Survey.