A tiny strip of sky that you could cover with your finger is packed with 50,000 galaxies, the Hubble space telescope reveals. The orbiting observatory spent a year snapping more than 500 photos of a patch of sky in the constellation of the Great Bear.

Stitched together they make up a mosaic that is the length of two full moons and just half a moon in width. But the mosaic shows a snowstorm of galaxies, each made up of millions, billions or even trillions of stars like the sun.

Astronomers say the cosmic panorama will give them fresh clues about the universe’s younger days, from its “pre-teen” years to young adulthood.

The many thousands of galaxies are unevenly scattered with some in groups and others widely spaced. One giant red galaxy reveals two black holes at its centre. Others are acting like lenses because their gravitational pull is distorting light from objects behind them.

The man who stitched the three-billion pixel Hubble mosaic together was astronomer Anton Koekemoer of the Space Telescope Science Institute in Baltimore. He said: “These images reveal a wealth of galaxies at many stages of their evolution through cosmic time.”

The width of a finger held at arm’s length could cover the patch of sky, which has been named the Groth Strip after a US physicist.

Three other space telescopes and four observatories on the ground have also carried out a close inspection of the strip of sky to support the photos from Hubble’s Advanced Camera for Surveys. Their results are published online this month in Astrophysical Journal Letters. Photo: Nasa/ESA.

• For more space reading, plus other bargains, check out the Skymania store!