A series of spectacular images of galaxies crashing into each other has been made public to celebrate the Hubble Space Telescope’s coming of age. Hubble was launched on April 24, 1990, and to mark the 18th anniversary space scientists have picked out 59 pictures of the cosmic collisions.

Exotic patterns of stars and dust clouds swirling and twisting their way across the sky are formed as the galaxies merge or pass through each other millions of light years from Earth. The scale of the collisions are so huge that they can take more than a billion years to be completed.

Hundreds of billions of stars are found in each of the galaxies but because they are spread out over such a large area it is rare for stars to crash directly into each other. However, the gravitational forces exerted as the galaxies close in on each other and merge cause tremendous changes in their structures, twisting them into strange and beautiful shapes.

Galactic pile-ups are thought to be one of the driving forces of star formation and stellar explosions. Among the biggest effects is the formation of long streams of dust and gas, known as tidal tails, which lead from and round the galaxies. Clouds of gas and dust pulled into the core of the galaxies can lead to bursts of star formation.

Britain's newest observatory

Play among the stars at Kielder on top of the Black Fell in Northumberland - the observatory opens on April 25

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As the clouds become thicker they heat up and radiate so spectacularly that they can emit several thousand billion times more light than the Sun.

Although galaxies are many thousands of light years across, there is comparatively little matter in them. “If you were to take all the matter in the Milky Way and bundle it up into a ball with the density of our Sun, and put it where the Sun is, it would only reach Pluto’s orbit,” said Lars Christensen, of the European Space Agency.

The 59 images, the largest single release from the Nasa and European Space Agency Hubble project, give an idea of the changes likely to be wrought on the Milky Way in two billion years when it collides with a giant neighbouring galaxy.

It will then be subsumed within the Andromeda galaxy and the twowill become a single elliptical body that has already been named Milkomeda.

The greatest view in space

— The Hubble Space Telescope orbits Earth at 5 miles a second and sends back enough images to fill 18 DVDs every week

— 1,000 proposals to use Hubble are received every year; only 200 are selected. The telescope is controlled by hundreds of engineers at its ground station in Maryland, US

— Hubble is expected to last until at least 2013. It will be replaced by the James Webb Space Telescope, sited a million miles farther from Earth

NASA, ESA, www.hubblesite.org

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