Two galaxies are caught in act of 'mating' in space

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The Independent Online
ASTRONOMERS USING the Hubble space telescope have captured the embrace of two spiral galaxies as they swirl together in a cosmic dance that will eventually give birth to a new star system.

Strong tidal forces caused by the gravitational pull of the galaxy on the left are clearly seen to distort the spiral shape of the smaller galaxy.

The interaction, which has taken place over tens of millions of years, has flung out stars and gas into long streamers stretching out 100,000 light years on the right hand of the image.

Calculations by a team led by Debra Elmegreen, of Vasser College in New York, and her husband, Bruce, of IBM's Research Division at Yorktown Heights, reveal that the smaller galaxy, catalogued as IC 2163, is swinging past its dancing partner, NGC 2207, in an anti-clockwise direction, having made its closest approach some 40 million years ago.

The astronomers believe that IC 2163 does not have sufficient energy to completely escape the gravitational attraction of NGC 2207 and is destined to be pulled back and forth to bring them closer together. Eventually, the two will collide in slow motion over a period of millions of years to form a much larger galaxy.

The near collision, in the direction of the constellation Canis Major, was captured by the Hubble camera with a high enough resolution to reveal the distinct dust lanes of the spiral arms of NGC 2207, silhouetted against IC 2163 in the background.

Large concentrations of gas and dust in both galaxies are believed to be the centres that will eventually erupt into regions of active star formation.Astronomers believe similar events helped our own spiral galaxy, the Milky Way, to form from the coalescence of smaller stellar clusters.

The Astronomer Royal, Review, page 9