THE Universe used to be far more violent than it is today. At last week鈥檚
meeting of the American Astronomical Society in Austin, Texas, researchers from
Iowa State University in Ames showed that early galaxies smashed into each other
more often than astronomers realised.
If a small galaxy plunges through the centre of a spiral galaxy, the shock
transforms the spiral into a ring鈥攕imilar to the ripple that forms when a
rock falls into a pond. These ring galaxies were thought to be relatively
rare.
But Russ Lavery found 10 times as many ring galaxies as expected when he used
the Hubble Space Telescope to look at objects up to eight billion light years
away. 鈥淕alaxies were probably colliding with each other more frequently than in
the present day,鈥� says Lavery. This adds weight to the idea that large
elliptical galaxies formed when spiral galaxies collided.
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