The paired galaxies are only a few of the scores of galaxies visible in a vast galactic cluster; 13 of them are the big blob-shaped remnants of recent collisions or pairs of colliding galaxies. Astronomers have taken pictures of colliding galaxies before, but these are from a cluster that is 8 billion light-years away. This means what Hubble is ``seeing'' is light that began its journey 8 billion years ago, when the universe was perhaps half its current age.

A light-year is the distance light travels in a year, approximately 6 trillion miles (10 trillion km). And these galaxies are merging at a furious rate, according to Pieter van Dokkum, of Groningen and Leiden universities in the Netherlands, who headed the team studying this data.

``It has been a real surprise,'' van Dokkum said in the statement. ``Collisions had never been observed before at this frequency. Many of the collisions involve very massive galaxies, and the end result will be even more massive galaxies.''

The merging process can take less than a billion years, a relatively short period in cosmic terms.