By Ron Cowen
Talk about big-time mergers. In the infant universe, marauding galaxies devoured each other, coalescing to form bigger galaxies. These hostile takeovers spewed out truly hot commodities—gas and dust that could become the ingredients for nascent stars.
A similar process may still be unfolding. Whenever two galaxies come close enough, their mutual gravity rips long streamers of gas and dust from each other. Some of these so-called tidal tails may become galaxies in their own right, undertaking the same evolution that their ancestors did billions of years ago.