THE SHAPE OF THINGS TO COME

摘要

Galaxies are just for starters. Say goodbye to the Universe as we know it, says Stuart Clark. Galaxy clusters are the largest objects in the Universe, so huge that individual galaxies are only specks of light within them. You wouldn't want our Galaxy to bump into one on a dark night. But that, it seems, is what fate has in store for us.Images from two new telescopes show that clusters are colliding, and in the process they are avidly consuming each other and all the matter around them. Once they have finished, astronomers believe, we will be in a very different-looking Universe from the one we see now— a Universe inhabited by a new race of giants called superclusters.That is a profound change from the status quo. For most of the 15 billion years since the big bang, the basic cosmic building blocks have been galaxies. These huge aggregations of dust and gas today hold anything from a million to more than a trillion stars. Our own Galaxy is a light heavyweight, holding around a hundred billion stars in a many-armed spiral about 50,000 light years across.