When the Universe was 'spongy'

Paranal probed very faint and distant galaxies

By BBC News Online science editor Dr David Whitehouse

New observations are supporting recent computer models that suggest the early Universe was "spongy", with galaxies forming along filaments, like droplets on a spider's web.

We have little doubt that ... we are seeing here a small cosmic filament in the early Universe

Palle Møller, ESO

Astronomers determined the distances to some very faint galaxies in the neighbourhood of a distant quasar - a very bright distant object thought to be a massive black hole swallowing matter - and plotted their positions on a three-dimensional map.

They found that the faint galaxies were located along narrow strands or filaments, as predicted by present theories for the development of the first structures in the Universe.

The scientists, who have been working with the Paranal Observatory in South America, say their observations show the way forward in the study of the early evolution of the Universe and, in particular, the structures that emerged soon after the Big Bang.

Computers first

For the past two decades, theoretical cosmologists have been in advance of their observational colleagues because of the rapid development of powerful computers.

With them, they have been able to construct "virtual universes", starting with slightly different initial conditions just after the Big Bang.

The new class of telescopes can see the required distance

But such computer simulations have little value unless they are compared with the way the Universe actually works, and nowhere is that comparison more important than with the large-scale structure of the cosmos.

Until recently, however, telescopes were not powerful enough to observe the extremely faint objects that would test computer predictions. The advent of giant telescopes, of the 8-10-metre class, has changed all that.

All recent computer simulations of the early Universe have one prediction in common: the first large-scale structures to form were long filaments connected at their ends by "nodes". The models typically look like a three-dimensional spider's web, or perhaps the neuronal structure of a brain.

Beads on a string

It is believed that the first galaxies would have formed inside the threads of the web. When they started emitting light, they would have been seen to mark out the otherwise invisible threads, much like beads on a string.

In the course of millions and billions of years, those early galaxies would stream along these threads, towards and into the "nodes". This is where galaxy clusters would be formed later.

Computer models have predicted the early structure

Recent observations, with the European Southern Observatory's (ESO) Very Large Telescope at Paranal, of a region around a quasar, whose light set off when the Universe was only 15% of its present age, have now identified a string of galaxies that map out a tight filament in the early Universe.

One of the researchers involved, Palle Møller, is excited by the finding. "We have little doubt that, for the first time, we are seeing here a small cosmic filament in the early Universe," he said.

"At this enormous distance, we see it at a time when the Universe was only about two billion years old. This is obviously in agreement with the predictions by the computer models of a web-like structure, lending further strong support to our current picture of the early development of the Universe in which we live."