Excerpts from “Dark matter: The cosmic web” in Astronomy magazine:
” When astronomers examine the universe on relatively small scales, like nearby galaxies, the cosmic architecture follows no obvious pattern. But if one can step back and secure a big-picture view, a grander structure becomes evident. Detailed supercomputer simulations, guided by the most extensive galaxy surveys conducted to date, suggest that the universe assumes the form of a vast network, referred to as the “cosmic web,” composed of thread-like filaments that extend tens or hundreds of millions of light-years. These fibers branch off in different directions, intersecting in places (or nodes) where clusters containing hundreds or thousands of galaxies are situated.
The filaments act as giant funnels that direct dark matter, hot gas, and even whole galaxies, drawn by the tug of gravity, toward dense galaxy clusters. Scientists also regard them as key structural elements in the cosmos — the girders and struts that link clusters to create superclusters. Indeed, scientists think the majority of dark matter is confined to theses filaments. But if the bulk of matter is essentially imperceptible to humans — with its primary constituent being, well, dark — how could astronomers ever get direct confirmation that this elaborate filament foundation really exists?
..Looking ahead, one item on [Harald] Ebeling’s agenda is to attach himself, along with several colleagues, to the Hubble Space Telescope’s “Frontier Fields” program that initially intends to investigate three other galaxy clusters over the next couple years (Depending on those results, the program might add two more clusters.) “The purpose of this study is to focus on the cluster cores, not to search for filaments,” Ebeling says, “but we’d like to look around the neighborhood if at all possible.”
[Jorg] Dietrich, for this part, is anxiously awaiting results from the Dark Energy Survey, set to begin this year using the 4-meter Victor M. Blanco Telescope in Chile, which astronomers expect will see some 100,000 galaxy clusters, most of which aren’t currently known. “This is the first time we’re doing a survey of this scale in the Southern Himisphere, where people haven’t looked systematically before, and we’re bound to turn up good places to look for filaments,” he says. “