Researchers have been creative in trying to trace the elusive cosmic web, the large-scale backbone of the cosmos.
They turned to slime mould (Physarum polycephalum), a single-cell organism found on Earth, to help astronomers build a map of the filaments in the local universe (within 500 million light-years from Earth) and find the gas within them.
Inspired by the organism’s behavior, they designed a computer algorithm and applied it to data containing the positions of 37,000 galaxies (“food” for the slime mould) mapped by the Sloan Digital Sky Survey. The algorithm produced a three-dimensional map of the underlying cosmic web’s intricate filamentary network, the purple structure in the image.
The three sets of inset boxes show some of those individual galaxies that were “fed” to the slime mould and the filamentary structure connecting them.
The galaxies are represented by the yellow dots in three of the inset images. Next to each galaxy snapshot is an image of the galaxies with the cosmic web’s connecting strands (purple) superimposed on them.
The cosmic web consists primarily of a mysterious substance known as dark matter and is also laced with low-density gas.
Dark matter cannot be seen, but it makes up the bulk of the universe’s material. The web provides the cosmic scaffolding upon which galaxies are built, and the gas within the web provides the fuel out of which galaxies form new stars.
The research team noted a striking similarity between how the slime mould builds complex filaments to capture new food, and how gravity, in shaping the universe, constructs the cosmic web strands between galaxies and galaxy clusters.
After using their algorithm to find the cosmic web filaments, the astronomers used archival observations from the Hubble Space Telescope to detect and study the gas permeating the web.