For the first time, astronomers have found direct evidence that the Universe is filled with a giant web-like structure of dark matter, arrayed in vast filaments between the galaxies.
A team including Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) researchers Norbert Werner and Aurora Simionescu and led by Jorg Dietrich of the University of Michigan, has presented evidence for the first detection of the presence of a cosmic web filament.
The filament in question stretches between two large galaxy clusters, known as Abell 222 and 223. The team's evidence for a filament is two-fold, according to the study published in the journal Nature.
On one hand, they were able to reconstruct the mass distribution of the two clusters and the region in between them using the technique of weak gravitational lensing.
Weak lensing is where a concentration of mass subtly distorts the observed shapes of background objects because of the way matter bends light.
In the case of the current measurement, weak lensing observations revealed that the mass distribution included an overdense filament between the two clusters.
From the X-ray data, they estimate that the mass of this collection of hot ordinary matter in the filament is about 6 trillion times the mass of the Sun.
Even so, it is only a tiny fraction of the total mass of the filament, which they estimate from the measurements to be ten or more times that, so that 90 per cent or more of the filament mass is in the form of dark matter, consistent with predictions that the cosmic web filaments are entirely dominated by dark matter, according to KIPAC statement.
"Actually observing the structure of the cosmic dark matter web would be a stunning confirmation of our current understanding of dark matter and dark energy over the history of the Universe, and could open the door to much deeper understanding going forward," researchers said.
Any observation of the web has evaded astronomers, until now. This observation is confirmation that a filament of dark matter exists between two massive galaxy clusters.
In the past 15 years, a remarkable consensus has emerged that the Universe is completely dominated by unseen dark matter and dark energy.
Linear filaments of dark matter stretch across the enormous distances between galaxy clusters, and where the filaments intersect mass is concentrated and galaxy clusters form and grow from ordinary matter.
The cosmic web structure arises due to the way that dark matter particles swarm together because of their gravitational attraction combined with the pull of the ever-expanding Universe.