“Found” –Primordial Filaments from Big Bang Hiding Half the Missing Matter of the Universe


Filaments of the Cosmic Web


A gas filament with a length of 50 million light years –unfathomably large thread-like structures of hot gas that surround and connect galaxies and galaxy clusters–has been observed by astronomers at the University of Bonn for the first time Its structure is uncannily similar to the predictions of recent computer simulations.

“A Tiny Aberration”

We owe our existence to a tiny aberration, reports the University of Bonn. Over the course of 13 billion years, since the Big Bang, “a kind of sponge structure developed: large ‘holes. without any matter, with areas in between where thousands of galaxies are gathered in a small space, so-called galaxy clusters, that should still be connected by remnant filaments of the primordial gas, like the gossamer-thin threads of a spider web.

“According to calculations, more than half of all baryonic matter in our universe is contained in these filaments—this is the form of matter of which stars and planets are composed, as are we ourselves,” explains Dr. Thomas Reiprich from the Argelander Institute for Astronomy at the University of Bonn. Yet it has so far escaped our gaze: Due to the enormous expansion of the filaments, the matter in them is extremely diluted: It contains just ten particles per cubic meter, which is much less than the best vacuum we can create on Earth.”

Gargantuan Filaments Fueled the Universe We See Today

In contrast to earlier belief that galaxies formed and then organized into clusters, in a bottom-up way, it is now generally believed that gargantuan filaments in the universe fueled the formation of clusters of galaxies and galaxies at places where the filaments crossed, creating dense regions of matter.

2019 research from the RIKEN Cluster for Pioneering Research and the University of Tokyo –used observations from the Multi Unit Spectroscopic Explorer (MUSE) at the ESO Very Large Telescope (VLT) in Chile and the Suprime-Cam at the Subaru telescope to make detailed observations of the filaments of gas connecting galaxies in a large, distant proto-cluster in the early Universe.–suggests that gas falling along massive filaments under the force of gravity in the early universe triggered the formation of starbursting galaxies and supermassive black holes, giving the universe the structure that we see today.

“Gargantuan Filaments” –Incubators of Supermassive Black Holes in Early Cosmos

Enter eRosita

With a new instrument, the eROSITA space telescope, Reiprich and his colleagues were able to make the gas fully visible for the first time. “eROSITA has very sensitive detectors for the type of X-ray radiation that emanates from the gas in filaments,” explains Reiprich about galaxy cluster Abell 3391/95 –a system of three galaxy clusters, which is about 700 million light years distant. The eROSITA images show not only the clusters and numerous individual galaxies, but also the gas filaments connecting these structures. The entire filament is 50 million light years long. But it may be even more enormous: The scientists assume that the images only show a section.. “It also has a large field of view—like a wide-angle lens, it captures a relatively large part of the sky in a single measurement, and at a very high resolution.” This allows detailed images of such huge objects as filaments to be taken in a comparatively short time.


ERosita image of Cosmic Web

In this view of the eROSITA image (right; left again a simulation for comparison) the very faint areas of thin gas are also visible. Credit: left: Reiprich et al., Space Science Reviews, 177, 195; right: Reiprich et al., Astronomy & Astrophysics

Confirmation of the Standard Model

“We compared our observations with the results of a simulation that reconstructs the evolution of the universe,” explains Reiprich. “The eROSITA images are strikingly similar to computer-generated graphics. This suggests that the widely accepted standard model for the evolution of the universe is correct.” Most importantly, the data show that the missing matter is probably actually hidden in the filaments.

Source: T.H. Reiprich et al. The Abell 3391/95 galaxy cluster system. A 15 Mpc intergalactic medium emission filament, a warm gas bridge, infalling matter clumps, and (re-) accelerated plasma discovered by combining SRG/eROSITA data with ASKAP/EMU and DECam data, Astronomy & Astrophysics (2020). DOI: 10.1051/0004-6361/202039590

The Daily Galaxy, Max Goldberg, via University of Bonn

Image Credit: at the top of the page shows a detailed computer simulation of complex structure of the cosmic web. Long filaments of dark matter (blue) connect knots of galaxies and galaxy clusters (pink), while gas (orange) permeates throughout. By modeling and observing the cosmic web, researchers are gaining insights into the structure and evolution of the early universe. Courtesy of the Illustris Collaboration