If you could zoom in very far to look at the universe at its grandest scale, you would see that it is made up of one colossal colossal web. Now astronomers have detected shock waves moving through this network, providing new insights into large-scale magnetic fields.
When the universe was young, it was more or less uniform, with essentially the same matter and magnetic fields in all directions. But over time, the distribution of dark matter pulled matter towards it, forming a gigantic network of dense filaments containing galaxies and clusters, weaving between vast voids.
This cosmic web was first theoretically proposed in the 1960s, and its structure has been modeled in simulations beginning in the 1980s. More recently, astronomers have been able to map and watch the glow of its filaments.
In the new study, scientists from ICRAR and CSIRO successfully observed radio emissions from shock waves traversing the cosmic web. It hasn’t been easy, as the signals are extremely faint and difficult to distinguish from the background of all the other radio broadcasts constantly ringing across the universe.
So the team instead focused on a less common variation: polarized radio signals, which are produced in the cosmic web as a result of a cascade of processes. Regions of the network that are denser in matter will attract even more matter by gravity. When matter falls into these regions, it heats the gases there, which radiate outward in the form of shock waves. When these shock waves reach the extremely cold vacuums, this interaction emits radio polarized light.
The team used data from several projects and observatories, including the Global Magneto-Ionic Medium Survey, the Planck Legacy Archive, the Owens Valley Long Wavelength Array, and the Murchison Widefield Array. This allowed them to stack data from polarized radio emissions detected above known cosmic web clusters and filaments, showing that the detections were indeed coming from the web.
“As very few sources emit radio polarized light, our research was less prone to contamination and we were able to provide much stronger evidence that we see shock wave emissions in the largest structures in the universe. which helps confirm our models for the growth of this large-scale structure,” said Dr. Tessa Vernstrom, lead author of the study.
The team says these new observations will help astronomers understand how magnetism works at the largest scales in the universe.
The research was published in the journal Scientists progress. The team describes the work in the video below.
Polarized Shockwaves Shake the Cosmic Web