A new study reveals that magnetic fields in the early universe were likely billions of times weaker than those of a small fridge magnet.
According to an international team of researchers, the strength of these early magnetic fields was similar to the magnetism produced by human brain neurons.
The researchers traced the subtle influence of “primordial magnetic fields” on the cosmic web, the vast, filamentary structure connecting galaxies.
The International School for Advanced Studies in Trieste led the study, collaborating with the Universities of Hertfordshire, Cambridge, Nottingham, Stanford, and Potsdam.
Use of computer simulations
The cosmic web is a dominant feature of the universe, yet its pervasive magnetization has long puzzled scientists.
It’s a puzzle why the vast, empty areas of the cosmic web are magnetized, since this phenomenon is only expected to occur near galaxies.
“Our hypothesis was that this could be a legacy of events occurring in cosmic epochs during the birth of the universe, and that magnetism was linked essentially to physical processes in the primordial universe,” explained Mak Pavičević, a SISSA Ph.D. student and lead author of the research.
“For example, the filaments would have become magnetized during the inflation process before the so-called ‘Big Bang’ or through events in later epochs, called phase transitions,” Pavičević added.
The international team ran over 250,000 computer simulations to test this ambitious hypothesis.
Vid Iršič from the University of Hertfordshire described it as “the most realistic and largest suite of state-of-the-art simulations of the influence of the primordial magnetic field on the intergalactic cosmic web.”
The team then compared the simulations with observational data.
The study confirmed a key finding: incorporating the effects of ancient, incredibly weak magnetic fields leads to a more accurate model of the cosmic web.
It demonstrated that a standard model of the universe containing a primordial magnetic field of approximately 0.2 nano-gauss fits—a unit of magnetic induction—fits the experimental data best.
This finding validates their hypothesis that the magnetism seen in the cosmic web, even in sparsely populated regions, is a direct legacy of events from the very early universe.
Limits on intensity
The study also established a low value for the early magnetic field intensity – a new upper limit several times lower than previous estimates.
“Our research thus places strict limits on the intensity of magnetic fields formed in the very early moments of the universe and is consistent with recent results obtained in independent data and studies on the cosmic microwave background,” the researchers wrote.
This discovery will improve the understanding of the early universe.
These nearly imperceptible primordial magnetic fields, despite their weakness, would have played a key role in the universe’s development.
The primordial magnetic fields likely increased the cosmic web’s density, which would have sped up the formation of stars and galaxies, thereby influencing the universe’s current structure.
The James Webb Space Telescope can further validate the findings.
The research also holds important implications for various theoretical models seeking to explain the formation of cosmic structures.
The study was published in the journal Physical Review Letters.