Mysterious dark matter may interact with cosmic ‘ghost particles’
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An illustration showing a dark matter halo around a spiral galaxy. | Credit: Robert Lea (created with Canva)
New research points to compelling new evidence that dark matter interacts with cosmic “ghost particles” called neutrinos. If so, then this interaction could pose a serious challenge to the Standard Model of cosmology, our current best model of the universe.
Neutrinos deserve their spooky nickname because when these chargeless, virtually massless particles travel through space at close to the speed of light, they barely interact with other particles, making their way through solid objects like planets. In fact, the interactions between these particles and other matter are so rare and fleeting that every second, about 100 trillion neutrinos pass through your body without you feeling anything. Dark matter is similar; Although it makes up about 85% of the matter in the universe, dark matter interacts very little, if at all, with ordinary matter and light. In fact, dark matter, effectively invisible, can only be inferred due to its interaction with gravity and its effect on light and conventional matter.
However, new findings from a team of researchers at the University of Sheffield suggest that there is a slight interaction, in the form of a minor exchange of momentum, between dark matter and neutrinos. This contradicts what is called “Cold dark matter Lambda (LCDM)” which attempts to explain the structure and evolution of the universe, according to which dark matter and neutrinos exist independently and do not interact with each other.
Evidence for this potentially paradigm-shifting suggestion comes from observations of the universe in its current state, conducted by the Dark Energy Camera of the Victor M. Blanco Telescope in Chile, galaxy maps created by the Sloan Digital Sky Survey, and details of the universe’s distant past collected by both the Atacama Cosmological Telescope (ACT) and the Atacama Space Telescope. European Space Agency (ESA) Planck Telescope spacecraft.
These observations revealed that the modern universe is less “lumpy” than it should be. This cosmic enigma could be explained by interactions between dark matter and neutrinos, which would impact how cosmic structures like galaxies form and evolve.
“Our results answer a long-standing enigma in cosmology. Measurements of the early universe predict that cosmic structures should have grown more strongly over time than we observe today,” team member Eleonora Di Valentino of the University of Sheffield said in a statement. “However, observations of the modern universe indicate that matter is slightly less clumped together than expected, indicating a slight lag between early and late measurements. This tension does not mean that the standard cosmological model is wrong, but it may suggest that it is incomplete.”
“Our study shows that interactions between dark matter and neutrinos could help explain this difference, providing new insight into how structure formed in the universe,” Di Valentino added.
The next step is to test this idea, which the team thinks is possible using precise observations from future telescopes of a cosmic fossil called the Cosmic microwave background (CMB), a remnant of an event that occurred in the universe shortly after the Big Bang. Astronomers could also test this theory using a specific effect that high-mass objects have on space, and therefore on light, a phenomenon called “gravitational lens“This would allow them to better measure the distribution of ordinary matter and dark matter.
“If this interaction between dark matter and neutrinos is confirmed, it would be a fundamental breakthrough,” said team member William Giarè from the University of Hawaii. “This would not only shed new light on a persistent mismatch between different cosmological probes, but also provide particle physicists with concrete direction, indicating which properties to look for in laboratory experiments to help finally unmask the true nature of dark matter.”
The team’s research was published January 2 in the journal Natural astronomy.
