A temperature not seen since the first microsecond of the birth of the universe has been recreated by scientists, and they discovered that the event did not unfold quite the way they expected. The interaction of energy, matter, and the strong nuclear force in the ultra-hot experiments conducted at the Relativistic Heavy Ion Collider (RHIC) was thought to be well understood. However, a detailed investigation has revealed that physicists are missing something in their model of how the universe works. A recent paper detailing the findings appears in the journal Physical Review Letters.

“It’s the things you weren’t expecting that are really trying to tell you something in science,” says Steven Manly, associate professor of physics and astronomy at the University of Rochester and co-author of the paper. “The basic nature of the interactions within the hot, dense medium, or at least the manifestation of it, changes depending on the angle at which it’s viewed. We don’t know why. We’ve been handed some new pieces to the puzzle and we’re just trying to figure out how this new picture fits together.”

“They said, ‘This can’t be. You’re violating boost invariance.’ But we’ve gone over our results for more than a year, and it checks out.” —

The cosmic optical background (COB) is the visible light emitted by all sources outside of the Milky Way. This faint glow of light, which can only be observed using very precise and sophisticated telescopes, could help astrophysics to learn more about the origins of the universe and what lies beyond our galaxy.

Last year, physicists working at different institutes across the United States published the most precise COB measurements collected so far, gathered by the New Horizons spacecraft, an interplanetary space probe launched by NASA over a decade ago. These measurements suggested that the COB is two times brighter than theoretical predictions.

Researchers at Johns Hopkins University have recently carried out a theoretical study exploring the possibility that this observed excess light could be caused by the decay of a hypothesized type of dark matter particles, known as axions. In their paper, published in Physical Review Letters, they showed that axions with masses between 8 and 20 eV could potentially account for the excess COB flux measured by the New Horizons team.