Scientists Uncover Potential Dark Matter Signature in Milky Way

A significant breakthrough in the quest to understand dark matter may have emerged from recent research. Scientists suggest that a faint glow emanating from the center of the Milky Way could be a vital clue in confirming the existence of this elusive material. The findings, led by Moorits Muru from the Leibniz Institute for Astrophysics Potsdam, were published on October 16, 2023, in the journal Physical Review Letters.

Dark matter, which constitutes approximately 27% of the universe’s total matter, has long perplexed scientists due to its invisibility. It neither absorbs nor reflects light, making direct detection through telescopes impossible. Despite decades of research involving underground particle detectors and space observatories, no one has yet managed to observe dark matter directly.

Recent computer simulations from Muru’s team indicate that the distribution of dark matter near the Milky Way’s center may not conform to the expected spherical shape. Instead, the research suggests it is flattened, resembling an egg. This shape aligns closely with the pattern of gamma rays detected by NASA’s Fermi Gamma-ray Space Telescope, which first identified a broad, hazy glow of high-energy light in 2008. The glow extends across approximately 7,000 light-years and is significantly brighter than existing models can account for.

The gamma-ray emissions had previously prompted various theories. Some researchers speculated that the rays were the result of collisions between invisible dark matter particles known as WIMPs (Weakly Interacting Massive Particles). Others proposed that these emissions originated from millisecond pulsars, which are rapidly spinning neutron stars that emit beams of radiation. The pulsar hypothesis gained traction due to the flattened appearance of the gamma-ray glow, which mirrored the structure of the Milky Way’s dense core.

To examine these competing theories, Muru and his team utilized powerful supercomputers to simulate the formation of the Milky Way, incorporating billions of years of galactic collisions and mergers. Their simulations revealed that these violent events left deep “fingerprints” on the distribution of dark matter within the galaxy’s core. The results indicate that when accounting for this complex history, the dark matter halo takes on a flattened shape that better matches the observed gamma-ray emissions.

Muru remarked, “We’re showing that dark matter also has this flattened shape. So, it does match the [gamma-ray] excess much better than expected before.” This finding reinforces the possibility that dark matter is indeed a strong candidate for the source of the Milky Way’s mysterious gamma-ray glow. However, the researchers caution that the pulsar theory is not completely ruled out, as both scenarios now appear “essentially indistinguishable.”

If future observations confirm that the gamma-ray excess arises from dark matter collisions, it would provide the first indirect evidence for the existence of WIMPs. More definitive answers may arrive by the late 2020s, when the Cherenkov Telescope Array Observatory (CTAO) begins its operations. The observatory, which will have sites in Chile and Spain, aims to observe gamma rays at a higher resolution than the Fermi telescope, potentially allowing scientists to differentiate between emissions from pulsars and dark matter particles.

Muru also highlighted the potential for studying gamma-ray emissions from smaller dwarf galaxies orbiting the Milky Way, which contain dense pockets of dark matter. “That’s where we hope to measure the signal,” he stated. “We’re really looking forward to these observations.”

Despite the challenges, scientists remain convinced of dark matter’s existence. The ongoing search for direct detection continues to be both a frustrating and exhilarating endeavor in modern physics. “For some reason, it still eludes us,” Muru noted. “And I think the mystery makes it even more interesting.” As research progresses, the scientific community eagerly anticipates new discoveries that could shed light on one of the universe’s most profound mysteries.