Astronomers may have glimpsed dark matter through gamma-ray emissions detected by NASA's Fermi telescope. A study led by Tomonori Totani suggests these signals arise from colliding weakly interacting massive particles in the Milky Way. While promising, the findings require further verification to confirm dark matter's presence.
Dark matter, an invisible substance that influences galaxy formation, has puzzled scientists since Fritz Zwicky proposed its existence in 1933. Observing galaxies in the Coma Cluster moving faster than expected based on visible matter, Zwicky inferred an unseen mass providing extra gravity. Over decades, evidence like gravitational lensing in the Bullet Cluster has supported this idea, though direct detection has remained elusive.
Dark matter constitutes about 27% of the universe, compared to 5% ordinary matter, with the rest being dark energy. Unlike visible matter, it does not interact with light, making it hard to observe directly. Theories posit it consists of weakly interacting massive particles (WIMPs), larger than protons and capable of annihilating each other to produce gamma rays when they collide.
In a study published on November 25 in the Journal of Cosmology and Astroparticle Physics, Tomonori Totani, an astronomy professor at the University of Tokyo, analyzed data from NASA's Fermi Gamma-ray Space Telescope. He identified gamma rays with 20 gigaelectronvolts of energy forming a halo-like structure toward the Milky Way's center. "We detected gamma rays with a photon energy of 20 gigaelectronvolts... extending in a halolike structure toward the center of the Milky Way galaxy," Totani told Phys.org. "The gamma-ray emission component closely matches the shape expected from the dark matter halo."
Totani noted that stars form a disk in the galaxy, while dark matter is thought to surround it spherically, influencing the radiation pattern. The emissions align with predictions for dark matter annihilation, lacking easy explanations from known sources.
However, Totani emphasizes the need for independent verification, including checks against emissions from dwarf galaxies. If confirmed, this could reveal a new particle beyond the Standard Model, reshaping fundamental physics and aiding understanding of dark energy, which accelerates cosmic expansion. "If correct, the true nature of dark matter, long the greatest mystery in cosmology, has been revealed," Totani said.