The mystery of dark matter — the unseen substance thought to bind galaxies — has taken an exciting turn. Recent simulations suggest that a faint glow in the center of the Milky Way could be a key indicator of dark matter’s presence.
According to Moorits Muru from the Leibniz Institute for Astrophysics in Germany, the evidence is still hard to pin down, but the signs are promising. Dark matter, making up about 27% of the universe, doesn’t interact with light, so it can’t be seen directly through telescopes. Over the years, scientists have tried various methods, from underground detectors to space missions, but they’ve struggled to find it.
New computer simulations by Muru’s team reveal that dark matter near the Milky Way’s center might not be shaped like a perfect sphere, as previously thought. Instead, it appears flattened, resembling an egg. This egg shape aligns closely with mysterious gamma rays detected by NASA’s Fermi Gamma-ray Space Telescope.
In 2008, Fermi first noticed a puzzling glow of high-energy light extending about 7,000 light-years from the galactic core. The brightness of this signal was far beyond what existing models could explain. Some scientists suggest that these rays result from collisions of dark matter particles known as WIMPs (weakly interacting massive particles), while others think they might originate from ancient, spinning neutron stars called millisecond pulsars.
Interestingly, the pulsar theory made sense because its light pattern matched the flattened appearance of the galaxy’s center. If dark matter were responsible, scientists originally expected a smooth, round glow. Muru’s team set out to test both theories. They used advanced supercomputers to recreate the formation of the Milky Way, simulating billions of years of cosmic events.
The results were intriguing. The simulated dark matter didn’t form a spherical shape but instead showed flattened, egg-like patterns that echoed the gamma-ray emissions observed by Fermi. Muru noted, “This shows that dark matter has a flattened shape, matching the [gamma ray] excess better than we expected.”
This connection adds weight to the idea that dark matter might indeed be behind the glow, but it doesn’t entirely eliminate the pulsar hypothesis. Presently, both theories appear “essentially indistinguishable.” If the gamma rays arise from dark matter interactions, it could provide the first indirect evidence that WIMPs exist.
By the late 2020s, the Cherenkov Telescope Array Observatory (CTAO) will begin taking high-resolution gamma-ray observations. This may help distinguish the origins of the glow—whether from pulsars or dark matter particles. Muru is also optimistic about examining gamma rays from smaller dwarf galaxies around the Milky Way, which also host dense pockets of dark matter.
Many scientists believe dark matter’s existence is undeniable. The ongoing search remains one of modern physics’ most intriguing and frustrating challenges. Muru reflects, “It’s still eluding us, which makes it even more interesting.”
For further reading on this research, check out the study published in Physical Review Letters.
