Deep in the heart of our galaxy, there is a faint but powerful glow that has puzzled scientists for more than a decade. Detected by NASA’s Fermi Gamma-ray Space Telescope, this glow is made of high-energy radiation called gamma rays, often linked to explosive cosmic events like dying stars. But this glow doesn’t fit the usual pattern. It sits in a diffuse, bulging shape at the Milky Way’s centre, suggesting something else might be at play. Astronomers have long debated whether the source is a cluster of old, fast-spinning stars or something far more elusive, dark matter, the mysterious substance thought to make up most of the universe.
The puzzling glow at the heart of the Milky Way
Back in 2008, when the Fermi telescope began sending back data, scientists noticed something unusual: a bright, central glow of gamma rays coming from the middle of our galaxy. Normally, gamma rays are produced when stars explode or when high-energy particles collide, but the intensity and shape of this glow didn’t quite match known patterns.For years, researchers have debated two main theories. One points to pulsars, which are the fast-spinning remains of massive stars that exploded long ago. These objects release strong beams of radiation and could, in theory, create the glow seen by Fermi. The other theory focuses on dark matter, an invisible form of matter that does not emit light but is believed to make up about 85 percent of all matter in the universe.The shape of the glow has long supported the pulsar theory, as it follows the “galactic bulge”, a dense area filled with old stars. If the glow were caused by dark matter, scientists expected it to appear more evenly spread and spherical. Yet, the mystery has persisted because there are not enough observed pulsars to explain the intensity of the light.
New simulations shift the focus back to dark matter
A recent study published in Physical Review Letters has brought new attention to the dark matter theory. Using advanced supercomputer simulations, researchers have shown that collisions between dark matter particles could also create the same bulge-like glow seen in Fermi’s data.This study relied on what is known as the Hestia simulation, a detailed model of how galaxies like the Milky Way evolve over billions of years. It suggests that dark matter in our galaxy might not be smoothly distributed but instead clumped together in a slightly uneven, nonspherical shape. When particles of dark matter, possibly Weakly Interacting Massive Particles (WIMPs), collide, they annihilate each other, releasing gamma rays.The shape of the glow produced in these simulations matched what astronomers have observed in the Milky Way, offering a fresh explanation that supports the dark matter hypothesis. One of the study’s co-authors, astrophysicist Joseph Silk, described the situation as evenly balanced between both theories. In his words, there is roughly a fifty percent chance that dark matter, and not pulsars, is the cause.
The long search for dark matter particles
Dark matter has remained one of the biggest mysteries in modern science. It was first proposed in the 1930s by Swiss astronomer Fritz Zwicky, and later confirmed indirectly in the 1970s when Vera Rubin and W. Kent Ford found that stars at the edges of galaxies were moving too fast to be held. together by visible matter alone. Something unseen, dark matter, was providing the missing gravity.But despite decades of research, no one has yet observed dark matter directly. Scientists have built massive underground detectors, such as the LZ Dark Matter Experiment in South Dakota, to look for evidence of WIMPs. These particles are thought to barely interact with normal matter, making them almost impossible to detect.The challenge lies in their subtlety. WIMPs do not absorb or emit light, meaning they pass through everything, even our own bodies, without leaving a trace. Yet, if two WIMPs meet and destroy each other, they should release energy in the form of gamma rays, just like the ones seen at the Milky Way’s centre. This makes gamma-ray studies one of the best indirect ways to search for dark matter.
What the new findings could mean for the future
The new simulation results do not end the debate, but they do make things far more interesting. If future research confirms that dark matter is behind the galactic glow, it would mark one of the most important discoveries in physics. It would finally provide proof of a substance that scientists have been hunting for nearly a century.Upcoming instruments like the Cherenkov Telescope Array will be able to study gamma rays at even higher energies and with greater accuracy. This could help distinguish whether the glow comes from pulsars or from dark matter collisions. If the radiation shows patterns more consistent with dark matter annihilation, it would be a major step forward in understanding how the universe is built.But if pulsars are confirmed as the true source, that too would be a meaningful result. It would expand our understanding of how stars age and die in dense regions of galaxies. Either way, the outcome will teach scientists something valuable about the forces shaping the cosmos.The mystery of the Milky Way’s central glow reminds us that even in the most studied parts of space, there is still much we don’t know. Whether the answer lies in ancient stars or invisible matter, each new finding brings us closer to understanding how galaxies, including our own, truly work.Also Read | Beyond the Moon: A closer look at Earth’s quiet asteroid companions
