Nearly 100 years ago, astronomer Fritz Zwicky made a strange discovery while studying the movement of galaxies.
He noticed that galaxies were moving far faster than their visible matter should allow. Something invisible seemed to be holding them together — an unknown form of mass that came to be called “dark matter.”
Since then, dark matter has remained one of the greatest mysteries in science.
Now, almost a century later, a researcher using data from NASA’s Fermi Gamma-ray Space Telescope believes we may finally be seeing signs of this invisible substance directly.
Dark matter cannot be seen with normal telescopes because it does not give off, block, or reflect light. In fact, it does not interact with normal matter in the same way as stars, planets, or gas do.
Scientists only know it exists because of the powerful gravitational pull it seems to exert on whole galaxies and clusters of galaxies. Without dark matter, galaxies would likely fly apart.
Many physicists believe dark matter may be made of unknown particles called “weakly interacting massive particles,” or WIMPs.
These particles would be heavier than protons but would rarely interact with anything, making them almost impossible to detect.
However, when two WIMPs collide, theory suggests they should destroy each other and release a sudden burst of energy in the form of gamma rays — the most energetic type of light in the universe.
For years, scientists have been scanning the sky for these specific gamma rays in places where dark matter is thought to be densest, such as the center of the Milky Way galaxy. Now, Professor Tomonori Totani at the University of Tokyo believes he has found exactly what they were looking for.
Using the latest data from the Fermi telescope, Totani detected gamma rays with an energy level of about 20 billion electron volts coming from a large, halo-shaped region around the Milky Way’s center. The shape and energy of this glow closely match what scientists would expect if dark matter particles were colliding and annihilating each other.
Even more exciting, the energy pattern matches predictions for WIMPs that are around 500 times heavier than a proton. The number of gamma rays detected also falls within the range that theoretical models had predicted.
According to Totani, this signal cannot be easily explained by other known causes such as exploding stars or black holes. That makes the dark matter interpretation especially strong.
“If this result proves correct,” Totani explained, “it would be the first time in history that humans have directly ‘seen’ dark matter.” He added that this would mean dark matter is made of a brand-new type of particle that does not exist in the current standard model of physics — a discovery that would completely reshape our understanding of the universe.
However, scientists are taking a cautious approach. Before declaring a true breakthrough, Totani’s findings must be checked by other researchers around the world. More observations are also needed to rule out any alternative explanation.
One important next step will be to look for the same type of gamma-ray signal in other dark-matter-rich locations, such as small dwarf galaxies orbiting the Milky Way. If the same pattern appears there too, it would provide much stronger evidence that the mysterious signals truly come from dark matter.
For now, the discovery offers a hopeful glimpse into something that has remained hidden for generations.
After nearly 100 years of searching, the invisible may finally be starting to reveal itself.
