Is dark matter responsible for our galaxy's glow?
What's the story
The center of our galaxy, the Milky Way, is home to a strange and diffuse glow that has baffled scientists for years. The light is emitted by gamma rays, a form of high-energy radiation usually associated with rapidly rotating or exploding stars. The Fermi Gamma-ray Space Telescope first observed this glow after its launch in 2008. Since then, it has fueled speculation about its origins.
Theories
Pulsars or dark matter?
Some astronomers think that pulsars, the rapidly spinning remnants of exploded stars, could be behind this galactic glow. Others have proposed that colliding particles of dark matter, an elusive and invisible substance thought to be five times more abundant than regular matter, could also be its source. However, the gamma ray glow's shape closely resembles that of the galactic bulge, a densely packed region at the center of our galaxy mainly composed of old stars, including pulsars.
Simulation findings
Recent simulations show dark matter collisions could explain the glow
Recent supercomputer simulations have shown that dark matter collisions could also be responsible for the bulge-shaped glow. This discovery lends credence to the dark matter theory. Joseph Silk, a professor of physics and astronomy at Johns Hopkins University and co-author of a study detailing these findings, said, "There's a 50% chance that it might be dark matter at this point." The study was published in Physical Review Letters.
Unsolved mystery
What is dark matter?
The existence of dark matter, first theorized by Swiss astronomer Fritz Zwicky in the 1930s and provided strong evidence through observations by American astronomers Vera Rubin and W. Kent Ford in the 1970s, has been a major problem in physics. They discovered that stars on the outskirts of spiral galaxies were moving too fast to be held together by visible matter and gravity alone. Despite decades of research, scientists have never directly observed this mysterious substance.
Distribution model
Mapping dark matter in Milky Way
Silk's study used supercomputers to map where dark matter should be in the Milky Way, based on its original formation. The previous models assumed a spherical shape for dark matter in our galaxy. However, Silk's simulation revealed that the central part of this invisible substance is actually squashed, more like egg-shaped. This matches closely with Fermi telescope data, suggesting a possible link between dark matter and gamma ray emissions at our galaxy's center.
Future prospects
What's next?
The Cherenkov Telescope Array Observatory (CTAO), a new instrument being built in Chile and Spain, will start returning data from 2027. It will detect gamma rays with much higher resolution than Fermi, potentially confirming whether gamma rays at the center of our galaxy are indeed a result of dark matter collisions. This could be a major breakthrough in the search for this elusive substance and provide evidence that some dark matter is made up of Weakly Interacting Massive Particles (WIMPs).