This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Dark matter could be a type of matter in the universe that does not emit, absorb or reflect detectable light and appears to interact very weakly with regular matter. Although physicists have observed gravitational effects attributed to dark matter, they have not yet been able to determine what it is made of.
One hypothesis is that dark matter consists of particles that sometimes annihilate, meaning that when two meet, they transform into other particles. Some hypothetical dark matter particles are predicted to produce gamma rays (i.e., a highly energetic form of light) during this process. A hint of these particles' presence could be an unusual concentration of gamma rays at a particular energy, instead of a smooth spread across different energies.
Such a concentration, called a gamma-ray line, might be detectable toward the center of our galaxy, the Milky Way, where dark matter is thought to be especially dense. The H.E.S.S. (High Energy Stereoscopic System) Collaboration, a large group of researchers at institutions worldwide, recently searched for a gamma-ray line using observations collected by the collaboration's array of telescopes in Namibia. These telescopes detect flashes of light produced when incoming gamma rays strike Earth's atmosphere.
The results of this research, published in a paper in Physical Review Letters, did not yield a convincing dark matter signal but set new limits on the possible annihilation of proposed dark matter particles. "Dark matter in the form of elementary massive electroweak particles (WIMPs) is among the most favored candidates to explain dark matter in the universe, from astrophysical to cosmological scales," Emmanuel Moulin, a researcher with the H.E.S.S. Collaboration, told Phys.org.
"After looking for WIMPs for more than two decades in the center of the Milky Way, long acknowledged as the most promising target to detect WIMPs via their self-annihilation in very-high-energy (E>100 GeV) gamma rays, the H.E.S.S. observatory acquired enough data to probe the relevant annihilation cross section of WIMPs." The H.E.S.S. Collaboration is the international research team that operates the H.E.S.S. system and analyzes its data. The system is an array of imaging atmospheric Cherenkov telescopes (IACTs) located in Namibia, in southern Africa.
"The data we analyzed consist of Cherenkov flashes of light generated by particles traveling faster than the speed of light in Earth's atmosphere," explained Alessandro Montanari, a researcher with the H.E.S.S. "These particles arrive in cascades, or showers, initiated by high-energy photons from the universe. With this technique, we could observe the most energetic phenomena, such as what we believe could happen when two dark matter particles annihilate promptly into two high-energy photons—what we call a spectral line from dark matter annihilation." Moulin, Montanari and their colleagues analyzed 546 hours of observations collected by the H.E.S.S. telescopes between 2014 and 2020, covering the region around the center of the Milky Way.
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