Astronomy: Allegedly First Direct Evidence of Dark Matter

A Japanese astronomer has allegedly achieved the first direct detection of dark matter, or at least what is currently the most convincing candidate. Tomonori Totani from the Department of Astronomy at the University of Tokyo reports this in a scientific paper and in statements to the media. He claims to have discovered the trace in data from NASA's Fermi Gamma-ray Space Telescope. The telescope detected particularly high-energy gamma radiation from a halo-like structure in the direction of the Milky Way center, which fits very well with what dark matter should produce. However, the claim is already facing criticism, and Totani admits that alternative explanations cannot be ruled out.

First Doubts

As explained by the university, the radiation detected by the space telescope is consistent with emissions that should arise if dark matter consists of weakly interacting particles or WIMPs (from "Weakly Interacting Massive Particles"). These would produce the high-energy gamma radiation when they annihilate each other. At the same time, the observed radiation "cannot be easily" explained by other astronomical phenomena, Totani says. If this proves to be correct, "then it would be the first time humanity has 'seen' dark matter," he explains. His work has been published in the Journal of Cosmology and Astroparticle Physics.

While Totani is convinced that he has found the first direct emissions of dark matter in the space telescope's data, there is already opposition. Speaking to Gizmodo, physicist Dan Hooper of the University of Wisconsin-Madison, for example, has pointed out that the space telescope's data has already been analyzed by many others. No one has classified the radiation as what his Japanese colleague has now done. He is not convinced. An anonymous researcher from Fermilab has acknowledged that the energy of 20 gigaelectronvolts is indeed very high. However, such radiation has already been found without being attributed to dark matter.

However, Totani's finding apparently fits with work presented just a month ago, which was led by the Leibniz Institute for Astrophysics Potsdam (AIP). Simulations conducted there have suggested that diffuse gamma-ray emission from the center of the Milky Way could provide the long-sought experimental evidence for dark matter. This also involved radiation that the Fermi space telescope has found and which originates from a halo of the Milky Way that is presumed to consist of dark matter. However, this long-known "gamma-ray excess" could also be due to ultradense neutron stars.

The question about the nature of dark matter is currently one of the most important in fundamental physics. Its existence has been postulated based on astronomical observations where stellar movements were measured that cannot be sufficiently explained by known matter and its gravity. Overall, there should be five times more dark matter in the cosmos than ordinary matter. Even more is attributed to the equally enigmatic dark energy. Currently, particles that could constitute dark matter are being searched for in various ways. For example, the "Light through the Wall Experiment" ALPS II at the German Electron Synchrotron (DESY) in Hamburg is pursuing exactly this goal.

(mho)