Astrophysicist Professor Tomonori Totani of the University of Tokyo has claimed that gamma rays from the centre of the Milky Way could represent the first direct evidence of dark matter. The findings, published in the Journal of Cosmology and Astroparticle Physics, suggest that the signal matches predictions for radiation emitted by dark matter particles.
Dark matter, first proposed in the 1930s by Swiss astronomer Fritz Zwicky, is an invisible substance thought to make up 27% of the universe. It neither emits nor absorbs light but exerts gravitational pull on galaxies. Despite decades of searching, no direct detection has been confirmed.
Totani analysed data from Nasa's Fermi Gamma-ray Space Telescope and observed a pattern of gamma rays consistent with a dark matter halo around the galactic centre. He proposes that dark matter consists of weakly interacting massive particles (WIMPs) about 500 times heavier than a proton, which annihilate each other to produce gamma rays.
However, other scientists urge caution. Professor Justin Read of the University of Surrey noted that the lack of similar signals from dwarf galaxies argues against Totani's interpretation. Professor Kinwah Wu of University College London added that extraordinary claims require extraordinary evidence, and this analysis has not yet reached that standard.
Totani acknowledged that further work is needed to rule out other astrophysical processes. He said the decisive factor would be detecting the same gamma-ray spectrum from other regions, such as dwarf galaxies.
