Astronomers detect spatial fluctuations of dark matter in far Universe

Researchers have for the first time detected fluctuations in dark matter distribution in the Universe on scales less than 30,000 light-years - smaller than that of massive galaxies. The discovery paves the way for a deeper understanding of the true nature of dark matter - the invisible material that makes up a significant fraction of the Universe's mass.

Dark matter is believed to have played an important role in the formation of structures such as stars and galaxies. The invisible material is not uniformly distributed in space and its gravity can slightly change the path of light (including radio waves) from distant light sources - an effect called gravitational lensing. Past observations of this effect have shown that dark matter is associated with relatively massive galaxies and clusters of galaxies, but its distribution at smaller scales is unknown.

Led by Professor Kaiki Taro Inoue at Kindai University in Osaka, Japan, the research team utilized the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to observe a distant quasar, named MG J0414+0534 4, which lies about 11 billion light-years away from Earth. This quasar in question displays a rare quadruple image thanks to the gravitational lensing effects of a galaxy in the foreground.

However, the positions and shapes of these quasar images did not match the calculations based solely on the gravitational pull of the foreground galaxy, suggesting that there is another factor or influence at play.

This discrepancy was caused by the effects of dark matter on a smaller scale than that of large galaxies is significant. These findings not only confirmed but also enriched the theoretical model of cold dark matter, according to which, the clumps of dark matter are distributed not just within galaxies but also in intergalactic spaces.

While it is challenging to detect these tiny clumps of dark matter, the high-resolution capabilities of ALMA, coupled with the lensing effect of the foreground galaxy, enabled this discovery.