A recent study has provided a breakthrough explanation for why the Milky Way’s neighboring galaxies are moving away from it, while another is hurtling towards us at a speed of 68 miles per second. Researchers discovered that a vast, flat sheet of dark matter surrounding our galaxy and Andromeda is drawing them into deep space, counteracting their gravitational attraction to the Local Group.
The study used simulations to model the interactions among dark matter, visible matter, and galaxies in the Local Group. The researchers found that this “flat” mass distribution explains why Andromeda is moving towards us, while most other nearby galaxies are receding from us. The sheet of dark matter anchors and attracts visible matter, overpowering the attraction between our galaxy and other neighboring galaxies.
The study also revealed that regions above and below the sheet are devoid of galaxies, with sparse areas forming deep Local Voids that expanded faster than average. This led to a concentration of material in the “walls” separating these voids, supporting the model’s accuracy in reconciling experimental results with astronomical observations.
Source: https://www.livescience.com/space/cosmology/every-major-galaxy-is-speeding-away-from-the-milky-way-except-one-and-we-finally-know-why