Milky Way Lies in a Hidden Plane of Dark Matter
TL;DR
New simulations indicate the Milky Way sits inside a vast, flattened sheet of matter dominated by dark matter, extending tens of millions of light-years. This planar mass distribution helps explain why nearby galaxies mostly drift away rather than be drawn toward the Milky Way, matching the observed motions of over 30 neighboring galaxies. Further observations will show whether such cosmic sheets are common elsewhere and how they shape galaxy formation.
There's an enormous, invisible sheet of strange stuff surrounding our entire Galaxy BBC Sky at Night Magazine
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