The dark matter in our own galaxy is acting much more 'aggressive' than we expected, potentially collapsing into high-density cores.
April 15, 2026
Original Paper
Bypassed Core Formation in Milky Way-Mass SIDM Halos: Implications for the Local Group Past-Pericenter Scenario
arXiv · 2604.08647
The Takeaway
Most models of the universe predict that dark matter should form 'puffy' cores in the center of galaxies. But this paper reveals that the Milky Way’s gravity is so strong it can force dark matter to skip that puffy phase and collapse instantly into a high-density 'core.' This 'bypassed core formation' changes our entire map of where dark matter is hiding in our neighborhood. It’s like finding out the 'atmosphere' of our galaxy is much more concentrated and violent than we thought. This discovery will tell us exactly where to point our detectors to finally catch a dark matter particle, potentially ending the search for the universe’s most elusive substance.
From the abstract
We consider a scenario in which the Milky Way (MW) and M31 have had a previous pericentric passage, and investigate its compatibility with self-interacting dark matter (SIDM). Using initial conditions sampled from Local Group (LG) analogues in the IllustrisTNG simulation, we perform controlled re-simulations of the MW-M31 orbit, evolving the system under both standard cold dark matter (CDM) and various SIDM cross-sections. We find that the deep baryonic potential of the MW preconditions the halo