Dark matter is the invisible scaffold of the universe. It doesn't shine, but its gravity holds stars in galaxies. In some models, dark matter particles can collide and exchange energy, like molecules in warm air. Then huge clouds of dark matter, called halos, start to behave like star clusters: heat flows from the center outward, the core contracts, and eventually collapses.
But real galaxies contain ordinary matter — gas and stars. When massive stars explode, they blast gas outward, puffing up and stirring everything around. This 'stellar wind' can heat and disperse the central part of a dark cloud, preventing it from collapsing. The authors of the new study ran a stress test: they numerically simulated how such violent feedback affects dark matter collapse.
The result was clear-cut. For very dense clouds, those where heat exchange is fast, collapse is only slightly slowed. It doesn't stop even with the most powerful explosions. For clouds of intermediate density, collapse can be delayed for billions of years, but as soon as stellar storms subside, it resumes. The final central density of such a cloud depends strongly on its violent history, explaining why galactic centers look different from galaxy to galaxy.
This strengthens the hypothesis about the nature of mysterious dark objects found via strong gravitational lensing of distant galaxies. They appear to be collapsed dark matter clouds — invisible but massive.
as written by the authors arXiv:2605.31335
We perform a stress test of gravothermal collapse in self-interacting dark matter (SIDM) halos under baryonic feedback using a semi-analytical oscillating-potential model in controlled N-body simulations. For high-concentration halos, where the SIDM thermalization timescale is short, gravothermal collapse is only mildly delayed and never stalled, even under extremely strong feedback. In contrast, the collapse of a median-concentration halo can be significantly delayed, but it resumes once feedback ceases. The final density profile of such halos depends sensitively on the episodic feedback history, producing a broad diversity in central densities. These results strengthen the interpretation of dense compact perturbers identified in recent strong-lensing observations as core-collapsed SIDM halos.
If dark matter could shine, its collapsed core would glow brighter than an entire galaxy, but only in 'dark light' that we can't see.
In Vernor Vinge's novel 'A Fire Upon the Deep,' dark matter is used for instantaneous communication across the galaxy — almost like an invisible web that in reality might collapse into dense knots.