This is the MACHO hypothesis, which seems to have fallen somewhat out of favor since we can measure this to some extent and we can't find anything close to the

This is the MACHO hypothesis, which seems to have fallen somewhat out of favor since we can measure this to some extent and we can't find anything close to the required mass [1]. Although it is likely there is unaccounted regular matter, I think it is considered unlikely that this will account for the 85% of "missing matter" that we need, not in its entirety and likely not for a significant part of that either. You will need a humongous amount of brown dwarfs to compete with the regular stars and known (supermassive) black holes that are already in the known 15%. [1]: https://en.wikipedia.org/wiki/Massive_compact_halo_object https://en.wikipedia.org/wiki/Massive_compact_halo_object "A survey of gravitational lensing effects in the direction of the Small Magellanic Cloud and Large Magellanic Cloud did not detect the number and type of lensing events expected if brown dwarfs made up a significant fraction of dark matter."