A study led by Przemek Mróz and colleagues analyzed 78.7 million stars in the Large Magellanic Cloud (LMC) over 20 years using the Optical Gravitational Lensing Experiment (OGLE) to search for long-timescale gravitational microlensing events. They found no events lasting more than a year, ruling out the presence of massive black holes in the Milky Way's dark matter halo. The results show that compact objects in the mass range 1.8×10⁻⁴ M☉ to 6.3 M☉ cannot make up more than 1% of dark matter, and those in the range 1.3×10⁻⁵ M☉ to 860 M☉ cannot exceed 10%. This conclusively rules out primordial black holes as a dominant source of gravitational waves. The study also found that all detected microlensing events can be explained by known astrophysical objects in the LMC or Milky Way disk. The results provide tight constraints on the abundance of primordial black holes in the Milky Way and LMC halos, with 95% upper limits on their contribution to dark matter. The findings suggest that the Milky Way's dark matter halo is not composed of massive black holes, and that the observed microlensing events are due to known stellar populations. The study also highlights the importance of long-term photometric observations in constraining dark matter models.A study led by Przemek Mróz and colleagues analyzed 78.7 million stars in the Large Magellanic Cloud (LMC) over 20 years using the Optical Gravitational Lensing Experiment (OGLE) to search for long-timescale gravitational microlensing events. They found no events lasting more than a year, ruling out the presence of massive black holes in the Milky Way's dark matter halo. The results show that compact objects in the mass range 1.8×10⁻⁴ M☉ to 6.3 M☉ cannot make up more than 1% of dark matter, and those in the range 1.3×10⁻⁵ M☉ to 860 M☉ cannot exceed 10%. This conclusively rules out primordial black holes as a dominant source of gravitational waves. The study also found that all detected microlensing events can be explained by known astrophysical objects in the LMC or Milky Way disk. The results provide tight constraints on the abundance of primordial black holes in the Milky Way and LMC halos, with 95% upper limits on their contribution to dark matter. The findings suggest that the Milky Way's dark matter halo is not composed of massive black holes, and that the observed microlensing events are due to known stellar populations. The study also highlights the importance of long-term photometric observations in constraining dark matter models.