MACHO (Massive Compact Halo Objects)

MACHOs, or Massive Compact Halo Objects, are hypothetical objects in space thought to contribute to the unseen mass in galaxy halos, affecting their gravitational pull. They include objects like black holes, neutron stars, brown dwarfs, or dense gas clouds—things that are difficult to see directly because they emit little or no light. MACHOs could help explain some of the universe's "missing" mass, but surveys like microlensing experiments suggest they don't make up enough of the total dark matter to account for all its effects. Thus, while they might contribute, they are unlikely to be the primary component of dark matter.