Massive compact halo object
= Massive compact halo object
{title2=MACHO}
A compact astronomical object proposed as a constituent of a galactic <dark matter halo>. It can be sought through <gravitational microlensing> even if its emitted light is undetectable. Stellar objects and remnants consume the cosmological <baryon> budget; primordial <black holes> do not obey that particular formation-budget argument. Exclusion bounds depend on the object's <mass>, the halo model and survey selection.