WIMPs and MACHOs ENCYCLOPEDIA OF ASTRONOMY AND ASTROPHYSICS

WIMP is an acronym for weakly interacting massive par-ticle and MACHO is an acronym for massive (astrophys-ical) compact halo object. WIMPs and MACHOs are two of the most popular DARK MATTER candidates. They repre-sent two very different but reasonable possibilities of what the dominant component of the universe may be. It is well established that somewhere between 90% and 99 % of the material in the universe is in some as yet undiscovered form. This material is the gravitational glue that holds together galaxies and clusters of galaxies and plays an important role in the history and fate of the universe. Yet this material has not been directly detected. Since extensive searches have been done, this means that this mysterious material must not emit or absorb appre-ciable electromagnetic radiation in any known wave