The identification of dark matter remains one of the key unresolved issues of modern astrophysics and cosmology. This dark matter is the dominant form of matter in the universe (~23% of the cosmic total of matter and energy), yet it cannot be seen (hence the term "dark" used to describe it) nor has its nature or composition been determined. It comprises unknown particles or objects that exert a gravitational force but do not emit any detectable light. It is not composed of ordinary atoms (that is, protons, neutrons, and electrons). Astronomical observations have revealed vast halos of invisible matter that surround galaxies and galaxy clusters. Evidence of dark matter comes from its gravitational effects on bright objects, such as stars and galaxies, as revealed by measurements of their motions. Several possible candidates have been suggested, including neutralinos (a new subatomic particle posited by the theory of supersymmetry), axions (another hypothetical particle), and even primordial black holes. This Spotlight feature seeks to provide factual information about what is known about dark matter and highlights ongoing cosmological investigations that help to explain our universe.
Back
Spotlight Home Page
|
|
