Knowra Giant Void Giant Void A giant void is an immense region of the universe with far fewer galaxies than surrounding structures. Its low density reflects the large-scale distribution of matter, not a complete absence of matter.
Cosmic web : The universe’s large-scale network of galaxy filaments, clusters, and intervening voids. Voids are the underdense spaces within this network.
Boötes Void : A large cosmic void in the direction of the constellation Boötes, identified in the 1980s. It is the best-known example of a giant void.
Void finder : An algorithm that identifies underdense regions in a galaxy catalogue or matter distribution. Different finder methods define the boundaries and sizes of giant voids.
Supervoid : An exceptionally large cosmic underdensity, whose exact definition depends on the structure-identification method. The term often describes the largest candidate voids, including some with disputed significance.
Gravitational instability : The growth of density differences as gravity attracts matter toward initially denser regions. Matter flows away from underdense regions toward denser structures, enlarging voids.
Eridanus Supervoid : A proposed large underdense region in the direction of the constellation Eridanus. It became widely discussed as a possible explanation for the CMB Cold Spot.
Redshift-space distortion : An apparent distortion of cosmic structure caused by galaxy motions affecting measured redshifts. Void galaxy motions produce characteristic distortions used to study gravity and expansion.
Galaxy cluster : A gravitationally bound system containing many galaxies, hot gas, and dark matter. Clusters are dense structures that voids lack and toward which surrounding matter flows.
Dark energy : The name for the unknown cause of the universe’s accelerated expansion. Accelerated expansion affects how quickly large-scale structure, including voids, evolves.
Local Void : A nearby underdense region adjoining the Local Group and the Local Sheet of galaxies. Its gravitational influence contributes to the motions of nearby galaxies.
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