Supervoid

A supervoid, also known as a cosmic void or a large void, is a vast region of outer space that contains very few galaxies. These are among the largest structures in the universe, extending hundreds of millions of light-years across. Supervoids are not truly empty but rather regions where the density of matter, including galaxies, dark matter, and gas, is significantly lower than the cosmic average. They are surrounded by denser regions of the universe, such as galaxy filaments and clusters.

The existence of supervoids is a prediction of the standard cosmological model, Lambda-CDM, which describes a universe dominated by dark energy and cold dark matter. These voids are thought to form as a natural consequence of the gravitational collapse of matter in the early universe. Denser regions attract more matter, leaving less material behind to form structures in intervening areas. Supervoids are often separated by walls or filaments of galaxies, forming a large-scale cosmic web.

The study of supervoids provides valuable insights into the distribution of matter in the universe and the nature of dark energy. By observing the distribution and evolution of galaxies within and around these voids, cosmologists can test and refine their models of the universe's expansion and structure formation. Some of the largest known supervoids include the Boötes Supervoid and the Hercules-Corona Borealis Great Wall, though the latter's status as a single supervoid is debated.