Map of the Boötes void
The Boötes void (sometimes also called "The Great Nothing") is an enormous region of space that contains few galaxies. It is located in the vicinity of the constellation Boötes, hence the name. Its center is located at approximately right ascension 14h 50m, declination 46°.
Details[]
The Boötes void is around 330 million light-years (236,000 megaparsecs) in diameter, or 0.27% of the diameter of the observable Universe. This makes the Boötes void one of the largest-known voids in the Universe, and is often referred to as a "supervoid". Its discovery was reported by Robert Kirshner in 1981, as part of a survey on galactic redshifts. The center of the Boötes void is around 700 million light years from Earth.
The void is not completely devoid of galaxies, as was shortly discovered. In 1987, J. Moody, Robert P. Kirshner, G. MacAlpine, and S. Gregory announced their findings of eight galaxies in the void, M. Strauss and John Huchra announced the discovery of a further three galaxies in 1988, and Greg Aldering, G. Bothun, Robert P. Kirshner, and Ron Marzke announced the discovery of fifteen galaxies in 1989. By 1997 there were 60 known galaxies in the Boötes void. Boötes void is the largest known void scientists have found.
According to astronomer Greg Aldering, the scale of the void is such that "If the Milky Way had been in the center of the Boötes void, we wouldn't have known there were other galaxies until the 1960s."
The Hercules Supercluster forms part of the near edge of the void.
So far, only 60 galaxies have been found in the Boötes void. Using a rough estimate of about 1 galaxy every 10 million light-years (4 times as far as Andromeda Galaxy from Earth), there should have been approximately 2,000 galaxies in the Boötes void.
Origins[]
There are no apparent inconsistencies between the existence of the Boötes void and the Lambda-CDM model of cosmological evolution. It has been theorized that this void may have been formed from the merging of smaller voids, much like the way soap bubbles coalesce to form large bubbles. This would account for the small number of galaxies that populate a roughly tube-shaped region running through the middle of the void.
Confusion with Barnard 68[]
The Boötes void is often associated with images of Barnard 68, a dark nebula that does not allow light to pass through; however, the images of Barnard 68 are much darker than those we observe of Boötes void, as the nebula is much closer and there are fewer stars in front of it, as well as being a physical mass that blocks light passing through.