This is a list of the largest cosmic structures so far discovered. The unit of measurement used is the light-year (distance traveled by light in one Julian year; approximately 9.46 trillion kilometres).
This list includes superclusters, galaxy filaments and large quasar groups (LQGs). The structures are listed based on their longest dimension.
The Local Supercluster (LSC or LS) is a supercluster of galaxies containing the Virgo Cluster and Local Group. The latter contains the Milky Way and Andromeda galaxies, among others. Sometimes referred to as Virgo Supercluster, the Local Supercluster is roughly centered on the Virgo Cluster, with the Local Group located near one edge and revolving around its center.
At least 100 galaxy groups and clusters are located within the supercluster diameter of 45 megaparsecs (147 million light-years; 1.39×10 kilometres). The Local Supercluster is one of about 10 million superclusters in the observable universe, with the main body of the supercluster, the Virgo Strand, connecting the Hydra-Centaurus and the Perseus–Pisces Superclusters. It is part of the Pisces–Cetus Supercluster Complex, a very large galaxy filament.
The Hercules–Corona Borealis Great Wall (HCB) or simply the Great Wall is a putative galaxy filament that, if confirmed, would be the largest known structure in the observable universe, measuring approximately 10 billion light-years in length (the observable universe is about 93 billion light-years in diameter). This massive superstructure is a region of the sky seen in the data set mapping of gamma-ray bursts (GRBs) that has been found to have a concentration of similarly distanced GRBs that is unusually higher than the expected average distribution. It was discovered in early November 2013 by a team of American and Hungarian astronomers led by István Horváth, Jon Hakkila and Zsolt Bagoly while analyzing data from the Swift Gamma-Ray Burst Mission, together with other data from ground-based telescopes. If confirmed, it would be the largest known formation in the universe, exceeding the size of the Huge-LQG by about a factor of two.
The overdensity lies at the Second, Third and Fourth Galactic Quadrants (NGQ2, NGQ3 and NGQ4) of the sky. Thus, it lies in the Northern Hemisphere, centered on the border of the constellations Draco and Hercules. The entire clustering consists of around 19 GRBs with the redshift ranges between 1.6 and 2.1.
A supercluster is a large group of smaller galaxy clusters or galaxy groups; they are among the largest known structures in the universe. The Milky Way is part of the Local Group galaxy group (which contains more than 54 galaxies), which in turn is part of the Virgo Supercluster, which is part of the Laniakea Supercluster, which is part of the Pisces–Cetus Supercluster Complex. The large size and low density of superclusters means that most of them, unlike clusters, expand with the Hubble expansion. The number of superclusters in the observable universe is estimated to be 10 million.
The Huge Large Quasar Group, (Huge-LQG, also called U1.27) is a possible structure or pseudo-structure of 73 quasars, referred to as a large quasar group, that measures about 4 billion light-years across. At its discovery, it was identified as the largest and the most massive known structure in the observable universe, though it has been superseded by the Hercules–Corona Borealis Great Wall at 10 billion light-years. Its existence has been disputed.
The Perseus–Pisces Supercluster (SCl 40) is one of the largest known structures in the universe. Even at a distance of 250 million light-years, this chain of galaxy clusters extends more than 40° across the northern winter sky. The Perseus–Pisces Supercluster is one of two dominant concentrations of galaxies (the other being the Laniakea Supercluster) in the nearby universe (within 300 million light-years). This supercluster also borders a prominent void, the Taurus Void, and is part of the Perseus–Pegasus Filament, which stretches for roughly a billion light years.
The Perseus–Pegasus Filament is a galaxy filament containing the Perseus–Pisces Supercluster and stretching for roughly a billion light-years (or over 300/h Mpc). Currently, it is considered to be one of the largest known structures in the universe. This filament is adjacent to the Pisces–Cetus Supercluster Complex.
The Shapley Supercluster or Shapley Concentration (SCl 124) is one of the largest concentrations of galaxies in the universe that forms a gravitationally interacting unit, thereby pulling itself together instead of expanding with the universe. It appears as a striking overdensity in the distribution of galaxies in the constellation of Centaurus. Its center is located roughly 650 million light-years away (z=0.046).
Latest observations suggest Shapley Concentration may contain the Laniakea (which in turn contains the Local Group, including the Milky Way) along with a few other nearby superclusters that are moving towards the structure.