There are structures in the universe that are larger than individual galaxies. These structures are known as galaxy clusters, galaxy superclusters, and cosmic filaments. Let's explore each of them:
Galaxy Clusters: A galaxy cluster is a collection of galaxies held together by gravity. It consists of tens to thousands of galaxies bound in a relatively small region of space. Galaxy clusters can span several million light-years across and contain vast amounts of dark matter, hot gas, and individual galaxies. Examples of galaxy clusters include the Virgo Cluster and the Coma Cluster.
Galaxy Superclusters: Galaxy superclusters are even larger structures that contain multiple galaxy clusters. They are some of the largest known structures in the universe, stretching across hundreds of millions of light-years. Superclusters are interconnected by vast cosmic voids, which are regions of relatively low matter density. The Milky Way is part of the Laniakea Supercluster, which contains thousands of galaxies.
Cosmic Filaments: Cosmic filaments are elongated, thread-like structures that connect galaxy clusters and superclusters. They are formed by the gravitational pull of matter, including dark matter. These filaments can span hundreds of millions of light-years and are believed to be the scaffolding upon which galaxy clusters and superclusters form. The filaments, along with the voids, make up the large-scale cosmic web structure of the universe.
The existence and sizes of these structures are inferred through observational data gathered from telescopes and other instruments. Astronomers use various techniques to measure the positions, velocities, and distances of galaxies. By mapping the distribution of galaxies and their motions, they can identify patterns and structures at different scales, allowing them to understand the hierarchical organization of the universe.
Modern surveys, such as the Sloan Digital Sky Survey (SDSS) and the Planck satellite mission, have significantly contributed to our knowledge of large-scale structures in the universe. These observations, combined with computer simulations and theoretical models, help us comprehend the vast cosmic landscape beyond individual galaxies.