Shapley Supercluster

The Shapley Supercluster is a dense concentration of galaxy clusters about 650 million light-years away in the direction of Centaurus. It is among the largest nearby concentrations of mass in the observable universe.

Galaxy cluster: A gravitationally bound system containing many galaxies, hot gas, and dark matter. The supercluster is made up of numerous galaxy clusters rather than one bound system.
Abell catalogue: A catalogue of rich galaxy clusters compiled from photographic surveys of the sky. Several prominent Shapley-region clusters were already catalogued as rich systems.
Galaxy: A gravitationally bound system of stars, stellar remnants, gas, dust, and dark matter. Galaxies are the luminous members grouped into the clusters that compose the supercluster.
Laniakea Supercluster: The supercluster-scale region containing the Milky Way and many neighboring galaxy groups. It is our home supercluster, while Shapley is a much more distant concentration beyond it.
X-ray astronomy: The study of celestial objects through the X-rays they emit. X-ray observations reveal the hot gas that marks and characterizes massive clusters in the region.
Peculiar velocity: An object's motion relative to the smooth expansion of the universe. The supercluster's gravitational pull contributes to the peculiar motions of galaxies in its vicinity.
George O. Abell: An American astronomer known for cataloguing galaxy clusters and studying large-scale structure. His cluster catalogue provided an early framework for recognizing rich concentrations in the region.
Intracluster medium: The hot, diffuse plasma filling the space between galaxies inside a galaxy cluster. Its X-ray emission helps astronomers identify and characterize clusters in the region.
Hydra-Centaurus Supercluster: A nearby concentration of galaxy clusters spanning the Hydra and Centaurus regions. It lies in the same broad southern-sky direction and is often discussed alongside Shapley.
Galaxy redshift: The shift of a galaxy's spectral lines toward longer wavelengths, commonly used to estimate its recession and distance. Redshifts distinguish the supercluster's distant members from foreground galaxies in the same direction.

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