Explanation:
What is the largest structure known?
The answer might depend on how one defines "structure."
A grouping of galaxies known as the
Sloan Great Wall
was discovered in the
Sloan Digital Sky Survey and is a
leading candidate.
The Sloan
Great Wall can be seen in this
digitally recast contour map of galaxies in the
Two Degree Field galaxy survey.
Galaxies within one billion
light
years, a
redshift of about 0.1, are depicted.
The labeled Sloan Great Wall spans over one billion light years,
longer than any structure ever measured.
Critics worry that the
Sloan Great Wall should not itself be
characterized as a coherent structure because it is not
currently gravitationally bound
together and parts of it might never become gravitationally bound.
Regardless, the beauty of the
local universe of galaxies
is evident in the image where several huge
superclusters
of galaxies --
clusters of galaxy clusters -- can also be seen.
These include the
Shapley
Supercluster of galaxies, part of the Pisces-Cetus Supercluster,
and part of the Horologium-Reticulum Supercluster.
