Hawaii scientist maps ‘supercluster’ of galaxies, names it Laniakea

A slice of the Laniakea Supercluster in the supergalactic equatorial plane—an imaginary plane containing many of the most massive clusters in this structure. The colors represent density within this slice, with red for high densities and blue for voids—areas with relatively little matter. Individual galaxies are shown as white dots. Velocity flow streams within the region gravitationally dominated by Laniakea are shown in white, while dark blue flow lines are away from the Laniakea local basin of attraction. (Rendering: SDvision interactive visualization software by DP at CEA/Saclay, France)

The immense supercluster of galaxies that contains the Milky Way has a new name.

University of Hawaii at Manoa astronomer R. Brent Tully led an international team of astronomers in defining the contours of the supercluster. They named it “Laniakea,” meaning “immense heaven” in Hawaiian.

It is meant to honor Polynesian navigators who used knowledge of the heavens to voyage across the immensity of the Pacific Ocean.

The paper explaining this work is the cover story of the September 4 issue of the journal “Nature.”

According to scientists, galaxies are not distributed randomly throughout the universe. Instead, they are found in groups that contain dozens of galaxies, and in massive clusters containing hundreds of galaxies, all interconnected in a web of filaments in which galaxies are strung like pearls.

Where these filaments intersect are structures called superclusters. These structures are interconnected, but they have poorly defined boundaries.

Researchers are proposing a new way to evaluate the large-scale structures by examining their impact on the motions of galaxies. A galaxy between two such structures will be caught in a gravitational tug-of-war in which the balance of the gravitational forces from the surrounding large-scale structures determines the galaxy’s motion. By mapping the velocities of galaxies throughout our local universe, the team was able to define the region of space where each supercluster dominates.

The Milky Way resides in the outskirts of one such supercluster, whose extent has for the first time been carefully mapped using these new techniques. This Laniakea Supercluster is 500 million light-years in diameter and contains the mass of 1017 (a hundred quadrillion) suns in 100,000 galaxies.

This study clarifies the role of the Great Attractor, a problem that has kept astronomers busy for 30 years. Within the volume of the Laniakea Supercluster, motions are directed inwards, as water streams follow descending paths toward a valley. The Great Attractor region is a large flat bottom gravitational valley with a sphere of attraction that extends across the Laniakea Supercluster.

The name Laniakea was suggested by Nawa’a Napoleon, an associate professor of Hawaiian Language and chair of the Department of Languages, Linguistics, and Literature at Kapiolani Community College, a part of the University of Hawaii system.

Read the abstract on Nature.com (full article behind a paywall).

Click here to watch a short video about Laniakea.

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