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EarthSky // Science Wire, Space Release Date: Sep 03, 2014

Astronomers define boundaries of our home supercluster and name it Laniakea

Our supercluster is 500 million light-years in diameter and contains the mass of a hundred million billion suns. Its new name is Hawaiian for “immense heaven.”

An international team of astronomers has defined the contours of the immense supercluster of galaxies that contains our own Milky Way. They have named the supercluster Laniakea, meaning immense heaven in Hawaiian. The name honors Polynesian navigators who used knowledge of the heavens to voyage across the immensity of the Pacific Ocean.

Galaxies are not distributed randomly throughout the universe. Instead, they are found in groups, like our own Local Group, 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, we find huge structures, called superclusters.

The superclusters appear to be interconnected, but the boundaries between them are poorly defined and not well understood. These astronomers have helped define the boundaries of our local supercluster.

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

Image credit: SDvision interactive visualization software by DP at CEA/Saclay, France.

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. The orange contour encloses the outer limits of these streams, a diameter of about 160 Mpc. This region contains the mass of about 100 million billion suns. Image credit: SDvision interactive visualization software by DP at CEA/Saclay, France.

R. Brent Tully, an astronomer at the University of Hawaii at Manoa, is the study’s lead researcher. He said:

We have finally established the contours that define the supercluster of galaxies we can call home. This is not unlike finding out for the first time that your hometown is actually part of much larger country that borders other nations.

This study also clarifies the role of the Great Attractor, a gravitational focal point in intergalactic space that influences the motion of our Local Group of galaxies and other galaxy clusters.

Within the boundaries of the Laniakea Supercluster, galaxy motions are directed inward, in the same way that 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 paper explaining this work is the cover story of the September 4 issue of the journal Nature.

According to what astronomers know now, the very early universe was more or less uniform as it expanded outward from the Big Bang.  But there were some areas of slightly higher density. And, over time, those areas of higher density became the superclusters.  Now -according to the most recent ideas about what the universe looks like - as we peer at the universe as a whole, it has this sort of

The very early universe was thought to be fairly uniform as it expanded outward from the Big Bang. But there were areas of slightly higher density. Over time, those denser areas drew matter to themselves. Now – according to modern ideas about what the universe as a whole looks like – the universe has this sort of “honey-comb” structure. The walls of the honeycomb are the superclusters of galaxies.

Bottom line: Astronomers at the University of Hawaii at Manoa have helped identify and define the boundaries of our local supercluster of galaxies. Our supercluster is 500 million light-years in diameter and contains the mass of a hundred million billion suns. Its new name is Laniakea, which is Hawaiian for immense heaven.

Read more about the study from the University of Hawaii