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.
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.
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.