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"Where in the universe is the Milky Way?

"Galaxies like ours huddle in clusters, and large-scale systems of galaxies, called superclusters, have vague boundaries that are difficult to define (especially from the inside): They’re all drawn to each other and interconnected in a web of filaments. Now for the first time, astronomers have constructed a map of the local universe. They’ve named our home supercluster Laniakea, Hawaiian for “immeasurable heaven.” The work was published in Nature this week.

"By examining the motions of galaxies, a team of cosmic map makers led by R. Brent Tully from the University of Hawaii charted the distribution of matter in the universe to identify superclusters. A galaxy stuck between two superclusters will be caught in a gravitational tug-of-war. The balance of these forces determines the galaxy’s motion, and measuring the velocity helps define the region of space where each supercluster dominates. With a catalog of 8,000 galaxies' velocities, the team built a galactic distribution map and located the points where cosmic flows -- along which galaxies travel -- diverge.

"The Laniakea supercluster, they found, is 520 million light-years in diameter and contains the mass of 100 million billion suns within 100,000 galaxies. Its name pays tribute to Polynesian navigators who used knowledge of the heavens to voyage across the Pacific Ocean."

Superclusters – regions of space that are densely packed with galaxies – are the biggest structures in the Universe. But scientists have struggled to define exactly where one supercluster ends and another begins. Now, a team based in Hawaii has come up with a new technique that maps the Universe according to the flow of galaxies across space.