The Milky Way is part of a much vaster galactic network than previously thought. The galaxy drifts along in a stream of galaxies on the outskirts of a newly identified collection of galaxy clusters, a supercluster named Laniakea. This supercluster — whose name means “heaven immeasurable” in Hawaiian — holds the mass of 100 million billion suns within a region that spans about 520 million light-years.
Astrophysicist R. Brent Tully of the University of Hawaii in Honolulu and colleagues sifted through data describing the positions and velocities of over 8,000 galaxies to get a fresh look at the Milky Way’s place in space. After accounting for the motion caused by the expansion of the universe, the team created a three-dimensional view of how gravity molds the galaxy’s cosmic neighborhood.
The new map, published in the Sept. 4 Nature, reveals Laniakea’s boundaries and weblike framework. The Milky Way lies along one of the lines of that web, in a tributary feeding one of many galactic rivers. Those streams converge in a gravitational valley roughly 200 million light-years away near two massive galaxy clusters: Norma and Centaurus. Their combined gravity appears to be drawing in other galaxies and clusters within Laniakea, including the Milky Way.
Watch Laniakea Supercluster to see how the Milky Way fits into this complex network of galaxies.