A better map of our cosmic neighbourhood
Astronomers have drawn a detailed map of our immediate cosmic neighbourhood – an immense supercluster of galaxies containing the Milky Way.
They have named it "Laniakea," meaning "immense heaven" in Hawaiian.
University of Hawaii at Manoa astronomer R. Brent Tully led the international team which explains its work in Nature this month.
Galaxies are not distributed randomly throughout the universe but 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, the astronomers say, we find huge structures, called "superclusters". These structures are interconnected, but they have poorly defined boundaries.
A galaxy lying between two of these 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 lies on the outskirts of the Laniakea Supercluster, which is 500 million light-years in diameter and contains the mass of 10^17 Suns in 100,000 galaxies.
There is a video giving a feel for the structure of our home supercluster and of galaxies and how they move in the nearby universe here.