Green Bank telescope helps researchers trace shape of Earth’s home “supercluster”

By Staff reports

GREEN BANK, W.Va. -- Astronomers making observations with the National Science Foundation’s Green Bank Telescope in Pocahontas County played a significant role in research that led to the discovery announced Wednesday that our Milky Way galaxy is part of a newly identified supercluster of galaxies stretching 500 million light years across the universe.

The discovery clarifies the boundaries of our galactic neighborhood and identifies previously unrecognized links among various galaxy clusters in the local universe.

“We have finally established the contours that define the supercluster of galaxies we call home,” said lead researcher R. Brent Tully, an astronomer at the University of Hawaii at Manoa. “This is not unlike finding out for the first time that your hometown is actually part of a much larger country that borders other nations.”

The paper explaining the work by the international research team led by Tully is the cover story for this week’s issue of the journal Nature.

Superclusters like the one that contains the Milky Way are among the largest structures in the universe, made up of groups of galaxies, like our own Local Group, that contain dozens of galaxies, and massive clusters that contain hundreds of galaxies, all interconnected by a web of filaments. Though the superclusters are interconnected, they have poorly defined boundaries.

To better refine cosmic map-making, Tully and his associates are proposing a new wayto evaluate large scale galaxy structures by examining their impact on the motions of galaxies. Galaxies passing between superclusters will be caught in a gravitational tug of war in which the balance of the gravitional forces from the surrounding large-scale structures determines the galaxy’s motion. By using the Green Bank Telescope and other radio telescopes to map the speeds of galaxies throughout our local universe, the team was able to define the region of space where each supercluster dominates. “Green Bank Telescope observations have played a significant role in the research leading to this new understanding of the limits and relationships among a number of superclusters,” said Tully.

Earth’s Milky Way galaxy is found in the outer reaches of one such supercluster, the boundaries of which have for the first time been mapped using these new techniques. The supercluster, named Laniakea -- Hawaiian for “immense heaven”-- hosts a gravitational focal point in intergalactic space that influences the motion of ouir Local Group of galaxies and its relationship to other galaxy clusters. Within the boundaries of the Laniakea supercluster, galaxy motions are directed inward, in the same way that water strams follow descending paths toward a valley.

Video presentations explaining the nature of the Laniakea supercluster can be seen on the National Radio Astronomy Observatory’s website at, and on YouTube.

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