Researchers Map And Name The Region Of The Universe Containing The Milky Way

Chuck Bednar for – Your Universe Online
Using a new mapping technique that takes into account the motions of nearby galaxies, and not just their distances, researchers from the University of Hawaii have discovered that the Milky Way resides on the outer edge of a massive, previously undetected supercluster of galaxies that they have dubbed Laniakea.

Laniakea, a moniker created from the words meaning “immeasurable heaven” in Hawaiian, spans 520 million light-years in diameter, explained Irene Klotz of Discovery News.
Based on its boundaries, which were identified by charting the flow of over 8,000 surrounding galaxies, Laniakea is more than five times larger than the cluster previously believed to have been home to the Milky Way.
“This discovery clarifies the boundaries of our galactic neighborhood and establishes previously unrecognized linkages among various galaxy clusters in the local Universe,” the National Radio Astronomy Observatory (NRAO) said in a statement Wednesday.
“We have finally established the contours that define the supercluster of galaxies we can call home,” added 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 much larger country that borders other nations.”
A paper detailing the researcher’s work, which will be featured as the cover story in the September 4 edition of the journal Nature, also reveals that the Laniakea supercluster contains the mass of one hundred million billion suns spread across 100,000 galaxies.
The largest structures in the known universe, superclusters are made up of groups containing dozens of galaxies, as well as massive clusters containing hundreds of galaxies. Even though all of these galaxies are interconnected in a web of filaments, the researchers pointed out that they tend to have poorly defined boundaries.
“To better refine cosmic mapmaking, the researchers are proposing a new way to evaluate these large-scale galaxy structures by examining their impact on the motions of galaxies,” the NRAO said. Galaxies between structures are caught in “a gravitational tug-of-war” in which the balance of those forces will determine the galaxy’s motion.
By using the National Science Foundation’s Green Bank Telescope (GBT) and similar instruments, the team mapped the velocities of galaxies throughout our local universe and was able to define the region of space where each supercluster was dominant. Thanks to these techniques, Tully and colleagues were able to carefully map the extent of the Laniakea supercluster for the first time.
According to Reuters, the new maps showed that, in addition to the Milky Way, the Virgo cluster and roughly 100,000 other galaxies are part of Laniakea. Furthermore, this supercluster is bordered by the Shapley, Hercules, Coma and Perseus-Pieces super-clusters, though the far edges of the neighboring galaxy complexes have not yet been fully determined.
“We don’t have the distance information to see the far sides of… our (super-cluster) neighbors and we haven’t seen far enough to understand what’s causing this full motion of our galaxy,” Tully told Klotz. “That’s really the goal, to look out far enough – probably three times farther than we are right now, probably requiring many thousands of more distance measurements, to map this larger region.”
Astronomer Elmo Tempel of the Tartu Observatory in Estonia added that since Laniakea “is the biggest structure in the local universe,” he was surprised that the supercluster had not been discovered sooner. He added that the discovery “is definitely interesting and hopefully will initiate studies that will map the local universe in more detail,” and that the study “will give us new perspective (on) how to analyze these problems in observations.”
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