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 Cosmology  

Superclusters – regions of space that are densely packed with galaxies – are the biggest structures in the Universe. 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. Redrawing the boundaries of the cosmic map, they redefine our home supercluster and name it Laniakea, which means ‘immeasurable heaven’ in Hawaiian.

Anew cosmic map is giving scientists an unprecedented look at the boundaries for the giant supercluster that is home to Earth's own Milky Way galaxy and many others. Scientists from the University of Hawaii even have a name for the colossal galactic group: Laniakea, Hawaiian for "immeasurable heaven."

The scientists who created the new 3D map suggest that the Laniakea supercluster of galaxies may even be part of a still-larger structure they have not fully defined yet.

The research has been published in the journal Nature.

"We live in something called 'the cosmic web,' where galaxies are connected in tendrils separated by giant voids," said lead study author Brent Tully, an astronomer at the University of Hawaii at Honolulu.

Along with the Illustris simulation of the universe, the Laniakea data processing and visualization are both staggering in complexity, and awe-inspiring in scope. For an even more detailed view of the video above, a longer video is available, with commentary.

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Galaxies are not spread randomly throughout the universe. Instead, they clump in groups, such as the one Earth is in, the Local Group, which contains dozens of galaxies. In turn, these groups are part of massive clusters made up of hundreds of galaxies, all interconnected in a web of filaments in which galaxies are strung like pearls. The colossal structures known as superclusters form at the intersections of filaments.

The giant structures making up the universe often have unclear boundaries. To better define these structures, astronomers examined Cosmic Flows-2, the largest-ever catalog of the motions of galaxies, reasoning that each galaxy belongs to the structure whose gravity is making it flow toward.
"We have a new way of defining large-scale structures from the velocities of galaxies rather than just  looking at their distribution in the sky," Tully said.

The new 3D map developed by Tully and colleagues shows that the Milky Way galaxy resides in the outskirts of the Laniakea Supercluster, which is about 520 million light-years wide. The supercluster is made up of about 100,000 galaxies with a total mass about 100 million billion times that of the sun.

The name Laniakea was suggested by Nawa'a Napoleon, who teaches Hawaiian language at Kapiolani Community College in Hawaii. The name is meant to honor Polynesian navigators who used their knowledge of the heavens to make long voyages across the immensity of the Pacific Ocean.

"We live in the Local Group, which is part of the Local Sheet next to the Local Void — we wanted to come up with something a little more exciting than 'Local,'" Tully told Space.com.

"We might find that we have to come up with another name for something larger than we're a part of — we're entertaining that as a real possibility."

This supercluster also includes the Virgo cluster and Norma-Hydra-Centaurus, otherwise known as the Great Attractor. These new findings help clear up the role of the Great Attractor, which is a problem that has kept astronomers busy for 30 years. Within the Laniakea Supercluster, the motions of galaxies are directed inward, as water flows in descending paths down a valley, and the Great Attractor acts like a large flat-bottomed gravitational valley with a sphere of attraction that extends across the Laniakea Supercluster.

Tully noted Laniakea could be part of an even larger structure.

"We probably need to measure to another factor of three in distance to explain our local motion," Tully said. "We might find that we have to come up with another name for something larger than we're a part of — we're entertaining that as a real possibility."



SOURCE  Space.com

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