Laniakea, the Newly Discovered Supercluster of Galaxies

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 total mass about 100 million billion times that of the sun. Scientists responsible for the new 3D map suggest that the newfound Laniakea Supercluster of galaxies may even be part of a still-larger structure they have not fully defined yet.

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.

Universe first forms stars and star clusters, with the first ones appearing when less than 200 million years have passed since the Big Bang. Over the next few hundred million years, structure begins to appear on larger scales, with the first galaxies forming, star clusters merging together, and even galaxies growing to attract matter from the lower-density regions nearby.

The Universe as we know it began some 13.8 billion years ago with the Big Bang. It was filled with matter, antimatter, radiation, etc.; All the particles and fields that we know of today, and possibly even more. From the earliest instants of the hot Big Bang, however, it wasn’t simply a uniform sea of these energetic quanta.

On the largest cosmic scales of all, planet Earth appears to be anything but special. Like hundreds of billions of other planets in our galaxy, we orbit our parent star; like hundreds of billions of solar systems. We revolve around the galaxy; like the majority of galaxies in the Universe, we’re bound together in either a group or cluster of galaxies. Like most galactic groups and clusters, we’re a small part of a larger structure containing over 100,000 galaxies: a Supercluster. Ours is named Laniakea: the Hawaiian word for “immense heaven.”

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 Supercluster form at the intersections of filaments.

In our own local corner of the Universe, the Milky Way can be found in a small neighborhood we call our local group. Andromeda is our local group’s largest galaxy, followed by the Milky Way at #2, the Triangulum galaxy at #3, and perhaps 60 significantly smaller dwarf galaxies strewn out over a volume spanning a few million light-years in three dimensions. Our local group is one of many small-ish groups in our vicinity, along with the M81 group, the Sculptor group, and the Maffei group.

Laniakea Supercluster Map

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.

A new 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 even have a name for the colossal galactic group: Laniakea, Hawaiian for “immeasurable heaven.”

The South Pole Wall lies immediately beyond the Laniakea Supercluster, wrapping the region like an arm. The densest part of it lies in the direction of the Earth’s South Pole, inspiring the name. It extends in a great arc of 200 degrees—more than a semicircle—reaching well into the northern sky. The concentration at the South Pole lies at a distance of 500 million light years.

Following the arm north, it folds inward to within 300 million light years of the Milky Way. Along the arm, galaxies are slowly moving toward the South Pole. And from there, across a part of the sky obscured from Earth by the Milky Way toward the dominant structure in the nearby universe, the Shapley connection.

The giant structures making up the universe often have unclear boundaries. To better define these structures, astronomers examined Cosmicflows-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.

About the author

Naqvi Syed

Naqvi Syed is is a freelance journalist who has contributed to several publications, including Spacepsychiatrist. He tackles topics like spaceflight, diversity, science fiction, astronomy and gaming to help others explore the universe. He works with Spacepsychiatrist from a long time.


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