Cosmic Structure Discovered Beyond the Milky Way

Laniakea Cluster (PC:UH Manoa)

An immense cosmic structure discovered by astronomers has been dubbed the South Pole Wall.

Led in part by Brent Tully at the University of Hawaiʻi Institute for Astronomy lead a team of astronomers in the mapping of the galaxies around the Milky Way. The South Pole Wall was found beyond the supercluster of galaxies, Laniakea.

The densest part of the cosmic structure lies in the direction of the Earth’s South Pole, inspiring the name, wrapping the region like an arm. 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.

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.

“We wonder if the South Pole Wall is much bigger than what we see. What we have mapped stretches across the full domain of the region we have surveyed. We are early explorers of the cosmos, extending our maps into unknown territory,” described Tully.

The team’s research was published in Astrophysical Journal.

The Milky Way galaxy, with its 100 billion stars, is part of the small Local Group of galaxies, which in turn is a suburb of the Virgo cluster with thousands of galaxies. The Virgo cluster in turn is an outer component of an even larger conglomeration of many rich clusters of galaxies, collectively called the “Great Attractor” because of its immense gravitational pull.

In 2014, the team mapped out the Laniakea Supercluster, the bundling of a hundred thousand galaxies over an even larger region, spanning 500 million light-years.

The South Pole Wall is as large as the Sloan Great Wall, one of the largest structures known in the Universe, but the new discovery is much closer.

University of Paris-Saclay cosmic cartographer Daniel Pomarede, one of the study’s lead authors, explained “One might wonder how such a large and not-so-distant structure remained unnoticed. This is due to its location in a region of the sky that has not been completely surveyed, and where direct observations are hindered by foreground patches of galactic dust and clouds. We have found it thanks to its gravitational influence, imprinted in the velocities of a sample of galaxies.”