According to Brent Tully of the University of Hawaii Institute of Astronomy, our place in the Universe, for so long one of the central mysteries of human earthly existence, has become a little clearer and scarier. Tully is leading an ongoing effort to map the distribution of galaxies around the Milky Way galaxy that recently discovered an immense structure in the vast cosmic network beyond Laniakea, a supercluster of galaxies and endless voids, including the Milky Way and a newly identified structure, the South Pole Wall.
“We wonder if the South Pole Wall is much bigger than what we see. What we have mapped extends throughout the domain of the region we have surveyed. We are the first explorers of the cosmos, extending our maps into unknown territory, ”observed Tully.
We have no idea where the map of the cosmos finally ends, says intrepid explorer and astrophysicist Martin Rees: “The volume of space-time within the range of our telescopes, what astronomers have traditionally called ‘the universe’, is just one small fraction of the aftermath of the big bang. We would expect many more galaxies located beyond the horizon, unobservable, each of which, along with any intelligence it harbors, will evolve like ours. “
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Beyond the Laniakea supercluster
The South Pole Wall lies immediately beyond the Laniakea Supercluster, named for the Hawaiian phrase for “huge sky,” which wraps around the region like an arm. The densest part is in the direction of the South Pole of the Earth, inspiring the name. It extends in a great arc of 200 degrees, more than a semicircle, reaching the northern sky. The concentration at the South Pole is at a distance of 500 million light years. Following the arm northward, it folds in less than 300 million light years from the Milky Way. Along the arm, galaxies slowly move toward the South Pole, and from there, through a part of the sky obscured from Earth by the Milky Way to the dominant structure in the nearby universe, the Shapley connection,
Over the past 40 years, there has been a growing appreciation of patterns in the distribution of galaxies in the Universe, reminiscent of geographic features such as mountain ranges and island archipelagos. 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 external component of an even larger conglomerate of many galaxy-rich clusters, collectively called the “Great Attractor” due to its immense gravitational pull. In 2014, the team mapped the Laniakea Supercluster, the cluster of 100,000 galaxies in an even larger region, spanning 500 million light-years.
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As big as Sloan’s Great Wall
The South Pole Wall is as big as the Sloan Great Wall, one of the largest known structures in the Universe, but the new discovery is much closer.
“One might wonder how such a large and not so distant structure went unnoticed,” says the cosmic cartographer at the University of Paris-Saclay, Daniel Pomarede, one of the study’s lead authors. “This is due to its location in a region of the sky that has not been fully studied, and where direct observations are hampered by patches of dust and galactic clouds in the foreground. We have found it thanks to its gravitational influence, imprinted on the speeds of a sample of galaxies. “
Source: Daniel Pomarède et al. Cosmicflows-3: The South Pole Wall, The Astrophysical Journal (2020). DOI: 10.3847 / 1538-4357 / ab9952
The Daily Galaxy, Sam Cabot, via the University of Hawaii at Manoa and the New York Times
Image at the top of the page: a visualization of the Laniakea supercluster, Tsaghkyan / Wikimedia Commons
