Scientists discover giant structure stretching 1.4 billion light-years across, call it the South Pole Wall
Here is the latest reminder that space is massive. Astronomers have discovered one of the biggest cosmic structures ever -- dubbed as the South Pole Wall -- which stretches 1.4 billion light-years across and consists of thousands of galaxies.
A light-year is the distance light travels in one Earth year. One light-year is about six trillion miles or nine trillion km. For perspective, the Milky Way is about 100,000 light-years across. The gigantic structure has remained undetected until now largely because parts of it sit half a billion light-years away behind the Milky Way. Discovering structures like this can add to our understanding of the universe, say experts.
The research team is describing it as a largescale structure observed in the direction of the South Celestial Pole. According to the scientists, the South Pole Wall rivals the Sloan Great Wall in extent, which is the sixth-largest cosmic structure discovered. The two have comparable size and morphology, they add. “Cosmographers discover the South Pole Wall, a giant filament stretching 1.4 billion light-years across. Located in the direction of the Celestial South Pole, it is comparable to the Sloan Great Wall, at half the distance,” tweeted study author Dr Daniel Pomarède from Paris-Saclay University, France. The research team also includes experts from the University of Hawaii, US; Université Clermont Auvergne, France; University of Lyon, France; and Hebrew University, Jerusalem.
The universe is a tapestry of galaxy congregations and vast voids. In this new study, which has been published in The Astrophysical Journal, researchers applied the same tools from an earlier study to map the size and shape of an extensive empty region they called the “local void” that borders the Milky Way Galaxy. Using the observations of galaxy motions, they inferred the distribution of mass responsible for that motion and constructed three-dimensional maps of our local universe.
Galaxies not only move with the overall expansion of the universe, but they also respond to the gravitational tug of their neighbors and regions with a lot of mass. As a consequence, relative to the overall expansion of the universe they are moving towards the densest areas and away from regions with little mass — the voids, explains the team.
The existence of the local void has been widely accepted, but it remained poorly studied because it lies behind the center of our galaxy and is therefore heavily obscured from our view. But the team has “now measured the motions of 18,000 galaxies in the Cosmicflows-3 compendium of galaxy distances, constructing a cosmographic map that highlights the boundary between the collection of matter and the absence of matter that defines the edge of the local void,” says the analysis. They used the same technique in 2014 to identify the full extent of our home supercluster of over one hundred thousand galaxies, giving it the name Laniakea, which means “immense heaven” in Hawaiian. For 30 years, astronomers have been trying to identify why the motions of the Milky Way, our nearest large galaxy neighbor Andromeda, and their smaller neighbors deviate from the overall expansion of the Universe by over 600 km/s (1.3 million mph). The new study shows that “roughly half of this motion is generated ‘locally’ from the combination of a pull from the massive nearby Virgo cluster and our participation in the expansion of the local void as it becomes ever emptier.”
The team studied the region called the zone of obscuration: an area in the southern part of the sky in which the bright light of the Milky Way blocks out much of what is behind and around it. According to the analysis, the South Pole Wall is adjacent to the “zone of obscuration caused by galactic dust.” It is located opposite the Shapley Supercluster across the zone of obscuration.
The researchers have created a huge map of a large section of material in the southernmost point of the sky that was previously unnoticed. It has a sweeping wing extending north on one side towards the constellation of Cetus and an arm in the opposite direction in the Apus constellation. According to the research team, the South Pole Wall may be bigger than it currently appears. “We will not be certain of its full extent, nor whether it is unusual until we map the universe on a significantly grander scale,” the authors write.