Astronomers discover South Pole Wall, a massive structure extending 1.4 billion light-years across
Magnificent 3D maps of the universe have unveiled one of the greatest cosmic structures ever discovered — an almost-inconceivable wall reaching 1.4 billion light-years across that includes hundreds of thousands of galaxies.
The South Pole Wall, as it's been christened, has been hiding in plain sight, residing undetected till now because huge portions of it remain half a billion light-years away behind the bright Milky Way galaxy. The South Pole Wall rivals in size the Sloan Great Wall, the sixth-largest cosmic structure found. (One light-year is approximately 6 trillion miles or 9 trillion kilometers, so this "biggest cosmic structure" is mind-bending humongous.)
Astronomers have long observed that galaxies are not scattered randomly throughout the universe but somewhat clump together in what's recognized as the cosmic web, tremendous strands of hydrogen gas in which galaxies are strung like pearls on a necklace that circle gigantic and mostly empty voids.
Mapping these intergalactic threads belongs to the range of cosmography, which is "the cartography of the cosmos," study researcher Daniel Pomarede, a cosmographer at Paris-Saclay University in France, described Live Science. Previous cosmographic work has mapped the size of other galactic assemblies, such as the present structural record holder, the Hercules-Corona Borealis Great Wall, which spans 10 billion light-years, or more than a tenth the size of the noticeable universe.
In 2014, Pomarede and his partners exposed the Laniakea supercluster, a galactic collection in which our own Milky Way remains. Lanaikea is 520 million light-years wide and includes approximately the mass of 100 million billion suns.
For their new map, the crew used newly-created sky surveys to inspect into a region termed the Zone of Galactic Obscuration. This is an area in the southern region of the sky in which the bright light of the Milky Way obstructs out much of what's behind and around it.
Cosmographers typically determine the distance to objects utilizing redshift, the speed at which an object is dropping from Earth due to the expansion in the size of the universe, which depends on their distance, Pomarede stated. The farther away an object is, the quicker it will appear to be dropping from Earth, research first made by astronomer Edwin Hubble in 1929 and which has held up ever since.
But he and his partners applied a somewhat distinctive method, watching at the wonderful velocity of galaxies. This measurement constitutes redshift but also takes into account the movement of galaxies around one another as they tug at each other gravitationally, Pomarede stated.
The benefit of the technique is that it can recognize hidden mass that is gravitationally affecting how galaxies move and therefore reveal the dark matter, that invisible stuff that emits no light but exerts a gravitational tug on anything near enough. (Dark matter also makes up the majority of the matter in the universe.) By working algorithms studying at peculiar motion in galactic records, the team was able to plot the three-dimensional arrangement of matter in and around the Zone of Galactic Obscuration. Their findings are described today (July 9) in The Astrophysical Journal.
The resulting map presents a mind-boggling bubble of matter more or less centered on the southernmost point of the sky, with a great sweeping wing stretching north on one side in the direction of the constellation Cetus and another stubbier arm opposite it in the direction of the constellation Apus.
Understanding how the universe seems on such huge scales helps validate our current cosmological models, Neta Bahcall, an astrophysicist at Princeton University in New Jersey who was not included in the work described Live Science. But deciding where precisely these huge, crisscrossing structures begin and end is critical, she continued. "When you look at the network of filaments and voids, it becomes a semantic question of what's connected," she stated. In their paper, the crew admits that they may not have plotted yet the entirety of the vast South Pole Wall. "We will not be certain of its full extent, nor whether it is unusual until we map the universe on a significantly grander scale," they wrote.