Astronomers have refined the parameters of the Vela Supercluster of galaxies. The object, 300 million light-years in diameter—almost 3,000 times larger than the Milky Way—contains approximately 33,800 trillion solar masses and is comparable to the Laniakea and Shapley Superclusters, and its gravitational influence exceeds even that of the Great Attractor. The supercluster is located approximately 870 million light-years from Earth, in the direction of the plane of the Milky Way, in the so-called zone of avoidance.
The Vela Supercluster was discovered in 2016. Even then, a team led by Renée C. Kraan-Korteweg of the University of Cape Town knew the object was exceptionally massive, but the previous estimate of its mass was insufficient to explain the observed motions of galaxies in our corner of the universe. The new work was led by Amber Hollinger of Université Claude Bernard Lyon 1.
The object is located near the plane of the Milky Way, in the so-called zone of avoidance. This region occupies approximately 20% of the entire sky and has long remained virtually inaccessible to astronomers. Interstellar dust in the Milky Way's disk either completely absorbs the light of distant galaxies or weakens it, causing a noticeable reddening, where the blue part of the spectrum is more attenuated than the red part.
The Kraan-Korteweg team used 65,518 galaxy distance measurements from the latest version of the CosmicFlows catalog, maintained by astronomers in France and Hawaii. They added 8,283 new redshift measurements for galaxies near the plane of the Milky Way. Additional observations were conducted with the South African Large Astrophysical Telescope (SALT) and the MeerKAT radio telescope, both located in South Africa. MeerKAT was able to detect galaxies directly in the zone of avoidance based on the radio emission of neutral hydrogen they contain—waves that pass almost unimpeded through the Milky Way's dusty disk.
Refined parameters showed that Vela is comparable in mass to the Shapley Supercluster, which is located 650 million light-years from Earth. The supercluster comprises more than 20 individual galaxy clusters. They combine to form two extended, flat structures (called "walls" in cosmology), each with a dense, massive core. The two "walls" are slowly moving closer together under the influence of their mutual gravitational attraction. Large superclusters form so-called cosmic flows—the barely perceptible movements of galaxies toward large centers of mass at distances of hundreds of millions and even billions of light-years.
One such center of mass is the Great Attractor. It is also hidden by the Milky Way's dust disk and is associated with the Laniakea Supercluster, of which our galaxy is a tiny part. Another such center is believed to be the aforementioned Shapley Supercluster. The previous estimate of Vela's mass was insufficient to explain the observed flows. The refined parameters closed this gap and showed that Vela's gravitational influence is even stronger than that of the Great Attractor.
"This discovery helps complete the map of the nearby Universe. For the first time, we clearly see one of the major gravitational players hidden by our galaxy," the researchers said in a statement. The Kraan-Korteweg team has given the supercluster the informal name "Vela-Banzi." In the Xhosa language (isiXhosa), spoken in South Africa, it translates as "widely opening."
Source:
Source: 3dnews.ru
