Understanding the nature of our cosmos requires an accurate map of the distribution of galaxies within it. For decades, astronomers suspected that something enormous lurked behind the dense dust disk of the Milky Way in our sky. Indirect, barely perceptible distortions in the motion of galaxies were discovered, indicating unexplained gravitational forces. But the structure itself and its size remained hidden in a hard-to-observe part of the sky.<\/p>\n
Now, using the South African MeerKAT radio telescope, astronomers have been able to focus on this hidden mass. The result, available as a preprint on arXiv and submitted to Astronomy & Astrophysics magazine<\/em> , represents the most detailed image to date of the Vela Supercluster. Discovered only recently, in 2016, this colossal galaxy cluster lies approximately 800 million light-years away and spans approximately 300 million light-years across.<\/p>\n The Vela Supercluster also lies beyond one of astronomy's most elusive obstacles: the zone of avoidance. This region, where the dense plane of the Milky Way blocks visible light, obscures nearly a fifth of the sky. Optical telescopes simply cannot see through it. "Vela was a kind of ghost," says Ren\u00e9e Kraan-Korteweg, a professor of astronomy at the University of Cape Town and an expert on large-scale structure in the local universe. Kraan-Korteweg led the team that discovered the Vela Supercluster and is a co-author of this paper. "We could infer its presence, but we couldn't determine its full size.".<\/p>\n The MeerKAT spacecraft, launched in 2018, changes this by using radio waves. Instead of relying on starlight, which is absorbed by dust, it detects the emission line of neutral hydrogen at a wavelength of 21 centimeters (which is in the radio range)\u2014a signal that passes virtually unimpeded through dust. Using this spacecraft to explore the scale of Vela has proven revolutionary.<\/p>\n The MeerKAT telescope is capable of detecting faint hydrogen signals in galaxies hidden behind the Milky Way. Each detection has its own unique "fingerprint": the frequency of the hydrogen line shifts depending on the galaxy's speed of recession\u2014a phenomenon called redshift. Since the speed of recession depends on distance due to the expansion of the universe, measuring this shift allows us to determine the distance to the galaxy.<\/p>\n \u00ab"By tracking the neutral hydrogen line in thousands of galaxies, we are effectively reconstructing its structure in three dimensions," explains Constantinos Kolokitas, a radio astronomer at the South African Radio Astronomy Observatory and a researcher affiliated with Rhodes University, who was not involved in the recent study.<\/p>\n The study discovered more than 2,000 previously unobserved galaxies, filling a previously existing gap in cosmic maps. What initially appeared as a faint cluster of matter has now evolved into a massive structure with two dense cores, likely moving toward each other within a larger gravitational system.<\/p>\n Crucially, the hydrogen signal does more than simply indicate the locations of galaxies. While it tracks hydrogen throughout the galaxy population, it is particularly effective at identifying cooler, denser gas reservoirs\u2014the raw material from which new stars form. In this sense, the map reveals not only the location of matter but also where favorable conditions for star formation may emerge in the future.<\/p>\n Now that Vela has been mapped, its scale is impossible to ignore. The structure is estimated to contain 30 million billion (3 x 10\u00b9\u2076) solar masses of material, making it one of the most massive known structures in the nearby Universe. Its enormous gravitational influence is changing astronomers' understanding of motion on cosmic scales.<\/p>\n \u00ab"In cosmology, mass determines fate," says Kolokitas. "Such structures create gravitational basins, regions that pull galaxies inward and lead to large-scale flows." This has far broader implications for our planet than might initially appear.<\/p>\n Astronomers have long known that the Local Group of galaxies\u2014the Milky Way, Andromeda, and their satellites\u2014moves through space at approximately 1.3 million miles per hour (2.2 million km\/h) relative to the cosmic microwave background radiation that permeates the entire universe. The gravitational pull of known structures like the Great Attractor and the Shapley Concentration explains much of this motion. But not all. Vela appears to provide some of this missing gravitational pull.<\/p>\n Due to its position and mass, it makes a significant contribution to the motion of our galaxy, helping to resolve a long-standing discrepancy in cosmic flow models.<\/p>\n Beyond its gravitational role, Vela demonstrates the fact that the Universe we have explored is incomplete.<\/p>\n Historically, astronomers have often implicitly viewed the Zone of Avoidance as a region of lesser importance, an empty patch where little of significance might reside. Vela has challenged this assumption. "This isn't just a minor adjustment," says Kraan-Korteweg. "We're talking about structures on the scale of the largest known formations in the universe, hidden in plain sight.".<\/p>\n If one such structure has managed to remain undetected for so long, then others may still be waiting in the wings. <\/p>\n This 3D map shows superstructures in the local universe. The curved regions surrounding each structure represent "pools" where matter accumulates, and the colored lines represent the motion of galaxies. Credit: J\u00e9r\u00f4me Leca, RSA Cosmos, Saint-\u00c9tienne, France (CC BY-ND 4.0)<\/p>\n MeerKAT's observations are already among the most sensitive ever conducted in the southern sky, but they are only a harbinger of what's to come. The upcoming Square Kilometre Array (SKA) project will deepen radio telescopic surveys by detecting fainter galaxies and tracing the fine threads that connect superclusters into a larger cosmic network spreading throughout the universe.<\/p>\n If the MeerKAT telescope has detected Vela's core, the SKA could reveal how it is connected to even larger structures beyond current detection capabilities. Over time, the zone of avoidance may cease to exist, as astronomers finally learn to see through it.<\/p>\n Even in a well-studied universe, large structures can remain undetected, and Vela's discovery proves this. What was once a blind spot has now become one of the most informative regions of the sky and key to understanding how galaxies, including our own, move through space. In this sense, this discovery isn't simply adding another structure to the map. It's a refinement of the map itself.<\/p>\n The article "Giant Supercluster Hiding Behind the Milky Way Discovered" first appeared in Astronomy Magazine.<\/p>","protected":false},"excerpt":{"rendered":" Understanding the nature of our cosmos requires an accurate map of the distribution of galaxies within it. For decades, astronomers have suspected that beyond the Milky Way's dense dust disk,\u2026<\/p>","protected":false},"author":1,"featured_media":15033,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[],"class_list":["post-15032","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news","hvn-theme-has-thumbnail"],"_links":{"self":[{"href":"https:\/\/imgist.ru\/en\/wp-json\/wp\/v2\/posts\/15032","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/imgist.ru\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/imgist.ru\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/imgist.ru\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/imgist.ru\/en\/wp-json\/wp\/v2\/comments?post=15032"}],"version-history":[{"count":1,"href":"https:\/\/imgist.ru\/en\/wp-json\/wp\/v2\/posts\/15032\/revisions"}],"predecessor-version":[{"id":158451,"href":"https:\/\/imgist.ru\/en\/wp-json\/wp\/v2\/posts\/15032\/revisions\/158451"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/imgist.ru\/en\/wp-json\/wp\/v2\/media\/15033"}],"wp:attachment":[{"href":"https:\/\/imgist.ru\/en\/wp-json\/wp\/v2\/media?parent=15032"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/imgist.ru\/en\/wp-json\/wp\/v2\/categories?post=15032"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/imgist.ru\/en\/wp-json\/wp\/v2\/tags?post=15032"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}} A view through the Milky Way<\/h2>\n
Hidden Heavyweight<\/h2>\n
Going deeper<\/h2>\n