Our galaxy, the Milky Way, hides a vast portion of the Universe. More than 20% of the sky is inaccessible to us, because galactic dust and stars block the light from background objects. This zone, called the "zone of avoidance", conceals numerous structures, including the Vela Supercluster, identified in 2016.
Astronomers use telescopes capable of capturing radiation that penetrates dust. The MeerKAT array in South Africa observes radio waves emitted by hydrogen in distant galaxies. Thanks to it and the SALT telescope, a team was able to identify new galaxies belonging to the supercluster.
Map of superclusters in our cosmic neighborhood, with the two dense cores of the Vela Supercluster.
Credit: Dr Jérôme Léca, RSA Cosmos, St Etienne, France.
Measurements of 65,518 distances from the CosmicFlows catalog, combined with 8,283 new sources, have revealed the true extent of the supercluster. Its mass reaches 338 million billion solar masses, spread over 300 million light-years. This is comparable to the Shapley Supercluster, one of the most massive known.
This colossal mass exerts such a strong gravitational pull that it influences the motion of galaxies far beyond what was previously assumed. The "cosmic flows", those streams of galaxies deflected by the expansion of the Universe, are partly caused by this hidden structure. Until now, these disturbances were attributed to the Great Attractor, but the Vela Supercluster plays an even more important role.
Researchers have dubbed this immense structure "Vela-Banzi", which means "to reveal widely" in the Xhosa language. This discovery completes our map of the nearby Universe, exposing a major gravitational actor that remained invisible for a long time. The study was published on the arXiv preprint server.