An international team led by University of Cape Town (UCT) astronomers has revealed the true, massive scale of the Vela Supercluster, a gargantuan cosmic structure previously hidden in a blind spot behind the Milky Way. Utilizing South Africa’s world-class MeerKAT radio telescope and the Southern African Large Telescope (Salt), researchers have finally pierced through the “Zone of Avoidance”, a region of dense interstellar dust and stars that obscures roughly 20% of the sky.
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The Vela Supercluster—affectionately dubbed “Vela-Banzi,” which means “revealing widely” in isiXhosa—is located approximately 800 million light years from Earth. The new data shows it is significantly more colossal than earlier estimates suggested, stretching across 300 million light years. Its mass is equivalent to a staggering 30 million billion suns, placing it on par with the Shapley Supercluster, previously thought to be the most massive structure in the nearby universe.
Its gravitational influence is so immense that it exceeds that of the famous Great Attractor, actively shaping the motion of galaxies across hundreds of millions of light years, including our own Local Group.
The breakthrough was achieved through a novel hybrid technique. Astronomers combined galaxy redshift measurements—indicating how fast galaxies are receding—with “peculiar velocity” data, which shows how galaxies move in response to gravity. The team processed over 65,000 distance measurements and added 8,000 new redshifts observed near the Milky Way’s plane.
While dust blocks visible light, MeerKAT’s ability to detect hydrogen gas at radio wavelengths allowed the team to “see” through the cosmic debris. Salt, the southern hemisphere’s largest optical telescope, provided critical follow-up observations.
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UCT Emeritus Professor Renée Kraan-Korteweg, who led the group, expressed exhilaration at the confirmation of a structure she first suspected over ten years ago. “It has finally confirmed the prominence of the Vela-Banzi supercluster,” she noted, highlighting the effectiveness of the new methodology.
The international collaboration included researchers from France, Australia, and Italy. This discovery not only maps a significant portion of our “hidden” neighbourhood but also reinforces South Africa’s growing status as a global hub for high-tech astronomy.
