A pair of gargantuan galaxies, which could be among the largest single objects in the Universe, have been unearthed by the MeerKAT telescope array in South Africa.
“They are more than 2 megaparsecs across, which is around 6.5 million lightyears, or 62 times the size of the Milky Way,” says Matthew Prescott from the University of the Western Cape, who took part in the study.
Such galaxies are extremely rare, so it’s unusual that the two were discovered so close to each other.
“We found these giant radio galaxies in a region of sky that is only about four times the area of the full Moon,” says Jacinta Delhaize from the University of Cape Town, who led the study.
“Based on our current knowledge of the density of giant radio galaxies in the sky, the probability of finding two of them in this region is less than 0.0003%. This means that giant radio galaxies are probably far more common than we thought.”
The apparent rareness of giant radio galaxies had been a puzzle for astronomers.
It’s currently thought that the behemoths are normal radio galaxies that have grown old and expanded to enormous size, but if this were the case, the number found would be more in line with their younger counterparts.
This problem could soon be resolved, however. MeerKAT is a precursor to the much more powerful Square Kilometre Array (SKA) telescope, which will be able to detect more radio galaxies than any telescope before it.
The SKA’s two giant arrays in South Africa and Australia are due to be completed in 2027, but could start observing from 2023.
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For more info on this story, visit www.sarao.ac.za.
Chris Lintott is a professor of astrophysics at the University of Oxford and a co-presenter of The Sky at Night.