Astronomers have reported the discovery of two giant radio galaxies, which are thought to be among the largest single objects in the universe. The two galaxies contain a large number of radio jets extending more than 6.5 million light-years – about twice the size of the Milky Way. Thanks to South Africa’s powerful MeerKAT telescope, the discovery was made possible and the results were published in the monthly notices of the Royal Astronomical Society. The discovery of these galaxies suggests that these cosmic leviathans are not as rare as previously thought.
Galaxies that emit large amounts of radio waves are fairly common in the universe, but there are only a few hundred radio jets larger than 2.2 million light-years. This “giant radio galaxy” has been considered a cosmic rarity. These two galaxies have been found in almost the same spot in the sky in the MeerKAT observations.
Lead author Dr. Jacinta Delhaize, from the University of Cape Town, said in a statement, “We found these huge radio galaxies in a region of the sky that is only 4 times larger than the full moon. 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 percent.” “That means giant radio galaxies are probably much more common than we thought!”
These two galaxies make up the top ten percent of all known giant radio galaxies. This work does not point to a yet-to-be-discovered population of giant radio galaxies but does provide some insight into why we have not yet found them. Even the largest galaxies are among the oldest, as it takes millions of light-years for these jets to launch into space. These newly discovered galaxies are much more interesting than galaxies of the size we have seen before, so missing populations may exceed the limits of our observations.
Dr. Delhaize added, “In the past, this population of galaxies was hidden from our ‘perspective’ by the technical limitations of radio telescopes. However, now it has been revealed for the impressive efficiency of the new genre telescope.” MeerKAT was designed to precede the intercontinental array of square telescopes arrays of wireless telescopes, with construction starting in full swing this year. It will be completed by 2027 and is expected to begin sky observation in early 2023. More giant galaxies like this are likely to be found soon.