Astronomers using NASA's Spitzer and Chandra space telescopes serendipitously discovered four gigantic galaxies merging into one:
"The galaxies that live in the middle of clusters like this are the biggest galaxies anywhere in the Universe," Dr Rines told the BBC News website.
"When this merger finishes, the giant galaxy left at the end will be one of the biggest ones in the Universe. This shows how these giant galaxies get assembled."