Using powerful telescopes to see through the galaxies' thick walls of gas and dust surrounding their cores, the academics have managed - for the first time - to observe supermassive black holes fall into each other and coalesce into an even more giant black hole.
The scientists said each of the black holes were said to once occupy the centre of one of the two original, smaller galaxies.
Previous work found that mergers of galaxies might help fuel the growth of supermassive black holes.
As mentioned, over the past 20 years or so, the NASA/ESA Hubble Space Telescope and the W. M. Keck Observatory in Hawaii observed the merging of the two galaxies, which culminated with a spectacular black holes collision.
Galactic mergers could give supermassive black holes the opportunity to rip apart stars and devour matter, releasing extraordinary amounts of light. "With these observations, we can begin to explore the fraction of objects that are merging in the youngest, most distant regions of the universe - which should be fairly frequent". While some research has shown a link between quasars and merging galaxies, other studies have found no such association.
"Seeing the pairs of merging galaxy nuclei associated with these huge black holes, so close together was pretty unbelievable", explained Michael Koss, a researcher at the Eureka Scientific Inc., and one of the scientists who studied the image released by NASA.
Numerous black holes pictured, which were an average of 330 million miles from Earth, were around the same size as both the Milky Way and Andromeda.
The scientists first searched for hidden black holes by sifting through 10 years' worth of X-ray data from NASA's Neil Gehrels Swift Observatory. Koss is an astrophysicist at scientific research company Eureka Scientific in Oakland, California.
The pictures show the final stages of a merger between two galactic nuclei in the galaxy NGC 6240. Then they looked at galaxies which matched these X-rays using data from NASA's Hubble Space Telescope and the Keck Observatory in Hawaii.
Credit: M. Koss (Eureka Scientific, Inc.)/NASA/ESA;Keck images: M. Koss (Eureka Scientific, Inc.)/W.M.
All in all, the scientists analyzed 96 galaxies observed with the Keck Observatory and 385 galaxies from the Hubble archive.
Something similar is expected to happen when our Milky Way galaxy crashes with the nearby Andromeda galaxy, though it's not expected to happen anytime soon, the researchers said.
There is still much to learn about black hole mergers, though. To find out more, check out the Computing AI & Machine Learning Live website.
The findings suggest that galactic mergers may indeed be a key process by which black holes grow to stupendous masses.
Their results suggest that more than 17 percent of these galaxies host a pair of black holes at their center, which are locked in the late stages of spiraling ever closer together before merging into a single, ultra-massive black hole.
"Right now, the galaxies are separated by millions of light-years, but we're moving toward Andromeda at 250,000 miles per hour [400,000 km/h]", Koss said.