A team of astronomers claim to have found several pairs of galaxies in the final stages of merging together into single, larger galaxies.
The research team add that it is the first time that such a phenomenon has been seen. They claim to have captured pairs of supermassive black holes, drawing closer together before they coalescence into one giant black hole.
We see two galaxy nuclei right when the images were taken. You can't argue with it; it's a very 'clean' result
The scientists said each of the black holes were said to once occupy the centre of one of the two original, smaller galaxies.
Led by University of Maryland alumnus Michael Koss, a research scientist at Eureka Scientific, the team surveyed hundreds of nearby galaxies using imagery from the W.M. Keck Observatory in Hawaii as well as NASA's Hubble Space Telescope.
"Seeing the pairs of merging galaxy nuclei associated with these huge black holes so close together was pretty amazing," Koss said. "In our study, we see two galaxy nuclei right when the images were taken. You can't argue with it; it's a very 'clean' result, which doesn't rely on interpretation."
The high-resolution images also provide a close-up preview of a phenomenon that astronomers suspect was more common in the early universe when galaxy mergers were more frequent.
When the black holes finally do collide, they will unleash powerful energy in the form of gravitational waves
"When the black holes finally do collide, they will unleash powerful energy in the form of gravitational waves, ripples in space-time recently detected for the first time by the twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors," the researchers' report said.
"The images also presage what will likely happen in a few billion years, when our Milky Way galaxy merges with the neighbouring Andromeda galaxy."
The added that both galaxies host supermassive black holes at their center, which will eventually smash together and merge into one larger black hole.
The results of the study suggest that more than 17 per cent of these galaxies host a pair of black holes at their centre, which are locked in the late stages of spiraling ever closer together before merging into a single, ultra-massive black hole.
What really enabled this particular study were the X-rays that can break through the cocoon of dust
The researchers said they were surprised to find such a high level of late-stage mergers, because most simulations suggest that black hole pairs spend very little time in this phase.
To check their results, they compared the survey galaxies with a control group of 176 other galaxies, from the Hubble archive, that lack actively growing black holes. In this group, only about one per cent of the surveyed galaxies were suspected to host pairs of black holes in the later stages of merging together.
This last step helped the researchers confirm that the luminous galactic cores found in their census of dusty interacting galaxies are indeed a signature of rapidly-growing black hole pairs headed for a collision.
According to the researchers, this finding is consistent with theoretical predictions, but until now, had not been verified by direct observations.
"People had conducted studies to look for these close interacting black holes before, but what really enabled this particular study were the X-rays that can break through the cocoon of dust," explained Koss.
"We also looked a bit farther in the universe so that we could survey a larger volume of space, giving us a greater chance of finding more luminous, rapidly-growing black holes."
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