Scientists Capture First-Ever Photos Of Supermassive Black Holes in the Midst of 'Hidden' Galactic Mergers

Thursday, 08 November 2018 - 1:49PM
Astronomy
Space
Black Holes
Thursday, 08 November 2018 - 1:49PM
Scientists Capture First-Ever Photos Of Supermassive Black Holes in the Midst of 'Hidden' Galactic Mergers
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NASA, ESA, and M. Koss (Eureka Scientific, Inc.)
Few things are more powerful, cataclysmic, or vast than a merger between supermassive black holes, but galactic mergers are one of them. Fortunately for scientists, the two often happen at the same time – almost all galaxies have a supermassive black hole at their center, which means most mergers culminate in an even larger black hole (and a lot of destruction). Scientists have theorized that galactic mergers are one of the main ways supermassive black holes grow, but that's been the subject of some debate – mostly because researchers haven't been able to capture clear pictures of black holes in the late stages of a merger... Until now.

The chief test for judging whether black holes are really growing during galactic mergers has been quasars, which are powerful jets of light and matter that shoot out of well-fed black holes. Some galactic mergers are accompanied by quasars, but some aren't. If those supermassive black holes are really gorging themselves on all that matter before combining into a larger hole, there should be obvious evidence of quasars.

The solution? It turns out there's way more gas and dust getting in the way of our observations than we thought. According to the new study, published in Nature:

"Recent observations have shown that a black hole is likely to become heavily obscured behind merger-driven gas and dust, even in the early stages of the merger, when the galaxies are well separated. Merger simulations further suggest that such obscuration and black-hole accretion peaks in the final merger stage, when the two galactic nuclei are closely separated."

To peer through all this junk, the researchers looked for the type of high-energy x-rays given off by feeding black holes, which should be able to penetrate the dense clouds of gas and dust. In all, they observed 481 galaxies using a new technique called adaptive optics, which allowed for much higher-resolution images. What they found was striking: 17% of the galaxies had a pair of black holes at their center, indicating that they were in the final stages of galactic mergers.

The discovery of these "hidden" mergers gives more credence to the idea that galaxy collisions are one of the chief ways supermassive black holes grow, but it also marks a new understanding of what lies ahead for the Milky Way, which is currently hurtling on a collision course with the Andromeda galaxy.

Brace for impact.

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