Unfriendly Merger

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Unfriendly Merger

A pair of supermassive black holes in the heart of a distant galaxy may be headed for an unfriendly merger. We could see them ram together in as little as three years, producing some big fireworks.

The black holes have a combined mass of roughly 200 million times the mass of the Sun. They’re in a galaxy that’s about a billion light-years from Earth. The galaxy is in the constellation Boötes the herdsman, which is dropping from view in the western sky at sunset.

Astronomers have kept an eye on the galaxy for a few years. Space telescopes found that X-rays from the galaxy’s heart go through an up-and-down cycle. Over a couple of years, the length of that cycle dropped from about a year to just three months.

A team of researchers said the peaks in the cycle could be produced as the black holes approach each other. As they do so, they kick out blobs of hot gas from the disks that encircle the black holes. The change in the timing of those peaks could mean that the black holes are pulling closer together. At the rate they’re approaching each other, they could merge in just three years. That would produce a huge outburst of X-rays and other forms of energy.

The merger also would produce an outburst of gravitational waves, which are faint ripples in space-time. No current instruments can detect the wavelengths the merger would produce, though, so they’ll remain unobserved.

Tomorrow: Lining up some close calls.

Script by Damond Benningfield

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