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Astronomers find a pair of orbiting supermassive black holes


Radio signals show two black holes, 15 billion times more massive than the Sun, orbit each other every 24,000 years.


An artist’s impression of two orbiting supermassive black holes.
An artist’s impression of two orbiting supermassive black holes.
Joshua Valenzuela / UNM

In a discovery more than a decade in the making, scientists have successfully measured and observed the orbital motion between two supermassive black holes (SMBHs), which could lead to significant inroads in our understanding of the cosmic behemoths.

To accomplish this feat, Greg Taylor, Karishma Bansal and their colleagues from the University of New Mexico in the US examined the frequencies of radio signals emitted from two colliding SMBHs, roughly 750 million light-years away from Earth.

These measurements were obtained over the course of 12 years using the Very Long Baseline Array – a system comprised of 10 radio telescopes across the US – and were plotted so that the scientists could map the trajectories of the SMBHs.

In a recent paper published in the Astrophysical Journal, Taylor, Bansal and their team have finally been able to confirm that these two SMBHs are part of a binary system, or rather, that they are in orbit with one another.

Bansal notes the reason this discovery has taken so long is that the orbital period of the SMBHs is about 24,000 years. That’s due to their incredible mass – together they are 15 billion times more massive than the Sun.

This means that, despite studying the objects for more than a decade, the team has yet to see the slightest curvature in the orbit of the two SMBHs.

The work of Taylor, Bansal and their colleagues will be invaluable in developing a better understanding of what causes mergers between SMBHs and increasing scientific knowledge about the evolution of galaxies and the role these phenomena play in it.

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Angus Bezzina is a writer from Sydney, Australia.
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