Astronomers Spot Two Supermassive Black Holes on a Collision Course

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Astronomers Spot Two Supermassive Black Holes on a Collision Course
A super-close supermassive black hole pair in a nearby galaxy.
The galaxy NGC 7727 (right) and a zoomed-in view (left) showing the two galactic nuclei that contain the supermassive black holes.

Through a standard telescope, the nearby galaxy NGC 7727 looks like a gossamer tumbleweed drifting in the night sky. But within it are two supermassive black holes locked in a dance that will end with their violent merger. As a team of astronomers recently found, these objects are closer to Earth than any other supermassive pair.

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One of the black holes is 6.3 million times the mass of the Sun, while the other is a whopping 154 million solar masses. The duo is located 89 million light-years from Earth in the constellation Aquarius. The team determined the objects’ masses by studying how their gravitational pulls affected stars in their vicinity.

Supermassive black holes lurk at the center of galaxies—our own galaxy hosts Sagittarius A*, a roughly 4 million solar mass black hole 26,000 light-years from Earth. When two galaxies merge, the black holes end up circling one another and eventually merging themselves. These black hole mergers are some of the most violent astrophysical phenomena in the universe, and they generate the gravitational waves famously predicted by Einstein and first observed in 2015.

The nearness of the NGC 7727 pair blew the previous record-holding pair out of the interstellar water—that pair was 470 million light-years from us. The team’s research is set to publish in Astronomy & Astrophysics.