Two Black Holes Circling Each Other Captured In Image For The Very First Time

Quasar OJ287 is not wildly famous, but it is so bright that it can be seen even by amateur astronomers. Its brightness is due to the extremely active supermassive black hole at its center. But the black hole is not alone; it has a companion, as some intriguing, first-of-a-kind radio images have witnessed.

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Active black holes can emit a jet of particles as they feed on material that surrounds them. The team behind these new images was finally able to distinguish the signature of not just one but two jets from the quasar, a hallmark sign of a second active black hole.

"For the first time, we managed to get an image of two black holes circling each other. In the image, the black holes are identified by the intense particle jets they emit. The black holes themselves are perfectly black, but they can be detected by these particle jets or by the glowing gas surrounding the hole," first author Mauri Valtonen from the University of Turku, Finland, said in a statement.

The peculiarity of this object has been known for a while. In visible light, there are 136 years' worth of observations of this object that show changes in brightness every 12 years. The implication is that the second black hole orbits the first in that time.

"Quasar OJ287 is so bright that it can be detected even by amateur astronomers with private telescopes. What is special about OJ287 is that it has been thought to harbor not one but two black holes circling each other in a 12-year orbit, which produces an easily recognizable pattern of light variations in the same period," added Valtonen.

The work estimates that the largest black hole is a whopping 18 billion times the mass of the Sun, with its "smaller" companion being around 150 million times the mass of the Sun. The authors argue that their model of the two black holes is in agreement with the radio observations (including space radio observations), as well as a huge optical flare seen in 2021.

"The image of the two black holes was captured with a radio telescope system that included the RadioAstron satellite. It was in operation a decade ago, when OJ287 was imaged. The satellite's radio antenna went halfway to the moon, which greatly improved the resolution of the image. In recent years, we have only been able to use Earth-based telescopes, where the image resolution is not as good," Valtonen says.

The study is published in The Astrophysical Journal.