Using data from the RadioAstron satellite, astronomers have obtained a radio image of two supermassive black holes at the center of a distant quasar. Coolant 287where the secondary black hole orbits the primary one every 12 years.
This Radio Astron image shows two supermassive black holes at the center of OJ 287, a galaxy located about 5 billion light-years away in the constellation Cancer: if the central component corresponds to the primary black hole, then the next one up marks the secondary black hole, and the tallest component represents a node in its jet; the elongation of individual components is not real, but a reflection of the beam shape. Image credit: Valtonen etc.., two: 10.3847/1538-4357/AE057E.
Quasars are extremely bright galactic nuclei whose light is created when the supermassive black hole at the center of the galaxy consumes cosmic gas and dust around it.
In the past, astronomers have been able to photograph the black hole at the center of the Milky Way and in the neighboring galaxy Messier 87.
“The quasar OJ 287 is so bright that even amateur astronomers using private telescopes can detect it,” said Dr Mauri Valtonen, an astronomer at the University of Turku.
“What's special about OJ 287 is that he was it was believed that it contained not one, but two black holes revolve around each other in a 12-year orbit, creating an easily recognizable pattern of brightness changes over the same period.”
“The earliest sightings of OJ 287 can be traced from old photographs back to the 19th century.”
“However, the existence of black holes, let alone quasars, was unthinkable back then.”
“OJ 287 was 'accidentally' included in the images when astronomers were focusing on other objects.”
Back in 1982, Dr Valtonen noticed that the object's brightness varied regularly over a 12-year period.
He went on to study OJ 287 as a university researcher, theorizing that the change in brightness was caused by two black holes orbiting each other.
Hundreds of astronomers are intensively monitoring the quasar to test whether the theory is correct and to get a complete picture of the orbital motion of black holes.
The orbital mystery was finally solved four years ago by University of Turku astronomer Lankeswar Dey.
The only remaining question was whether both black holes could be detected at the same time.
NASA's TESS satellite responded and detected light from both black holes.
However, they were still only visible as a single dot because images taken under normal lighting do not have high enough resolution to show the black holes individually.
An image with a resolution 100,000 times higher was required, which is possible with radio telescopes.
In the current study, Dr. Valtonen and his colleagues compared earlier theoretical calculations with radio imaging.
The two black holes appeared in the image exactly where they were expected.
This gave the researchers an answer to a question that had remained open for 40 years: whether pairs of black holes even exist.
“For the first time, we have been able to image two black holes orbiting each other,” Dr Valtonen said.
“In the image, black holes are identified by the intense jets of particles they emit.”
“Black holes themselves are completely black, but they can be detected by jets of particles or by the glowing gas surrounding the hole.”
Scientists have also identified a completely new type of jet coming from the black hole.
The jet emerging from the secondary black hole in OJ 287 swirls like a spinning garden hose.
“This is because the smaller black hole is moving rapidly around the primary black hole, and its jet is deflected depending on its current motion,” the authors say.
Their paper was published in Astrophysical Journal.
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Mauri J. Valtonen etc.. 2025. Identification of a secondary jet in a radio astronomy image of OJ 287. APJ 992, 110; two: 10.3847/1538-4357/AE057E
