The image shows two bright points, each representing a jet of high-energy particles emitted by one of the black holes.
The discovery centres on quasar OJ287, located five billion light-years from Earth in the constellation Cancer. Quasars are the luminous cores of distant galaxies, powered by the gravitational energy of supermassive black holes.
Researchers have released the first confirmed image of two black holes orbiting each other. The observation confirms a theory that has remained unproven for more than 40 years.
The black holes themselves remain invisible, but the image provides clear visual evidence of their position, motion, and dual existence. The larger of the two has a mass estimated at 18 billion times that of the Sun. The smaller is around 150 million times the Sun’s mass.
The team behind the discovery used radio data collected a decade ago by the RadioAstron satellite, whose antenna extended to nearly halfway between Earth and the Moon. This allowed for an image resolution roughly 100,000 times higher than that achieved by Earth-based telescopes.
Mauri Valtonen, an astronomer at the University of Turku and lead author of the study published in the Astrophysical Journal, said the image marks the first direct evidence of a binary black hole system. “For the first time, we managed to get an image of two black holes circling each other. The black holes are identified by the intense particle jets they emit,” he said.
The existence of two black holes in OJ287 was first suggested in 1982. Aimo Sillanpää, then a graduate student at the University of Turku, observed that the brightness of the quasar changed regularly over a 12-year cycle. The pattern implied that two massive objects were orbiting each other and affecting the quasar’s brightness as they passed through surrounding matter.
For decades, scientists monitored the object using various observational tools, including the NASA TESS satellite, which captured visible light from both black holes. However, those observations lacked the resolution to separate the two sources. Only radio telescopes, particularly those operating in space, could deliver the needed clarity.
The new image was compared to predictions from models developed by researchers, including calculations by Lankeswar Dey, a doctoral researcher from Mumbai who contributed to orbit predictions for the OJ287 system. The jets appeared exactly where the models said they should, confirming both the orbital pattern and the binary nature of the system.
The scientists also detected a new phenomenon in the smaller black hole’s jet. The jet twists in different directions, resembling the motion of a garden hose as it spins. The team attributes this to the speed and direction of the black hole’s orbit, which alters the trajectory of the jet over time. They believe future images will show the jet’s orientation changing as the black hole moves.
The presence of two black holes at the centre of a quasar supports long-standing predictions about the evolution of galaxies. Black hole mergers are thought to be common in galactic history, but direct visual proof has been rare. Until now, evidence of binary systems relied on indirect observations, such as gravitational waves or variations in light from distant objects.
Valtonen said that the achievement depended on combining past data with modern theoretical models. “The two black holes were exactly where we expected them to be,” he said.
The use of the now-retired RadioAstron satellite was key to the success of the project. Since 2019, radio observations have relied on ground-based telescopes, which do not have the same imaging capacity.
The image of the two black holes was produced by analysing the radio emissions from OJ287 captured during RadioAstron’s mission. Scientists identified the lower two bright spots in the image as the jets from the black holes. A third bright spot was traced to the smaller black hole’s jet.
The discovery follows earlier black hole imaging milestones. In 2019, astronomers captured the first image of a black hole in the galaxy Messier 87. Later, a similar image was obtained from the centre of the Milky Way. Both were single black holes.
The new image is the first to show two supermassive black holes locked in a stable orbit around each other. The system’s 12-year orbital period means researchers can track future movements and verify the pattern of interactions between the pair.
Valtonen said that even amateur astronomers can detect light from OJ287, though the two black holes themselves remain beyond the range of optical telescopes.
HT