A first in the history of science: They were viewed simultaneously

Located approximately 5 billion light-years away, these two black holes orbit each other in a 12-year orbit. The observation was made possible by highly sensitive data from radio telescopes both on Earth and in space. What caught the astronomers' attention was not the light emitted from the black holes, but the near-light-speed particle jets surrounding them.

The larger component of the system is a supermassive black hole known as OJ287, a blazar with a mass 18 billion times that of the Sun. The smaller black hole emits a pulsating jet, like a swirling garden hose or a wagging dog tail.

"Black holes cannot be seen directly because they are completely dark. However, their location can be detected thanks to their jets," said astronomer Mauri Valtonen of the University of Turku in Finland and lead author of the study.

In fact, observations of the OJ287 system date back to the 19th century. At that time, the existence of black holes was unknown, but the system's intermittent brightening and dimming patterns attracted attention. From the 1980s onward, it was suggested that these irregularities could be explained by a pair of black holes. However, until now, a telescope powerful enough to resolve these two black holes separately has not been achieved.

This milestone came thanks to the Russian-built space telescope RadioAstron, which was active between 2011 and 2019. Its antenna, with its range from Earth to the Moon, provided previously unattainable resolution. This image, compared to previous calculations, confirmed that both black holes' particle jets were located where they should be.

However, scientists remain cautious. They haven't ruled out the possibility that the two jets in the image could be superimposed, meaning that a single black hole could actually be involved. The team notes that future, high-resolution observations like those from RadioAstron will allow the "tail wagging" motion of the smaller black hole to be clearly visible.