Two Black Holes Spinning Together 5 Billion Light Years Away. The Picture that Confirms an Astronomy Suspect 40 Years in the Making.
So far, astronomers had only managed to detect solitary black holes – like those in the Milky Way or Messier 87 – or deduce the existence of pairs from gravitational waves after a merger. But this time there is a real image, a portrait of two cosmic giants spinning around each other.
This was possible thanks to an international team led by Mauri Valtonen, from the University of Turku (Finland), and a network of radio telescopes on Earth and in space. The Russian satellite RadioAstron played a key role: it allowed to distinguish two separate sources within the bright glow of the quasar.
“Black holes themselves are invisible, but their particle jets reveal their presence,” explained Valtonen. “In the image, you can see two of these jets: one large and stable, and the other smaller and twisted, curving as it orbits the first.”
### Forty years looking at the same light
Since the 1980s, astronomers had noticed that its brightness increased periodically, every 12 years, as if something – or someone – regularly interrupted the flow of matter from the quasar. That pattern, observed for the first time by Aimo Sillanpää, led to a hypothesis: Decades of models, simulations, and observations reinforced the idea, but the visual proof was missing.
That proof came in the form of an image taken before RadioAstron ended its mission, revealing that the main black hole has a mass 18,000 times greater than that of the Sun, while the secondary, much lighter.
### A milestone that rewrites modern astrophysics
Visually confirming a binary system opens up a new way to study how black holes grow and merge, the most energetic processes in the universe.
However, they warn that doubts persist: the two jets could, in theory, come from the same source with a complex structure. Only a future space mission with the resolution of RadioAstron will be able to definitively dispel the uncertainty.
For now, the truth is that the image exists, and it shows what was only a suspicion for forty years. They dance in a spiral at the heart of OJ287, reminding us that even in the farthest cosmos, time – like space – can also have a partner.
