A supermassive binary black hole system https://www.mpg.de/19917498/0217-radi-oj287-blackholes-150300-x?c=12135602
A large-scale observation campaign with four observatories is examining the nucleus of the active galaxy OJ 287. The telescopes are observing from radio waves to the X-rays and gamma-rays. A series of recurring brightness outbursts strengthens the suspicion of a supermassive black hole binary. At 100 million solar masses, the heavier of the two is a hundred times lighter than previously assumed.
Max Planck Institute for Radio Astronomy has now revised the previously favoured model