A decade of cosmic flickering reveals new clues about a rare giant binary black hole system

A multi-institutional study coordinated by the Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, tracked the changing brightness, colour, and polarization of the peculiar blazar OJ 287 over a decade (2015 to 2025). Located about 4 billion light years away, OJ 287 is a rare giant binary black hole system containing two supermassive black holes in a 12-year orbit that produce powerful plasma jets. The international team utilized ground- and space-based telescopes across the electromagnetic spectrum to produce extensive optical time-series data, helping determine the relative positions of the black holes, estimate the central black hole mass at least 3.89 billion solar masses, and advance studies in multimessenger astronomy.