In 2023, astrophysicists announced the detection of a “hum” of gravitational waves permeating the universe. They hypothesized that this background signal emanated from millions of merging pairs of supermassive black holes (SMBHs), each billions of times more massive than our Sun.

However, theoretical simulations showed that as pairs of these mammoth celestial objects spiral closer together, their approach stalls when they are roughly a parsec apart — a distance of about three light years — thereby preventing a merger.

Not only did this “final parsec problem” conflict with the theory that merging SMBHs were the source of the gravitational wave background, it was also at odds with the theory that SMBHs grow from the merger of less massive black holes.

Now, a team including Gonzalo Alonso-Álvarez has shown that pairs of SMBHs can indeed break through the one-parsec barrier and merge into a single larger black hole. According to their new calculations, SMBHs continue to draw closer together because of previously overlooked interactions with particles within the vast cloud of dark matter surrounding them.

More information here: https://www.artsci.utoronto.ca/news/astrophysicists-uncover-supermassive-blackholedark-matter-connection-solving-final-parsec