There may be two supermassive black holes in a distant galaxy on the verge of merging. A high-energy burst of light first observed in 2021 was not consistent with being a supernova, but it did fit with what would be expected when two supermassive black holes orbiting each other pass through a cloud of gas.
What most caught my eye was that they are expected to merge in about 70,000 years. These black holes are estimated to be about 2.7 light years away from each other, and yet they must be radiating away so much energy in the form of gravitational waves that they are close to merging with each other in a relatively short time, astronomically speaking.