ONCE A MONTH MERGERS. “With this new discovery of neutron star-black hole mergers outside our galaxy, we have found the missing type of binary. We can finally begin to understand how many of these systems exist, how often they merge, and why we have not yet seen examples in the Milky Way.” The researchers believe that one of these violent mergers occurs about once a month within a billion light-years of Earth.“
https://www.cnn.com/2021/06/29/world/black-hole-neutron-star-merger-scn/index.html