An article published in “The Astrophysical Journal Letters” reports the detection of gravitational waves emitted by two cases of mergers of a black hole with a neutron star. Scientists from the LIGO, Virgo, and KAGRA collaborations examined data collected by the Advanced LIGO and Advanced Virgo detectors to find evidence of this type of merger in two events detected in January 2020. Previously, there were other candidates but the data left various doubts about the nature of the objects that merged.