The Conversation has published an article by me and Andrew Norton on the probable recent discovery by gravitational microlensing of the first isolated, quiescent black hole:
Astronomers famously snapped the first ever direct image of a black hole in 2019, thanks to material glowing in its presence. But many black holes are actually near impossible to detect. Now another team using the Hubble Space Telescope seems to have finally found something nobody has seen before: a black hole which is completely invisible. The research, which has been posted online and submitted for publication in the Astrophysical Journal, is yet to be peer-reviewed.