Harvard astrophysicist Avi Loeb has raised a provocative question that could rewrite our understanding of the universe: Have we just detected a 'black hole moon'?
On 12 November 2025, the international LIGO/Virgo/KAGRA (LVK) collaboration recorded an unusual gravitational wave signal labelled S251112cm. This detection was not remarkable for its volume, but for its impossible weight. One component of the merger appeared to be a sub-solar mass object, weighing significantly less than our Sun.
