A detector just found a black hole so incredibly small that it couldn't have come from a dying star.
March 30, 2026
Original Paper
Primordial Black Hole interpretation of the sub-solar merger event S251112cm
arXiv · 2603.25795
The Takeaway
Stars have a minimum weight required to collapse into a black hole, creating a natural 'size floor' for these objects. Finding one lighter than the Sun suggests it might be a 'primordial' black hole, a relic formed during the first seconds of the Big Bang rather than from a dying star.
From the abstract
The LIGO-Virgo-KAGRA (LVK) candidate event S251112cm suggests the presence of at least one compact object with sub-solar masses. Since such objects cannot be produced through standard stellar evolution, this observation provides a potential indication of non-standard formation channels. Primordial black holes (PBHs), formed from the collapse of primordial density fluctuations in the early Universe, are a well-motivated candidate. We investigate the interpretation of S251112cm as the merger of tw