Is Dark Matter Just Black Holes Made During the Big Bang?

Advocates of the primordial black hole hypothesis still have a lot of convincing to do. “There are things that are weird about some of the LIGO sources, but we can explain everything that we’ve seen so far through normal stellar evolutionary process.” Selma de Mink, an astrophysicist at Harvard University who has sketched out theories for how stars alone can produce the heavy black hole binaries seen by LIGO, is more blunt: “I think astronomers can laugh a bit about it.” Finding just one black hole of sub-solar mass—which should be common, according to the primordial black hole scenario, and which can’t form from stars—would transform this entire debate. And with every subsequent observing run, LIGO has increased its sensitivity, allowing it to eventually either find such small black holes or set strict limits on how many can exist. But if primordial black holes exist at a range of masses, and if they’re packed into dense, massive clusters, those results could be less significant than researchers thought, García-Bellido said. The addition came at the behest of Günther Hasinger, ESA’s science director, who made the case that primordial black holes could explain multiple mysteries.