Fight Clubs of the Cosmos

Astronomers thought they had black hole formation figured out: massive star burns out, collapses under its own gravity, done. Except some of these objects are too big for that story to hold. A new study published May 7, 2026, says the largest stellar-mass black holes weren't born, they were built.

Researchers identified two distinct populations of stellar-mass black holes. Those under 45 times the mass of our sun formed the expected way, from the collapse of dying stars. But those over 45 solar masses are a different problem entirely. Astronomers have long suspected they're too massive to have come from a single stellar collapse.

The tell is in the spin. The bigger ones spin faster, and their rotation axes point in wildly different directions compared to the smaller population. That kind of erratic, inconsistent rotation is a signature of violence, not orderly stellar death. That shift in spin behavior above 45 solar masses doesn't fit a single-star origin story, but it makes sense if those black holes had already survived multiple mergers inside dense star clusters.

The leading explanation is sequential: smaller black holes colliding, merging, colliding again, each round producing something heavier and stranger. Picture a cosmic demolition derby running on loop over millions of years, each collision producing something bigger and more disoriented than what came before.

Gravitational waves from merging black holes encode the mass and spin of the original objects in the system, which means LIGO and its counterparts aren't just detecting events. They're reading the biographies of objects that have been through the grinder more than once.

The biggest black holes aren’t born. They’re forged by repeated cataclysmic collisions.

Read the full story at EarthSky, May 7, 2026

Hot Take: Black holes broke rules one and two of Fight Club: they’re talking about the clashes, and loudly, via gravitational waves.