Neutrinos Reveal Hidden Black Holes ✦
Spinning black holes can build particle clouds around them, giving off neutrinos—those almost untouchable 'ghost particles'. If dark matter were made of such holes, Earth's detectors would have already picked up an excess signal. But data from Borexino and Super-Kamiokande say otherwise: black holes are probably not the main ingredient of dark matter. Seems it's hiding deeper.
In the 1970s, Vera Rubin noticed that stars on the outskirts of galaxies were moving faster than expected — that's how dark matter was discovered. One hypothesis: it's made of primordial black holes — clumps of matter that formed in the first moments after the Big Bang. They were searched for via gravitational lensing, but black holes with the mass of a mountain, compressed to the size of an atom, remained elusive.
A new approach is to use neutrinos. A spinning black hole, like a spinning top in a puddle, splashes out energy, creating a cloud around itself and producing a stream of neutrinos. This mechanism was first described by Roger Penrose. Unlike the slow Hawking evaporation (discovered by Stephen Hawking), spin gives a detectable signal. Scientists calculated how many of these 'drops' reach Earth, accounting for the stretching of space and energy losses along the way — cosmological redshift, which is influenced by the accelerating expansion driven by dark energy.
Comparison with data from the Borexino, KamLAND, and Super-Kamiokande detectors showed that such black holes can make up only a tiny fraction of dark matter. So the main components are something else, and neutrinos become a tool to find them. The method is based on the echoes of the first moments in the cosmic microwave background.
🎯 A black hole with the mass of a mountain, compressed to a point smaller than an atomic nucleus, spinning, spews neutrino jets — millions of particles per second, like a tiny cosmic firehose.