Researchers want to use black holes as particle accelerators

Why build a large particle accelerator when there are much larger ones in space? Supermassive black holes could become the future research sites where scientists gain insights into dark matter, say Andrew Mummery and Joseph Silk from Johns Hopkins University. This could make the construction of expensive facilities on Earth superfluous.

Dark matter makes up the largest part of the universe, about 85 percent. It does not interact with light and therefore remains hidden. All known particles interact with light, which is why dark matter cannot consist of standard particles. All attempts to get hold of it have so far failed.

Particle accelerators such as the Large Hadron Collider (LHC) in Geneva accelerate protons and other subatomic particles to almost the speed of light and then cause them to collide with each other. Previously unknown particles can be discovered in energy discharges and decay products, such as the Higgs boson in 2012.

“One of the big hopes for particle accelerators like the Large Hadron Collider is that they will create dark matter particles, but we haven't seen any evidence of that yet,” Silk said. “That's why we're currently discussing building a much more powerful version, a next-generation supercollider.”

A supercollider will be expensive

However, such a facility could cost 30 billion US dollars and take 40 years to build. Mummery and Silk have a different idea: in an article in the journal Physical Review Letters, they propose using supermassive black holes as particle accelerators.

Supermassive black holes, which have millions or even billions of times the mass of the sun, are often located at the center of a galaxy. Like a planet, such a black hole rotates around its axis, but much faster due to its intense gravitational field. An accretion disk of matter rotates around such a black hole. The black hole attracts this and ejects part of it in the form of plasma jets at almost the speed of light. According to the researchers, these events could produce the same effects as a man-made particle accelerator.

Researchers on Earth could observe the particle collisions with observatories with which they already observe cosmic events such as supernovae or massive black hole eruptions. Such detectors already exist, such as the IceCube Neutrino Observatory at the South Pole or the Kilometer Cube Neutrino Telescope in the Mediterranean, which recently recorded a neutrino with an energy record.

“If supermassive black holes can produce these particles through high-energy proton collisions, then we could get a signal on Earth, really high-energy particles flying fast through our detectors,” Silk said. “That would be evidence of a new kind of particle accelerator in the most mysterious objects in the universe, reaching energies that can't be reached in any terrestrial accelerator. We would see something with a strange signature that may provide evidence of dark matter.”

(wpl)