Hidden power in the Milky Way: physicists have discovered new particle accelerators in space.

Astrophysicists have discovered that small black holes in systems with ordinary stars can accelerate particles to extreme speeds, allowing them to achieve very high energy levels. This challenges existing theories regarding the acceleration of cosmic particles. The discovery was made when scientists detected high-energy gamma rays from an unexpected source, which turned out to be a low-mass system known as a microquasar. The research has been published in The Astrophysical Journal Letters, reports Phys.

Cosmic Rays

Subatomic particles, such as electrons and protons, continuously arrive on Earth from the interstellar space of our Milky Way galaxy. These particles are among the fastest in the universe and are referred to as cosmic rays.

The exact mechanisms by which particles are accelerated to very high energies remain one of the biggest mysteries in astrophysics. It is believed that plasma jets emitted by black holes provide an ideal environment for particle acceleration. However, the precise process of acceleration is still unclear.

Microquasars

The strongest plasma jets in the Milky Way are produced by stellar-mass black holes that are part of a system with an ordinary star. Such systems are called microquasars. When a star moves too close to a black hole, the latter begins to absorb the star, ejecting some of the matter into space in the form of jets.

Astrophysicists suggest that these jets are the most efficient particle accelerators in space. Microquasars typically come in two varieties: low mass and high mass, depending on the mass of the star in the system. Less massive quasars are found in our galaxy much more frequently.

However, so far, evidence of particle acceleration has only been found in high-mass microquasars. This indicates that low-mass microquasars cannot serve as particle accelerators.

The authors of the study used the Fermi Space Telescope to examine a microquasar called GRS 1915+105, which consists of a black hole and a star smaller than our Sun. It turned out that the black hole emits powerful plasma jets into space that can accelerate particles to extreme speeds.

A New Particle Accelerator in Space

This discovery demonstrates that even relatively small microquasars can contribute to the flow of high-energy particles, that is, cosmic rays.

Astrophysicists detected sustained gamma radiation from the microquasar, which has energies exceeding 10 billion electron volts, indicating that the system may accelerate particles to even higher energies than previously thought possible for such low-mass systems.

Observations show that protons are accelerated in the jets of black holes, after which they escape and interact with nearby gas, generating gamma photons.

This discovery suggests that low-mass microquasars, which are more prevalent in our galaxy than their massive counterparts, can collectively make a significant contribution to the cosmic rays reaching Earth.

Although this discovery does not solve the long-standing mystery of the origin of cosmic rays, it adds an important piece to the puzzle, indicating that the mechanisms for particle acceleration in the universe are more diverse than previously believed.