Black hole observations solve cosmic-ray mystery

Data from an African observatory show that jets from a collapsed star are capable of producing some of the Galaxy’s fastest particles.


Pinpointing the Origin of Energetic Particles

An array of telescopes in Namibia has pinpointed the origin of some of the most energetic particles in the Galaxy. The observations suggest that particles of matter emitted by a black hole in the Manatee Nebula are accelerated to near-light-speed.

The findings, published on 25 January in Science by researchers at the High Energy Stereoscopic System (HESS), contribute to the understanding of cosmic rays and their origins. Cosmic rays are fast-moving atomic nuclei and other particles that constantly collide with Earth's upper atmosphere.

Cosmic Rays from Black Hole Jets

The research indicates that plasma jets from black holes, even smaller ones known as microquasars, could be a source of cosmic rays. Microquasars are several times more massive than the Sun and are also bright sources of X-rays and radio waves. The energies produced by microquasars may fall between those produced by supernovae and quasars, contributing to the cosmic-ray population.

Astrophysicist Laura Olivera-Nieto and her team studied a microquasar called SS 433, which forms a binary system with a large star in the Aquila Constellation. Matter ejected from the star spirals around the black hole and generates highly energetic jets. The researchers believe that the Manatee Nebula, a shell of dust and gas formed from a supernova, is the source of the cosmic rays produced by SS 433.

Locating the Source of Cosmic Rays

Due to magnetic fields, cosmic-ray particles originating from a microquasar travel to Earth in spirals, making it impossible to trace their paths back to a specific source. However, astrophysicists can search for γ-ray photons, which are produced in the same processes that accelerate cosmic-ray particles. Astronomers at the High Energy Stereoscopic System (HESS) have precisely located the γ-ray emission in the Manatee Nebula, indicating where the cosmic rays are likely produced.

HESS uses imaging techniques to detect flashes of light produced by particles in the upper atmosphere. This allows for the precise location of the γ-ray photons and reveals that they are generated internally within the jets rather than through collisions with other matter. The discovery supports the idea that X-ray binaries, including microquasars, are capable of accelerating cosmic rays.