Scientists may have solved a cosmic mystery: microquasars, stellar systems consisting of a black hole and a star, could be the source of high-energy cosmic rays hitting the Earth.
A microquasar is a black hole that, in a binary system, devours matter from a nearby star, hence their nickname of "vampire black hole". This matter is then ejected in the form of high-speed jets from the poles of the black hole. These jets seem to play a crucial role in the acceleration of cosmic particles.
Illustration of a black hole absorbing matter from a star in a microquasar.
Image Credit: NASA/ CXC/M.Weiss
Cosmic rays, discovered in 1912, are particles of very high energy, much more powerful than those generated by the Large Hadron Collider (LHC), the largest and most powerful particle accelerator on Earth.
The study focuses on the microquasar SS 433, located in the debris of the supernova W50, about 18,000 light-years from Earth. This microquasar includes a black hole of about 10 to 15 times the mass of the Sun and a white supergiant star. The matter jets emitted by SS 433 shape the W50 nebula, giving it a shape resembling a manatee.
The team used the High Energy Stereoscopic System (H.E.S.S.) in Namibia to observe SS 433. They detected very high-energy gamma rays emanating from the microquasar's jets, suggesting that these jets accelerate particles to high speeds.
These findings indicate that microquasars, like SS 433, could be significant sources of high-energy cosmic rays. However, SS 433 cannot be the direct source of the most energetic cosmic particles reaching Earth, due to its young age and distance. Nonetheless, other older and closer microquasars could contribute to these cosmic rays.
This research opens up new perspectives on the role of microquasars in our galaxy and could help to better understand the particle acceleration mechanisms.
Cosmic Rays: An Extreme Energetic Phenomenon
Cosmic rays are extremely energetic subatomic particles coming from space. Primarily composed of protons (hydrogen nuclei) and sometimes heavier atomic nuclei, they travel through the Universe at speeds close to that of light. When they reach the Earth's atmosphere, these cosmic rays interact with air molecules, creating a shower of secondary particles observable by various instruments.
These particles were discovered in the early 20th century and remain a crucial subject of study in astrophysics. Their exact origin is still partly mysterious, but they are thought to come from various sources, like supernovas, black holes, pulsars, and, as recent research indicates, microquasars.
What makes cosmic rays particularly intriguing is their extremely high energy, often much higher than we can produce in particle accelerators on Earth. Some of these rays have energy billions of times higher than that generated by the Large Hadron Collider (LHC).
Cosmic rays are not only important for understanding the energetic phenomena of the universe. They also have an impact on Earth. For example, they can affect the electronic systems of satellites and aircraft. Moreover, they contribute to the production of radionuclides in the atmosphere, which is used in fields like carbon-14 dating in archaeology.
The study of cosmic rays is therefore essential for understanding not only the physical processes at work in our Universe but also for apprehending their effects on our planet and our technology. Current research, like those conducted on microquasars, helps scientists unravel the mysteries of these particles and better understand the energetic universe we live in.