Scientists have discovered that small black holes paired with ordinary stars can accelerate particles to extraordinary energies, challenging our understanding of cosmic particle acceleration. The finding comes from research at the Max Planck Institute for Nuclear Physics in Germany, where astronomers detected high-energy gamma rays from an unexpected source – a relatively small stellar system known as a microquasar.
The discovery centers on a cosmic duo called GRS 1915+105, where a black hole slowly consumes matter from a companion star smaller than our Sun. As this cosmic feast occurs, it launches powerful jets of material into space that can accelerate particles to extreme velocities.
“Up until now this was only observed in rare high-mass-microquasar systems,” notes Dr. Laura Olivera-Nieto from the Max Planck Institute for Nuclear Physics and Dr. Guillem MartÃ-Devesa from the University of Trieste, who led the research published in The Astrophysical Journal Letters.
The finding is particularly significant because it reveals that even relatively small cosmic systems can contribute to the stream of high-energy particles bombarding Earth from space. These particles, known as cosmic rays, are among the fastest-moving objects known in the universe, but their origins have long puzzled scientists.
Using NASA’s Fermi satellite, the team analyzed 16 years of data to detect a faint but persistent gamma-ray signal from the system. The energy levels observed – higher than 10 billion electron volts – indicate that these cosmic systems are capable of accelerating particles to even higher energies than previously thought possible for their size.
The research challenges previous assumptions about which cosmic systems can serve as particle accelerators. Until now, scientists believed that only microquasars with massive companion stars, like SS 433 which contains a star ten times heavier than our Sun, could generate such high-energy emissions.
Supporting evidence came from observations using Japan’s Nobeyama 45-meter radio telescope, which revealed sufficient gas material around the source to explain how these accelerated particles might produce the observed gamma rays through collisions.
This discovery suggests that similar small black hole systems, which are far more common in our galaxy than their larger counterparts, might collectively contribute significantly to the cosmic rays reaching Earth. The implications extend beyond our understanding of these particular systems to questions about how galaxies evolve and how matter behaves under extreme conditions.
The findings open new avenues for studying cosmic particle acceleration, particularly in systems previously thought too small to be significant contributors. As telescopes become more sensitive, astronomers expect to find more examples of these miniature but powerful cosmic accelerators.
While this single discovery won’t solve the long-standing mystery of cosmic ray origins, it adds a crucial piece to the puzzle by showing that the universe’s particle acceleration mechanisms are more diverse than previously understood.
“These findings indicate that even microquasars hosting a low-mass star are capable of particle acceleration,” the researchers explain in their paper. The work could lead to a fundamental shift in how scientists view the contribution of these systems to our galaxy’s cosmic ray content.