Black holes famously swallow just about anything that drifts too close, but it turns out their cosmic appetite may have a surprising influence on Earth. Recent findings, based on 16 years of data from NASA’s Fermi Gamma-ray Space Telescope, suggest that even smaller-scale black holes—known as “microquasars”—can accelerate particles to astonishing speeds. These high-energy particles, or “cosmic rays,” constantly bombard our planet, and astronomers are now taking a closer look at how mini-star-munching black holes might play a bigger role than previously believed.
Small but Mighty: The Surprising Power of Microquasars
When most of us hear “black hole,” we picture supermassive giants lurking at the centers of galaxies, churning out intense light shows known as quasars. However, there’s another category of black holes called microquasars. These involve stellar-mass black holes—just a few times heavier than our Sun—locked in close orbit with a companion star. Over time, the black hole slowly siphons material from its stellar partner.
This steady “snacking” is far less dramatic than the tidal disruption events that tear stars apart in one violent gulp. Despite that gentler approach, new research shows these mini black holes can launch incredibly potent jets of matter, turning them into natural particle accelerators capable of creating high-energy gamma rays.
A New Target in the Sky: GRS 1915+105
Astronomers led by Guillem Martí-Devesa (Università di Trieste) and Laura Olivera-Nieto (Max Planck Institute for Nuclear Physics) focused on a specific microquasar called GRS 1915+105—also known by the name “V1487 Aquilae.” Unlike previously studied microquasars that feed on large, massive stars, GRS 1915+105 involves a black hole devouring a star only about half the mass of our Sun.
Surprisingly, this miniature cosmic cannibal generates powerful outflows—relativistic jets—that can hurl charged particles to near-light speeds. As these jets collide with surrounding material, they can produce gamma rays, an indicator that a particle accelerator is at work. The Fermi telescope’s 16-year data set revealed a gamma-ray signal coming from GRS 1915+105, signaling it’s an active contributor of high-energy cosmic rays.
Microquasars vs. Quasars
Quasars: Powered by supermassive black holes millions or billions of times the Sun’s mass, typically found at the centers of galaxies. Microquasars: Driven by smaller stellar-mass black holes—only a few to a few dozen times heavier than the Sun—feeding on a nearby companion star.
What unites them is the presence of energetic, near-light-speed jets. The discovery that even low-mass microquasars can produce gamma rays indicates that these objects may be more abundant cosmic accelerators than scientists realized.
Why It Matters: Cosmic Rays and Earth
The presence of cosmic rays on Earth—mainly protons and electrons—has long fascinated astrophysicists. Their origins have been hotly debated, with possibilities ranging from exploding stars (supernova remnants) to blazars and quasars in distant galaxies. Now, microquasars join the list of suspected major contributors.
Given that low-mass stars are far more common in our galaxy than massive ones, there could be many more “quiet” microquasars out there steadily eating smaller stars and creating gamma-ray signals. If that’s the case, the cosmic-ray budget reaching Earth might need some serious updating.
Next Steps: A Cosmic Census of Star-Eaters
Scientists hope to apply these findings to other microquasar systems that show no obvious signs of high-energy activity. By comparing “quiet” microquasars to luminous ones like GRS 1915+105, researchers aim to uncover why only some of these black hole-star duos become potent particle accelerators.
According to the team, this research could help refine our understanding of how particle acceleration works and shed light on the role these cosmic engines play in seeding the galaxy—and Earth—with high-energy particles.
This fresh look at GRS 1915+105 shows that you don’t need a towering supermassive black hole to unleash extreme cosmic power. Even small black holes with small snack-sized stars can generate jets strong enough to hurl particles across the galaxy. As these findings suggest, the Milky Way may harbor more of these lesser-known (yet mighty) microquasars than we think—each one possibly churning out cosmic rays that eventually rain down on our planet.
Researchers have published these results in The Astrophysical Journal Letters, marking an exciting step toward understanding just how influential these stellar-mass black holes can be. If you’ve ever wondered where those mysterious cosmic rays pelting our atmosphere come from, keep your eyes on the skies—because the smallest star-gobbling black holes might just be packing the biggest punch.