High-energy cosmic rays traced to Milky Way’s central black hole

Science : Earth’s atmosphere is constantly pelted by charged subatomic particles from space called cosmic rays. Scientists have traced the particles’ origins to several sources inside and outside the galaxy, though such detective work is difficult because the particles don’t travel on straight-line trajectories. Now a team of researchers has identified a new culprit in the production of high-energy cosmic rays: Sagittarius A*, the supermassive black hole at the center of the Milky Way. Scientists with the High Energy Stereoscopic System (HESS), a five-telescope array in Namibia, based their conclusion on an abundance of gamma rays emanating from the central region of the galaxy. Although Sagittarius A* seems relatively inactive, the researchers propose that strong electric and magnetic fields near the black hole fling protons at enormous speeds. Those protons then crash into gas molecules and produce gamma rays, which HESS can detect. The study concludes that while supernova explosions are thought to produce many of the speediest cosmic rays within the galaxy, Sagittarius A* may be responsible for particles with especially high PeV energies.