By Nadia Drake
Some of the mysterious, high-energy cosmic rays that bombard Earth may hatch from a colossal, gassy superbubble carved into space by hyperactive young stars in the Cygnus X region of the sky.
“We can pin down that — at least in this region — there are cosmic ray sources,” says astronomer and astrophysicist Isabelle Grenier, who led the study reported in the Nov. 25 Science. “It proves the point that cosmic ray factories are hiding in these environments.”
Cosmic rays are actually subatomic particles — mostly protons and electrons — that zip across space, perhaps spurred to nearly light-speed by supernova shockwaves or stellar winds. Because they’re charged, the particles are bounced around by magnetic fields during their journeys, making it difficult to follow their paths back to the beginning. “It’s like trying to cross a Jacuzzi,” says Grenier, of the University of Paris Diderot.
To get around this wandering particle problem, Grenier and the team decided to track gamma rays, which are produced when cosmic rays collide with interstellar particles and which the team could use to trace the rays’ origins. The team aimed the space-based Fermi Large Area Telescope toward Cygnus, hoping to spy a telltale glimmer from gamma rays inside the region’s superbubble, which is more than 100 light-years across and contains more than 500 massive stars.