Astronomers have been able to observe the powerful shock waves produced during the cosmic pinball game of energetic particles slamming into the gas surrounding galaxy NCG 3079. Thanks to the sharp eye of NASA’s Chandra X-ray telescope, researchers were able to see the shock waves in two large superbubbles exploding from the core of the galaxy.
NCG 3079 is a spiral galaxy like the Milky Way located 67 million light-years from us. The two superbubbles are perpendicular to the disk of the galaxy and stretch for 4,900 and 3,600 light-years each. These superbubbles might be the origin of the most powerful energetic cosmic rays.
What researchers have detected is the interaction between the gas surrounding the galaxy and the particles accelerated by the central supermassive black hole and associated magnetic field. When the gas and charged particles meet, shock waves form. When particles cross the shock wave front, they get accelerated by the tangled magnetic fields present and then they shoot out with energy a hundred times higher than what we can produce in the largest particle colliders.
As reported in the Astrophysical Journal, the team thinks that the radio and X-ray emission from the bubbles that allowed Chandra to detect them is clear evidence that the particles must have been accelerated there, rather than simply scattered. They would have lost too much energy being transported from the galaxy core.
Researchers have a couple of ideas on how the particles are first thrown away from the center of the galaxy. The supermassive black hole there might have gone through a feeding period, and during the frenzy of gobbling up material, some might have been thrown out of the galaxy. Another explanation is star formation feedback pushing gas out of the core.
Researchers believe that these superbubbles might tell us something about our own galaxy. In 2010, astronomers discovered that the Milky Way had two large bubbles, stretching above and below the center of the galaxy for a total length of 50,000 light-years. They are known as the Fermi Bubbles after the gamma-ray telescope Fermi, which was instrumental in their discovery. However, the Fermi Bubbles are much older than what we see in NGC 3079 and more energetic.