Astrophysicists have discovered that star-forming regions in nearby galaxies shine brightly with gamma-rays — yet more evidence that supernovae are a driving engine behind cosmic rays, the particles that continuously bombard the Earth. The results were announced today by the Fermi gamma ray space telescope team, which is holding a symposium this week in Washington DC to celebrate its one-year results.

The Fermi team looked at a nearby satellite galaxy, the Large Magellanic Cloud, and found gamma-rays — the most energetic part of the electromagnetic spectrum — emanating from a known starburst region. This suggests that the life-and-death fury in these regions — strong winds from massive, short-lived and hot stars, and shock waves from supernovae explosions — is responsible for accelerating cosmic rays, which in turn create a gamma-ray signal. Cosmic rays are protons or other ionized particles, and they create light in the form of similarly high-energy gamma rays when they collide with other material.

Team member Jürgen Knödlseder, of the Center for the Study of Space Radiation in Toulouse, France, said he was surprised to see how well confined the gamma-rays were to the starburst region. In the Milky Way, cosmic rays have been whipped into a diffuse halo by galactic magnetic fields. Knödlseder says that perhaps the chaotic region creates an intense and tangled magnetic field that keeps the cosmic rays in place.

Scientists from the Veritas observatory — a ground-based gamma-ray observatory — chipped in with results from a two year survey. These showed that gamma-rays of even higher energy than those detected by Fermi are streaming in from two nearby galaxies with known star-forming regions. This suggests that not only are star-forming regions responsible for generating the gamma-rays (via cosmic rays), but that the regions can make very high energy particles indeed.

Image: NASA/DOE/Fermi LAT Collaboration