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Cosmic Rays Traced to Centers of Star Birth

from Science News

WASHINGTON, D.C. -- Astronomers have for the first time traced gamma rays, the most energetic form of light, to galaxies undergoing a frenzy of star birth. The finding, which has revealed a new class of galactic gamma-ray sources, is not unexpected. But it provides new hints about the origin of many cosmic rays, the high-speed protons and other charged particles of extraordinarily high energies that bombard Earth.

According to the prevailing theory, cosmic rays are accelerated to energies of billions to trillions of electron volts by the expanding shock waves generated when massive stars explode as supernovas. (Cosmic rays with even higher energies are thought to be powered by supermassive black holes at the centers of galaxies.)

Kinks in a galaxy's magnetic field keep the particles, mainly protons and other charged particles, bouncing back and forth like ping-pong balls between the advancing shock wave and the region just in front of it, revving up the particles to these high energies, the model suggests.