Web edition: February 21, 2013
About 100 years ago, researchers discovered a large numbers of very small particles slamming into Earth’s upper atmosphere at high speeds. The mystery particles arrived from all directions. They came from an unknown source apparently outside our solar system. Scientists called them “cosmic rays.”
Now, a century later, a team of scientists has found the origins of most cosmic rays. They are born from clouds of gas surrounding the ancient and massive explosions of distant stars.