Cosmic rays are accelerated toward Earth by the same kind of supernova explosions that carved this bubble into the Large Magellanic Cloud. (Credit: Gemini South Telescope in Chile; composite by Travis Rector of the University of Alaska Anchorage)
Sometime in the last few million years, a not-so-far-off supernova sent charged particles known as cosmic rays out in all directions. The scattered, stripped nuclei of radioactive iron isotopes eventually made their way to Earth as part of a larger stream of material. Now, researchers at Washington University in St. Louis have found traces of this stream bombarding our planet, bringing interstellar atomic debris crashing into Earth.
