WASHINGTON—About two billion years ago in a galaxy far beyond our Milky Way, a big star met its demise in a massive explosion called a supernova that unleashed a huge burst of gamma rays, which pack the most energy of any wave in the electromagnetic spectrum.
Those waves traversed the cosmos and finally reached Earth last year. This gamma-ray burst, researchers said on Tuesday, caused a significant disturbance in Earth’s ionosphere, a layer of the planet’s upper atmosphere that contains electrically charged gases called plasma.
