Researchers had previously linked sunquakes to solar flares, eruptions on the sun that can send powerful bursts of x-rays, ultraviolet light, and matter into space. (See video: "Solar Flares Cause 'Sunquakes.'")

On February 15, 2011, researchers spied two sunquakes and a solar flare that occurred around the same time—but the flare wasn't hot enough to have spawned the seismic waves.

"The heat and radiation from solar flares is thought to drive a pressure wave to the surface, like thunder from a lightning bolt. But for this February 15th event, it wasn't like that," said Sergei Zharkov, a space scientist at University College London, who presented the new findings about sunquakes last month at the 2012 National Astronomy Meeting in