Video: 'Giant hole' in sun spotted by spacecraft The giant coronal hole, which covers nearly a quarter of the sun's surface, was filmed releasing solar material and gases into space. It was observed between July 13-18 this year by the Solar and Heliospheric Observatory, or Soho spacecraft. According to Nasa, coronal holes are "dark, low density regions of the sun's outermost atmosphere, the corona. They contain little solar material, have lower temperatures, and therefore, appear much darker than their surroundings. They are a typical feature of the sun, but they appear in different places and can be of a different frequency, depending on the sun's activity cycle. "While it's unclear what causes coronal holes, they correlate to areas on the sun where magnetic fields soar up and away, failing to loop back down to the surface, as they do elsewhere," according to Nasa's Karen Fox. Courtesy: Nasa, Esa, Soho