Don Pettit is a NASA astronaut recently returned from the International Space Station, orbiting our world. He has uploaded this fantastic series of images depicting star trails. How did he do it? He took long exposure photos (using slow camera shutter speed).
According to Pettit, he took multiple 30-second long exposure, then 'stacked' them together using imaging software, and thus producing this amazing gallery, of star trails and our planet as the space station revolves it at a speed of 28,000 km/h (17,500 mph)!