This amazing photo was taken by astronaut Don Pettit on board the International Space Stations—of which you can see a chunk at the top of the frame. It's part of a whole series of absolutely stunning photos that you need to go check out as soon as you have a free 20 minutes to spend staring at your monitor and going, "Woah," to yourself over and over.
Here's what Pettit had to say about the process.
"My star trail images are made by taking a time exposure of about 10 to 15 minutes. However, with modern digital cameras, 30 seconds is about the longest exposure possible, due to electronic detector noise effectively snowing out the image. To achieve the longer exposures I do what many amateur astronomers do. I take multiple 30-second exposures, the 'stack' them using imaging software, thus producing the longer exposure."
Via Smithsonian, which is where you can find the rest of Don Pettit's photos.