These photos were taken by astronaut Don Pettit on board the International Space Stations.
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.
(Source: Boing Boing)