A picture of Denmark, Sewden and Norway under aurora taken by ESA astronaut Tim Peake during his six-month Principia on the International Space Station.
He is performing more than 30 scientific experiments for ESA and taking part in numerous others from ESA’s international partners.
More about the Principia mission: http://www.esa.int/principia
More photos from Tim on his flickr photostream: https://www.flickr.com/photos/timpeake