The sun is currently zipping through one of the Milky Way's spiral arms at a relative speed of about 23 kilometres per second, ploughing through thin clouds of interstellar dust and gas. At the same time, a stream of particles blowing out from the sun – the solar wind – inflates a bubble of plasma around the solar system, called the heliosphere.
Astronomers have long assumed that the sun's motion through the galaxy squashes and spreads the heliosphere into a bullet shape, with an extended tail at the back (see image). We have seen similar tails in pictures of speeding stars elsewhere in the galaxy. But until now it has been hard to see for sure what our own sun's tail might look like.