This newly released image from NASA’s Spitzer Space Telescope shows Kappa Cassiopeiae, a visible star in the constellation Cassiopeia the Queen. It is a massive, hot supergiant moving at around 2.5 million mph relative to its neighbors (that’s 1,100 kilometers per second, in contrast to about 30 miles per second for the speed of our Earth in orbit around the sun). See the streaky red glow of material in its path? That is the bow shocks from Kappa Cassiopeiae, moving ahead of its star – 4 light-years ahead – as the star speeds through our Milky Way galaxy.
Bow shocks can often be seen in front of the fastest, most massive stars in the galaxy. They form where the magnetic fields and wind of particles flowing off a star collide with the diffuse, and usually invisible, gas and dust that fill the space between stars.
How these shocks light up tells astronomers about the conditions around the star and in space. Slow-moving stars like our sun have bow shocks that are nearly invisible at all wavelengths of light, but fast stars like Kappa Cassiopeiae create shocks that can be seen by Spitzer’s infrared detectors.
Think how incredible it is that this shock is created about 4 light-years ahead of Kappa Cassiopeiae. This is about the same distance that we are from Proxima Centauri, the next-nearest star to our Earth and sun.