Kappa Cassiopeiae is speeding through space so quickly, it is building a shock wave in front of its path of travel. This feature is seen in a new image released by NASA and Jet Propulsion Laboratories.
This hot, supergiant star, also called HD 2905, is traveling at 2.5 million miles an hour when measured next to its neighbors. At this speed, the star could travel between Boston and Charlotte, North Carolina, in just one second. Kappa Cassiopeiae lies 4,000 light years away from our home world, and is invisible from Earth without a telescope. Using a visual aid, the star can be seen in the constellation Cassiopeia.
As it travels, gas is unable to move out of the way of the object in time, and the material accumulates in front of the star in a bow shock. This is similar to the air which builds up in front of an aircraft approaching the speed of sound.
The bow shock forms when tiny particles material, trapped in the magnetic field of the star, interact with the interstellar medium. These features have been observed before, accompanying some of the fastest-moving stars in the galaxy. This bow shock lies 4 light-years in front of the star, roughly the distance between the Sun and Proxima Centauri, its nearest stellar neighbor. This great distance shows the impact HD 2905 is having on nearby systems.
Some astronomers believe these bow shocks may be shaped by the magnetic field of the Milky Way. If true, it could give researchers a way of seeing these otherwise-invisible lines of force. This would be similar to viewing magnetic fields by placing iron fillings on a paper, draped over a magnet. Some of the fine detail in the bow shock may be the result of these galactic fields.
This stunning new picture was taken by the Spitzer Space Telescope, launched from Cape Canaveral in 2003. That observatory is in a heliocentric orbit, revolving around the Sun, lagging slightly behind the Earth.
Spitzer was designed to last just two-and-a-half years, and ran out of coolant in 2009. Many instruments aboard the craft became unusable. Since that time, the Spitzer Warm Mission has used two detectors that are still operational.
All stars move relative to one another, and create smaller shock waves. For slower-moving specimens like our Sun, the bow shock is invisible over all wavelengths of light. It is only the great speed of HD 2905 that makes its wave visible to the infrared detectors aboard the Spitzer observatory.
In the image, the bow shock is seen in red. Green features are hydrocarbons lying between Kappa Cassiopeiae and the Earth, illuminated by starlight.
