Golden Arc’s or bow shocks are boundaries that for a star, as is Kappa Cassiopeiae, are typically the edge of the astrosphere. The astrosphere is where the stellar wind meets the interstellar medium. The interstellar medium is the matter that exists in the space between the star systems in a galaxy. This matter would include gas in ionic, atomic, and molecular form, dust, and cosmic rays.
Included below are two pictures that will provide a more visual explanation.
“CAPTURED THE GOLDEN ARCs of KAPPA CASSIOPEIAE”; Kappa Cassiopeiae is a star also known as HD 2905. It is huge and fast. Said to be moving 2.5 million miles per hour relative to its neighbors. Read that sentence again and focus on relative to its neighbors.
Quick special relativity lesson: Planet A and Planet B are moving in the same direction, one at 90 mph and the other at 110 mph. What is planet B’s relative speed to Planet A. 20 mph. Taking specialk relativity into account – we put the planets going opposite directions and what does planet A observe Planet B moving at now? 190 mph.
But this particular star, a rogue or run away star in the Cassiopeia constellation is moving very fast, in normal terms is moving about 683.5 mile per second.
A star that big moving that fast creates the bow shocks. This phenomenon is a rare effect, sort of. Our Sun has bow shocks of its own but because it moves much more slowly the bow shocks are not visible in any wave length. (The bow shocks seen here were captured using infrared equipment.)
Notice the faint greens and the vivid red colors. The green is from the carbon molecules (aka polycyclic aromatic hydrocarbons) What can you see? Kappa Cassiopeiae is visible to the human eye and calls home. One of the things so awesome about it is this bow shock appears 4 light years in advance of the star.
So while these bow shocks create the pretty pictures that NASA has provided, they also provide information to scientists as to the conditions immediately surrounding the star and surrounding space: Things such as magnetic fields which are also invisible but show a little bit of their structure when mixed with the surrounding dust and gas.