The rogue runaway star Kappa Cassiopeiae — also known as HD 2905 — is the subject of a stunning new image taken by NASA’s Spitzer Space Telescope. The image shows, in detail, the incredible bow shock created by the star’s ‘rapid’ movement through the galaxy.
Bow shocks could be described as something somewhat like the distant relative of the Aurora Borealis that we see here on the Earth. They are created by the collision of the magnetic fields and stellar winds that flow from stars, and the diffuse, and usually nearly invisible, gas and dust that fills the open spaces of a galaxy.
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In this case, the speedster star is known as Kappa Cassiopeiae, or HD 2905 to astronomers. It is a massive, hot supergiant moving at around 2.5 million mph relative to its neighbors (1,100 kilometers per second). But what really makes the star stand out in this image is the surrounding, streaky red glow of material in its path. Such structures are called bow shocks, and they can often be seen in front of the fastest, most massive stars in the galaxy.
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.
The bow shock in this image is located, incredibly, more than 4 light-years ahead of Kappa Cassiopeiae — for some perspective, that’s around the same distance that we’re located from Proxima Centauri, the closest star to our Sun. Certainly gives an idea of the incredible pressure created by the movement of this mega-star.
For those wondering, the ‘delicate red filaments’ in the bow shock are thought to be (possibly) the “tracing out of features of the magnetic field that runs throughout our galaxy.” An interesting thought. Wonder if it’s true?
Kappa Cassiopeiae can be seen with the naked eye, it’s located in the constellation of Cassiopeia.
Image Credit: NASA/Jet Propulsion Laboratory