X-Rays Expose the Boundary Where an Ancient Supernova Slowed Down, Called RCW 86

In the year 185, sky watchers in China noticed a guest star that flared brilliantly enough to be visible during the day for weeks before disappearing. That brief flash turned out to be a white dwarf star breaking itself apart in a Type Ia supernova. Centuries later, its memory is preserved in the faint form of RCW 86, a gigantic shell of blazing gas speeding outward at millions of miles per hour, by NASA’s IXPE (Imaging X-ray Polarimetry Explorer) mission.

Shockwaves from that explosion sped across a low-density zone carved out over time by the fading star system’s winds. The wave merely kept traveling until it reached a solid wall of denser material at the edge of the low-density area. When that happened, the surge slowed and bounced back the other direction, resulting in a reflected shock, which is precisely what scientists were hoping for.

Thanks to data from NASA’s IXPE mission, we now have a good idea of where that reflected shock is located on the outer rim. IXPE measures the polarization of X-rays, which reveals the direction of the magnetic fields woven through the heated gas. By the way, while looking at the southwestern rim recently, researchers noted that the polarization remained low, which rules out the possibility of ultra perfectly matched magnetic fields less than a light year wide.

Instead, the fields appear braided, as one would expect in the thin portions left behind after the shock that produced the cavity. That contributes significantly to our understanding of how supernova remnants provide particles with the boost they require to travel nearly as rapidly as light. Those accelerated particles produce the synchrotron X-rays that IXPE and its partner telescopes can detect.

So, when you combine images from IXPE, Chandra, and XMM-Newton and add some context with an optical star field, choose yellow tones to indicate lower energy X-rays and blue for higher energy ones, as they create a more complete picture of the event. You can really pinpoint the exact location where that ancient explosion impacted the brakes and altered direction forever.

Astronomers continue to investigate similar remnants because each one provides another look into the processes that seeded the universe with heavy metals and cosmic rays. Despite receiving less attention than some other space observatories, IXPE continues to provide fresh observations. Every fresh set of data tells you that space is just full of more levels of detail waiting for the appropriate tool to come along and uncover them.