Zombie star filaments in historic supernova SN 1181

Oct. 25 () –

Observations with a spectrograph in the WM Keck telescope in Hawaii have offered an unprecedented view of strange filaments emanating from the zombie star in supernova remnant SN 1181.

In 1181, a new star shone near the Cassiopeia constellation for six months before disappearing. This eventrecorded as a “guest star” by Chinese and Japanese observers almost a millennium agohas baffled astronomers for centuries. It is one of the few supernovae documented before the invention of telescopes. Furthermore, it was the one that remained “orphan” the longest, meaning that none of the celestial objects visible today could be attributed to it.

Now known as supernova SN 1181, its remnant could only be traced in 2021 to the Pa 30 nebula, found in 2013 by amateur astronomer Dana Patchick while examining an archive of images from the WISE telescope as part of a citizen science project.

But this nebula is not a typical supernova remnant. In fact, astronomers were intrigued to find a surviving “zombie star” at its center, a remnant within the remnant. Supernova 1181 is believed to have occurred when a thermonuclear explosion was triggered in a dense, dead star called a white dwarf. Normally, the white dwarf would be completely destroyed in this type of explosion, but in this case, part of the star survived, leaving behind a sort of “zombie star.” This type of partial explosion is called a type Iax supernova.

Even more intriguing, from this zombie star Strange filaments emanated that resembled the petals of a dandelion flower. Now, ISTA Associate Professor Ilaria Caiazzo and lead author Tim Cunningham, a NASA Hubble Fellow at the Harvard-Smithsonian Center for Astrophysics, have investigated this structure in detail.

The team was able to study this strange supernova remnant in detail thanks to Caltech’s Keck Cosmic Web Imager (KCWI). The KCWI is a spectrograph located above 4,000 meters at the WM Keck Observatory in Hawaii, near the summit of the Mauna Kea volcano, Hawaii’s highest peak.

KCWI was designed to detect some of the weakest and darkest light sources in the universe, collectively called the “cosmic web.” Additionally, it is so sensitive and intelligently designed that it can capture spectral information from every pixel in an image. It can also measure the movement of matter in a stellar explosion, creating something like a 3D movie of a supernova. KCWI does this by examining how light moves as it moves towards or away from us, a physical process similar to the familiar Doppler effect we know from sirens. that change tone when an ambulance speeds by.

In this way, instead of just seeing the typical static image of a fireworks display, common in supernova observations, the researchers were able to create a detailed 3D map of the nebula and its strange filaments. Furthermore, they were able to show that the material in the filaments traveled ballistically at approximately 1,000 kilometers per second. “This means that the ejected material has not slowed down or accelerated since the explosion,” says Cunningham. in a statement. “Therefore, from the measured velocities, looking back in time allowed us to locate the explosion almost exactly to the year 1181.”

EVIDENCE OF AN UNUSUAL ASYMMETRY

Beyond the dandelion-shaped filaments and their ballistic expansion, The overall shape of the supernova is more unusual. The team was able to show that the ejecta (the material within the filaments that is ejected away from the explosion site) is unusually asymmetric. This suggests that the asymmetry is due to the initial explosion itself. Additionally, the filaments appear to have a sharp inner edge, showing an internal “hole” surrounding the zombie star.

“Our first detailed 3D characterization of the velocity and spatial structure of a supernova remnant tells us a lot about a unique cosmic event that our ancestors observed centuries ago. But it also raises new questions and poses new challenges that astronomers will need to address in the future. future”, concludes Caiazzo.