Supernova remnant called Pa 30—the leftover remains of a supernova explosion that was witnessed from Earth in the year 1181, unusual filaments of sulfur protrude beyond a dusty shell of ejected material.

The remains of the original star that exploded, now a hot inflated star which may cool to become a white dwarf, are seen at the center of the remnant. The Keck Cosmic Web Imager (KCWI) at the W.M. Keck Observatory in Hawai‘i has mapped the strange filaments in 3-D and shown that they are flying outward at approximately 1,000 kilometers per second. In 1181, Japanese and Chinese astronomers saw a bright light appear in the constellation Cassiopeia. It shone for six months, and those ancient observers couldn’t have known it was an exploding star. To them, it looked like some type of temporary star that shone for 185 days. In the modern astronomical age, we’ve learned a lot more about the object. It was a supernova called SN 1181 AD, and we know that it left behind a remnant “zombie” star. Research titled “Expansion Properties of the Young Supernova Type Iax Remnant Pa 30 Revealed.” examines the supernova’s aftermath and the strange filaments of gas it left behind.

Though it was seen almost 850 years ago, only modern astronomers have been able to explain SN 1181. For a long time, it was an orphan. While astronomers were able to identify the modern remnants of many other historical supernovae, SN 1181 was stubborn. Finally, in 2013, amateur astronomer Dana Patchick discovered a nebula with a central star and named it Pa 30. Research in 2021 showed that Pa 30 is the remnant of SN 1181. The SN exploded when two white dwarfs merged and created a Type 1ax supernova. SN 1181 is unusual. When supernovae explode, there’s usually only a black hole or a neutron star left as a remnant. But SN 1181 left part of a white dwarf behind, an intriguing object astronomers like to call a zombie star. Strange filaments resembling dandelion petals extend from this strange star, adding to the object’s mystery. Researchers have gotten a new, close-up look at Pa 30 and published their results in The Astrophysical Journal Letters.