Pa 30 lies 7,500 light-years away in the constellation Cassiopeia and is thought to be the leftover of SN 1181, a supernova so named because Chinese and Japanese astronomers recorded its brief appearance as a naked-eye object in the year 1181. Eight surviving texts date its appearance to between August 4 and 6 of that year, and the object remained visible for 185 days.
"It's rare to get this level of detail on a supernova we can date to a specific week in history," said Cunningham, an assistant professor of astronomy and astrophysics at the University of Warwick who led the international research team.
The new image, captured by the Gemini North telescope on Mauna Kea in Hawaii, reveals about 10 times more filamentary structures in Pa 30 than previously seen. "These images give us the clearest picture yet of Pa 30's structure, and it's not what we expected," Cunningham said. "The filaments are made of chains of tiny knots rather than smooth streaks, providing new constraints on the nature of the space around the star before it exploded and the physical processes that have shaped the expanding ejecta."
The knot-like structures may have resulted from variations in temperature or density in the material surrounding the star as the explosion's debris expanded.
SN 1181 is one of only five supernovas in the Milky Way known to have been witnessed from Earth before the telescope was invented in the Netherlands in 1608.
Pa 30 also contains a surviving star almost exactly at its center, which is highly unusual because supernova explosions typically send stars away from their original positions. Researchers said this suggests the original explosion was highly symmetrical.
The remnant is thought to be a Type Iax supernova, a lower-energy, incomplete explosion of a white dwarf star that can leave behind a remnant known as a "zombie star." Unlike standard Type Ia supernovas, which destroy their stars, it is the only Type Iax supernova ever found.