A “guest star” documented by medieval astronomers nearly 850 years ago has yielded new insights, as researchers have captured the sharpest images yet of its explosive remnants.
Fresh observations of Pa 30, believed to be the remnant of the historic supernova SN 1181, reveal that its dazzling, firework-like filaments are not smooth streams of material. Instead, they are composed of chains of tiny gas knots.
SN 1181 takes its name from records by Chinese and Japanese astronomers who observed its brief appearance in 1181 as a naked-eye object in Cassiopeia. Eight surviving texts place its emergence between August 4 and 6 of that year, and the object remained visible for 185 days.
“It is rare to obtain this level of detail for a supernova we can date to a specific week in history,” said Timothy Cunningham, assistant professor of astronomy and astrophysics at the University of Warwick, who led the international research team studying the object.
SN 1181 is among just five Milky Way supernovae observed from Earth before the telescope’s invention. Optical instruments first appeared in the Netherlands in 1608. Today, advanced ground-based telescopes produce exceptionally detailed images of those historic remnants. The latest image, captured by the Gemini North telescope on Mauna Kea in Hawaii, reveals roughly ten times more filamentary structures in Pa 30 than previously observed. This extraordinary detail offers astronomers new clues about the unusual explosion and the environment surrounding the progenitor star.
“These images provide the clearest picture yet of Pa 30’s structure, and it is not what we anticipated,” said Cunningham, whose team published its findings in The Astrophysical Journal. “The filaments consist of chains of tiny knots rather than smooth streaks, offering new constraints on the conditions around the star before it exploded and the physical processes that shaped the expanding ejecta.”
The knot-like structures may have formed due to variations in temperature or density in the material surrounding the star as the explosion’s debris expanded.
Pa 30 also features another unusual characteristic: a surviving star positioned almost exactly at the remnant’s center. This is highly unusual because supernova explosions typically propel stars away from their original locations. It suggests the original explosion was highly symmetrical, according to the researchers.
Furthermore, Pa 30 is believed to be a Type Iax supernova. Unlike standard Type Ia supernovae, which destroy their stars, a Type Iax event is a lower-energy, incomplete explosion of a white dwarf that can leave behind a remnant known as a “zombie star.” It is the only Type Iax supernova ever identified.
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