Mauna Kea, Hawaii — In a groundbreaking discovery, astronomers using the Keck Cosmic Web Imager at the W. M. Keck Observatory have unlocked new insights into a celestial event that puzzled observers nearly a millennium ago. The event, a supernova witnessed in 1181 and long known as SN 1181, was recorded by Chinese and Japanese astronomers of the era as a dazzling “guest star” that briefly outshone other celestial bodies in the constellation Cassiopeia.
The recent findings, detailed in The Astrophysical Journal Letters on October 24, showcase a three-dimensional map of peculiar filamentary structures that radiate from what is now known to be the remnant of this ancient explosion. These filaments, which vividly resemble the plume of a dandelion, consist of material ejected during the supernova and have now been visualized in unprecedented detail.
Explaining the significance of the findings, Christopher Martin, a professor of physics at the California Institute of Technology and the lead developer of the imaging equipment used, remarked, “Previously, our view of the supernova remnant was akin to a static photograph of a fireworks show. With the Keck Cosmic Web Imager, however, we can track the ongoing movement of the explosion’s debris, providing a dynamic ‘movie’ of its outward flight across space.”
The structure of these remnants offers clues about the type of explosion that occurred. It is believed that SN 1181 was a rare Type Iax supernova, possibly caused by a collision or interaction between two white dwarf stars, leading to a thermonuclear explosion. Unlike more powerful supernovas, this event was a partial explosion that, fascinatingly, left behind a “zombie star” rather than completely destroying the white dwarf involved.
After the supernova was first noticed through historical records, its remnant was not identified until 2013 by amateur astronomer Dana Patchick, who noticed a nebula in images from NASA’s retired Wide-field Infrared Survey Explorer mission. The nebula was dubbed Pa 30. Albert Zijlstra, a professor of astrophysics at the University of Manchester, connected this nebula to SN 1181 in 2021, a finding that elucidated one of the long-standing mysteries of astronomical history.
Recent observations in 2023 illuminated these strange filaments glowing with sulfur emissions within the nebula. The unusual configuration and behavior of these filaments sparked new research interest. “Because this explosion failed to completely obliterate its star, it was dimmer than a typical supernova, which aligns with historical observations that note its visible presence for just six months,” remarked Ilaria Caiazzo, assistant professor at the Institute of Science and Technology Austria.
The Keck Cosmic Web Imager’s capabilities facilitated critical measurements of the filaments’ velocities, revealing they are ejecting from the nebula at roughly 2.2 million miles per hour. The data also hinted at the dynamics of these emissions, displaying redshifts and blueshifts that resemble the Doppler effect, similar to the changing pitch of a siren as an ambulance passes.
“We find the material in the filaments to be expanding ballistically, meaning it has been neither slowing down nor accelerating since the explosion itself,” said Tim Cunningham, a NASA Hubble Fellow at the Center for Astrophysics | Harvard & Smithsonian.
Further study of the 3D imaging pointed to a large cavity and evidence of an asymmetrical blast within the nebula. Cunningham explained that “the filaments seem to emerge more from an outer shell rather than spanning from the central to outer regions, which brings up new questions about their formation.”
While the existence of the filaments aligns with phenomena observed in planetary nebulas, their precise nature and origin remain elusive, requiring additional observations and theoretical work to fully understand the processes at play in this celestial artifact from the year 1181. As research continues, each discovery adds a piece to the puzzle, progressively unveiling the violent but awe-inspiring beauty of the universe.