Nearly 850 years after medieval stargazers documented a brilliant new light in the northern sky, astronomers have captured the sharpest view yet of its explosive aftermath, revealing unexpected clumpy structures and a rare surviving star.
The observations focus on Pa 30, a supernova remnant located roughly 7,500 light-years away in the constellation Cassiopeia. The cloud of debris is linked to SN 1181, an explosion recorded between Aug. 4 and Aug. 6 in the year 1181 by observers in China and Japan, where it shone as a naked-eye “guest star” for about 185 days.
Chains of cosmic knots
Astronomers directing the Gemini North telescope on Mauna Kea in Hawaii examined the expanding debris cloud in unprecedented detail, according to findings published in The Astrophysical Journal. Rather than displaying smooth, flowing streams of gas, the newly captured images revealed intricate filaments formed out of linked chains of dense knots.
The telescope’s Gemini Multi-Object Spectrograph gathered light through specialized filters tuned to singly-ionized sulfur, uncovering approximately 10 times more filamentary structures than earlier observations had detected. Researchers suggested that variations in the density and temperature of surrounding space before the blast helped sculpt the gas into clumps as the blast wave pushed outward.
“The planetary region of our solar system could fit in each knot about ten times with room to spare,” said study co-author Ilaria Caiazzo, an assistant professor at the Institute of Science and Technology Austria, in a statement reported by Futurism.
A surviving white dwarf
Beyond the beaded gas trails, Pa 30 holds another major surprise: a stellar core that withstood the cataclysm. Most standard supernovas destroy their progenitor stars entirely or violently kick remnants far away from the blast’s original ground zero.
In Pa 30, however, researchers found the surviving white dwarf resting almost perfectly at the dead center of the surrounding nebula. This alignment indicates that the star suffered practically no recoil kick, pointing to a remarkably symmetrical detonation.
Scientists classify the blast as a Type Iax supernova, a weaker and incomplete thermonuclear explosion that can produce what astronomers call a “zombie star.” Such rare events are thought to occur when two Earth-sized white dwarfs merge. The white dwarf at the center of Pa 30 remains intensely active, maintaining an estimated temperature of 200,000 degrees Celsius and driving stellar winds at speeds reaching 16,000 kilometers per second, Universe Today reported.
Unlocking ancient skies
SN 1181 ranks among only five supernovas inside the Milky Way documented by skywatchers prior to the telescope’s emergence in 1608. Pa 30 remains the only recognized Type Iax supernova remnant discovered in our home galaxy.
“It’s rare to get this level of detail on a supernova we can date to a specific week in history,” lead author Timothy Cunningham, an assistant professor at the University of Warwick, said in a statement.
Researchers noted that further scrutiny with higher-resolution instruments, including the Hubble Space Telescope, could refine measurements of the remnant’s expansion. Scientists also hope these findings will aid the hunt for other hidden zombie stars that exploded centuries ago across the galaxy.
