Astronomers using the Gemini North telescope have captured the most detailed view yet of Pa 30, the only known supernova remnant of its kind in the Milky Way, revealing that its smooth streaks are actually chains of gas knots resembling pearls on a string.
Observations of Pa 30 Reveal Chains of Gas Knots
Located roughly 7,500 light-years from Earth, Pa 30 is the remnant of a historical stellar explosion witnessed and recorded independently in Japanese, Chinese, and Arabic historical sources in 1181. First identified by a citizen scientist in 2013, the object has long remained a puzzle for researchers studying the aftermath of stellar blasts.
An international team co-led by Ilaria Caiazzo, an assistant professor at the Institute of Science and Technology Austria (ISTA), and Tim Cunningham from the Center for Astrophysics | Harvard & Smithsonian, who is now an assistant professor at the University of Warwick, utilized the Gemini North telescope on Mauna Kea in Hawai’i to inspect the nebula. By analyzing ionized sulfur and doubly ionized oxygen emission lines, the team resolved filamentary features ten times as many as previous images could resolve.
The data demonstrate that these filaments consist of tight chains of gas knots with strikingly uniform sizes. Each individual knot is wide enough to fit the planetary region of our solar system roughly ten times over.
The Surviving Zombie Star and Symmetrical Explosion Dynamics
Adding to the uniqueness of Pa 30 is a surviving white dwarf star at its core, often described as a ‘zombie star’ left behind by an incomplete stellar explosion known as a Type Iax supernova. Researchers propose that the event originated from a collision between two white dwarfs—extremely dense, Earth-sized stellar remnants that have exhausted their fuel and shed their outer layer.
Unlike many supernova remnants where an asymmetrical blast imparts a violent physical kick to any surviving stellar core, the zombie star in Pa 30 sits almost perfectly in the center of the nebula. Explosions conserve momentum, and the absence of a substantial transverse kick speed indicates that the original blast was exceptionally symmetric. Caiazzo noted that researchers practically do not see the star moving away from the center at all.
Search for Similar Galactic Remnants
The Gemini North telescope, situated at an elevation exceeding 4,200 meters as part of the International Gemini Observatory funded by the U.S. National Science Foundation and run by NSF NOIRLab, provided the necessary high-resolution imaging capabilities. Cunningham pointed out that while Type Iax supernovae are rare, reliable historical records of stellar explosions extend back only about a thousand years, leaving open the possibility that similar remnants remain undetected in the dark of the Milky Way.
As astronomy enters the big data era, the team plans to leverage these detailed findings to screen large datasets. By utilizing the distinctive properties of Pa 30, researchers hope to identify similar objects in the Milky Way and in nearby galaxies where resolving the remnants of such stellar explosions remains feasible.
