Astronomers have observed the faint nebula Pa 30, located 7,500 light-years away in Cassiopeia, and found filaments of glowing sulfur gas surrounding it. Astronomers believe that the bethe filaments result from two white dwarfs colliding and merging, creating a “magnetic monster” of a star that blows its material into space. The merging of the two white dwarfs resulted in a relatively tepid burst of light, leaving behind a surviving star in a type of “failed” supernova astronomers call Type Iax supernova. This is the first time this type of supernova has been found in the Milky Way that can be easily studied.

The observation of Pa 30 bolsters the case that the nebula is a Type Iax supernova. Moreover, the observations pin down the object’s age and give it a strong case for being the solution to a 900-year-old astronomical mystery. In 1181, Chinese and Japanese astronomers recorded a “guest star” in this region of the sky. It was only about as bright as the brightest star—perhaps magnitude -1, modest for a supernova in our galaxy. Scientists had thought that the remnant of this event was a nebula called 3C 58 that housed a pulsar, a type of rapidly rotating neutron star leftover from a supernova. However, that was called into question by observations in the past few decades that estimated 3C 58’s age to be much younger than the age of the event.

According to researchers, Pa 30 is a unique object with scarcely any observational precedent. An amateur astronomer discovered the object in 2013, and multiple professional observatories conducted follow-up observations. It was not until 2018 that some French amateur astronomers using an 8-inch scope found that the nebula harbored a very blue star at its center. They notified one of the research groups that had observed Pa 30, a team at the University of Hong Kong (HKU), who began reanalyzing their data. A Russian team was the first to propose that the star was the remnant of a double-white dwarf Type Iax supernova, spinning rapidly with a magnetic field strong enough to accelerate the winds; their research was published in Nature. However, the HKU team provided new insights in a paper published in the Astrophysical Journal Letters.

While the nebula did not have much glowing oxygen gas, the HKU team found it had some sulfur. Their spectra revealed that this sulfur travels away from the central star at about 2.5 million mi/h (4 million km/h). Assuming this is debris from the Type Iax supernova and using the Wide Infrared Survey Explorer (WISE) image to reference how far this gas had traveled, they estimated that the supernova had occurred about 1,000 years ago, plus or minus about 250 years.

This new research is available as a preprint on arXiv at the time of writing.

References

• Caparas, G. (2021, October 4). Historical “Guest Star” of 1181 Was Actually a Rare Supernova. Modern Sciences. https://modernsciences.org/historical-guest-star-of-1181-was-actually-a-rare-supernova/
• Fesen, R. A., Schaefer, B. E., & Patchick, D. (2023). Discovery of an Exceptional Optical Nebulosity in the Suspected Galactic SN Iax Remnant Pa 30 Linked to the Historical Guest Star of 1181 CE. arXiv. https://doi.org/10.48550/arXiv.2301.04809
• Gvaramadze, V. V., Gräfener, G., Langer, N., Maryeva, O. V., Kniazev, A. Y., Moskvitin, A. S., & Spiridonova, O. I. (2019). A massive white-dwarf merger product before final collapse. Nature, 569(7758), 684–687. https://doi.org/10.1038/s41586-019-1216-1
• Ritter, A., Parker, Q. A., Lykou, F., Zijlstra, A. A., Guerrero, M. A., & Le Dû, P. (2021). The remnant and origin of the historical supernova 1181 ad. The Astrophysical Journal Letters, 918(2), L33. https://doi.org/10.3847/2041-8213/ac2253
• Zastrow, M. (2023, February 28). ‘Fireworks’ sparked by survivor of stellar collision. Astronomy. https://astronomy.com/news/2023/02/fireworks-sparked-by-survivor-of-stellar-collision