An illustration of two white dwarfs just prior to merging he two shock regions of the remnant SNR 1181.The ultimate cosmic"cold case" has lingered for 843 years — and now, space detectives may have solved it at last. In 1181 AD, as the Genpei War raged in Japan, a mystery"guest star" briefly flashed over Asia's skies. Astronomers had puzzled over the brief event until 2021, when a team of researchers tracked it to its location in the cosmos.
White dwarfs are the cooling stellar embers created when stars with masses similar to that of the sun die. As these stars exhaustin their cores, the outward push of radiation pressure created by this process also ends. This ends a stellar tug-of-war that the radiation pressure has waged with the inward push of the stars' own gravities for billions of years.
A diagram showing the two shock regions of the remnant SNR 1181. The bright white at the center is the white dwarf.Just after its formation as this white dwarf span, the object should have been shedding a rapid stream of particles called a""If the wind had started blowing immediately after SNR 1181's formation, we couldn’t reproduce the observed size of the inner shock region," Ko explained.