Astronomers solve 900-year-old cosmic mystery surrounding China’s 1181 AD supernova

A 900-year-old cosmic mystery surrounding the origins of a famous supernova first spotted over China in 1181 AD has finally been solved, according to an international team of astronomers.

New research released today (September 15, 2021) indicates that a rapidly expanding cloud (or nebula), called Pa30, surrounding one of the hottest stars in the Milky Way, known as the Star of Parker, matches the profile, location and age of the historic supernova.

There have only been five bright supernovae in the Milky Way in the last millennium (as of 1006). Among these, the Chinese supernova, also known as the “Chinese Guest Star” of 1181 AD, has remained a mystery. It was initially seen and documented by Chinese and Japanese astronomers in the 12th century who said it was as bright as the planet Saturn and remained visible for six months. They also recorded an approximate sky location of the sighting, but no confirmed remains of the explosion have even been identified by modern astronomers. The other four supernovae are now well known to modern science and include the famous Crab Nebula.

The source of this 12th-century explosion remained a mystery until this latest discovery by a team of international astronomers from Hong Kong, UK, Spain, Hungary and France, including Professor Albert Zijlstra from the University of Manchester. In the new article, astronomers discovered that the Pa 30 nebula is expanding at an extreme speed of over 1,100 km per second (at this speed, the journey from Earth to the Moon would take only five minutes). They use this speed to derive an age of around 1,000 years, which would coincide with the events of 1181 AD.

Professor Zijlstra (professor of astrophysics at the University of Manchester) explains: “Historical reports place the guest star between two Chinese constellations, Chuanshe and Huagai. Parker’s star fits the position well. This means that the age and location correspond to the events of 1181. “

Pa 30 and Parker’s Star have already been offered following a merger of two White Dwarfs. It is believed that such events lead to a rare and relatively weak type of supernova called an Iax-type supernova.

Professor Zijlstra added: “Only about 10% of supernovae are of this type and they are not well understood. The fact that SN1181 was weak but faded very slowly corresponds to this type. It is the only event of this type where we can study both the remaining nebula and the merged star, as well as a description of the explosion itself. “

The fusion of residual stars, white dwarfs and neutron stars, gives rise to extreme nuclear reactions and forms heavy elements that are very rich in neutrons such as gold and platinum. Prof Zijlstra said: “The combination of all this information such as age, location, brightness of the event and the historically recorded duration of 185 days, indicates that Parker’s Star and Pa30 are the counterparts of SN 1181. This is the only Iax-type supernova where detailed studies of the remaining star and nebula are possible. It’s nice to be able to solve both a historical mystery and an astronomical mystery. ”