A 900-year-old cosmic mystery surrounding the origins of a famous supernova
first spotted over China in 1181AD has finally been solved, according to an
international team of astronomers.
New research published today (September 15, 2021) says that a faint, fast
expanding cloud (or nebula), called Pa30, surrounding one of the hottest
stars in the Milky Way, known as Parker’s Star, fits the profile, location,
and age of the historic supernova.
There have only been five bright supernovae in the Milky Way in the last
millennium (starting in 1006). Of these, the Chinese supernova, which is
also known as the ‘Chinese Guest Star’ of 1181AD has remained a mystery. It
was originally 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 location in the
sky of the sighting, but no confirmed remnant of the explosion has even been
identified by modern astronomers. The other four supernovae are all now well
known to modern day science and include the famous Crab nebula.
The source of this 12th century explosion remained a mystery until this
latest discovery made by a team of international astronomers from Hong Kong,
the UK, Spain, Hungary and France, including Professor Albert Zijlstra from
The University of Manchester. In the new paper, the astronomers found that
the Pa 30 nebula is expanding at an extreme velocity of more than 1,100 km
per second (at this speed, traveling from the Earth to the Moon would take
only 5 minutes). They use this velocity to derive an age at around 1,000
years, which would coincide with the events of 1181AD.
Prof Zijlstra (Professor in Astrophysics at the University of Manchester)
explains: “The historical reports place the guest star between two Chinese
constellations, Chuanshe and Huagai. Parker’s Star fits the position well.
That means both the age and location fit with the events of 1181.”
Pa 30 and Parker’s Star have previously been proposed as the result of a
merger of two White Dwarfs. Such events are thought to lead to a rare and
relatively faint type of supernova, called a ‘Type Iax supernova’.
Prof Zijlstra added: “Only around 10% of supernovae are of this type and
they are not well understood. The fact that SN1181 was faint but faded very
slowly fits this type. It is the only such event where we can study both the
remnant nebula and the merged star, and also have a description of the
explosion itself.”
The merging of remnant stars, white dwarfs and neutron stars, give rise to
extreme nuclear reactions and form heavy, highly neutron-rich elements such
as gold and platinum. Prof. Zijlstra said: “Combining all this
information such as the age, location, event brightness and historically
recorded 185-day duration, indicates that Parker’s star and Pa30 are the
counterparts of SN 1181. This is the only Type Iax supernova where detailed
studies of the remnant star and nebula are possible. It is nice to be able
to solve both a historical and an astronomical mystery.”
Reference:
The Remnant and Origin of the Historical Supernova 1181 AD by Andreas
Ritter, Quentin A. Parker, Foteini Lykou, Albert A. Zijlstra, Martín A.
Guerrero and Pascal Le Du, 15 September 2021, The Astrophysical Journal.
DOI: 10.3847/2041-8213/ac2253
Tags:
Space & Astrophysics