Cosmic mystery is Solved after 900 years

Written by The Daily Mail on September 22, 2021. Posted in Current News

A 900-year-old cosmic mystery surrounding the origins of a supernova first spotted over China in 1181 has finally been solved.

A faint, fast expanding nebula called Pa30 has been identified as the source of the 12th century explosion, which Chinese and Japanese astronomers said was as bright as the planet Saturn and remained visible for six months.

Experts said Pa30, which surrounds Parker’s Star — one of the hottest stars in the Milky Way — 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, including the famous Crab nebula, but the origins of all bar the ‘Chinese Guest Star’ have been well known.

Despite 12th century astronomers recording an approximate location in the sky of the 1181 sighting, no confirmed remnant of the explosion had ever been identified until now.

The discovery was made by a team of international astronomers from Hong Kong, the UK, Spain, Hungary and France at the Kitt Peak observatory in Arizona (seen below).

In a new research paper, they found that the Pa30 nebula is expanding at an extreme velocity of more than 1,100 km per second (at this speed, travelling from the Earth to the Moon would take just five minutes).

They used this velocity to derive an age at around 1,000 years, which would coincide with the events of 1181.

Professor Albert Zijlstra, from the University of Manchester, was one of the astronomers involved in the research.

He said: ‘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.‘

It has previously been suggested that Pa30 and Parker’s Star formed as a result of the merger of two white dwarfs.

A white dwarf is what stars like the sun become at the end of their lives when they have used up all their nuclear fuel.

Such merger events of white dwarfs are thought to lead to a rare and relatively faint type of supernova, called a ‘Type 1ax supernova‘.

Professor Zijlstra said: ‘Only around 10 per cent 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.

Professor Zijlstra added: ‘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.‘

The research has been published in the The Astrophysical Journal Letters.

See more here: dailymail.co.uk

Editor’s note: There are two known types of supernova. The first type occurs in binary star systems when one of the two stars, a carbon-oxygen white dwarf, steals matter from its companion star. Eventually, the white dwarf accumulates too much matter, causing the star to explode, resulting in a supernova. The second type of supernova occurs at the end of a single star’s lifetime.

As the star runs out of nuclear fuel, some of its mass flows into its core. Eventually, the core becomes so dense it’s gravity overcomes the electroweak force, and the core collapses in a few seconds, resulting in another giant explosion. Many elements found on Earth are synthesised by transmutation of the elements in the cores of stars and these elements travel on to form new generations of stars and planets.

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