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In the 12th century, Chinese and Japanese astronomers spotted a new light in the sky shining as bright as Saturn. They identified it as a powerful star explosion known as a supernova and marked its approximate location in the sky – but its cause has remained a mystery.
Today, astronomers say they’ve solved the 840-year-old puzzle: two extremely dense stars collided in the Milky Way and caused a supernova. The explosion likely resulted in the formation of a scorching star, now known as Parker’s Star, and a nebula, an expanding shell of gas and dust, known as Pa 30.
This supernova, or the so-called Chinese guest star, from the year 1181 – which remained visible from August 6 to February 6 of the same year – is just one of nine historically recorded supernovas in our galaxy, according to the study, published in September. 15 inch Letters from the astrophysical journal. Astronomers have identified the remains of only a handful of these supernovas, but the Chinese guest star was the only supernova from the past millennium whose remains had yet to be found.
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Some previous studies had suggested that another nebula, known as 3C 58, which is located near the marked location of the supernova, could be its remains. But many factors, such as the age of the nebula, cast doubt on this theory. “So far, there has been no other known viable candidate for the remainder,” the authors wrote in the study.
Astronomers discovered the Pa 30 nebula in 2013. Then, in the new study, the researchers calculated how quickly Pa 30 is growing. They discovered that it was climbing at a blazing speed of 684 miles per second (1,100 kilometers per second). Knowing this rate, they calculated that the nebula must have been born about 1,000 years ago, which would place its origins at the time of this ancient supernova.
Researchers also had historical documents describing the star. “Historical reports place the guest star between two Chinese constellations, Chuanshe and Huagai. Parker’s star fits the position well,” Albert Zijlstra, professor of astrophysics at the University of Manchester in the UK, said in a press release. “This means that the age and location correspond to the events of 1181.”
Previously, researchers had proposed that Pa 30 and Parker’s Star were the result of the fusion of two white dwarfs, extremely dense stars that used up all of their nuclear fuel, the statement said. Such mergers lead to a relatively weak and rare type of supernova known as a lax-type supernova.
The AD 1181 supernova was weak and faded very slowly, suggesting it was likely a lax-type supernova, Zijlstra said in the statement. “The combination of all this information – such as age, location, brightness of the event and the historically recorded duration of 185 days” – suggests that Parker’s star and Pa 30 are the remains of this ancient supernova, Zijlstra said.
It is the only known lax supernova for which astronomers can conduct detailed studies on the remaining star and nebula, he added. “It’s nice to be able to solve both a historical mystery and an astronomical mystery,” Zijlstra said.
Originally posted on Live Science.
Editor’s Note: This article has been updated to clarify that when the two super dense stars collided, it caused a supernova. Scientists say the Pa 30 nebula, which was first discovered in 2013, is the remnant of the supernova.
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