Two White Dwarfs Collided With Each Other And Triggered A Supernova In 1181 AD, Causing A Mysterious Star To Appear In Asia’s Skies Before Disappearing Again
In 1181 AD, during the Genpei War, a mysterious star appeared in Asia’s skies for a brief time before disappearing again. For 843 years, the cosmic event was a source of confusion for astronomers.
No one knew what it really was or why it had shown up. But in 2021, researchers managed to track down its location. Still, the cause of the event is unclear.
A team of scientists used computer modeling techniques and observational analysis to reconstruct the event, now called supernova (SN) 1181.
They discovered that it was a supernova triggered by two white dwarfs colliding with each other in a rare occurrence.
The structure of the remnant white dwarf and the impact of the collision were left behind. Then, 20 to 30 years ago, high-speed stellar winds started blowing from the surface of the remnant white dwarf. This discovery could help astronomers gain a better understanding of supernova varieties.
“There are many accounts of this temporary guest star in historical records from Japan, China, and Korea. At its peak, the star’s brightness was comparable to that of Saturn,” said Takatoshi Ko, the lead author of the study from the Department of Astronomy at the University of Tokyo.
For about 180 days, the star remained visible until it gradually dimmed and could no longer be detected by the human eye.
Because of how old the remnant of the SN 1181 explosion is now, it is very dark, which made it hard to find.
White dwarfs are small, dense stars that are created when stars with masses similar to the sun’s die by exhausting all their nuclear fuel.
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As a result, they collapse and shed their outer layers, which eventually drift away, leaving behind what are known as white dwarfs.
White dwarfs are drawn toward each other by gravitational waves, so they’ll often collide. Usually, a collision destroys both white dwarfs involved, but in rare cases, a single white dwarf is left behind in an event known as Type lax supernovas.
The new research suggests that SN 1181 is a Type lax supernova. It should’ve begun emitting a “stellar wind” right after its formation, but it only started recently, perhaps as late as two decades ago. The stellar wind is a rapid stream of particles.
The findings imply that some form of nuclear fusion is still taking place within the white dwarf, causing it to “burn” once again.
It could be the result of the Type lax supernova that people saw back in 1181 during the Genpei War, a national civil war between the Taira and Minamoto clans.
It began in 1180 and ended five years later. Afterward, the Kamakura shogunate was established.
The team will confirm their findings through further observations using the Very Large Array telescope in New Mexico and the Subaru Telescope in Hawaii.
The study was published in the Astrophysical Journal.
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