The mystery of China's supernova 900 years ago points to a strange nebula
This image is of the Hubble Space Telescope's AG star in the constellation, a variable star in a critical state of explosion. (Image source: NASA, European Space Agency, U.S. Space Telescope Science Institute)
In 1181 AD, Astronomical observers in China and Japan discovered a new point of light as bright as Saturn, which lasted more than six months before disappearing. Hundreds of years later, the researchers believe they have finally found the source of this mysterious phenomenon.
This event, like the famous Crab Nebula's Big Bang in 1054, was one of the few nearby bright flashes in the historical record. But unlike the Crab Nebula, this peculiar event in 1181 is difficult to determine.
In the historical record, some clues have been left useful to modern astronomers. First, temporally: this "guest star" continued to shine for 185 days from August 6, 1181 to February 6, 1182; in addition, the record also shows its orientation in the sky, between the ancient Chinese "Chuanshe Star" and "Canopy Star", near the present constellation Cassiopeia.
Fragments of information left over from the historical record allowed a team of researchers to find a possible source of this ancient shining bright spot: a supernova. Its wreckage now forms a rapidly expanding nebula called Pa30. In the new study, scientists from Hong Kong, The United Kingdom, Spain, Hungary and France found that Pa30 dust and gas can move as fast as it can move from Earth to the Moon in 5 minutes. By calculating this velocity backwards, the researchers determined that the nebula coincided with a supernova explosion event around 1181.
The team found that Pa30 formed from a rare and relatively faint supernova called an "Iax-type supernova." Albert Zistra said in his report on the new study: "Only about 10% of supernovae belong to this category, and people don't know much about them. The SN1181 is very faint, but the process of gradually fading light is very long, which is in line with this type. Albert Zistra is an astrophysicist at the University of Manchester in the United Kingdom.
Pseudo-color images of Parker's star and the Pa30 nebula, scientists now believe, are related to the supernova discovered in 1181. (Image source: The University of Hong Kong)
Scientists also found that Parker's star, one of the hottest stars in the Milky Way, may also correspond to the supernova event of 1181. This nebula and stars are thought to be the result of two faint stars , known as white dwarfs , " that collided massively and then merged.
"This is the only Iax supernova that allows for a detailed study of the remnants of stars and nebulae," Zistra adds: "It's great to be able to solve both a historical mystery and an astronomical mystery at the same time." ”
【Related knowledge】
Supernovae ( / su p r no v / plural : supernovae / su p r no vi / or supernovas , abbreviated : SN and SNe ) are powerful and bright stellar explosions. Such short-lived astronomical events occur during the final evolution of massive stars, or when white dwarfs are triggered to undergo runaway nuclear fusion. The first objects after the explosion, called ancestral stars, either collapsed into neutron stars or black holes, or were completely destroyed. Supernovae have optical luminosity peaks comparable to those of the entire Milky Way galaxy and then decline within weeks or months.
Supernovae are more energetic and energetic than novae. In Latin, nova means "new", and in astronomy it means: a new bright star that appears briefly and temporarily. With the prefix "super-", it is possible to distinguish between supernovae and ordinary novae, which are much less luminous. The term supernova was coined by Walter Budd and Fritz Zwicky in 1929.
The latest supernova observed directly in the Milky Way in time is the Kepler supernova of 1604; but remnants of supernovae that are newer than its time have been discovered. Observations of supernovae in other galaxies suggest that they should appear in the Milky Way on average three times a century. These supernovae are almost certainly capable of being observed by modern astronomical telescopes. The most recent supernova visible to the naked eye in time is SN1987A, an explosion of a blue giant star located in the Great Magellanic Galaxy, one of the Milky Way's moon galaxies.
Theoretical studies have shown that most supernovae are triggered by one of two basic mechanisms: the sudden rekindling of nuclear fusion in degenerate stars (such as white dwarfs), or the sudden gravitational collapse of the cores of massive stars. In the former type of event, the star temperature rises enough to trigger runaway nuclear fusion, which completely destroys the star. The possible cause of this is the accumulation of mass, which comes from accretion or amalgamation from companion stars. In the latter type of event, the core of a massive star may collapse suddenly, releasing gravitational energy at the level of a supernova. Although some of the observed supernovae are more complex than these two simplified theories, astrophysical mechanics, established as an important branch of research in the field of astrophysics, is generally accepted by the astronomical community.
Supernovae can expel some solar-mass material at speeds of up to a few percent of the speed of light. It will trigger an expanding shock wave that hits the interstellar medium around it like an expanding shell of gas and dust, which is observed as a remnant of a supernova. Supernovae are the main source of elements in the interstellar medium, from oxygen to rubidium. The expanding shock waves of supernovae can trigger the formation of new stars. Supernova remnants may be a major source of cosmic rays. In addition, supernovae may also produce gravitational waves, although so far, gravitational waves have only been detected in the merger event of black holes and neutron stars.
BY: space
FY: Peppercorns
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