Astronomers Solve 8th Century Mystery Of ‘Zombie Stars’

Jakarta, CNN Indonesia —

After being a puzzle for 843 years, the explosion of a star no supernova in 1181 that left a trail of light for months to come sky the night was finally resolved.

At that time, this amazing object looked as bright as Saturn in the constellation Cassiopeia. Chinese and Japanese history records him as a “guest star.”

Chinese astronomers use the term to refer to temporary objects in the sky, often comets or supernovae, which are violent explosions of stars at the end of their lives.

The object, now known as SN 1181, was one of a handful of supernovae recorded before the invention of the telescope, and has puzzled astronomers for centuries.

A new study describes SN 1181 in detail for the first time by creating a computer model of the supernova’s evolution from shortly after its initial eruption to the present day.

The research team compared the model with archival telescope observations of the nebulae (large clouds of gas and dust) seen today, which are remnants of that monumental event.

The researchers said the analysis identified SN 1181 as a rare type of supernovae known as Type Iax.

What is unique is that thermonuclear explosions could be the result of not one, but two white dwarf stars (white dwarfs, dense dead stars that have consumed their nuclear fuel).

Both collided violently but did not explode completely, leaving behind a “zombie star.”

“There are 20 or 30 Type Iax supernova candidates,” said Takatoshi Ko, lead author of the study published July 5 in The Astrophysical Journal, quoted from CNN.

“But it’s the only one we know of in our own galaxy,” he continued, who is a doctoral student in astronomy at the University of Tokyo.

The study also found, inexplicably, that the high-speed wind, detected in previous studies, began to blow from the surface of the zombie star about 20 years ago.

Revealing the mechanisms behind these supernova events, experts say, could help astronomers better understand the life and death of stars and how stars contribute to planet formation.

The supernova explosion failed

In 2021 Albert Zijlstra, professor of astrophysics at the University of Manchester, England, found the star back to a nebula in the constellation Cassiopeia.

Amateur astronomer Dana Patchick discovered the nebula in 2013 while exploring NASA’s Wide-Field Infrared Survey Explorer or WISE archives. But Zijlstra, who was not involved in the new study, was the first to link it to SN 1181.

“During the peak of Covid, I spent a quiet evening sitting at home,” Zijlstra said.

“I mapped the supernova to the nebula using charts from ancient Chinese catalogs. I think it’s generally accepted now – lots of people have seen it and they agree it’s correct . This is what’s left of that supernova.”

The nebula is about 7,000 light years from Earth, and at its center is a rapidly rotating Earth-sized object known as a white dwarf. This feature is unusual for a supernova remnant because the explosion should have destroyed the white dwarf.

Zijlstra and his co-authors wrote a study in September 2021 about these findings. The report suggests that SN 1181 may fall into the elusive category of Type Iax supernovae due to the presence of these “zombie” white dwarfs.

In the most common Type Ia supernova, a white dwarf that forms when a Sun-like star has exhausted its fuel begins to collect material from other nearby stars.

Many stars are in pairs, or binary systems, unlike the Sun. The white dwarf collects material until it collapses under its own gravity, managing nuclear fusion with a big explosion that creates one of the brightest objects in the universe.

A rarer type of Iax is a condition where this eruption, for some reason, stops.

“One possibility is that Type Iax was not an explosion, but a merger of two white dwarfs,” Zijlstra said. “The two come together, collide at high speed, and that can produce a lot of energy. That energy causes the sudden brightness of the supernova.”

The large impact could explain another strange aspect of the zombie star SN 1181. The star does not contain hydrogen or helium, which is very unusual in space, said Zijlstra.

“About 90 percent of the universe is made up of hydrogen and the rest is almost entirely helium. Everything else is very rare,” he said.

You have to look for 10,000 atoms before you find one that is not hydrogen or helium. However, our star (the Sun) has only [terutama] That. So, clearly, something extreme has happened [bintang zombie].”

Star wind

Knowing where to look for SN 1181, and suspecting that it might be a Type Iax remnant, Ko and his colleagues set to work to uncover the remaining mysteries.

“By accurately monitoring the time evolution of the remnant, we were able to obtain the detailed characteristics of the SN 1181 explosion for the first time. We confirmed that these precise characteristics are consistent with a Type Iax supernova,” Ko said.

Ko’s analysis shows that two separate shock regions formed the remnant of SN 1181. The outer shock region was formed when material was ejected by a supernova explosion and when e to interstellar space (a region unaffected by the star’s gravity).

The latest category of deep tremors is more difficult to explain. Research suggests that this region could be a sign that the star is starting to burn again, centuries after the explosion, leading to a surprising discovery.

“It seems that high-speed winds started blowing from the star’s surface only 20 to 30 years ago,” Ko said.

Normally, these fast streams of particles that astronomers call stellar winds should be blowing from white dwarfs as a byproduct of the star’s rapid rotation immediately after a supernova explosion.

“We don’t fully understand why the star ruled and the strong wind started so recently,” said Ko.

“We theorize that the star exploded because SN 1181 was a Type Iax supernova, which is an incomplete explosion. As a result, the material ejected by the explosion did not escape completely and remained under the gravitational influence of the central white dwarf. it may eventually enter the white dwarf due to its gravity, which will cause it to flare up again.”

However, Zijlstra noted, that theory is opposed to observations that show the brightness of the star has declined over the past century.

“It is not clear how that relates to the wind blowing,” he said. “I hope the star grows brighter rather than fading.”

The researchers are preparing further observations of SN 1181 with two instruments that they have never used before: the very large array of radio telescopes in New Mexico and the Subaru Telescope in Hawaii.

This research, Ko said, will help inform scientists’ knowledge of all supernovae. Objects like SN 1181 are also important in the creation of many of the elements that also make up the Earth.

“These very energetic events can create elements heavier than iron, such as the rare earths,” Zijlstra said.

“It’s valuable to have examples of events like this from 1,000 years ago where we can still see the material that was sent out, and maybe in the future we can see exactly what elements were removed.” created in these events.”

[Gambas:Video CNN]

(team/air)