https://safirsoft.com Study: Milky Way's hottest star may be an ancient supernova remnant

The "Parker Star" is surrounded by the Pa30 nebula, which was discovered in 2013.

In August 1181, astronomers in China and Japan saw a bright "guest star" in the night sky that we now know to be a supernova - one of Few of the supernovae recorded in our Milky Way galaxy that can be seen with the naked eye. He was visible unarmed. It shone for a full six months before it disappeared. Astronomers have not been able to identify the remnants of SN 1181's source for centuries, and these details are important in determining which class this supernova belongs to. An international team of astronomers now believes they have identified the source as one of the hottest stars in the Pa30 nebula

As we wrote earlier, there are two known types of supernovae, depending on the mass of the main star. An iron core supernova occurs with massive stars (more than ten solar masses), which plummet so sharply that they cause a massive and catastrophic explosion. Temperatures and pressures rise to such an extent that the carbon in the star's core begins to boil. This stops the decay of the nucleus, at least temporarily, and this process continues over and over with heavier nuclei. When the fuel is completely depleted, the iron core (by then) collapses into a black hole or neutron star.

Then there is a thermonuclear supernova. Smaller stars (up to about eight solar masses) gradually cool down and turn into dense ash cores known as white dwarfs. If a white dwarf that has run out of nuclear fuel is part of a binary system, it can remove matter from its companion and add mass until its nucleus is high enough for carbon fusion to occur.

Read more Ad The newly discovered supernova may be of the same type as the one found in 1054.

There are also rare types. Chinese astronomers recorded one of the oldest and most famous "guest stars" on July 4, 1054. This was visible in broad daylight for 23 days. The remnants now form the Crab Nebula. Some have speculated that SN 1054 was a so-called "electron acceptor" supernova, which was first described 40 years ago. In June, we reported that a team of astronomers had identified a second newest supernova - called SN 2018zd - that meets all criteria for an electron-accepting supernova. In this scenario, the star is not heavy enough to produce a supernova with a decaying iron core, yet it is not light enough to prevent its complete collapse. Instead, these stars stop the fusion process when their cores are made of oxygen, neon, and magnesium. In this scenario, the electrons are fired by the neon and magnesium in the nucleus, causing the nucleus to tilt under its own weight. The end result is a supernova.

Based on this new analysis, it appears that SN 1181 belongs to another relatively rare group known as Type Iax. It belongs to the type Ia category, where the supernova is the result of a binary star system, one of which is a white dwarf. Normally, white dwarfs remove hydrogen and helium from their companion star, eventually destroying the white dwarf in the process by hitting a critical mass and detonating. But there are cases, such as SN 2012Z, where the white dwarf loses only half its mass and leaves the zombie star one of the survivors.

Color images of Parker's star and the Pa30 nebula, which scientists now believe are related to the report of a supernova seen in 1181. Zoom/false color images of Parker's star and the Pa30 nebula, which scientists now believe is linked to reports of a supernova in 1181. Andreas Ritter et al. , 2021

"Supernova 1181 has so far been the only historical supernova surviving in the past millennium without a specific counterpart." For years, it was likely the remnant of a radio and X-ray star known as 3C-58, which is now spinning about 15 times per second. This means that the pulsar has not lost much of its rotational energy in the past 900 years. In contrast, the remnant of SN 1054, the Crab Nebula, lost about two-thirds of its rotational energy. According to recent 3C-58 Radio polls, it is likely that the pulsar is much older than SN 1181 and therefore cannot survive. Enter the disc nebula like Pa30, first discovered by astronomers in 2013, that surrounds the rare and massive Wolf-Rayet star known as Parker Star. The authors noted that the dust and gas Pa30 was expanding at more than 1,100 kilometers per second, and the team used this speed to determine its age: about 1,000 years. This makes it a great candidate for the remnant SN 1181.

"Historical reports place the guest star between two Chinese constellations, Quanxi and Huajai. Parker's star fits the situation well," said Albert Zelstra, author of an article at the University of Manchester. This means that both age and location correspond to the events of 1181. "

Astronomers previously hypothesized that Pa30 and the Parker Star were created by the collision and fusion of two white dwarf stars to produce an Iax supernova." Only about 10 percent of supernovae of this type are known, Zijlstra and colleagues said. “This is the only event where we can study the remaining nebula and the merging star and we also have an explanation for the explosion. I am glad that I can solve the historical and astronomical mystery.”

DOI: Astrophysical Journal Letters, 2021. 10.3847/2041-8213/ac2253 (about DOIs).

Study: Milky Way's hottest star may be an ancient supernova remnant
study-milky-way-s-hottest-star-may-be-an-ancient-supernova.html

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