Astronomers discovered a third type of supernova

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Astronomers discovered a third type of supernova. An international team of astronomers has discovered the first concrete evidence of an electron-capturing supernova, believed to be the result of the explosion of massive supersyntotic branched giant stars.

Las Cumbres / Hubble composite image of the electron capture supernova SN 2018zd (large white dot on the right) and the starburst galaxy NGC 2146 (on the left). Image Credit: NASA / ESA / Hubble

Third type of supernova

“One of the main questions in astronomy is to compare how stars evolve and die. Many links are still missing, so this is very exciting,” said Professor Stefano, an astrophysicist in the Department of Physics at the University of California at Davis. Valenti said.

Historically, there have been two main types of supernovae: the thermonuclear supernova and the iron core collapse supernova. A thermonuclear supernova is the explosion of a white dwarf star after gaining matter in a binary star system. These white dwarfs have dense cores that remain after a low-mass star, about 8 times the mass of the Sun, reaches the end of its life.

In an iron core collapse supernova, a massive star, about 10 times the mass of the Sun, runs out of nuclear fuel and its iron core collapses, forming a black hole or neutron star. It was first introduced in 1980 by University of Tokyo astronomer Dr. As predicted by Kenichi Nomoto, electron capture supernovae lie on the boundary line between these two types of supernovae.

“While gravity is always trying to crush a star, what prevents most stars from collapsing is the ongoing fusion or, where the fusion has stopped, the fact that the atoms are not squeezed,” explained the researchers. astronomers.. In an electron capture supernova, some of the electrons in the oxygen-neon-magnesium nucleus break apart at their atomic nuclei in a process called electron capture.

Supernova

The removal of electrons causes the core of the star to bend and collapse under its own weight, resulting in an electron-capturing supernova. In the new study, the researchers focused on a supernova event called SN 2018zd, which was detected on March 2, 2018. They discovered that this stellar explosion had many unusual characteristics, some of which were first observed in a supernova.

It helped that SN 2018zd was relatively close, just 31 million light-years away, on the outskirts of NGC 2146, a barred spiral galaxy in the constellation Camelopardalis. This allowed the team to examine archival images taken before the explosion with the NASA / ESA Hubble Space Telescope and locate a possible ancestral star before the explosion.

The observations were consistent with a recently identified super asymptotic giant branch star (SAGB) in the Milky Way, but were inconsistent with models of red supergiants, progenitors of common iron core collapse supernova. The scientists analyzed all the published data on supernovae and found that while some had some predicted indicators for electron-capturing supernovae, only SN 2018ZD had all six: a clear SAGB ancestor, a strong pre-supernova mass loss, a composition unusual stellar chemistry, a weak explosion, little radioactivity, and a neutron-rich core.

“We started by asking ‘What is this weird?’ We then investigated all aspects of SN 2018ZD and realized that they could all be explained in an electron capture scenario, “said Daiichi Hiramatsu, a graduate student in the Department of Physics at the University of California, Santa Barbara and the Las Observatory.

Artist’s impression of a super asymptotic giant branch star (left) and its core (right) composed of oxygen (O), neon (Ne), and magnesium (Mg); A supersyntotic giant branch star is the final state of stars in a mass range of about 8-10 solar masses, whose core is supported by the pressure of electrons (E-); When the nucleus becomes dense enough, the neon and magnesium begin to eat electrons (so-called electron capture reactions), reducing the pressure of the nucleus and inducing a supernova explosion that collapses the nucleus. Image Credits: S. Wilkinson, Las Cumbres Observatory.

The discovery also reveals some of the mysteries of SN 1054, the famous supernova that occurred in the Milky Way in 1054 CE. According to Chinese records, the eruption was so strong that it could be seen for 23 days during the day and almost two years at night. The resulting remnant, the Crab Nebula, has been studied in great detail.

SN 1054 was previously the best candidate for an electron-capturing supernova, but this was uncertain in part because the explosion occurred about a thousand years ago. The new result raises the belief that the event was an electron-capturing supernova.

“I am very happy that the electron capture supernova was discovered, which my colleagues and I predicted, and that it had a connection to the Crab Nebula 40 years ago,” said Dr. Nomoto. It is a wonderful case of combining observation and theory. The team’s article was published in the journal Nature Astronomy.

Astronomers have discovered a new type of supernova and solved an ancient mystery: A third type of supernova was observed in the galaxy NGC 2146, about 31 million light years from Earth. Supernova 2018zd is the first example of a new type of supernova. supernova

Joseph Depscale, STSCI

Just when you think we know a lot about the stars above, something pops up and illuminates them even more. Literally, in this case, thanks to the observation of a new type of supernova. The discovery has interesting implications for a mysterious bright light that appeared in the sky in 1054.

Published Monday in Nature Astronomy, a report by an international team of scientists confirms a type of stellar explosion never seen before. Before the discovery, only two types of supernova were thought of: a core collapse supernova (which occurs when a massive star runs out of fuel and its core collapses into a black hole or neutron star) and a neutron star. Thermonuclear supernova (which occurs when a white dwarf star explodes).

However, starting in the 1980s it was speculated that another type might exist. Kenichi Nomoto of the University of Tokyo predicted a third type in 1980 called an “electron capture supernova.” This refers to supernovae resulting from fuel starvation, in which gravitational forces were found in the atomic nuclei of the electron nuclei, thus collapsing in on themselves.

Evidence suggesting the existence of an electron-capturing supernova includes giant stars that lost most of their mass before the explosion. The mass in question must have an unusual chemical composition. There should be minimal radioactive fallout after a supernova and the core should contain neutron-rich elements.

Spectral analysis of a supernova, originally detected in March 2018, provides new evidence for the theory of an electron-capturing supernova. Nicknamed “Supernova 2018zd”, there are several key factors that suggest its electron-trapping nature: it showed a high degree of mass loss before the explosion, it has an unusual chemical composition, it produced a weak explosion. leaves a nucleus rich in neutrons.

Delighted to see his theory gain weight, Nomoto commented on the development and contributed to the article. “I am very happy that the electron capture supernova was discovered, which my colleagues and I predicted and belonged to the Crab Nebula 40 years ago. It is a wonderful case of combining observation and theory,” he said. This is a composite image of the Crab Nebula, which has long been raised as the result of an electron-capturing supernova.

Crab Nebula Link

One of the brightest mysteries in supernova history, the origins of the Crab Nebula have long been unclear. A supernova is believed to have occurred in the Milky Way in AD 1054. Historical accounts allege that it was so bright that it could be seen during the day for 23 days and at night for almost two years. Today its remains are known as the Crab Nebula.

Despite being extensively studied, it was difficult to determine whether the nebula was possibly the result of an electron-capturing supernova, largely because the explosion occurred about a thousand years ago. However, with this new supernova discovery, it is believed that we can more confidently state that the Crab Nebula is the result of an electron-capturing supernova.

“This supernova is really helping us decode the millennial record of cultures around the world,” said Dr. Andrew Howell, leader of the Global Supernova Project and a staff scientist at Las Cumbres Observatory. The Crab Nebula, not fully understood, among other things, we have incredible modern records of this supernova. “

“In the process, he’s teaching us about fundamental physics: how some neutron stars form, how extreme stars live and die, and how we are made of elements and scattered throughout the universe.” With more to learn about this new type of supernova, it’s hard not to stare up into the night sky for exciting new flames of immense brightness.

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