Some stars end life with explosions: the moths play an important role

According tomedia reports, an astrophysical study suggests that some stars end their lives in the form of an explosion in which the moth element may have played a crucial role. Astronomers love to study the life cycle of stars, including how different stars die.

Some stars end life with explosions: the moths play an important role

Pictured is the Crab Nebula. Its ultimate fate may be as described in the article.

像太阳这样质量较小的恒星会不断膨胀,最终抛却外层物质、转变为矮星;大型恒星则会以超新星爆发的形式发生剧烈爆炸,内核会变成黑洞或中子星。但对于质量介于太阳7到11倍之间的中等质量恒星,仍有许多疑问没有解决。它们是会抛离外层、还是会爆炸呢?如果它们最终会发生超新星爆发,那么最终产物又是什么?要想弄清这些问题,一定程度上将取决于我们对氖的理解程度有多深。

During death, medium-mass stars gradually run out of hydrogen and helium. Computer simulations show that they form a core of several elements, oxygen, radon, and magnesium. These stars may lose part of the hydrogen outer layer and become a dim white dwarf, but if the core becomes large enough, it may collapse into a neutron star.

But these stellar cores are odd because the pressure generated by the gravitational pull of the inward squeeze can be offset by the quantum mechanics rules that govern the behavior of electrons. The quantum properties of the two electrons cannot be identical, thus limiting the minimum distance that can be achieved between them, thus applying a “simple and pressure” to the core. The rate at which the thorium atoms capture electrons plays a crucial role in the process. This process releases energy that “ignites” oxygen in the star, causing an explosion. But the fate of the star will vary depending on when the energy is released and the time of subsequent explosions.

A recent paper by Oliver Kirsebom of Dalhousie University in Canada looked at the reverse process of capturing electrons, the process by which fluorine atoms lose an electron and become argon. To do this, they bombarded a carbon film with a beam of fluorine atoms at the JYFL Accelerator Laboratory in Finland. By analyzing the probability of fluorine decay becoming argon, the researchers calculated in reverse the frequency at which a thorium atom captures an electron in a core of oxygen, argon, and magnesium. Their calculations are much higher than previous observations, so the core density required to ignite oxygen is lower, eventually leading to a thermonuclear explosion that turns the star into a white dwarf rather than a neutron star.

“It’s a very rare nuclear leap that is often overlooked. “Under certain conditions, it can have a significant impact on the evolution of the star, ” says Colsbury. “

Carla Frohlich, of the Department of Physics at the University of Northern California, commented that the team’s results were “a milestone in the field of precision nuclear astrophysics”. For decades, she points out, scientists have wanted to measure this “no-jump”. The phenomenon of fast-moving is very rare on Earth, but may be much more common in the extreme environment of the stellar core.

In another study, led by Shuai Zha, a postdoctoral researcher at Stockholm University and published in the Astrophysical Journal, scientists built a model of the death process of a star 8.4 times the mass of the sun. The energy released by the electronic capture process ignites oxygen, which in turn burns out other metals in the core and creates an explosion wave. The paper found that the ultimate fate of a star depends on the number of electrons and the critical density. Once the density exceeds this threshold, the star’s core collapses into a neutron star, and if the core is below the threshold, the core explodes and disintegrates.

The researchers speculated that the density of the star’s core was higher than the critical value, so they believe that it was the argon element that caused the core to collapse into a neutron star. But the team’s research predates Cosby. They plan to compare the findings of the two teams in a forthcoming paper.

There are still many doubts about these stars, Colesbehm explains, such as convection in the star’s core and the way matter transmits heat. In these processes, other complex and difficult processes of nuclear change may also play a role.

“There are a lot of conflicting views about the ultimate fate of these stars. Convection in stars and other issues… We do need to learn more. Colesbehm pointed out. He hopes that more advanced accelerator laboratories will help scientists study more unstable rare particles and isotopes. In addition, astronomical studies may find white dwarfs with more heavy elements, which may be remnants of an explosion in the core of oxygen, argon, and magnesium.