About 11300 years ago, a massive star changed on the precipice of annihilation. He pulsed energy by expelling his external layers, losing the material in space. Finally, he exploded like a supernova, and his rest is one of the most studied supernova remains (SNR). This is called Cassiopeia A (case A) and new observations with the Chandra X -ray telescope reveal more details on its disappearance.
The Star of Case progenitors had between 15 and 20 solar masses, although certain estimates go up to 30 solar masses. It was probably a red supergiant, although there was a debate on his nature and the path he followed to explode as a supernova. Some astrophysicists think he may be a wolf star.
In any case, he finally exploded like a supernova in a basic act. Once he built an iron core, the star could no longer support and explode. The light of the disappearance of cases A reached the earth around the 1660s.
There is no definitive recovery record that see the explosion of the supernova in the sky, but astronomers have studied the SNR case an SNR in modern times and through several wavelengths.
New research in the astrophysical journal explains the new discoveries of Chandra. It is entitled “Inhomogenic stellar mixture in the last hours before the Cassiopeia a supernova.” The main author is Toshiki Sato from Meiji University in Japan.
“It seems that each time we look closely at the data from Chandra de Cas A, we learn something new and exciting,” said the main author Sato in a press release. “Now we have taken this invaluable X -ray data, have combined them with powerful computer models and found something extraordinary.”
One of the problems of the study of supernovae is that their possible explosions are what triggers our observations. A detailed understanding of the last moments before the explosion of a supernova is difficult to obtain. “In recent years, theorists have paid great attention to the end interior processes within the massive stars, because they can be essential to reveal the mechanisms of supernova focused on neutrino and other potential transients of the collapse of massive stars,” write the authors in their article. “However, it is difficult to directly observe the last hours of a massive star before the explosion, because it is the Supernova event which triggers the start of an intense observation study.”
SN explosion driving of a massive star implies the nucleosynthesis of increasingly deep elements more deeply in its interior. The surface layer is hydrogen, then the helium is following, then carbon and even heavier elements under the external layers. Finally, the star creates iron. But iron is a barrier to this process, because if lighter elements release energy when they merge, iron requires more energy to undergo an additional fusion. The iron accumulates in the nucleus, and once the nucleus reaches approximately 1.4 solar masses, there is not enough external pressure to avoid collapse. Gravity wins, the nucleus collapses and the star explodes.
Chandra’s observations, combined with modeling, give astrophysicists a look inside the star during his last moments before collapse.
“Our research shows that just before the star of cases A was collapsed, part of an inner layer with large quantities of silicon went outwards and collapsed in a neighboring layer with a lot of neon,” said Kai Matsunaga co-author of the University of Kyoto in Japan. “This is a violent event where the barrier between these two layers disappears.”
The results were twice. The silicon -rich material traveled outwards, while the material rich in neon lights was traveling inward. This created an inhomogenic mixture of the elements, and small regions rich in silicon were found near small regions rich in neon.
This is part of what researchers call a “shell fusion”. They say that this is the final phase of stellar activity. It is an intense burn where the oxygen combustion shell swallows the external carbon and the neon shell deep inside the star. This only happens a few moments before the star explosion as a supernova. “In the violent convective layer created by the fusion of shells, which is abundant in the stellar layer rich in O, is burned when it is pulled inward, and if, which is synthesized inside, is transported outwards,” explain the authors in their research.
The regions rich in silicon and rich in intertwined silicon are proof of this process. The authors explain that silicon and neon did not mix with the other elements immediately before or immediately after the explosion. Although astrophysical models predicted this, it has never been observed before. “Our results provide the first observational proof that the final stellar combustion process quickly modifies the internal structure, leaving a pre-supernova asymmetry,” explain the researchers in their article.
For decades, astrophysicists thought that SN explosions were symmetrical. The first observations supported the idea, and the basic idea behind the nucleus column supernovae also supported symmetry. But this research changes the fundamental understanding of supernova explosions as asymmetrical. “The coexistence of the compact ejecta regions in the regimes” rich in o- / ne “and” Rich o- / If “implies that the fusion did not completely homogenate the layer rich in o before collapsing, leaving behind inhomogeneities of multi-scale composition and fields of asymmetrical velocity,” the researchers write in their conclusion.
This asymmetry can also explain how neutron stars left behind get their acceleration kick and lead to high -speed neutron stars.
These last moments in the life of a supernova can also trigger the explosion itself, according to the authors. The turbulence created by internal bustle can have helped the explosion of the star.
“Perhaps the most important effect of this change in the structure of the star is that he may have helped to trigger the explosion itself,” said co-author Hiroyuki Uchida also from the University of Kyoto. “Such a final internal activity of a star can change her fate – whether or not she will shine like a supernova.”
“For a long time in the history of astronomy, it was a dream of studying the internal structure of the stars”, write the researchers in the conclusion of their article. This research gave astrophysicists an overview of the last moments of a off -sister star before the explosion. “This moment has not only a significant impact on the fate of a star, but also creates a more asymmetrical supernova explosion,” they conclude.
THE original version of this article was published on Universe today.
