These enhanced supernovae, a completely new object to science , have been scientifically dubbed a “magneto-rotational hypernova” , and it seems to be the most likely explanation for the unusual composition of another star in our Milky Way; a mystery that has hung over our galaxy for 13,000 million years.
Unusual features
With 10 times more energy than a normal supernova, the star that made this find turns out to have many more metals, such as gold and uranium, than other stars of a similar age. Since the merger of neutron stars would not even be enough to explain the large amount of metals that this star has, scientists propose the existence of a previously unknown type of collapse that can happen to a very young star and that helps provide all the neutrons. needed for those metals.
Known as SMSS J200322.54-114203.3 and located in the Milky Way’s halo some 7,500 light years away from Earth , the star, a red giant , has an extremely low iron to hydrogen ratio, “about 3,000 times lower. than the Sun “, according to David Yong, from the Australian National University and leader of the work published in the journal Nature ; and abundance of certain heavy elements such as thorium and uranium . And it appears to be extremely old: a member of the second generation of stars born in the universe, dating back about 13 billion years.
Remember that the first generation of stars was composed mainly of hydrogen and helium and the heavier elements only emerged after their lives passed, became supernovae and collapsed into neutron stars or black holes.
Its heavy elements come from a supernova-like predecessor event
Therefore, the additional neutrons needed in these heavy elements could only come from the violent collapse of a very early star, “amplified by rapid rotation and the presence of a strong magnetic field,” the scientists explain. As we have seen, the mysterious celestial body is extremely rare, not only because it has very little iron, but also because of the high levels of heavier elements.
Simulations suggest that the event was a magnetorotational hypernova, created with the death of a highly magnetized star that was rapidly rotating at least 25 times the mass of the sun. When these stars explode at the end of their lives as a type of enhanced supernova, they can have the energetic and neutron-rich environments necessary to forge heavy elements.
“We now find the observational evidence for the first time that directly indicates that there was a different type of hypernova that produced all the stable elements in the periodic table at once : an explosion from the collapse of the core of a fast-spinning, strongly magnetized massive star.” says Chiaki Kobayashi, a co-author of the study. “It is the only thing that explains the results.”
According to experts, these hypernovae would be rare, accounting for just 1 in 1,000 supernovae , but they would be even 10 times more frequent than neutron star mergers today and would produce similar amounts of heavy elements per event.
Hypernovae have been known since the late 1990s. However, this is the first time that one combining rapid rotation and strong magnetism has been detected.
Referencia: r-Process elements from magnetorotational hypernovae, Nature (2021). DOI: 10.1038/s41586-021-03611-2 , www.nature.com/articles/s41586-021-03611-2
