This article was first published by The Conversation. Space.com's Expert voices: Op-Ed and Insights was contributed by the publication.David Yong is an Academic at the Research School of Astronomy and Astrophysics of Australian National UniversityGary Da Costa, Emeritus Professor Astronomy, Australian National UniversityIt was believed that neutron-star mergings were the only way heavy metals (heavier than Zinc) could be made. These mergers are the result of the mashup between the remnants from two massive stars in an binary system.We know that heavy elements were created shortly after the Big Bang. This was when the universe was very young. There was not enough time for neutron star mergings to have occurred back then. Therefore, another source was required to explain the existence of early heavy elements within the Milky Way.First evidence of another source of heavy elements is provided by the discovery in the Milky Ways Halo of an ancient star SMSS 1142. This is the region roughly spherical surrounding the galaxy.The Milky Way galaxy has a halo of hot gases that surrounds it. This halo is constantly being replenished with hot gases from stars born or dying. The halo is home to only 1% of the stars in the galaxy. Image credit: NASA JPLOur research, published in Nature, shows that the heavy elements found in SMSS J2003-1142 are likely to have been produced by a collapsing star with strong magnetic fields and a mass approximately 25 times the sun.This explosion is called a "magnetorotational supernova."Related: A rare 'hypernova" explosion was detected at the fringes of Milky Way.Stellar alchemyRecent evidence has shown that neutron-star mergings are one source of heavy elements in the galaxy. This is what happens when two neutron star systems merge in an energy event known as a "kilonova". This creates heavy elements.Binary star systems are composed of two stars orbiting around the same centre of mass. A neutron star merging is a type stellar collision between two neutron stars within a binary system. This can lead to the production of heavy elements. (Image credit NASAExisting models of the chemical evolution in our galaxy show that neutron star mergings could not have created the particular patterns of elements seen in SMSS J2003-1142.Continue reading: The signals from the spectacular neutron star merger are slowly disappearingRelic from the early universeSMSS J2003-1142 first was observed from Australia in 2016. It was then re-observed in September 2019 by a telescope at The European Southern Observatory in Chile.These observations led us to study the star's chemical composition. Our analysis showed that the iron content of the stars was approximately 3,000 times less than that of the sun. This means that SMSS J2003-1142 has a chemically primitive iron content.It is likely that the elements you see in it were created by one parent star just after the Big Bang.Signs of a rapidly spinning star that has collapsedThe chemical composition of SMSSJ2003-1142 can provide information about the parent star's nature and properties. Its unusually high levels of nitrogen, zinc, and heavy elements such as europium or uranium are particularly important.SMSS J2003-1142 has high levels of nitrogen, which indicates that the parent star experienced rapid rotation. High zinc levels indicate that the explosion had a much higher energy than a normal supernova. This would indicate that it was a hypernova. Large amounts of uranium require a lot of neutrons.SMSS J2003-1142 contains heavy elements that are evidence of an early magnetorotational supernova explosion.Our work provides evidence that both magnetorotational and neutron-star mergers are sources of heavy elements in the galaxy.What about neutron star mergings?How can we be sure that it wasn't only neutron star mergers which led to the elements found in SMSS J2003-1142. This is possible for a number of reasons.Our hypothesis states that all elements in SMSS J2003-1142 would have been made by a single parent star. However, the process of making the same elements through neutron-star merging would have taken much longer. This time would not have been possible at the beginning of the galaxy's creation when these elements were created.Neutron star mergers only make heavy elements. Therefore, additional sources like regular supernovae would have to have occurred in order to explain the other heavy elements such as calcium observed in SMSS J2003-1142. While this scenario is possible, it is less likely.The magnetorotational supernovae model is able to provide a better fit to data and can even explain the composition SMSS J2003-1142 by a single event. It is possible that magnetorotational and neutron-star supernovae could work together to explain how the Milky Way's heavy elements were created.Continue reading: The race for more elements to be added to the periodic tableThis article was republished by The Conversation under Creative Commons. You can read the original article.Follow Expert Voices to keep up with the debates and issues. You can also join the conversation on Facebook and Twitter. These views are the author's and may not reflect those of the publisher.
