Earlier this year we at Modern Sciences did a piece on how the work of two bored astronomers gave us a more illustrated glimpse of the beginnings of the elements in the periodic table; however, new findings published in the Monthly Notices of the Royal Astronomical Society may shed some new light on the topic.
An international team of experts, headed by scientists from Germany’s GSI Helmholtzzentrum für Schwerionenforschung, took a deep dive into the details within black hole mechanics and phenomena using detailed computer simulations—all in an attempt to get to the bottom of where heavy elements like gold (Au) and uranium (U) truly come from.
Based on the currently accepted understanding in the sciences, heavy elements like gold and uranium are produced by the collisions of very massive objects like neutron stars and black holes, and was given credence by the detection of gravitational waves back in 2017.
However, a group of experts think there’s much more left unexplored about the topic; this prompted Dr. Oliver Just, lead author and from GSI’s Relativistic Astrophysics group, to get to the bottom of it all.
Their prime candidate was black holes with accretion disks, or a black hole surrounded by stellar material like gas and dust that orbit around the black hole. These black holes are likely formed from phenomena like the merger of two neutron stars. (Find out more about how black holes form in our earlier piece about them.)
Thing is, most experts think that heavy elements like gold are only produced under a high amount of neutrons, as this environment enables the rapid neutron capture process (r-process) that most scientists think synthesize these rare elements across the universe.
In their landmark study, Dr. Just and team “systematically investigated […] the conversion rates of neutrons and protons for a large number of [accretion] disk configurations by means of elaborate computer simulations.”
It was only after combing through these simulations that they found some key details about how these heavy elements may form. For one, the mass of the accretion disk surrounding the black hole must play within 0.01 to 0.1 solar masses, or 0.01 to 0.1 times the mass of our own Sun. Within this range, accretion disks become “very rich in neutrons,” according to Dr. Just in a news release by EurekAlert!.
These neutrons form as protons capture electrons; positive merges with negative, creating a neutron and releasing a neutrino—which is a nearly-massless, and also neutral, subatomic particle. According to the findings of Dr. Just and team, should a resulting black hole accretion disk land between the range of solar masses they described, neutrons are sure to be in plentiful supply, allowing the r-process to take place—and, subsequently, the generation of heavy elements like gold and uranium.
Data obtained from these simulations are expected to be augmented by data from the next generation of particle accelerators, like GSI’s very own Facility for Antiproton and Ion Research (FAIR) that’s currently under construction. Data from particle accelerators like FAIR can then be used to isolate and identify light signals gathered from these faraway accretion disks to truly ascertain the presence of these heavy elements.
Said co-author Dr. Andreas Bauswein: “[With] the next generation of accelerators, such as FAIR, it will be possible to measure [these light signals] with unprecedented accuracy in the future. The well-coordinated interplay of theoretical models, experiments, and astronomical observations will enable us researchers in the coming years to test neutron star mergers as the origin of the r-process elements.”
References
- GSI Helmholtzzentrum für Schwerionenforschung. (2021, November 15). Where does gold come from? — New insights into element synthesis in the universe. EurekAlert! https://www.eurekalert.org/news-releases/934890
- Just, O., Goriely, S., Janka, H.-T., Nagataki, S., & Bauswein, A. (2021). Neutrino absorption and other physics dependencies in neutrino-cooled black hole accretion disks. Monthly Notices of the Royal Astronomical Society, stab2861. https://doi.org/10.1093/mnras/stab2861
