Precious gold and heavy metals in Earth and throughout the universe may have been spewed out by a rare type of collapsing star.
Scientists have long determined that light elements such as hydrogen and helium were generated in the moments after the creation of the universe. Many of these lighter elements form inside stars and are ejected upon their deaths in supernovas.
However, the origins of the heavy elements such as gold, plutonium, and uranium remain a mystery — until now.
Scientists Trace Origins Of Gold To Collapsing Stars
In a study published in the journal Nature, scientists suggested that collapsars spurred the creation of gold and other heavy elements in the universe.
Collapsars are massive stars that are rapidly spinning, which collapse into black holes with the outer layers exploding into a supernova.
Around these collapsars are accretion disks swirling around the black hole. These disks are rich in material, since black holes are what study co-author and astrophysicist Brian Metzger call "fussy eaters."
"We find that in these accretion disks, a lot of material circularizes around the newly born black hole," Daniel Siegel, study lead author and a theoretical physicist at the Perimeter Institute for Theoretical Physics in Waterloo, Canada, said to Space.com.
He added that in the innermost regions of the disks that are extremely hot and dense, particles interact so protons convert into neutrons.
"[It's] the initial conditions needed for the formation of heavy elements, such as gold and platinum," Siegel pointed out.
To create the heavier elements of the periodic table, atomic nuclei usually need to undergo a phenomenon known as "r-process," which means it absorbs neutrons very quickly and go through radioactive decay.
It's been long suggested, and recently supported with new research, that the collision of two neutron stars generates the conditions required for the r-process to occur.
The findings of the new study demonstrate that there is another way for the process to come into fruition. In fact, the authors say that most of the gold and other heavy elements in the universe are likely to have originated from collapsars, not neutron star mergers.
Collapsars Create More Elements At A Faster Rate
One problem with attributing the universe's gold to neutron star collisions is that it takes a very long time for this type of dense stars to merge. It's unclear whether mergers have occurred enough to produce the heavy elements that have been detected in ancient stars from the early universe.
On the other hand, collapsars can happen even just after a star begins to form.
Furthermore, one collapsar can produce so much more material than a neutron star merger, specifically 30 times more r-process material.
A single collapsar could potentially generate a few hundred times the Earth's mass in gold, according to Metzger.
Findings of the study show that collapsars should produce at least 80 percent of all the heavy elements in the Milky Way, while neutron star mergers should produce the other 20 percent.