Scientists are closer than ever before to understanding how stars forge the elements that comprise our planet, bodies and pretty much everything else around us — and they’re gaining a clearer picture of where star explosions fit into the story.
New research reported in two different papers looks at how stars forge elements as they explode and how these supernova explosions spread those elements — and other elements stars have forged during their lifetimes — throughout the cosmos.
Astronomers have been studying the bright supernova deaths of massive stars for centuries, but they still don’t quite understand how these explosions proceed.
The first paper looked at one way to investigate supernovas. It uses a radioactive element produced by these explosions called titanium-44, which lingers long after supernovas fade. Researchers have now collected experimental evidence that determines how much titanium-44 is created in a supernova, finding that these cosmic explosions produce 35% more of this element than expected.
With this knowledge in hand, scientists can now develop robust computer models of supernovas and compare these models with astronomical observations. This could bring them much closer to understanding how these explosions progress.
“It’s exciting to see just how far the field has come,” Christopher Cousins, a postdoctoral researcher in the University of Surrey’s Nuclear Physics Group, said in a statement. “A measurement like this would have been considered out of reach only a couple of decades ago, but it now gives us new insight into one of the biggest unanswered questions in astrophysics.”
The second paper honed in on a particular brand of stellar explosion called a Type I supernova. These occur when a dense stellar remnant called a neutron star drags material from a companion stellar body. The intense gravitational influence of the neutron star — a stellar corpse that has one to two times the mass of the sun crammed into a body about 12 miles (20 kilometers) wide — means that, when this stolen stellar matter hits their surfaces, a thermonuclear explosion is triggered.
These blasts forge heavy elements and release incredible amounts of energy, some in the form of X-ray bursts.
The authors of this paper, hailing from the Facility for Rare Isotope Beams (FRIB) in Michigan, studied the nuclear reaction that triggers X-ray bursts in greater detail than has been possible before.
This revealed the long-debated role of the so-called nickel-copper cycle, the temporary trapping of nuclear material during supernovas. Scientists previously didn’t know if material was trapped in the nickel-copper cycle during X-ray bursts.
This research reveals that this does happen, but only in small proportions. It gives scientists a clearer picture of how Type I supernovas proceed.
“Despite decades of research, we still don’t fully understand the nuclear reactions that power some of the universe’s most spectacular stellar explosions,” said Gavin Lotay of the University of Surrey.
“These two studies give us a much clearer picture of how these explosions happen, allowing us to compare our models more closely with astronomical observations and bringing us closer to understanding how the chemical elements are created and spread throughout the universe,” he added.
The two papers were published in the July edition of the journal Physical Review Letters.
