Two Studies Reveal New Details of How Exploding Stars Forge the Elements

Two new studies bring scientists closer to understanding how exploding stars forge the chemical elements that make up planets, bodies and everything else in the universe, and how those elements spread through space. Both papers, published in the July issue of Physical Review Letters, look at different aspects of how supernovae — the explosive deaths of massive stars — create and disperse elements.

The first study focused on titanium-44, a radioactive element produced by supernovae that lingers long after the explosion fades. Researchers measured how much titanium-44 a supernova creates, finding that these explosions produce 35% more of the element than expected — a result that will let scientists build more accurate computer models of supernovae to compare against astronomical observations. "It's exciting to see just how far the field has come," said Christopher Cousins, a postdoctoral researcher in the University of Surrey's Nuclear Physics Group. "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 study examined a Type I supernova, which occurs when a neutron star — a remnant with one to two times the sun's mass packed into a body about 12 miles (20 kilometres) wide — pulls material from a companion star until the stolen matter triggers a thermonuclear blast, forging heavy elements and releasing X-ray bursts. Researchers at the Facility for Rare Isotope Beams (FRIB) in Michigan studied these reactions in more detail than before, confirming that nuclei become briefly trapped in a "nickel-copper cycle" during the blast, though only in small proportions.

Gavin Lotay of the University of Surrey said scientists still don't fully understand the nuclear reactions that power some of the universe's most spectacular stellar explosions, despite decades of research. He said the two studies give a clearer picture of how the explosions happen, letting scientists compare their models more closely with astronomical observations.