“One of the universe’s overriding mysteries is where heavy elements originate.” — JAMES LAT TIMER

Mass Separator facility to measure the
mass of a pure sample of zinc-82. The
researchers compared this mass with
predictions in various computer simu-
lations and determined that zinc-82 is
probably too light to be stable beneath a
neutron star’s surface. That’s in line with
the most well-supported prediction of
neutron star composition.

A newly formed neutron star (marked
by arrow) sits in the center of the
supernova remnant Cassiopeia A,
about 11,000 light-years away.

Astrophysicists have long looked for
another astronomical process with
enough energy to forge heavier elements
from protons and neutrons.

Lattimer believes this aspect of the study is not its greatest contribution; previous experiments had already shown that the leading model was more accurate than others. Instead, he is most impressed by the technique’s potential to pin down the characteristics of other exotic nuclei that may exist in neutron stars.

One potential explanation is that these elements form in the midst of the extreme heat and energy of supernovas — no neutron stars required. But simulations show that these explosions have an insufficient quantity of neutrons. That need for neutrons leads to a competing idea: that heavy elements form when two neutron stars collide and some of their crustal material escapes into space.

34 neutrons in the most common form of zinc. The challenge was isolating and measuring the rare isotope, most of which would decay in less than a second.

At the CERN lab outside Geneva,

Wolf’s team used the On-Line Isotope

Scientists want to create this compositional profile because neutron stars may be the source of many of the universe’s heavy elements. Fusion reactions in the cores of regular stars produce carbon, oxygen, nitrogen and other elements essential for life. But the heaviest element that fusion can construct is iron.

To evaluate this possibility, theorists need to improve models of neutron star composition. Mass measurements of heavy atoms like zinc-82, Wolf says, will help them do that. Then astronomers can survey the abundances of heavy elements in various stars and compare them with predictions of what would be produced in neutron star collisions.